package service

import (
	"sort"
	"strings"

	"github.com/Tencent/WeKnora/internal/modelcontext"
)

// wikiSlugHandles maps real wiki slugs to short, low-entropy model handles
// (ref-1, ref-2, …) so the ingest editor LLM never has to reproduce a
// high-entropy slug verbatim — most importantly the UUID-based summary slugs
// (summary/<knowledgeID>) that models routinely mangle by inserting or
// dropping hex digits. The model copies the tiny handle; we translate handles
// back to real slugs on output.
//
// This is the generation-stage counterpart to wiki_write_page's slug
// validation: rather than repairing a mangled slug after the fact, it removes
// the opportunity to mangle at the source. It mirrors the chunk-handle
// (c000/c001) indirection already used by the chunk-citation pass in
// wiki_ingest_cite.go.
//
// Handle allocation and reverse lookup are owned by modelcontext.HandleTable;
// this wrapper contains only the Wiki-link rewrite semantics.
type wikiSlugHandles struct {
	table *modelcontext.HandleTable
}

func newWikiSlugHandles() *wikiSlugHandles {
	return &wikiSlugHandles{table: modelcontext.NewHandleTable("ref-", 0, 1)}
}

// handle returns the stable handle for a real slug, assigning a fresh one on
// first use. An empty slug returns "". Handles have no '/' so they can never
// collide with a namespaced real slug (entity/…, summary/…).
func (h *wikiSlugHandles) handle(realSlug string) string {
	if h == nil {
		return ""
	}
	return h.table.Register(realSlug)
}

// empty reports whether no handles have been assigned yet.
func (h *wikiSlugHandles) empty() bool { return h == nil || h.table.Empty() }

// encodeContent rewrites [[realSlug|disp]] / [[realSlug]] occurrences to their
// handle form, but only for slugs present in `known`. Unknown links are left
// untouched. Assigns handles on demand so a slug that appears only in the body
// (not in the listing) still gets a consistent handle.
func (h *wikiSlugHandles) encodeContent(content string, known map[string]struct{}) string {
	if content == "" || len(known) == 0 {
		return content
	}
	out, _ := rewriteDeadWikiLinks(content, func(norm, _ string) (string, bool) {
		if _, ok := known[norm]; !ok {
			return "", false
		}
		return h.handle(norm), true
	})
	return out
}

// decodeContent rewrites [[handle|disp]] / [[handle]] occurrences back to their
// real slug. Handles with no mapping are left untouched — they fall through to
// the ordinary parse/dead-link-cleanup path, which is the correct behavior for
// anything the model invented that isn't a known reference.
func (h *wikiSlugHandles) decodeContent(content string) string {
	if content == "" || h.empty() {
		return content
	}
	out, _ := rewriteDeadWikiLinks(content, func(norm, _ string) (string, bool) {
		real, ok := h.table.Resolve(norm)
		if !ok {
			return "", false
		}
		return real, true
	})
	return out
}

// Citation candidates use a separate handle namespace from source chunks and
// page links. Sort durable slugs so concurrent batches and process restarts see
// the same mapping. Only the declaration field is rewritten: entity names,
// descriptions and other source-derived text are never edited by replacement.
func encodeWikiCitationCandidates(candidates string) (string, *modelcontext.HandleTable) {
	allowed := wikiCandidateSlugSet(candidates)
	slugs := make([]string, 0, len(allowed))
	for slug := range allowed {
		slugs = append(slugs, slug)
	}
	sort.Strings(slugs)
	handles := modelcontext.NewHandleTable("s", 3, 0)
	for _, slug := range slugs {
		handles.Register(slug)
	}
	lines := strings.Split(candidates, "\n")
	for i, line := range lines {
		trimmed := strings.TrimSpace(line)
		declaration := strings.TrimPrefix(trimmed, "- slug: ")
		slug, rest, hasMetadata := strings.Cut(declaration, ",")
		if handle, ok := handles.Handle(slug); ok {
			lines[i] = "- id: " + handle
			if hasMetadata {
				lines[i] += "," + rest
			} else {
				// Lightweight callers may supply only a slug. Retain its name
				// and type as semantic context, never as the output identifier.
				kind, name, _ := strings.Cut(slug, "/")
				lines[i] += ", type: " + kind + ", name: " + name
			}
		}
	}
	return strings.Join(lines, "\n"), handles
}