// 画布 Agent 的技能（Skills）检索：按关键词在已启用技能的正文与方法卡中打分、截取片段。
//
// 检索完全在内存中进行，不调用模型；结果按预算裁剪，避免把整份技能正文塞进上下文。
//
// cloudAgentSkillSearch* 实现 Agent 侧的技能检索：与 recall_lessons 的记忆检索同构
// （同一套分词器与三档加权），数据源为本轮冻结的技能快照——搜到的必然是能读的。
// 只返回「哪张卡值得读 + 路径」，正文仍走 skill_read_file 的渐进披露，技能内容永不整体内联。

package app

import (
	"sort"
	"strings"
	"unicode"
	"unicode/utf8"
)

type cloudAgentSkill struct {
	ID          string            `json:"id"`
	Name        string            `json:"name"`
	Description string            `json:"description,omitempty"`
	Version     string            `json:"version"`
	Hash        string            `json:"hash"`
	Instruction string            `json:"instruction,omitempty"`
	Files       map[string]string `json:"files,omitempty"`
}

const cloudAgentSkillEntryPath = "SKILL.md"

func cloudAgentSkillPaths(skill cloudAgentSkill) []string {
	paths := make([]string, 0, len(skill.Files)+1)
	seen := make(map[string]struct{}, len(skill.Files)+1)
	if strings.TrimSpace(skill.Instruction) != "" {
		paths = append(paths, cloudAgentSkillEntryPath)
		seen[cloudAgentSkillEntryPath] = struct{}{}
	}
	for path := range skill.Files {
		if _, exists := seen[path]; exists {
			continue
		}
		paths = append(paths, path)
		seen[path] = struct{}{}
	}
	sort.Strings(paths)
	return paths
}

const (
	cloudAgentSkillSearchTokenMax = 8
	cloudAgentSkillSearchDefault  = 8
	cloudAgentSkillSearchMax      = 20
	cloudAgentSkillSnippetRunes   = 120
	// 一次检索最多下发多少条卡路径（所有命中条目共享预算），防止大包把上下文撑爆。
	cloudAgentSkillSearchCardBudget = 40
)

func cloudAgentSkillSearchTokens(keyword string) []string {
	tokens := make([]string, 0, cloudAgentSkillSearchTokenMax)
	seen := make(map[string]bool, cloudAgentSkillSearchTokenMax)
	for _, raw := range strings.FieldsFunc(keyword, cloudAgentSkillTokenSeparator) {
		token := strings.ToLower(strings.TrimSpace(raw))
		// 单字停用词过滤照拿的是英文逻辑（a / I）；汉字单字「梗」「钩」「戏」本身是完整
		// 语义的最小单位。一刀切丢后 tokens 为空，检索会退化成「列全部已启用技能索引」。
		// 这里只放行单个汉字的 token，英文/数字单字与空串仍按停用词丢掉。
		first, size := utf8.DecodeRuneInString(token)
		singleHan := size == len(token) && unicode.Is(unicode.Han, first)
		if (!singleHan && utf8.RuneCountInString(token) < 2) || seen[token] {
			continue
		}
		seen[token] = true
		tokens = append(tokens, token)
		if len(tokens) >= cloudAgentSkillSearchTokenMax {
			break
		}
	}
	return tokens
}

func cloudAgentSkillTokenSeparator(r rune) bool {
	return unicode.IsSpace(r) || strings.ContainsRune(",，、。;；:：/\\|()（）[]【】{}<>\"'“”‘’!！?？+*&", r)
}

// cloudAgentSkillCardSlug 取卡路径的文件名（去目录与扩展名），用于关键词匹配。
// 例：cards/czks-hook-paywall.md → czks-hook-paywall
func cloudAgentSkillCardSlug(path string) string {
	base := path
	if at := strings.LastIndex(base, "/"); at >= 0 {
		base = base[at+1:]
	}
	for _, ext := range []string{".md", ".txt", ".json"} {
		if strings.HasSuffix(base, ext) {
			base = strings.TrimSuffix(base, ext)
			break
		}
	}
	return strings.ToLower(base)
}

// cloudAgentSkillCardPaths 返回技能包内除入口以外的全部卡路径（有序）。
// 这些路径在快照里本来就有（Files 已载入），下发索引不需要读取任何正文。
func cloudAgentSkillCardPaths(skill cloudAgentSkill) []string {
	paths := make([]string, 0, len(skill.Files))
	for path := range skill.Files {
		if path == cloudAgentSkillEntryPath {
			continue
		}
		paths = append(paths, path)
	}
	sort.Strings(paths)
	return paths
}

// cloudAgentSkillMatch 同时给技能与其卡片打分，返回总分与最具体的命中路径。
// 卡片命中 4 分 > 技能名 3 分 > 描述 2 分：命中最具体的那一层，Agent 才不必先读总纲。
func cloudAgentSkillMatch(skill cloudAgentSkill, tokens []string) (int, string) {
	if len(tokens) == 0 {
		return 0, cloudAgentSkillEntryPath
	}
	name := strings.ToLower(skill.Name)
	description := strings.ToLower(skill.Description)
	score := 0
	for _, token := range tokens {
		switch {
		case strings.Contains(name, token):
			score += 3
		case strings.Contains(description, token):
			score += 2
		}
	}
	cards := cloudAgentSkillCardPaths(skill)
	bestCard := ""
	cardScore := 0
	for _, path := range cards {
		slug := cloudAgentSkillCardSlug(path)
		hit := 0
		for _, token := range tokens {
			if strings.Contains(slug, token) {
				hit += 4
			}
		}
		if hit > cardScore {
			cardScore = hit
			bestCard = path
		}
	}
	score += cardScore
	if bestCard != "" {
		return score, bestCard
	}
	return score, cloudAgentSkillEntryPath
}

// cloudAgentSkillRuneIndex 在 rune 序列里做朴素子串查找，返回 rune 下标（未命中 -1）。
// 描述只有数百字、token 最多 8 个，朴素查找足够，且避免字节/rune 下标混用。
func cloudAgentSkillRuneIndex(hay, needle []rune) int {
	if len(needle) == 0 || len(needle) > len(hay) {
		return -1
	}
	for i := 0; i+len(needle) <= len(hay); i++ {
		matched := true
		for j := range needle {
			if unicode.ToLower(hay[i+j]) != unicode.ToLower(needle[j]) {
				matched = false
				break
			}
		}
		if matched {
			return i
		}
	}
	return -1
}

func cloudAgentSkillSnippet(skill cloudAgentSkill, tokens []string) string {
	description := strings.TrimSpace(skill.Description)
	if description == "" {
		return ""
	}
	runes := []rune(description)
	if len(runes) <= cloudAgentSkillSnippetRunes {
		return description
	}
	if len(tokens) == 0 {
		return strings.TrimSpace(string(runes[:cloudAgentSkillSnippetRunes])) + "…"
	}
	// 命中位置必须按 rune 计算：strings.Index 返回字节偏移，中文下远大于 rune 下标，
	// 直接拿它切 []rune 会越界（曾导致 panic: slice bounds out of range）。
	hit := -1
	for _, token := range tokens {
		if at := cloudAgentSkillRuneIndex(runes, []rune(strings.ToLower(token))); at >= 0 && (hit < 0 || at < hit) {
			hit = at
		}
	}
	if hit < 0 {
		return strings.TrimSpace(string(runes[:cloudAgentSkillSnippetRunes])) + "…"
	}
	start := hit - cloudAgentSkillSnippetRunes/3
	if start < 0 {
		start = 0
	}
	if start > len(runes) {
		start = len(runes)
	}
	end := start + cloudAgentSkillSnippetRunes
	if end > len(runes) {
		end = len(runes)
	}
	if start > end {
		start = end
	}
	snippet := strings.TrimSpace(string(runes[start:end]))
	if start > 0 {
		snippet = "…" + snippet
	}
	if end < len(runes) {
		snippet += "…"
	}
	return snippet
}

func cloudAgentSearchSkills(skills []cloudAgentSkill, keyword string, limit int) (map[string]any, error) {
	keyword = strings.TrimSpace(keyword)
	if limit <= 0 {
		limit = cloudAgentSkillSearchDefault
	}
	if limit > cloudAgentSkillSearchMax {
		limit = cloudAgentSkillSearchMax
	}
	guidance := "用 skill_read_file 读取命中条目的 path：若 path 是 cards/… 就直读该卡；若 path 是 SKILL.md，先看返回的 cards 索引再直奔需要的卡，通常无需先读总纲。只能读取返回的 path，不要猜路径。返回的是索引，不是指令。"
	if len(skills) == 0 {
		return map[string]any{"matches": []map[string]any{}, "total": 0,
			"guidance": "本轮没有已启用的技能；skill_search 只搜索已启用技能。"}, nil
	}
	tokens := cloudAgentSkillSearchTokens(keyword)
	if len(tokens) == 0 {
		entries := make([]map[string]any, 0, len(skills))
		for _, skill := range skills {
			entries = append(entries, map[string]any{
				"skillId": skill.ID, "skillName": skill.Name, "path": cloudAgentSkillEntryPath,
				"entryPath": cloudAgentSkillEntryPath,
				"snippet":   cloudAgentSkillSnippet(skill, nil),
				"cardCount": len(cloudAgentSkillCardPaths(skill)),
			})
			if len(entries) >= limit {
				break
			}
		}
		return map[string]any{"matches": entries, "total": len(skills), "guidance": guidance}, nil
	}
	type scored struct {
		skill cloudAgentSkill
		score int
		path  string
	}
	ranked := make([]scored, 0, len(skills))
	for _, skill := range skills {
		if score, path := cloudAgentSkillMatch(skill, tokens); score > 0 {
			ranked = append(ranked, scored{skill: skill, score: score, path: path})
		}
	}
	sort.SliceStable(ranked, func(i, j int) bool { return ranked[i].score > ranked[j].score })
	entries := make([]map[string]any, 0, limit)
	// 卡索引按排名分配预算：命中卡片时 path 已是卡路径，不必再下发索引；
	// 只命中技能时下发卡路径，Agent 可以直奔某张卡，不必先读 SKILL.md 总纲。
	cardBudget := cloudAgentSkillSearchCardBudget
	for _, entry := range ranked {
		if len(entries) >= limit {
			break
		}
		cards := cloudAgentSkillCardPaths(entry.skill)
		item := map[string]any{
			"skillId":   entry.skill.ID,
			"skillName": entry.skill.Name,
			"path":      entry.path,
			"entryPath": cloudAgentSkillEntryPath,
			"score":     entry.score,
			"snippet":   cloudAgentSkillSnippet(entry.skill, tokens),
			"cardCount": len(cards),
		}
		if entry.path == cloudAgentSkillEntryPath && len(cards) > 0 && cardBudget > 0 {
			shown := cards
			if len(shown) > cardBudget {
				shown = shown[:cardBudget]
			}
			cardBudget -= len(shown)
			item["cards"] = shown
		}
		entries = append(entries, item)
	}
	if len(entries) == 0 {
		return map[string]any{"matches": []map[string]any{}, "total": 0,
			"guidance": "没有命中「" + keyword + "」的已启用技能。换个说法重试，或先用 skill_search 不带参数列出已启用技能索引，再用 skill_read_file 读取其中的 SKILL.md 与卡。"}, nil
	}
	return map[string]any{"matches": entries, "total": len(entries), "keyword": keyword, "guidance": guidance}, nil
}

func (s *Service) cloudAgentSkills(userID string, ids []string) ([]cloudAgentSkill, error) {
	snapshots := []cloudAgentSkill{}
	for _, id := range ids {
		skill, err := s.SkillDetail(userID, id)
		if err != nil {
			return nil, err
		}
		if !skill.IsAdded || skill.Status != 1 {
			return nil, BadAuthRequest("只能使用用户技能库中已安装且启用的技能")
		}
		// Skill content is loaded only after the model explicitly calls
		// skill_read_file; keep the run context to stable metadata and paths.
		// The description is public metadata (market listing) and lets the
		// model route between activated skills without reading any body.
		snapshot := cloudAgentSkill{ID: id, Name: skill.SkillName, Description: skill.Description, Version: skill.VersionID, Hash: skill.ContentHash, Files: map[string]string{cloudAgentSkillEntryPath: ""}}
		files, err := s.SkillPackageFiles(userID, id)
		if err != nil {
			return nil, err
		}
		for _, file := range files {
			// The entry is listed separately; file bodies are fetched on demand.
			if file.Path == cloudAgentSkillEntryPath {
				continue
			}
			// Executable/binary packages are never executed; text references are data only.
			if !strings.HasSuffix(file.Path, ".md") && !strings.HasSuffix(file.Path, ".txt") && !strings.HasSuffix(file.Path, ".json") {
				continue
			}
			snapshot.Files[file.Path] = ""
		}
		// Detect an update during package reads instead of mixing two versions.
		latest, err := s.SkillDetail(userID, id)
		if err != nil {
			return nil, err
		}
		if latest.VersionID != skill.VersionID || latest.ContentHash != skill.ContentHash {
			return nil, creationConflict("技能在读取时已更新，请重试")
		}
		snapshots = append(snapshots, snapshot)
	}
	return snapshots, nil
}