package service

import (
	"context"
	"errors"
	"fmt"
	"github.com/Tencent/WeKnora/internal/accesspolicy"
	"path/filepath"
	"slices"
	"strings"
	"time"
	"unicode"
	"unicode/utf8"

	"github.com/Tencent/WeKnora/internal/agent/skills"
	"github.com/Tencent/WeKnora/internal/agent/token"
	"github.com/Tencent/WeKnora/internal/application/repository"
	apperrors "github.com/Tencent/WeKnora/internal/errors"
	"github.com/Tencent/WeKnora/internal/im"
	"github.com/Tencent/WeKnora/internal/types"
	"github.com/Tencent/WeKnora/internal/types/interfaces"
	"github.com/google/uuid"
	"gorm.io/gorm"
	"gorm.io/gorm/clause"
)

const MaxInstructionSkillBytes = 256 << 10
const maxInstructionSkillTokens = 16000
const maxInstructionSkillBindings = 32

// InstructionSkillService reuses the native catalog for non-executable rules.
// Markdown imports are private to their creator; administrators may inspect
// them. Native executable skills keep their existing workspace sharing policy.
type InstructionSkillService struct {
	db     *gorm.DB
	agents interfaces.CustomAgentService
}

func NewInstructionSkillService(db *gorm.DB, agents interfaces.CustomAgentService) *InstructionSkillService {
	return &InstructionSkillService{db: db, agents: agents}
}

type InstructionSkillView struct {
	ID              string    `json:"id"`
	Name            string    `json:"name"`
	Description     string    `json:"description"`
	Version         string    `json:"version"`
	Instructions    string    `json:"instructions,omitempty"`
	CreatedBy       string    `json:"created_by"`
	VersionSourceID string    `json:"version_source_id,omitempty"`
	CreatorName     string    `json:"creator_name,omitempty"`
	InstructionOnly bool      `json:"instruction_only"`
	Visibility      string    `json:"visibility"`
	Enabled         bool      `json:"enabled"`
	UpdatedAt       time.Time `json:"updated_at"`
}

func instructionSkillView(ctx context.Context, row types.TenantSkillCatalogEntity, body bool) InstructionSkillView {
	row.EnsureInstructionDefaults()
	v := InstructionSkillView{ID: row.ID, Name: row.Name, Description: row.Description, Version: row.Version, CreatedBy: row.CreatedBy, InstructionOnly: true, UpdatedAt: row.UpdatedAt}
	v.Visibility, v.Enabled = row.Visibility, row.Enabled
	if snapshot := accesspolicy.FromContext(ctx); snapshot != nil {
		if global, managed := snapshot.Publications["skills:"+row.ID]; managed {
			v.Visibility = "private"
			if global {
				v.Visibility = "global"
			}
		}
	}
	v.VersionSourceID = row.VersionSourceID
	if body {
		v.Instructions = row.Instructions
	}
	return v
}

func instructionIdentity(ctx context.Context, write bool) (uint64, string, bool, error) {
	tenant, ok := types.TenantIDFromContext(ctx)
	user, userOK := types.UserIDFromContext(ctx)
	role := types.TenantRoleFromContext(ctx)
	floor := types.TenantRoleViewer
	if write {
		floor = types.TenantRoleContributor
	}
	if !ok || tenant == 0 || !userOK || user == "" || types.IsSyntheticUserID(user) || !role.HasPermission(floor) {
		return 0, "", false, apperrors.NewForbiddenError("没有技能操作权限")
	}
	return tenant, user, assetAdministrator(ctx), nil
}

func (s *InstructionSkillService) List(ctx context.Context) ([]InstructionSkillView, error) {
	tenant, _, _, err := instructionIdentity(ctx, false)
	if err != nil {
		return nil, err
	}
	var rows []types.TenantSkillCatalogEntity
	q := s.db.WithContext(ctx).Where("tenant_id = ? AND instruction_only = ?", tenant, true)
	if err = q.Order("updated_at DESC").Find(&rows).Error; err != nil {
		return nil, err
	}
	out := make([]InstructionSkillView, 0, len(rows))
	for _, row := range rows {
		if !instructionSkillReadable(ctx, &row) {
			continue
		}
		out = append(out, instructionSkillView(ctx, row, false))
	}
	s.fillCreatorNames(ctx, out)
	return out, nil
}

func (s *InstructionSkillService) Get(ctx context.Context, id string) (*InstructionSkillView, error) {
	tenant, _, _, err := instructionIdentity(ctx, false)
	if err != nil {
		return nil, err
	}
	var row types.TenantSkillCatalogEntity
	q := s.db.WithContext(ctx).Where("id = ? AND tenant_id = ? AND instruction_only = ?", id, tenant, true)
	if err = q.First(&row).Error; err != nil {
		if errors.Is(err, gorm.ErrRecordNotFound) {
			return nil, apperrors.NewNotFoundError("技能不存在或无权访问")
		}
		return nil, err
	}
	if !instructionSkillReadable(ctx, &row) {
		return nil, apperrors.NewNotFoundError("技能不存在或无权访问")
	}
	v := instructionSkillView(ctx, row, true)
	views := []InstructionSkillView{v}
	s.fillCreatorNames(ctx, views)
	v = views[0]
	return &v, nil
}

func (s *InstructionSkillService) fillCreatorNames(ctx context.Context, views []InstructionSkillView) {
	ids := make([]string, 0, len(views))
	for _, view := range views {
		if view.CreatedBy != "" {
			ids = append(ids, view.CreatedBy)
		}
	}
	if len(ids) == 0 {
		return
	}
	var users []struct {
		ID       string
		Username string
	}
	if err := s.db.WithContext(ctx).Model(&types.User{}).Select("id, username").Where("id IN ?", ids).Find(&users).Error; err != nil {
		return
	}
	names := map[string]string{}
	for _, user := range users {
		names[user.ID] = user.Username
	}
	for i := range views {
		views[i].CreatorName = names[views[i].CreatedBy]
	}
}

func parseInstructionMarkdown(filename, name, description string, content []byte) (*types.TenantSkillCatalogEntity, error) {
	if !strings.EqualFold(filepath.Ext(filename), ".md") || len(content) == 0 || len(content) > MaxInstructionSkillBytes || !utf8.Valid(content) || strings.ContainsRune(string(content), 0) {
		return nil, apperrors.NewBadRequestError("请上传不超过 256 KB 的 UTF-8 Markdown（.md）文件")
	}
	text := strings.TrimSpace(strings.TrimPrefix(string(content), "\ufeff"))
	body, version := text, ""
	if strings.HasPrefix(text, "---\n") || strings.HasPrefix(text, "---\r\n") {
		parsed, err := skills.ParseSkillFile(text)
		if err != nil {
			return nil, apperrors.NewBadRequestError("技能 Markdown 的头部格式无效：" + err.Error())
		}
		body = parsed.Instructions
		if strings.TrimSpace(name) == "" {
			name = parsed.Name
		}
		if strings.TrimSpace(description) == "" {
			description = parsed.Description
		}
		version, err = parseSkillBundleVersion(text)
		if err != nil {
			return nil, apperrors.NewBadRequestError("技能版本格式无效")
		}
	}
	name = strings.TrimSpace(name)
	if name == "" {
		name = strings.TrimSuffix(filepath.Base(filename), filepath.Ext(filename))
	}
	if name == "" || len([]rune(name)) > 100 || strings.IndexFunc(name, unicode.IsControl) >= 0 || strings.ContainsAny(name, `/\`) {
		return nil, apperrors.NewBadRequestError("技能名称必填、最多 100 字且不能包含路径或控制字符")
	}
	body = strings.TrimSpace(body)
	if body == "" {
		return nil, apperrors.NewBadRequestError("技能正文不能为空")
	}
	if len([]rune(description)) > 1000 || len(version) > 64 {
		return nil, apperrors.NewBadRequestError("技能说明或版本过长")
	}
	estimator, err := token.NewEstimator()
	if err != nil {
		return nil, err
	}
	if estimator.EstimateString(body) > maxInstructionSkillTokens {
		return nil, apperrors.NewBadRequestError("技能正文过长，请控制在约 16000 Token 以内")
	}
	return &types.TenantSkillCatalogEntity{Name: name, Description: strings.TrimSpace(description), Version: version, Instructions: body, InstructionOnly: true, BundleSHA256: skillArchiveSHA256(content)}, nil
}

func (s *InstructionSkillService) Import(ctx context.Context, filename, name, description string, content []byte) (*InstructionSkillView, error) {
	tenant, user, _, err := instructionIdentity(ctx, true)
	if err != nil {
		return nil, err
	}
	row, err := parseInstructionMarkdown(filename, name, description, content)
	if err != nil {
		return nil, err
	}
	row.ID, row.TenantID, row.CreatedBy = uuid.NewString(), tenant, user
	row.EnsureInstructionDefaults()
	err = s.db.WithContext(ctx).Transaction(func(tx *gorm.DB) error {
		var existing types.TenantSkillCatalogEntity
		err := tx.Clauses(clause.Locking{Strength: "UPDATE"}).Where("tenant_id = ? AND created_by = ? AND name = ? AND instruction_only = ? AND version_source_id = ''", tenant, user, row.Name, true).First(&existing).Error
		if errors.Is(err, gorm.ErrRecordNotFound) {
			return tx.Create(row).Error
		}
		if err != nil {
			return err
		}
		row.ID, row.CreatedBy, row.CreatedAt = existing.ID, existing.CreatedBy, existing.CreatedAt
		existing.EnsureInstructionDefaults()
		row.Visibility, row.Enabled = existing.Visibility, existing.Enabled
		row.UpdatedAt = time.Now()
		return tx.Model(&existing).Updates(map[string]any{"description": row.Description, "version": row.Version, "instructions": row.Instructions, "bundle_sha256": row.BundleSHA256, "updated_at": row.UpdatedAt}).Error
	})
	if err != nil {
		if isUniqueViolation(err) {
			return nil, apperrors.NewConflictError("同名技能已被创建，请刷新列表后重试")
		}
		return nil, err
	}
	v := instructionSkillView(ctx, *row, true)
	views := []InstructionSkillView{v}
	s.fillCreatorNames(ctx, views)
	v = views[0]
	return &v, nil
}

// Delete locks the definition before its references, matching Mount's lock
// order. Detachment and deletion commit together; denied or failed deletions
// leave every Agent configuration intact.
func (s *InstructionSkillService) Delete(ctx context.Context, id string, detach bool) error {
	tenant, user, admin, err := instructionIdentity(ctx, true)
	if err != nil {
		return err
	}
	return s.db.WithContext(ctx).Transaction(func(tx *gorm.DB) error {
		var skill types.TenantSkillCatalogEntity
		q := tx.Clauses(clause.Locking{Strength: "UPDATE"}).Where("id = ? AND tenant_id = ? AND instruction_only = ?", id, tenant, true)
		if !admin {
			q = q.Where("created_by = ?", user)
		}
		if err := q.First(&skill).Error; err != nil {
			if errors.Is(err, gorm.ErrRecordNotFound) {
				return apperrors.NewNotFoundError("技能不存在或无权删除")
			}
			return err
		}
		// Read/lock tenant Agent rows in stable order. The skill lock prevents
		// new mount requests from racing this reference scan.
		var agents []types.CustomAgent
		if err := tx.Clauses(clause.Locking{Strength: "UPDATE"}).Where("tenant_id = ?", tenant).Order("id").Find(&agents).Error; err != nil {
			return err
		}
		ids := []string{}
		for _, a := range agents {
			if slices.Contains(a.Config.InstructionSkillIDs, id) {
				ids = append(ids, a.ID)
			}
		}
		if len(ids) > 0 && !detach {
			return apperrors.NewConflictError("技能已挂载到 Agent，可一键解绑全部关联后删除").WithDetails(map[string]any{"agent_ids": ids, "can_detach": true})
		}
		for _, a := range agents {
			if !slices.Contains(a.Config.InstructionSkillIDs, id) {
				continue
			}
			a.Config.InstructionSkillIDs = slices.DeleteFunc(slices.Clone(a.Config.InstructionSkillIDs), func(selected string) bool { return selected == id })
			if err := tx.Model(&a).Updates(map[string]any{"config": a.Config, "updated_at": time.Now()}).Error; err != nil {
				return err
			}
		}
		return tx.Delete(&skill).Error
	})
}

type InstructionSkillMountRequest struct {
	AgentIDs []string `json:"agent_ids"`
	SkillIDs []string `json:"skill_ids"`
	Mode     string   `json:"mode"` // add (default), remove, replace
}
type InstructionSkillMountResult struct {
	AgentID   string    `json:"agent_id"`
	SkillIDs  []string  `json:"instruction_skill_ids"`
	UpdatedAt time.Time `json:"updated_at"`
}

func (s *InstructionSkillService) Mount(ctx context.Context, req InstructionSkillMountRequest) ([]InstructionSkillMountResult, error) {
	tenant, user, admin, err := instructionIdentity(ctx, true)
	if err != nil {
		return nil, err
	}
	agentIDs, skillIDs := dedupPreservingOrder(req.AgentIDs), dedupPreservingOrder(req.SkillIDs)
	if len(agentIDs) == 0 || len(agentIDs) > 100 || len(skillIDs) > maxInstructionSkillBindings {
		return nil, apperrors.NewBadRequestError("请选择 1–100 个 Agent，每个 Agent 最多挂载 32 个技能")
	}
	if req.Mode == "" {
		req.Mode = "add"
	}
	if req.Mode != "add" && req.Mode != "remove" && req.Mode != "replace" {
		return nil, apperrors.NewBadRequestError("挂载方式应为 add、remove 或 replace")
	}
	if req.Mode != "replace" && len(skillIDs) == 0 {
		return nil, apperrors.NewBadRequestError("请选择技能")
	}
	// Use the native service's visibility guard (including private digital-human
	// Agents) before acquiring row locks. The write ownership is rechecked below.
	for _, id := range agentIDs {
		a, err := s.agents.GetAgentByID(ctx, id)
		if err != nil || a == nil || a.TenantID != tenant || (!admin && a.CreatedBy != user) {
			return nil, apperrors.NewForbiddenError("所选 Agent 不存在或没有修改权限")
		}
	}
	slices.Sort(agentIDs)
	out := make([]InstructionSkillMountResult, 0, len(agentIDs))
	err = s.db.WithContext(ctx).Transaction(func(tx *gorm.DB) error {
		if req.Mode != "remove" {
			var rows []types.TenantSkillCatalogEntity
			q := tx.Clauses(clause.Locking{Strength: "SHARE"}).Where("tenant_id = ? AND id IN ? AND instruction_only = ?", tenant, skillIDs, true)
			if err := q.Find(&rows).Error; err != nil {
				return err
			}
			if len(rows) != len(skillIDs) {
				return apperrors.NewNotFoundError("部分技能不存在或不属于当前工作空间")
			}
			for _, row := range rows {
				row.EnsureInstructionDefaults()
				if !row.Enabled || !instructionSkillReadable(ctx, &row) {
					return apperrors.NewForbiddenError("所选文字技能已停用或无权使用")
				}
			}
		}
		for _, id := range agentIDs {
			// Native built-ins are virtual until first customized. Materialize
			// the tenant's default inside this transaction so bulk mounts stay
			// atomic and do not fail merely because no row existed yet.
			if types.IsBuiltinAgentID(id) {
				if !admin {
					return apperrors.NewForbiddenError("只有管理员可以修改内置 Agent")
				}
				builtin := types.GetBuiltinAgent(id, tenant)
				if builtin == nil {
					return apperrors.NewNotFoundError("内置 Agent 不存在")
				}
				builtin.EnsureDefaults()
				if err := tx.Clauses(clause.OnConflict{DoNothing: true}).Create(builtin).Error; err != nil {
					return err
				}
			}
			var agent types.CustomAgent
			if err := tx.Clauses(clause.Locking{Strength: "UPDATE"}).Where("tenant_id = ? AND id = ?", tenant, id).First(&agent).Error; err != nil {
				return err
			}
			if !admin && agent.CreatedBy != user {
				return apperrors.NewForbiddenError("只能为自己创建的 Agent 挂载技能")
			}
			selected := slices.Clone(agent.Config.InstructionSkillIDs)
			switch req.Mode {
			case "add":
				selected = dedupPreservingOrder(append(selected, skillIDs...))
			case "replace":
				selected = slices.Clone(skillIDs)
			case "remove":
				selected = slices.DeleteFunc(selected, func(id string) bool { return slices.Contains(skillIDs, id) })
			}
			if len(selected) > maxInstructionSkillBindings {
				return apperrors.NewBadRequestError("每个 Agent 最多挂载 32 个文字技能")
			}
			if selected == nil {
				selected = []string{}
			}
			agent.Config.InstructionSkillIDs = selected
			// Validate the binding while allowing owners to repair a disabled
			// Agent. Execution still checks its actual persisted enabled state.
			validationAgent := agent
			validationAgent.EnsureDefaults()
			validationAgent.Enabled = true
			// Removing bindings must also work when another remaining skill has
			// been revoked or deleted. Execution still validates every dependency.
			if req.Mode != "remove" {
				if _, err := ResolveAgentInstructionPrompt(ctx, repository.NewTenantSkillRepository(tx), &validationAgent); err != nil {
					return err
				}
			}
			now := time.Now()
			if err := tx.Model(&agent).Updates(map[string]any{"config": agent.Config, "updated_at": now}).Error; err != nil {
				return err
			}
			out = append(out, InstructionSkillMountResult{AgentID: id, SkillIDs: selected, UpdatedAt: now})
		}
		return nil
	})
	if err != nil {
		return nil, err
	}
	return out, nil
}

type instructionCatalogReader interface {
	GetCatalog(context.Context, uint64, string) (*types.TenantSkillCatalogEntity, error)
}

// ResolveAgentInstructionPrompt is shared by native QA and other generation
// surfaces. Call it after the native Agent access check; returned text belongs
// in the system context and never grants executable tools or sandbox access.
func ResolveAgentInstructionPrompt(ctx context.Context, repo instructionCatalogReader, agent *types.CustomAgent) (string, error) {
	if agent == nil {
		return "", nil
	}
	agent.EnsureDefaults()
	if !agent.Enabled {
		return "", apperrors.NewForbiddenError("Agent 已停用或无权使用")
	}
	if strings.Contains(agent.Config.SystemPrompt, "<!-- weknora:digital-human:") {
		guard, ok := repo.(interface {
			CheckDigitalHumanAgentExecution(context.Context, *types.CustomAgent) error
		})
		if !ok {
			return "", apperrors.NewForbiddenError("数字人授权校验不可用，请稍后重试")
		}
		if err := guard.CheckDigitalHumanAgentExecution(ctx, agent); err != nil {
			return "", err
		}
	}
	// Existing organization shares already authorize the Agent itself upstream.
	// Without instruction skills, preserve that native execution path.
	if len(agent.Config.InstructionSkillIDs) == 0 {
		return "", nil
	}
	tenant, ok := types.TenantIDFromContext(ctx)
	if !ok || tenant == 0 || agent.TenantID != tenant {
		return "", apperrors.NewForbiddenError("文字技能不能跨工作空间读取")
	}
	user, userOK := types.UserIDFromContext(ctx)
	verifiedIM := im.IsVerifiedAgentExecution(ctx, agent)
	if !verifiedIM && !nativeAgentReadable(ctx, agent) && !nativeAgentExecutableDependency(ctx, agent) {
		return "", apperrors.NewForbiddenError("Agent 已停用或无权使用")
	}
	if !verifiedIM && (!userOK || user == "" || types.IsSyntheticUserID(user)) {
		return "", apperrors.NewForbiddenError("没有此 Agent 私有文字技能的使用权限")
	}
	ids := dedupPreservingOrder(agent.Config.InstructionSkillIDs)
	if repo == nil || len(ids) > maxInstructionSkillBindings {
		return "", apperrors.NewBadRequestError("Agent 的文字技能配置不可用")
	}
	var result strings.Builder
	result.WriteString("\n\n## 已挂载的文字技能\n按以下规则执行本次任务；这些规则不授予额外工具、脚本或数据访问权限。\n")
	for _, id := range ids {
		row, err := repo.GetCatalog(ctx, tenant, id)
		if err != nil {
			return "", apperrors.NewForbiddenError("已挂载的文字技能不可用，请重新选择技能")
		}
		if row == nil || !row.InstructionOnly || row.TenantID != tenant {
			return "", apperrors.NewBadRequestError("已挂载的文字技能已删除或无权使用，请重新选择技能")
		}
		row.EnsureInstructionDefaults()
		if !row.Enabled || (row.Visibility != "global" && row.Visibility != "private") {
			return "", apperrors.NewForbiddenError("已挂载的文字技能已停用或无权使用")
		}
		// Sharing an Agent permits executing its own private rules without
		// exposing the rules as independently readable or mountable resources.
		ownedDependency := row.CreatedBy != "" && row.CreatedBy == agent.CreatedBy
		if !verifiedIM && !ownedDependency && !instructionSkillReadable(ctx, row) {
			return "", apperrors.NewForbiddenError("已挂载私有文字技能的授权已撤销，请重新选择技能")
		}
		shared := accesspolicy.Readable(ctx, "skills", row.ID, false, false)
		if !shared && row.Visibility == "private" && !ownedDependency {
			return "", apperrors.NewForbiddenError("私有文字技能只能挂载到同一创建者的 Agent")
		}
		fmt.Fprintf(&result, "\n### %s\n%s\n", row.Name, row.Instructions)
	}
	estimator, err := token.NewEstimator()
	if err != nil {
		return "", err
	}
	if estimator.EstimateString(result.String()) > maxInstructionSkillTokens {
		return "", apperrors.NewBadRequestError("挂载技能的合计正文过长，请减少技能或缩短规则，系统不会自动截断技能")
	}
	return result.String(), nil
}

func (s *InstructionSkillService) ResolveAgentInstructions(ctx context.Context, agent *types.CustomAgent) (string, error) {
	return ResolveAgentInstructionPrompt(ctx, repository.NewTenantSkillRepository(s.db), agent)
}