package service

import (
	"context"
	"errors"
	"fmt"
	"regexp"
	"slices"
	"sort"
	"strconv"
	"strings"
	"time"

	"github.com/Tencent/WeKnora/internal/application/repository"
	"github.com/Tencent/WeKnora/internal/logger"
	"github.com/Tencent/WeKnora/internal/types"
	"github.com/Tencent/WeKnora/internal/types/interfaces"
	"github.com/google/uuid"
	"github.com/redis/go-redis/v9"
)

// wikiLinkRegex matches [[wiki-link]] syntax in markdown content
var wikiLinkRegex = regexp.MustCompile(`\[\[([^\]]+)\]\]`)

// wikiInlineChunkCitationRegex matches internal short handles emitted by the
// wiki ingest prompt while it classifies supporting chunks. The stable source
// relationship lives in WikiPage.ChunkRefs, so these handles have no meaning
// to readers and must not leak into generated Markdown.
var wikiInlineChunkCitationRegex = regexp.MustCompile(`[ \t]*\[c\d{3,}(?:\s*[,;]\s*c\d{3,})*\]`)

func stripWikiInlineChunkCitations(content string) string {
	return wikiInlineChunkCitationRegex.ReplaceAllString(content, "")
}

func stripWikiPageInlineChunkCitations(page *types.WikiPage) {
	if page == nil {
		return
	}
	page.Content = stripWikiInlineChunkCitations(page.Content)
	page.Summary = stripWikiInlineChunkCitations(page.Summary)
}

// wikiPageService implements the WikiPageService interface
type wikiPageService struct {
	repo            interfaces.WikiPageRepository
	chunkRepo       interfaces.ChunkRepository
	kbService       interfaces.KnowledgeBaseService
	taskPendingRepo interfaces.TaskPendingOpsRepository
	redisClient     *redis.Client
}

// NewWikiPageService creates a new wiki page service
func NewWikiPageService(
	repo interfaces.WikiPageRepository,
	chunkRepo interfaces.ChunkRepository,
	kbService interfaces.KnowledgeBaseService,
	taskPendingRepo interfaces.TaskPendingOpsRepository,
	redisClient *redis.Client,
) interfaces.WikiPageService {
	return &wikiPageService{
		repo:            repo,
		chunkRepo:       chunkRepo,
		kbService:       kbService,
		taskPendingRepo: taskPendingRepo,
		redisClient:     redisClient,
	}
}

// CreatePage creates a new wiki page
func (s *wikiPageService) CreatePage(ctx context.Context, page *types.WikiPage) (*types.WikiPage, error) {
	if page.ID == "" {
		page.ID = uuid.New().String()
	}
	if page.Slug == "" {
		return nil, errors.New("wiki page slug is required")
	}
	if page.KnowledgeBaseID == "" {
		return nil, errors.New("knowledge_base_id is required")
	}
	if page.Status == "" {
		page.Status = types.WikiPageStatusPublished
	}
	if page.Version == 0 {
		page.Version = 1
	}
	page.LastEditSource = types.WikiEditSourceFromContext(ctx)
	page.LastEditorID, _ = types.UserIDFromContext(ctx)
	stripWikiPageInlineChunkCitations(page)

	// Parse outbound links from content
	page.OutLinks = s.parseOutLinks(page.Content)
	if err := s.applyFolderToPage(ctx, page); err != nil {
		return nil, err
	}
	normalizeWikiHierarchy(page)

	now := time.Now()
	page.CreatedAt = now
	page.UpdatedAt = now

	if err := s.repo.Create(ctx, page); err != nil {
		return nil, fmt.Errorf("create wiki page: %w", err)
	}

	// Update inbound links on target pages
	s.updateInLinks(ctx, page.KnowledgeBaseID, page.Slug, page.OutLinks)

	return page, nil
}

// UpdatePage updates an existing wiki page.
//
// Version bump policy: the `version` column is intended to track the user-
// visible content revision, not every row rewrite. We therefore bump it only
// when at least one of the user-facing fields actually changes — title,
// content, summary, page_type, or status. Bookkeeping-only writes (refreshing
// source_refs after re-ingest when the body is identical, rebuilding the index
// page with the same directory, cross-link injection that ends up replacing
// nothing, etc.) still persist through `UpdateMeta` but leave `version`
// untouched so consumers can treat a bump as a real edit signal.
func (s *wikiPageService) UpdatePage(ctx context.Context, page *types.WikiPage) (*types.WikiPage, error) {
	existing, err := s.repo.GetBySlug(ctx, page.KnowledgeBaseID, page.Slug)
	if err != nil {
		return nil, fmt.Errorf("get existing page: %w", err)
	}
	if guard, ok := types.WikiPageWriteGuardFor(ctx, page.ID); ok && !guard.Matches(existing) {
		return nil, repository.ErrWikiPageConflict
	}
	writeCtx := types.WithWikiPageWriteGuard(ctx, existing)
	stripWikiPageInlineChunkCitations(page)

	oldOutLinks := existing.OutLinks

	// Snapshot user-visible fields BEFORE mutation so we can decide whether
	// this is a real content change or just bookkeeping.
	contentChanged := existing.Title != page.Title ||
		existing.Content != page.Content ||
		existing.Summary != page.Summary ||
		existing.PageType != page.PageType ||
		existing.Status != page.Status ||
		!slices.Equal(existing.Aliases, page.Aliases)

	// Keep an unmutated copy of the version being replaced: it becomes the
	// revision snapshot when this turns out to be a real content change.
	prev := *existing

	existing.Title = page.Title
	existing.Content = page.Content
	existing.Summary = page.Summary
	existing.PageType = page.PageType
	existing.Aliases = append(types.StringArray(nil), page.Aliases...)
	existing.SourceRefs = page.SourceRefs
	existing.ChunkRefs = page.ChunkRefs
	existing.PageMetadata = page.PageMetadata
	existing.ParentSlug = page.ParentSlug
	existing.FolderID = page.FolderID
	existing.SortOrder = page.SortOrder
	existing.Status = page.Status
	existing.UpdatedAt = time.Now()

	// CategoryPath is a derived cache of FolderID — recompute it from the
	// folder chain rather than trusting whatever the caller sent.
	if err := s.applyFolderToPage(ctx, existing); err != nil {
		return nil, err
	}

	// Outbound links are a pure derivative of content, so they only shift
	// when content shifts. Re-parse unconditionally to stay consistent with
	// the stored body.
	existing.OutLinks = s.parseOutLinks(existing.Content)
	normalizeWikiHierarchy(existing)

	if contentChanged {
		// The new version is authored by whoever is driving this write.
		existing.LastEditSource = types.WikiEditSourceFromContext(ctx)
		existing.LastEditorID, _ = types.UserIDFromContext(ctx)

		// Snapshot the superseded version and write the new one atomically,
		// so the content of every past version is preserved and a failed
		// update leaves no snapshot behind.
		if err := s.repo.UpdateWithRevision(writeCtx, existing, revisionFromPage(&prev)); err != nil {
			return nil, fmt.Errorf("update wiki page: %w", err)
		}
		// Bound per-page history; best-effort — a failed prune only means
		// slightly more storage until the next content change.
		s.pruneRevisions(ctx, existing.ID, existing.Version)
	} else {
		// No user-visible change — persist bookkeeping fields but preserve
		// the version so downstream consumers can rely on it.
		if err := s.repo.UpdateMeta(writeCtx, existing); err != nil {
			return nil, fmt.Errorf("update wiki page meta: %w", err)
		}
	}

	// Update inbound links: remove old, add new. If content didn't change,
	// oldOutLinks == existing.OutLinks and these calls are effectively no-ops.
	s.removeInLinks(ctx, existing.KnowledgeBaseID, existing.Slug, oldOutLinks)
	s.updateInLinks(ctx, existing.KnowledgeBaseID, existing.Slug, existing.OutLinks)

	return existing, nil
}

// UpdatePageMeta updates only metadata (status, source_refs) without version bump or link re-parse.
func (s *wikiPageService) UpdatePageMeta(ctx context.Context, page *types.WikiPage) error {
	if _, guarded := types.WikiPageWriteGuardFor(ctx, page.ID); !guarded {
		ctx = types.WithWikiPageWriteGuard(ctx, page)
	}
	normalizeWikiHierarchy(page)
	page.UpdatedAt = time.Now()
	return s.repo.UpdateMeta(ctx, page)
}

// UpdateAutoLinkedContent persists content produced by machine-only link
// decorators (cross-link injection / dead-link cleanup) without bumping
// `version`. Out-links are re-parsed from the new body and bidirectional
// in-link references on target pages are refreshed so link navigation stays
// consistent — only the user-facing revision counter is preserved.
func (s *wikiPageService) UpdateAutoLinkedContent(ctx context.Context, page *types.WikiPage) error {
	writeCtx := ctx
	if _, guarded := types.WikiPageWriteGuardFor(writeCtx, page.ID); !guarded {
		writeCtx = types.WithWikiPageWriteGuard(writeCtx, page)
	}
	existing, err := s.repo.GetBySlug(ctx, page.KnowledgeBaseID, page.Slug)
	if err != nil {
		return fmt.Errorf("get existing page: %w", err)
	}
	if guard, _ := types.WikiPageWriteGuardFor(writeCtx, page.ID); !guard.Matches(existing) {
		return repository.ErrWikiPageConflict
	}

	oldOutLinks := existing.OutLinks

	existing.Content = stripWikiInlineChunkCitations(page.Content)
	existing.OutLinks = s.parseOutLinks(existing.Content)
	existing.UpdatedAt = time.Now()

	if err := s.repo.UpdateAutoLinkedContent(writeCtx, existing); err != nil {
		return fmt.Errorf("update auto-linked content: %w", err)
	}
	// Link rewrite compensation must use this successful write's snapshot.
	page.Content, page.OutLinks, page.UpdatedAt = existing.Content, existing.OutLinks, existing.UpdatedAt

	s.removeInLinks(ctx, existing.KnowledgeBaseID, existing.Slug, oldOutLinks)
	s.updateInLinks(ctx, existing.KnowledgeBaseID, existing.Slug, existing.OutLinks)

	return nil
}

// revisionFromPage builds the immutable snapshot row for the given page
// state. EditSource on the snapshot is the author of THAT version — the
// page's provenance columns as they stood while the version was current —
// not whoever is performing the write that supersedes it.
func revisionFromPage(p *types.WikiPage) *types.WikiPageRevision {
	return &types.WikiPageRevision{
		ID:              uuid.New().String(),
		TenantID:        p.TenantID,
		KnowledgeBaseID: p.KnowledgeBaseID,
		PageID:          p.ID,
		Slug:            p.Slug,
		Version:         p.Version,
		Title:           p.Title,
		PageType:        p.PageType,
		Status:          p.Status,
		Content:         p.Content,
		Summary:         p.Summary,
		Aliases:         append(types.StringArray(nil), p.Aliases...),
		EditSource:      types.NormalizeWikiEditSource(p.LastEditSource),
		EditorID:        p.LastEditorID,
		EditedAt:        p.UpdatedAt,
		CreatedAt:       time.Now(),
	}
}

// pruneRevisions bounds one page's snapshot history after it advanced to
// currentVersion. Machine-authored snapshots are dropped once they fall out
// of the recent window; human/agent/revert ones survive until the hard cap,
// so pipeline churn on a hot page cannot evict the edits users care about.
func (s *wikiPageService) pruneRevisions(ctx context.Context, pageID string, currentVersion int) {
	req := types.WikiRevisionPruneRequest{
		PageID:              pageID,
		KeepFromVersion:     currentVersion - types.WikiMaxRevisionsPerPage,
		PrunableSources:     types.WikiPrunableEditSources,
		HardKeepFromVersion: currentVersion - types.WikiMaxRevisionsHardCap,
	}
	if req.KeepFromVersion <= 0 && req.HardKeepFromVersion <= 0 {
		return
	}
	if err := s.repo.PruneRevisions(ctx, req); err != nil {
		logger.Warnf(ctx, "prune wiki page revisions for %s failed: %v", pageID, err)
	}
}

// ErrWikiRevertToCurrentVersion is returned when a revert targets the version
// the page is already on — a client-side mistake (usually a stale history
// list), not a server fault, so handlers map it to 400.
var ErrWikiRevertToCurrentVersion = errors.New("cannot revert to the current version")

// ListRevisions returns the stored historical snapshots for a page (newest
// first, content omitted) plus the page's current version.
func (s *wikiPageService) ListRevisions(
	ctx context.Context, kbID string, slug string, limit int, offset int,
) (*types.WikiPageRevisionListResponse, error) {
	page, err := s.repo.GetBySlug(ctx, kbID, slug)
	if err != nil {
		return nil, err
	}
	revs, total, err := s.repo.ListRevisions(ctx, kbID, page.ID, limit, offset)
	if err != nil {
		return nil, fmt.Errorf("list wiki page revisions: %w", err)
	}
	return &types.WikiPageRevisionListResponse{
		Revisions:      revs,
		Total:          total,
		CurrentVersion: page.Version,
	}, nil
}

// GetRevision returns one historical snapshot with content.
func (s *wikiPageService) GetRevision(
	ctx context.Context, kbID string, slug string, version int,
) (*types.WikiPageRevision, error) {
	page, err := s.repo.GetBySlug(ctx, kbID, slug)
	if err != nil {
		return nil, err
	}
	return s.repo.GetRevision(ctx, kbID, page.ID, version)
}

// RevertPageToVersion rolls the page back to a stored revision by applying
// that revision's content fields as a regular edit: the pre-revert state is
// snapshotted, version advances, links are re-parsed. Placement (folder,
// sort order) and provenance refs keep their current values — a revert is
// about content, not about undoing directory moves.
func (s *wikiPageService) RevertPageToVersion(
	ctx context.Context, kbID string, slug string, version int,
) (*types.WikiPage, error) {
	page, err := s.repo.GetBySlug(ctx, kbID, slug)
	if err != nil {
		return nil, err
	}
	if version == page.Version {
		return nil, ErrWikiRevertToCurrentVersion
	}
	rev, err := s.repo.GetRevision(ctx, kbID, page.ID, version)
	if err != nil {
		return nil, err
	}

	target := *page
	target.Title = rev.Title
	target.Content = rev.Content
	target.Summary = rev.Summary
	target.PageType = rev.PageType
	target.Status = rev.Status
	target.Aliases = append(types.StringArray(nil), rev.Aliases...)

	return s.UpdatePage(types.WithWikiEditSource(ctx, types.WikiEditSourceRevert), &target)
}

// GetPageBySlug retrieves a wiki page by its slug
func (s *wikiPageService) GetPageBySlug(ctx context.Context, kbID string, slug string) (*types.WikiPage, error) {
	page, err := s.repo.GetBySlug(ctx, kbID, slug)
	if err != nil {
		return nil, err
	}
	stripWikiPageInlineChunkCitations(page)
	return page, nil
}

// GetPageByID retrieves a wiki page by its ID
func (s *wikiPageService) GetPageByID(ctx context.Context, id string) (*types.WikiPage, error) {
	page, err := s.repo.GetByID(ctx, id)
	if err != nil {
		return nil, err
	}
	stripWikiPageInlineChunkCitations(page)
	return page, nil
}

// ListPages lists wiki pages with optional filtering and pagination
func (s *wikiPageService) ListPages(ctx context.Context, req *types.WikiPageListRequest) (*types.WikiPageListResponse, error) {
	pages, total, err := s.repo.List(ctx, req)
	if err != nil {
		return nil, err
	}
	for _, page := range pages {
		stripWikiPageInlineChunkCitations(page)
		normalizeWikiHierarchy(page)
	}

	pageSize := req.PageSize
	if pageSize < 1 {
		pageSize = 20
	}
	page := req.Page
	if page < 1 {
		page = 1
	}
	totalPages := int(total) / pageSize
	if int(total)%pageSize > 0 {
		totalPages++
	}

	return &types.WikiPageListResponse{
		Pages:      pages,
		Total:      total,
		Page:       page,
		PageSize:   pageSize,
		TotalPages: totalPages,
	}, nil
}

// DeletePage soft-deletes a wiki page
func (s *wikiPageService) DeletePage(ctx context.Context, kbID string, slug string) error {
	page, err := s.repo.GetBySlug(ctx, kbID, slug)
	if err != nil {
		return err
	}

	// Remove inbound link references from pages this page links to
	s.removeInLinks(ctx, kbID, slug, page.OutLinks)

	// Delete the page
	if err := s.repo.Delete(ctx, kbID, slug); err != nil {
		return err
	}

	// Drop the snapshot history too: the page is gone from every read path,
	// so its revisions are unreachable rows holding full content bodies.
	// Best-effort — the page is already deleted and cannot be rolled back.
	if err := s.repo.DeleteRevisionsByPage(ctx, page.ID); err != nil {
		logger.Warnf(ctx, "delete wiki page revisions for %s failed: %v", page.ID, err)
	}

	// Delete synced chunk
	s.deleteChunkForPage(ctx, page)

	return nil
}

// GetIndex returns the index page for a knowledge base
func (s *wikiPageService) GetIndex(ctx context.Context, kbID string) (*types.WikiPage, error) {
	page, err := s.repo.GetBySlug(ctx, kbID, "index")
	if err != nil {
		if errors.Is(err, repository.ErrWikiPageNotFound) {
			// Create default index page
			return s.createDefaultPage(ctx, kbID, "index", "Index", types.WikiPageTypeIndex,
				"# Wiki Index\n\nThis is the index page. It will be automatically updated as pages are added.\n")
		}
		return nil, err
	}
	return page, nil
}

// wikiIndexContentPageTypes enumerates the page types that make up a wiki's
// user-visible directory. The index page is excluded; any
// LLM-created type we do not recognize surfaces under a generic "other"
// bucket.
var wikiIndexContentPageTypes = []string{
	types.WikiPageTypeSummary,
	types.WikiPageTypeEntity,
	types.WikiPageTypeConcept,
	types.WikiPageTypeSynthesis,
	types.WikiPageTypeComparison,
}

// GetIndexView builds the structured index response without ever
// materializing a multi-MB directory markdown string. Intro is read from
// the index wiki_page row (which now carries only intro text — see
// rebuildIndexPage). Each requested page_type is paginated independently
// with ListByTypeLight so reads stay O(page_size) rather than O(total
// pages in the KB).
//
// `pageTypes` narrows which groups to include; empty = all content types.
// `limit` is the per-group window size (defaults to 50, capped at 200).
// `cursor` is an opaque offset string; currently we use the stringified
// offset so clients can resume where they left off. Because different
// page_types paginate independently, `cursor` applies uniformly to every
// group — if the caller wants per-group cursors it should request one
// type at a time via `pageTypes`. That simplifies the wire format and
// matches the frontend's tabbed UX.
func (s *wikiPageService) GetIndexView(
	ctx context.Context,
	kbID string,
	pageTypes []string,
	limit int,
	cursor string,
) (*types.WikiIndexResponse, error) {
	indexPage, err := s.GetIndex(ctx, kbID)
	if err != nil {
		return nil, fmt.Errorf("load index page: %w", err)
	}

	if limit <= 0 {
		limit = 50
	}
	if limit > 200 {
		limit = 200
	}
	offset := 0
	if cursor != "" {
		v, parseErr := strconv.Atoi(cursor)
		if parseErr != nil || v < 0 {
			return nil, fmt.Errorf("invalid cursor %q", cursor)
		}
		offset = v
	}

	// Default to every known content type when the caller passes no
	// filter. Any unknown request-time type is passed through verbatim so
	// future page types (declared in types/wiki_page.go) start showing
	// up in the index the moment the LLM starts creating them, without a
	// handler change.
	selected := pageTypes
	if len(selected) == 0 {
		selected = append([]string{}, wikiIndexContentPageTypes...)
	}

	groups := make([]types.WikiIndexGroup, 0, len(selected))
	for _, pt := range selected {
		entries, total, listErr := s.repo.ListByTypeLight(ctx, kbID, pt, limit, offset)
		if listErr != nil {
			return nil, fmt.Errorf("list %s pages: %w", pt, listErr)
		}
		if entries == nil {
			entries = []types.WikiIndexEntry{}
		}
		for i := range entries {
			normalizeWikiIndexEntryHierarchy(&entries[i], pt)
		}
		next := ""
		// Only emit a cursor when a full page was returned AND more rows
		// remain past `offset + limit`. A short page or one that exactly
		// consumed the remainder should signal end-of-feed.
		if len(entries) == limit && int64(offset+len(entries)) < total {
			next = strconv.Itoa(offset + limit)
		}
		groups = append(groups, types.WikiIndexGroup{
			Type:       pt,
			Total:      total,
			Items:      entries,
			NextCursor: next,
		})
	}

	// The intro used to be stored on indexPage.Summary while
	// indexPage.Content held intro + directory markdown. After the
	// directory was lifted out of wiki_pages the content column holds
	// only the intro. Fall back to Summary for KBs that haven't been
	// re-ingested since the change so the response is never blank.
	intro := indexPage.Content
	if strings.TrimSpace(intro) == "" {
		intro = indexPage.Summary
	}

	return &types.WikiIndexResponse{
		Intro:   intro,
		Version: indexPage.Version,
		Groups:  groups,
	}, nil
}

// GetGraph returns a slice of the wiki link graph for visualization.
//
// Two modes are supported:
//
//   - WikiGraphModeOverview (default): returns the top `Limit` pages sorted
//     by link_count (in+out), plus every edge that connects two surviving
//     nodes. This is what the frontend fetches on the first graph open —
//     4万-page wikis would otherwise ship ~30MB of JSON and crash the
//     browser trying to render 100k SVG elements.
//
//   - WikiGraphModeEgo: returns the BFS neighborhood of `Center` up to
//     `Depth` undirected hops, capped at `Limit` total nodes. The
//     frontend uses this to drill down when the user clicks / searches a
//     node in the overview.
//
// `Types` is an optional page_type allow-list applied to both the candidate
// node set and (in ego mode) the frontier expansion. Leaving it empty means
// no type filter.
//
// `Limit <= 0` disables the cap entirely and is reserved for internal
// callers like the lint service that need to walk every page. The HTTP
// handler always clamps Limit into a safe range so external traffic can
// never opt out of truncation.
//
// Implementation note: pages are still fetched via repo.ListAll. At 4万
// pages that's ~10MB of rows + deserialization, which is already on the
// expensive side but still tractable and keeps the repository interface
// unchanged. Pushing the filter/top-N down into SQL is a follow-up step
// (cache layer + DB-side projection) — see CLAUDE.md plan.
func (s *wikiPageService) GetGraph(ctx context.Context, req *types.WikiGraphRequest) (*types.WikiGraphData, error) {
	if req == nil {
		return nil, errors.New("wiki graph request is required")
	}

	pages, err := s.repo.ListAll(ctx, req.KnowledgeBaseID)
	if err != nil {
		return nil, err
	}
	return computeGraphSubset(pages, req)
}

// computeGraphSubset is the pure I/O-free core of GetGraph. It takes the
// full page list and a request description and returns the subgraph the
// caller asked for. Extracted from GetGraph so tests can exercise the
// mode/limit/type-filter behavior without plumbing a full repository mock.
func computeGraphSubset(pages []*types.WikiPage, req *types.WikiGraphRequest) (*types.WikiGraphData, error) {
	mode := req.Mode
	if mode == "" {
		mode = types.WikiGraphModeOverview
	}

	// Pre-compute link_count and the type allow-list used for candidate
	// filtering. We keep the full page list around so ego mode can still
	// traverse through neighbors whose type is in the allow-list.
	typeAllow := make(map[string]bool, len(req.Types))
	for _, t := range req.Types {
		if t != "" {
			typeAllow[t] = true
		}
	}
	hasTypeFilter := len(typeAllow) > 0

	familiarSet := make(map[string]struct{}, len(req.FamiliarKnowledgeIDs))
	for _, id := range req.FamiliarKnowledgeIDs {
		if id = strings.TrimSpace(id); id != "" {
			familiarSet[id] = struct{}{}
		}
	}

	pageBySlug := make(map[string]*types.WikiPage, len(pages))
	linkCount := make(map[string]int, len(pages))
	for _, p := range pages {
		pageBySlug[p.Slug] = p
		linkCount[p.Slug] = len(p.InLinks) + len(p.OutLinks)
	}

	// Select the node slug set for the requested slice.
	var selected map[string]struct{}
	switch mode {
	case types.WikiGraphModeEgo:
		if req.Center == "" {
			return nil, errors.New("ego graph requires a center slug")
		}
		if _, ok := pageBySlug[req.Center]; !ok {
			return nil, fmt.Errorf("ego center slug %q not found", req.Center)
		}
		depth := req.Depth
		if depth < 1 {
			depth = 1
		}
		selected = bfsEgoSlugs(pageBySlug, req.Center, depth, typeAllow, req.Limit)
	default:
		// overview: keep only type-allowed candidates, sort by link_count desc, cap.
		candidates := make([]*types.WikiPage, 0, len(pages))
		for _, p := range pages {
			if hasTypeFilter && !typeAllow[p.PageType] {
				continue
			}
			candidates = append(candidates, p)
		}
		sort.SliceStable(candidates, func(i, j int) bool {
			li := linkCount[candidates[i].Slug]
			lj := linkCount[candidates[j].Slug]
			if li != lj {
				return li > lj
			}
			// Stable tiebreaker keeps the API deterministic between calls.
			return candidates[i].Slug < candidates[j].Slug
		})
		if req.Limit > 0 && len(candidates) > req.Limit {
			candidates = candidates[:req.Limit]
		}
		selected = make(map[string]struct{}, len(candidates))
		for _, p := range candidates {
			selected[p.Slug] = struct{}{}
		}
	}

	// Build nodes from the selected set.
	nodes := make([]types.WikiGraphNode, 0, len(selected))
	for slug := range selected {
		p := pageBySlug[slug]
		nodes = append(nodes, types.WikiGraphNode{
			Slug:      p.Slug,
			Title:     p.Title,
			PageType:  p.PageType,
			LinkCount: linkCount[slug],
			Familiar:  p.BuiltFrom(familiarSet),
		})
	}
	// Deterministic node ordering — the map iteration above is random.
	sort.Slice(nodes, func(i, j int) bool {
		if nodes[i].LinkCount != nodes[j].LinkCount {
			return nodes[i].LinkCount > nodes[j].LinkCount
		}
		return nodes[i].Slug < nodes[j].Slug
	})

	// Build edges, keeping only edges whose endpoints both survived selection.
	var edges []types.WikiGraphEdge
	for _, p := range pages {
		if _, ok := selected[p.Slug]; !ok {
			continue
		}
		for _, target := range p.OutLinks {
			if _, ok := selected[target]; !ok {
				continue
			}
			edges = append(edges, types.WikiGraphEdge{
				Source: p.Slug,
				Target: target,
			})
		}
	}

	// total is the count of candidate nodes before truncation — i.e. the
	// population the frontend would need to fetch if it asked for the
	// whole graph. For overview this respects the type filter; for ego
	// it is the total KB page count (the user still sees "X of Y" based
	// on the full wiki, not a filtered denominator).
	total := len(pages)
	if mode == types.WikiGraphModeOverview && hasTypeFilter {
		total = 0
		for _, p := range pages {
			if typeAllow[p.PageType] {
				total++
			}
		}
	}

	meta := types.WikiGraphMeta{
		Mode:      mode,
		Total:     total,
		Returned:  len(nodes),
		Truncated: len(nodes) < total,
	}
	for _, n := range nodes {
		if n.Familiar {
			meta.FamiliarCount++
		}
	}
	if mode == types.WikiGraphModeEgo {
		meta.Center = req.Center
		meta.Depth = req.Depth
		if meta.Depth < 1 {
			meta.Depth = 1
		}
	}

	return &types.WikiGraphData{
		Nodes: nodes,
		Edges: edges,
		Meta:  meta,
	}, nil
}

// bfsEgoSlugs computes the undirected BFS neighborhood of `center` up to
// `depth` hops using both inbound and outbound links. Type-filtered pages
// are excluded from the result but are also NOT traversed through — so a
// filter that hides "index" pages will not leak the whole wiki via the
// index. The caller guarantees center exists in pageBySlug.
func bfsEgoSlugs(
	pageBySlug map[string]*types.WikiPage,
	center string,
	depth int,
	typeAllow map[string]bool,
	limit int,
) map[string]struct{} {
	hasTypeFilter := len(typeAllow) > 0
	centerPage, ok := pageBySlug[center]
	if !ok {
		return map[string]struct{}{}
	}
	// If the center itself fails the type filter we honor the filter and
	// return an empty set — the handler will surface Returned=0.
	if hasTypeFilter && !typeAllow[centerPage.PageType] {
		return map[string]struct{}{}
	}

	visited := map[string]struct{}{center: {}}
	frontier := []string{center}

	for hop := 0; hop < depth; hop++ {
		if limit > 0 && len(visited) >= limit {
			break
		}
		next := make([]string, 0, len(frontier))
		for _, slug := range frontier {
			p, ok := pageBySlug[slug]
			if !ok {
				continue
			}
			neighbors := make([]string, 0, len(p.OutLinks)+len(p.InLinks))
			neighbors = append(neighbors, p.OutLinks...)
			neighbors = append(neighbors, p.InLinks...)
			for _, nb := range neighbors {
				if _, seen := visited[nb]; seen {
					continue
				}
				np, exists := pageBySlug[nb]
				if !exists {
					continue
				}
				if hasTypeFilter && !typeAllow[np.PageType] {
					continue
				}
				visited[nb] = struct{}{}
				next = append(next, nb)
				if limit > 0 && len(visited) >= limit {
					break
				}
			}
			if limit > 0 && len(visited) >= limit {
				break
			}
		}
		frontier = next
		if len(frontier) == 0 {
			break
		}
	}

	return visited
}

// GetStats returns aggregate statistics about the wiki
func (s *wikiPageService) GetStats(ctx context.Context, kbID string) (*types.WikiStats, error) {
	counts, err := s.repo.CountByType(ctx, kbID)
	if err != nil {
		return nil, err
	}

	var total int64
	for _, c := range counts {
		total += c
	}

	orphans, err := s.repo.CountOrphans(ctx, kbID)
	if err != nil {
		return nil, err
	}

	// Count total links
	pages, err := s.repo.ListAll(ctx, kbID)
	if err != nil {
		return nil, err
	}
	var totalLinks int64
	for _, p := range pages {
		totalLinks += int64(len(p.OutLinks))
	}

	// Get recent updates (last 10)
	listReq := &types.WikiPageListRequest{
		KnowledgeBaseID: kbID,
		Page:            1,
		PageSize:        10,
		SortBy:          "updated_at",
		SortOrder:       "desc",
	}
	recentPages, _, err := s.repo.List(ctx, listReq)
	if err != nil {
		return nil, err
	}

	var pendingTasks int64
	var pendingIssues int64
	var isActive bool
	if s.taskPendingRepo != nil {
		// Pending wiki ingest ops live in task_pending_ops keyed by
		// (task_type="wiki:ingest", scope="knowledge_base", scope_id=kbID).
		pendingTasks, _ = s.taskPendingRepo.PendingCount(ctx, wikiTaskType, wikiTaskScope, kbID)
	}
	if s.redisClient != nil {
		// The "active batch in progress" flag is still a Redis-only
		// short-lived signal (per-process lock with TTL renew); not
		// worth migrating since it carries no durable state.
		activeFlag, _ := s.redisClient.Exists(ctx, "wiki:active:"+kbID).Result()
		isActive = activeFlag > 0
	}

	issues, _ := s.ListIssues(ctx, kbID, "", "pending")
	pendingIssues = int64(len(issues))

	return &types.WikiStats{
		TotalPages:    total,
		PagesByType:   counts,
		TotalLinks:    totalLinks,
		OrphanCount:   orphans,
		RecentUpdates: recentPages,
		PendingTasks:  pendingTasks,
		PendingIssues: pendingIssues,
		IsActive:      isActive,
	}, nil
}

// RebuildLinks re-parses all pages and rebuilds bidirectional link references
func (s *wikiPageService) RebuildLinks(ctx context.Context, kbID string) error {
	pages, err := s.repo.ListAll(ctx, kbID)
	if err != nil {
		return err
	}

	// Build slug-to-page map
	pageMap := make(map[string]*types.WikiPage)
	for _, p := range pages {
		pageMap[p.Slug] = p
	}

	// Clear all inbound links first
	for _, p := range pages {
		p.InLinks = types.StringArray{}
	}

	// Re-parse outbound links and rebuild inbound links
	for _, p := range pages {
		p.OutLinks = s.parseOutLinks(p.Content)
		for _, target := range p.OutLinks {
			if tp, exists := pageMap[target]; exists {
				tp.InLinks = append(tp.InLinks, p.Slug)
			}
		}
	}

	// Save all pages (link rebuild is metadata-only, no version bump)
	for _, p := range pages {
		if err := s.UpdatePageMeta(ctx, p); err != nil {
			logger.Warnf(ctx, "wiki: failed to update links for page %s: %v", p.Slug, err)
		}
	}

	return nil
}

// ListAllPages retrieves all non-archived wiki pages without pagination.
func (s *wikiPageService) ListAllPages(ctx context.Context, kbID string) ([]*types.WikiPage, error) {
	return s.repo.ListAll(ctx, kbID)
}

// ListByType returns every wiki page of a given type for a KB. Exposed so
// callers like intro regeneration can load only the page type they need
// (summaries) instead of paying for the full ListAll scan.
func (s *wikiPageService) ListByType(ctx context.Context, kbID string, pageType string) ([]*types.WikiPage, error) {
	return s.repo.ListByType(ctx, kbID, pageType)
}

// ListPagesBySourceRef exposes the repository's source-ref lookup so higher
// layers (delete flow, retract reconciliation) can re-query the current wiki
// state without depending on a stale caller-captured slug list.
func (s *wikiPageService) ListPagesBySourceRef(ctx context.Context, kbID string, knowledgeID string) ([]*types.WikiPage, error) {
	return s.repo.ListBySourceRef(ctx, kbID, knowledgeID)
}

// ListSlugsBySourceRef returns just the slugs of pages that cite the given
// knowledge id. Backed by the source_refs GIN index added in migration
// 000041 — the wiki ingest pipeline uses it as a cheap "before" snapshot
// when reconciling old vs new extraction sets.
func (s *wikiPageService) ListSlugsBySourceRef(ctx context.Context, kbID string, knowledgeID string) ([]string, error) {
	return s.repo.ListSlugsBySourceRef(ctx, kbID, knowledgeID)
}

// ListBySlugs is the lazy fetcher used by wiki ingest's batch context.
// Returns lightweight projections (no content / source_refs / chunk_refs)
// for the requested slugs, in a single IN query. Used in place of the
// pre-batch ListAllPages dump that historically pulled hundreds of MB
// for KBs in the tens of thousands of pages.
func (s *wikiPageService) ListBySlugs(ctx context.Context, kbID string, slugs []string) (map[string]*types.WikiPageLite, error) {
	return s.repo.ListBySlugs(ctx, kbID, slugs)
}

// ListSummariesByKnowledgeIDs is the lazy fetcher for the retract /
// reparse branches of reduceSlugUpdates. Returns the content of each
// surviving summary page keyed by its source knowledge id.
func (s *wikiPageService) ListSummariesByKnowledgeIDs(ctx context.Context, kbID string, kids []string) (map[string]string, error) {
	return s.repo.ListSummariesByKnowledgeIDs(ctx, kbID, kids)
}

// ExistsSlugs reports which of the given slugs are live (non-archived,
// non-deleted) in the KB. Used by cleanDeadLinks to validate out-link
// targets before stripping them.
func (s *wikiPageService) ExistsSlugs(ctx context.Context, kbID string, slugs []string) (map[string]bool, error) {
	return s.repo.ExistsSlugs(ctx, kbID, slugs)
}

// ListAllSlugs returns every non-archived slug in the KB. Used by lint
// to compute the live-slug set without paying for ListAll's full row
// materialization.
func (s *wikiPageService) ListAllSlugs(ctx context.Context, kbID string) ([]string, error) {
	return s.repo.ListAllSlugs(ctx, kbID)
}

// ListPagesCursor is the lint-side cursor pagination over wiki_pages.
func (s *wikiPageService) ListPagesCursor(ctx context.Context, kbID string, cursor string, limit int) ([]*types.WikiPage, string, error) {
	return s.repo.ListPagesCursor(ctx, kbID, cursor, limit)
}

// ListByTypeRecent caps the page count for first-time index intro
// generation so the LLM prompt stays bounded on large KBs.
func (s *wikiPageService) ListByTypeRecent(ctx context.Context, kbID string, pageType string, limit int) ([]types.WikiIndexEntry, error) {
	return s.repo.ListByTypeRecent(ctx, kbID, pageType, limit)
}

// FindSimilarPages performs a pg_trgm similarity search; used by the
// dedup pre-filter to surface candidate merge targets.
func (s *wikiPageService) FindSimilarPages(ctx context.Context, kbID string, query string, pageTypes []string, limit int) ([]*types.WikiPageLite, error) {
	return s.repo.FindSimilarPages(ctx, kbID, query, pageTypes, limit)
}

// FindPagesByNormalizedTitle looks up exact same-type title identities for
// wiki ingest, independent of the trigram top-K used for semantic dedup.
func (s *wikiPageService) FindPagesByNormalizedTitle(ctx context.Context, kbID, pageType, identity string) ([]*types.WikiPageLite, error) {
	return s.repo.FindPagesByNormalizedTitle(ctx, kbID, pageType, identity)
}

// FindPagesByNormalizedTitles looks up several normalized title identities
// in one query so wiki ingest does not seq-scan once per extracted item.
func (s *wikiPageService) FindPagesByNormalizedTitles(ctx context.Context, kbID, pageType string, identities []string) ([]*types.WikiPageLite, error) {
	return s.repo.FindPagesByNormalizedTitles(ctx, kbID, pageType, identities)
}

// ListDistinctCategoryPaths returns the existing wiki folder paths. Used by
// wiki ingest's taxonomy planner to ground folder reuse.
func (s *wikiPageService) ListDistinctCategoryPaths(ctx context.Context, kbID string, maxPaths int) ([][]string, error) {
	return s.repo.ListDistinctCategoryPaths(ctx, kbID, maxPaths)
}

// CountByType is a service-layer pass-through over the repo. Used by
// the index intro path to frame the LLM prompt's "showing N of M" hint.
func (s *wikiPageService) CountByType(ctx context.Context, kbID string) (map[string]int64, error) {
	return s.repo.CountByType(ctx, kbID)
}

// SearchPages performs full-text search over wiki pages
func (s *wikiPageService) SearchPages(ctx context.Context, kbID string, query string, limit int) ([]*types.WikiPage, error) {
	return s.repo.Search(ctx, kbID, query, limit)
}

// --- Internal helpers ---

// parseOutLinks extracts [[wiki-link]] slugs from markdown content
func (s *wikiPageService) parseOutLinks(content string) types.StringArray {
	matches := wikiLinkRegex.FindAllStringSubmatch(content, -1)
	seen := make(map[string]bool)
	var links types.StringArray

	for _, match := range matches {
		if len(match) > 1 {
			slug := strings.TrimSpace(match[1])
			// Handle [[slug|display name]] format — slug is the first part
			if parts := strings.SplitN(slug, "|", 2); len(parts) == 2 {
				slug = strings.TrimSpace(parts[0])
			}
			slug = normalizeSlug(slug)
			if slug != "" && !seen[slug] {
				seen[slug] = true
				links = append(links, slug)
			}
		}
	}
	return links
}

// normalizeSlug normalizes a wiki link slug
func normalizeSlug(slug string) string {
	slug = strings.ToLower(strings.TrimSpace(slug))
	slug = strings.ReplaceAll(slug, " ", "-")
	return slug
}

// slugNamespace returns the prefix of a slug up to (but excluding) the first
// '/', e.g. "summary/abc" -> "summary". Slugs without a '/' map to "".
func slugNamespace(slug string) string {
	if i := strings.IndexByte(slug, '/'); i >= 0 {
		return slug[:i]
	}
	return ""
}

// rewriteDeadWikiLinks walks every [[slug]] / [[slug|display]] occurrence in
// content and lets `resolve` decide, per link, whether to rewrite the slug.
// `resolve` receives the normalized slug and its display text and returns the
// replacement slug plus true to rewrite, or ("", false) to leave the link
// untouched. Display text is preserved verbatim. This is a pure helper — the
// resolution policy lives entirely in the callback.
func rewriteDeadWikiLinks(content string, resolve func(normSlug, display string) (string, bool)) (string, bool) {
	changed := false
	out := wikiLinkRegex.ReplaceAllStringFunc(content, func(match string) string {
		inner := match[2 : len(match)-2]
		rawSlug := inner
		display := ""
		if parts := strings.SplitN(inner, "|", 2); len(parts) == 2 {
			rawSlug = parts[0]
			display = strings.TrimSpace(parts[1])
		}
		norm := normalizeSlug(rawSlug)
		if norm == "" {
			return match
		}
		newSlug, ok := resolve(norm, display)
		if !ok || newSlug == "" || newSlug == norm {
			return match
		}
		changed = true
		if display != "" {
			return "[[" + newSlug + "|" + display + "]]"
		}
		return "[[" + newSlug + "]]"
	})
	return out, changed
}

// RepairContentLinks rewrites [[slug]] / [[slug|display]] references in
// `content` whose target does not exist in the KB but is almost certainly a
// mangled form of a real page. The canonical case: an LLM re-typed a summary
// page's UUID-based slug and inserted/dropped a hex digit
// (summary/…06fb5d5b5b5e → summary/…06fb14d5b14b14e), producing a link that
// 404s and can never be recovered by exact lookup.
//
// Unlike stripDeadWikiLinks (the ingest cleanup pass), this method is
// REWRITE-ONLY: a dead link is corrected only when a confident live candidate
// exists; otherwise it is left completely untouched. It NEVER strips a link to
// plain text, so it is safe on any write path — including writes whose targets
// legitimately do not exist yet (those simply stay as-is until they do).
//
// The candidate pool for each dead link is scoped to live slugs that share the
// same namespace prefix (a dead `summary/<uuid>` only resolves against live
// `summary/*` slugs). Scoping keeps the bigram-similarity lever safe: distinct
// high-entropy UUIDs in one namespace don't collide, while a one-character
// mangle stays comfortably above threshold against its true source.
//
// Returns the possibly-updated content and whether any rewrite happened.
// Errors are only returned for hard repo failures; callers may treat repair as
// best-effort and ignore them.
func (s *wikiPageService) RepairContentLinks(
	ctx context.Context, kbID, selfSlug, content string,
) (string, bool, error) {
	if strings.TrimSpace(content) == "" {
		return content, false, nil
	}
	outLinks := s.parseOutLinks(content)
	if len(outLinks) == 0 {
		return content, false, nil
	}

	existMap, err := s.repo.ExistsSlugs(ctx, kbID, outLinks)
	if err != nil {
		return content, false, err
	}
	deadPrefixes := make(map[string]struct{})
	for _, l := range outLinks {
		if l == selfSlug || existMap[l] {
			continue
		}
		deadPrefixes[slugNamespace(l)] = struct{}{}
	}
	if len(deadPrefixes) == 0 {
		return content, false, nil
	}

	allSlugs, err := s.repo.ListAllSlugs(ctx, kbID)
	if err != nil {
		return content, false, err
	}
	liveByPrefix := make(map[string]map[string]struct{})
	var candidateSlugs []string
	for _, sl := range allSlugs {
		ns := slugNamespace(sl)
		if _, want := deadPrefixes[ns]; !want {
			continue
		}
		set, ok := liveByPrefix[ns]
		if !ok {
			set = make(map[string]struct{})
			liveByPrefix[ns] = set
		}
		set[sl] = struct{}{}
		candidateSlugs = append(candidateSlugs, sl)
	}
	if len(candidateSlugs) == 0 {
		return content, false, nil
	}

	// Build a title -> slug reverse lookup for candidate pages so the
	// display-text lever (the safest, most precise one) can fire. Bounded to
	// the relevant namespaces so this stays cheap even on large KBs.
	titleToSlug := make(map[string]string)
	if lites, lerr := s.repo.ListBySlugs(ctx, kbID, candidateSlugs); lerr == nil {
		for _, lp := range lites {
			if lp != nil && lp.Title != "" {
				titleToSlug[lp.Title] = lp.Slug
			}
		}
	}

	resolveCache := make(map[string]string)
	newContent, changed := rewriteDeadWikiLinks(content, func(norm, display string) (string, bool) {
		if norm == selfSlug || existMap[norm] {
			return "", false
		}
		key := norm + "\x00" + display
		if cached, ok := resolveCache[key]; ok {
			return cached, cached != ""
		}
		resolved, ok := resolveDeadSlug(norm, display, liveByPrefix[slugNamespace(norm)], titleToSlug)
		if !ok || resolved == norm {
			resolveCache[key] = ""
			return "", false
		}
		resolveCache[key] = resolved
		return resolved, true
	})
	return newContent, changed, nil
}

// updateInLinks adds the source slug to the in_links of target pages
func (s *wikiPageService) updateInLinks(ctx context.Context, kbID string, sourceSlug string, targets types.StringArray) {
	for _, targetSlug := range targets {
		targetPage, err := s.repo.GetBySlug(ctx, kbID, targetSlug)
		if err != nil {
			continue // target page may not exist yet
		}
		if !containsString(targetPage.InLinks, sourceSlug) {
			writeCtx := types.WithWikiPageWriteGuard(ctx, targetPage)
			targetPage.InLinks = append(targetPage.InLinks, sourceSlug)
			if err := s.UpdatePageMeta(writeCtx, targetPage); err != nil {
				logger.Warnf(ctx, "wiki: failed to update in_links for %s: %v", targetSlug, err)
			}
		}
	}
}

// removeInLinks removes the source slug from the in_links of target pages
func (s *wikiPageService) removeInLinks(ctx context.Context, kbID string, sourceSlug string, targets types.StringArray) {
	for _, targetSlug := range targets {
		targetPage, err := s.repo.GetBySlug(ctx, kbID, targetSlug)
		if err != nil {
			continue
		}
		newInLinks := removeString(targetPage.InLinks, sourceSlug)
		if len(newInLinks) != len(targetPage.InLinks) {
			writeCtx := types.WithWikiPageWriteGuard(ctx, targetPage)
			targetPage.InLinks = newInLinks
			if err := s.UpdatePageMeta(writeCtx, targetPage); err != nil {
				logger.Warnf(ctx, "wiki: failed to update in_links for %s: %v", targetSlug, err)
			}
		}
	}
}

// deleteChunkForPage removes the synced chunk for a wiki page. Chunk sync is
// optional wiring, so a service built without a chunk repository just skips
// it rather than taking the delete down with it.
func (s *wikiPageService) deleteChunkForPage(ctx context.Context, page *types.WikiPage) {
	if s.chunkRepo == nil {
		return
	}
	chunkID := "wp-" + page.ID
	if err := s.chunkRepo.DeleteChunk(ctx, page.TenantID, chunkID); err != nil {
		logger.Warnf(ctx, "wiki: failed to delete chunk for page %s: %v", page.Slug, err)
	}
}

// createDefaultPage creates the default index page.
func (s *wikiPageService) createDefaultPage(ctx context.Context, kbID string, slug string, title string, pageType string, content string) (*types.WikiPage, error) {
	// Get KB to get tenant ID
	kb, err := s.kbService.GetKnowledgeBaseByIDOnly(ctx, kbID)
	if err != nil {
		return nil, fmt.Errorf("get knowledge base: %w", err)
	}

	page := &types.WikiPage{
		ID:              uuid.New().String(),
		TenantID:        kb.TenantID,
		KnowledgeBaseID: kbID,
		Slug:            slug,
		Title:           title,
		PageType:        pageType,
		Status:          types.WikiPageStatusPublished,
		Content:         content,
		Summary:         title,
		Version:         1,
	}
	normalizeWikiHierarchy(page)

	if err := s.repo.Create(ctx, page); err != nil {
		return nil, fmt.Errorf("create default %s page: %w", slug, err)
	}
	return page, nil
}

func normalizeWikiHierarchy(page *types.WikiPage) {
	if page == nil {
		return
	}
	page.ParentSlug = strings.TrimSpace(page.ParentSlug)

	cleanPath := types.StringArray(types.CleanWikiCategoryPath(page.CategoryPath))
	page.CategoryPath = cleanPath
	page.Depth = len(cleanPath)

	display := strings.TrimSpace(page.Title)
	if display == "" {
		display = strings.TrimSpace(page.Slug)
	}
	page.WikiPath = buildWikiPath(page.PageType, cleanPath, display)
}

func normalizeWikiIndexEntryHierarchy(entry *types.WikiIndexEntry, pageType string) {
	if entry == nil {
		return
	}

	cleanPath := types.StringArray(types.CleanWikiCategoryPath(entry.CategoryPath))
	entry.CategoryPath = cleanPath
	entry.Depth = len(cleanPath)

	display := strings.TrimSpace(entry.Title)
	if display == "" {
		display = strings.TrimSpace(entry.Slug)
	}
	entry.WikiPath = buildWikiPath(pageType, cleanPath, display)
}

// buildWikiPath assembles the normalized, sortable "page_type/cat.../title"
// breadcrumb used for directory ordering. Empty segments are skipped.
func buildWikiPath(pageType string, categoryPath []string, display string) string {
	parts := make([]string, 0, len(categoryPath)+2)
	if pt := strings.TrimSpace(pageType); pt != "" {
		parts = append(parts, pt)
	}
	parts = append(parts, categoryPath...)
	if display != "" {
		parts = append(parts, display)
	}
	return strings.Join(parts, "/")
}

// containsString checks if a string slice contains a given string
func containsString(slice []string, s string) bool {
	for _, v := range slice {
		if v == s {
			return true
		}
	}
	return false
}

// removeString removes a string from a slice
func removeString(slice []string, s string) types.StringArray {
	result := make(types.StringArray, 0, len(slice))
	for _, v := range slice {
		if v != s {
			result = append(result, v)
		}
	}
	return result
}

// CreateIssue logs a new issue for a wiki page
func (s *wikiPageService) CreateIssue(ctx context.Context, issue *types.WikiPageIssue) (*types.WikiPageIssue, error) {
	if issue.ID == "" {
		issue.ID = uuid.New().String()
	}
	if err := s.repo.CreateIssue(ctx, issue); err != nil {
		return nil, fmt.Errorf("create wiki page issue: %w", err)
	}
	return issue, nil
}

// ListIssues retrieves issues for a knowledge base
func (s *wikiPageService) ListIssues(ctx context.Context, kbID string, slug string, status string) ([]*types.WikiPageIssue, error) {
	return s.repo.ListIssues(ctx, kbID, slug, status)
}

// UpdateIssueStatus updates an issue's status
func (s *wikiPageService) UpdateIssueStatus(ctx context.Context, issueID string, status string) error {
	return s.repo.UpdateIssueStatus(ctx, issueID, status)
}

// --- Folder tree (wiki_folders) ---

// wikiFolderSegments splits a materialized folder path ("AI/RAG") into cleaned
// segments. Empty/blank path yields nil (the wiki root).
func wikiFolderSegments(path string) []string {
	if strings.TrimSpace(path) == "" {
		return nil
	}
	return types.CleanWikiCategoryPath(strings.Split(path, "/"))
}

// applyFolderToPage refreshes a page's derived category_path cache from its
// authoritative FolderID. Root ("") clears the path. A folder id that does not
// resolve is treated as a hard error so we never silently misplace a page.
func (s *wikiPageService) applyFolderToPage(ctx context.Context, page *types.WikiPage) error {
	if page == nil {
		return nil
	}
	if strings.TrimSpace(page.FolderID) == "" {
		page.FolderID = ""
		page.CategoryPath = nil
		return nil
	}
	folder, err := s.repo.GetFolderByID(ctx, page.KnowledgeBaseID, page.FolderID)
	if err != nil {
		if errors.Is(err, repository.ErrWikiFolderNotFound) {
			return fmt.Errorf("wiki page references unknown folder %q", page.FolderID)
		}
		return fmt.Errorf("resolve page folder: %w", err)
	}
	page.CategoryPath = types.StringArray(wikiFolderSegments(folder.Path))
	return nil
}

// GetFolder retrieves a single folder by id.
func (s *wikiPageService) GetFolder(ctx context.Context, kbID string, id string) (*types.WikiFolder, error) {
	return s.repo.GetFolderByID(ctx, kbID, id)
}

// ListChildFolders returns the direct children of parentID for a tree view
// scoped to pageTypes. PageCount is recursive (the folder's whole subtree) so
// a parent reflects everything filed beneath it. A folder is shown when its
// subtree holds a page matching pageTypes. Wholly-empty folders (no pages of
// any type underneath) are only listed when multiple types are requested —
// the merged knowledge view — so single-type tabs like summary do not surface
// empty containers.
func (s *wikiPageService) ListChildFolders(
	ctx context.Context, kbID string, parentID string, pageTypes []string,
) ([]types.WikiFolderNode, error) {
	all, err := s.repo.ListAllFolders(ctx, kbID)
	if err != nil {
		return nil, err
	}
	scopedDirect, err := s.repo.CountPagesByFolder(ctx, kbID, pageTypes)
	if err != nil {
		return nil, err
	}
	allDirect := scopedDirect
	if len(pageTypes) > 0 {
		allDirect, err = s.repo.CountPagesByFolder(ctx, kbID, nil)
		if err != nil {
			return nil, err
		}
	}
	recScoped := recursiveFolderCounts(all, scopedDirect)
	recAll := recursiveFolderCounts(all, allDirect)
	showEmptyFolders := len(pageTypes) > 1
	// A folder belongs in this view if it (recursively) contains a page of the
	// requested types, or — only in the merged knowledge view — if it is a
	// completely empty container with no pages of any type underneath.
	relevant := func(id string) bool {
		if recScoped[id] > 0 {
			return true
		}
		if showEmptyFolders {
			return recAll[id] == 0
		}
		return false
	}

	out := make([]types.WikiFolderNode, 0)
	for _, f := range all {
		if f.ParentID != parentID || !relevant(f.ID) {
			continue
		}
		hasChildren := false
		for _, g := range all {
			if g.ParentID == f.ID && relevant(g.ID) {
				hasChildren = true
				break
			}
		}
		out = append(out, types.WikiFolderNode{
			WikiFolder:  *f,
			PageCount:   recScoped[f.ID],
			HasChildren: hasChildren,
		})
	}
	return out, nil
}

// recursiveFolderCounts maps each folder id to the sum of `direct` page counts
// over the folder and all of its descendants, using the materialized path so a
// single pass over the (navigation-sized) folder set suffices.
func recursiveFolderCounts(all []*types.WikiFolder, direct map[string]int64) map[string]int64 {
	res := make(map[string]int64, len(all))
	for _, f := range all {
		sum := direct[f.ID]
		prefix := f.Path + "/"
		for _, g := range all {
			if g.ID != f.ID && strings.HasPrefix(g.Path, prefix) {
				sum += direct[g.ID]
			}
		}
		res[f.ID] = sum
	}
	return res
}

// validateFolderName trims and rejects blank names or names carrying directory
// separators (a folder name is a single tree level).
func validateFolderName(name string) (string, error) {
	name = strings.TrimSpace(name)
	if name == "" {
		return "", errors.New("folder name is required")
	}
	if strings.ContainsAny(name, "/｜|／") {
		return "", fmt.Errorf("folder name %q must not contain a path separator", name)
	}
	return name, nil
}

// CreateFolder creates a new empty folder under parentID.
func (s *wikiPageService) CreateFolder(
	ctx context.Context, kbID string, tenantID uint64, parentID string, name string,
) (*types.WikiFolder, error) {
	name, err := validateFolderName(name)
	if err != nil {
		return nil, err
	}

	parentPath := ""
	depth := 1
	if parentID != types.WikiFolderRootID {
		parent, err := s.repo.GetFolderByID(ctx, kbID, parentID)
		if err != nil {
			return nil, err
		}
		parentPath = parent.Path
		depth = parent.Depth + 1
	}

	if _, err := s.repo.GetChildFolderByName(ctx, kbID, parentID, name); err == nil {
		return nil, repository.ErrWikiFolderConflict
	} else if !errors.Is(err, repository.ErrWikiFolderNotFound) {
		return nil, err
	}

	path := name
	if parentPath != "" {
		path = parentPath + "/" + name
	}
	now := time.Now()
	folder := &types.WikiFolder{
		ID:              uuid.New().String(),
		TenantID:        tenantID,
		KnowledgeBaseID: kbID,
		ParentID:        parentID,
		Name:            name,
		Path:            path,
		Depth:           depth,
		CreatedAt:       now,
		UpdatedAt:       now,
	}
	if err := s.repo.CreateFolder(ctx, folder); err != nil {
		return nil, fmt.Errorf("create wiki folder: %w", err)
	}
	return folder, nil
}

// FindOrCreateFolderPath resolves a category path to a leaf folder id, creating
// any missing intermediate folders along the way. Concurrency-safe against the
// unique (kb, parent, name) constraint via a re-fetch on create conflict.
func (s *wikiPageService) FindOrCreateFolderPath(
	ctx context.Context, kbID string, tenantID uint64, path []string,
) (string, []string, error) {
	clean := types.CleanWikiCategoryPath(path)
	if len(clean) == 0 {
		return types.WikiFolderRootID, nil, nil
	}
	parentID := types.WikiFolderRootID
	parentPath := ""
	for depth, name := range clean {
		child, err := s.repo.GetChildFolderByName(ctx, kbID, parentID, name)
		if err != nil {
			if !errors.Is(err, repository.ErrWikiFolderNotFound) {
				return "", nil, err
			}
			fp := name
			if parentPath != "" {
				fp = parentPath + "/" + name
			}
			now := time.Now()
			child = &types.WikiFolder{
				ID:              uuid.New().String(),
				TenantID:        tenantID,
				KnowledgeBaseID: kbID,
				ParentID:        parentID,
				Name:            name,
				Path:            fp,
				Depth:           depth + 1,
				CreatedAt:       now,
				UpdatedAt:       now,
			}
			if cerr := s.repo.CreateFolder(ctx, child); cerr != nil {
				// Lost a create race (or unique violation): the sibling must
				// now exist — re-fetch it rather than failing the whole plan.
				child, err = s.repo.GetChildFolderByName(ctx, kbID, parentID, name)
				if err != nil {
					return "", nil, fmt.Errorf("create wiki folder %q: %w", fp, cerr)
				}
			}
		}
		parentID = child.ID
		parentPath = child.Path
	}
	return parentID, clean, nil
}

// MovePage relocates a page into folderID ("" = root) and refreshes its cached
// category path. Bookkeeping-only write (no version bump).
func (s *wikiPageService) MovePage(
	ctx context.Context, kbID string, slug string, folderID string,
) (*types.WikiPage, error) {
	page, err := s.repo.GetBySlug(ctx, kbID, slug)
	if err != nil {
		return nil, err
	}
	page.FolderID = strings.TrimSpace(folderID)
	if err := s.applyFolderToPage(ctx, page); err != nil {
		return nil, err
	}
	if err := s.UpdatePageMeta(ctx, page); err != nil {
		return nil, fmt.Errorf("move wiki page: %w", err)
	}
	return page, nil
}

// RenameOrMoveFolder renames and/or reparents a folder, then recomputes the
// materialized path/depth of the entire subtree and the cached category path of
// every page underneath. Guards against cycles (moving a folder into itself or
// one of its descendants) and sibling name collisions.
func (s *wikiPageService) RenameOrMoveFolder(
	ctx context.Context, kbID string, id string, newName string, newParentID string, moveParent bool,
) (*types.WikiFolder, error) {
	folder, err := s.repo.GetFolderByID(ctx, kbID, id)
	if err != nil {
		return nil, err
	}

	name := folder.Name
	if strings.TrimSpace(newName) != "" {
		if name, err = validateFolderName(newName); err != nil {
			return nil, err
		}
	}

	targetParent := folder.ParentID
	if moveParent {
		targetParent = newParentID
	}

	parentPath := ""
	depthBase := 0
	if targetParent != types.WikiFolderRootID {
		if targetParent == folder.ID {
			return nil, errors.New("cannot move a folder into itself")
		}
		parent, err := s.repo.GetFolderByID(ctx, kbID, targetParent)
		if err != nil {
			return nil, err
		}
		if parent.Path == folder.Path || strings.HasPrefix(parent.Path, folder.Path+"/") {
			return nil, errors.New("cannot move a folder into its own descendant")
		}
		parentPath = parent.Path
		depthBase = parent.Depth
	}

	if existing, err := s.repo.GetChildFolderByName(ctx, kbID, targetParent, name); err == nil {
		if existing.ID != folder.ID {
			return nil, repository.ErrWikiFolderConflict
		}
	} else if !errors.Is(err, repository.ErrWikiFolderNotFound) {
		return nil, err
	}

	oldPath := folder.Path
	newPath := name
	if parentPath != "" {
		newPath = parentPath + "/" + name
	}
	if newPath == oldPath && targetParent == folder.ParentID {
		return folder, nil // no-op
	}

	all, err := s.repo.ListAllFolders(ctx, kbID)
	if err != nil {
		return nil, err
	}
	now := time.Now()
	affected := make([]string, 0)
	var updated *types.WikiFolder
	for _, f := range all {
		switch {
		case f.ID == folder.ID:
			f.ParentID = targetParent
			f.Name = name
			f.Path = newPath
			f.Depth = depthBase + 1
		case strings.HasPrefix(f.Path, oldPath+"/"):
			f.Path = newPath + f.Path[len(oldPath):]
			f.Depth = len(wikiFolderSegments(f.Path))
		default:
			continue
		}
		f.UpdatedAt = now
		if err := s.repo.UpdateFolder(ctx, f); err != nil {
			return nil, err
		}
		affected = append(affected, f.ID)
		if f.ID == folder.ID {
			updated = f
		}
	}

	if err := s.recomputePagesForFolders(ctx, kbID, affected); err != nil {
		return nil, err
	}
	if updated == nil {
		updated = folder
	}
	return updated, nil
}

// recomputePagesForFolders refreshes the cached category_path/wiki_path/depth of
// every page filed under any of the given folder ids (used after a folder
// subtree is moved/renamed). Bookkeeping-only writes (no version bump).
func (s *wikiPageService) recomputePagesForFolders(ctx context.Context, kbID string, folderIDs []string) error {
	if len(folderIDs) == 0 {
		return nil
	}
	pages, err := s.repo.ListPagesByFolderIDs(ctx, kbID, folderIDs)
	if err != nil {
		return err
	}
	for _, page := range pages {
		if err := s.applyFolderToPage(ctx, page); err != nil {
			return err
		}
		if err := s.UpdatePageMeta(ctx, page); err != nil {
			logger.Warnf(ctx, "wiki: recompute folder path for page %s failed: %v", page.Slug, err)
		}
	}
	return nil
}

// DeleteFolder removes a folder that has no pages and no child folders. The UI
// must relocate contents first; this keeps deletion non-destructive.
func (s *wikiPageService) DeleteFolder(ctx context.Context, kbID string, id string) error {
	if _, err := s.repo.GetFolderByID(ctx, kbID, id); err != nil {
		return err
	}
	children, err := s.repo.ListChildFolders(ctx, kbID, id)
	if err != nil {
		return err
	}
	if len(children) > 0 {
		return repository.ErrWikiFolderNotEmpty
	}
	pages, err := s.repo.ListPagesByFolderIDs(ctx, kbID, []string{id})
	if err != nil {
		return err
	}
	if len(pages) > 0 {
		return repository.ErrWikiFolderNotEmpty
	}
	return s.repo.DeleteFolder(ctx, kbID, id)
}

// PruneEmptyFolderChains removes folders that became empty after retracting a
// document, followed by any ancestors made empty by those removals. It only
// considers the supplied folder chains, so intentionally-empty folders
// elsewhere in the wiki are preserved. Callers must wait for the KB's ingest
// queue to drain before invoking this method: taxonomy planning creates a
// folder before reduce writes the page that will reference it.
func (s *wikiPageService) PruneEmptyFolderChains(
	ctx context.Context, kbID string, folderIDs []string,
) ([]string, error) {
	if len(folderIDs) == 0 {
		return nil, nil
	}
	all, err := s.repo.ListAllFolders(ctx, kbID)
	if err != nil {
		return nil, err
	}
	byID := make(map[string]*types.WikiFolder, len(all))
	for _, folder := range all {
		if folder != nil {
			byID[folder.ID] = folder
		}
	}

	candidates := make(map[string]*types.WikiFolder)
	for _, id := range folderIDs {
		seen := make(map[string]struct{})
		for id != types.WikiFolderRootID {
			if _, cycle := seen[id]; cycle {
				break
			}
			seen[id] = struct{}{}
			folder := byID[id]
			if folder == nil {
				break
			}
			candidates[id] = folder
			id = folder.ParentID
		}
	}

	ordered := make([]*types.WikiFolder, 0, len(candidates))
	for _, folder := range candidates {
		ordered = append(ordered, folder)
	}
	sort.Slice(ordered, func(i, j int) bool {
		if ordered[i].Depth == ordered[j].Depth {
			return ordered[i].Path > ordered[j].Path
		}
		return ordered[i].Depth > ordered[j].Depth
	})

	deleted := make([]string, 0, len(ordered))
	for _, folder := range ordered {
		children, err := s.repo.ListChildFolders(ctx, kbID, folder.ID)
		if err != nil {
			return deleted, err
		}
		if len(children) > 0 {
			continue
		}
		pages, err := s.repo.ListPagesByFolderIDs(ctx, kbID, []string{folder.ID})
		if err != nil {
			return deleted, err
		}
		if len(pages) > 0 {
			continue
		}
		if err := s.repo.DeleteFolder(ctx, kbID, folder.ID); err != nil {
			if errors.Is(err, repository.ErrWikiFolderNotFound) ||
				errors.Is(err, repository.ErrWikiFolderNotEmpty) {
				continue
			}
			return deleted, err
		}
		deleted = append(deleted, folder.ID)
	}
	return deleted, nil
}

// InjectCrossLinks scans affected pages and injects [[wiki-links]] for mentions
// of other wiki page titles in the content. Pure text replacement, no LLM call.
// Shares the linkifyContent helper with the ingest pipeline so both paths honor
// the same code-block / existing-link / word-boundary rules.
func (s *wikiPageService) InjectCrossLinks(ctx context.Context, kbID string, affectedSlugs []string) {
	allPages, err := s.ListAllPages(ctx, kbID)
	if err != nil || len(allPages) < 2 {
		return
	}

	refs := collectLinkRefs(allPages)
	if len(refs) == 0 {
		return
	}

	affectedSet := make(map[string]bool, len(affectedSlugs))
	for _, slug := range affectedSlugs {
		affectedSet[slug] = true
	}

	var updated int
	for _, p := range allPages {
		if !affectedSet[p.Slug] {
			continue
		}
		if p.PageType == types.WikiPageTypeIndex {
			continue
		}

		newContent, changed := linkifyContent(p.Content, refs, p.Slug)
		if !changed {
			continue
		}
		p.Content = newContent
		if err := s.UpdateAutoLinkedContent(ctx, p); err != nil {
			logger.Warnf(ctx, "wiki: cross-link injection failed for %s: %v", p.Slug, err)
			continue
		}
		updated++
	}

	if updated > 0 {
		logger.Infof(ctx, "wiki: injected cross-links in %d pages", updated)
	}
}

// RebuildIndexPage was historically called by agent write/rename tools to
// refresh the index page's directory listing after a page mutation.
//
// The directory is no longer persisted in wiki_pages.content — it is
// assembled on demand by GetIndexView from the lightweight ListByTypeLight
// projection, so individual page writes don't need to redo O(N) string
// concatenation and rewrite a multi-MB TEXT column anymore. Keeping the
// method name lets existing agent tool call sites (wiki_write_page,
// wiki_rename_page) compile unchanged; the body is now intentionally a
// no-op.
//
// The intro that still lives on the index row is managed separately by
// the ingest pipeline (see wikiIngestService.rebuildIndexPage) on batch
// completion, which is where we actually have the LLM + change description
// context needed to rewrite it.
func (s *wikiPageService) RebuildIndexPage(ctx context.Context, kbID string) error {
	_ = ctx
	_ = kbID
	return nil
}