package app

import (
	"context"
	"net/http"
	"strings"
	"sync"
	"time"
)

// One keyword list for the whole product. Before this, messages had no check at
// all, posts had none, and adoption had its own comma-separated config string —
// three different answers to the same question. The list is cached because it
// is read on every message and written a few times a week.

type contentKeyword struct {
	ID     int64
	Word   string
	Scope  string
	Action string
}

type keywordCache struct {
	mutex    sync.RWMutex
	words    []contentKeyword
	loadedAt time.Time
}

var keywords = &keywordCache{}

const keywordCacheTTL = time.Minute

func (a *App) loadKeywords(ctx context.Context) []contentKeyword {
	keywords.mutex.RLock()
	if time.Since(keywords.loadedAt) < keywordCacheTTL {
		defer keywords.mutex.RUnlock()
		return keywords.words
	}
	keywords.mutex.RUnlock()

	rows, err := a.db.QueryContext(ctx, `SELECT id,word,scope,action FROM content_keywords WHERE status=1`)
	if err != nil {
		return nil
	}
	defer rows.Close()
	loaded := []contentKeyword{}
	for rows.Next() {
		var item contentKeyword
		if rows.Scan(&item.ID, &item.Word, &item.Scope, &item.Action) == nil && strings.TrimSpace(item.Word) != "" {
			item.Word = strings.ToLower(strings.TrimSpace(item.Word))
			loaded = append(loaded, item)
		}
	}
	keywords.mutex.Lock()
	keywords.words = loaded
	keywords.loadedAt = time.Now()
	keywords.mutex.Unlock()
	return loaded
}

func invalidateKeywordCache() {
	keywords.mutex.Lock()
	keywords.loadedAt = time.Time{}
	keywords.mutex.Unlock()
}

// matchKeyword returns the first word this text trips and what to do about it.
// A "block" anywhere wins over a "review": the stricter rule is the one the
// operator meant.
func (a *App) matchKeyword(ctx context.Context, scope, text string) (string, string) {
	if strings.TrimSpace(text) == "" || !a.configBool(ctx, "moderation.keywords_enabled", true) {
		return "", ""
	}
	lowered := strings.ToLower(text)
	hit, action := "", ""
	for _, item := range a.loadKeywords(ctx) {
		if item.Scope != "all" && item.Scope != scope {
			continue
		}
		if !strings.Contains(lowered, item.Word) {
			continue
		}
		if item.Action == "block" {
			a.countKeywordHit(ctx, item.ID)
			return item.Word, "block"
		}
		if hit == "" {
			hit, action = item.Word, "review"
		}
	}
	if hit != "" {
		for _, item := range a.loadKeywords(ctx) {
			if item.Word == hit {
				a.countKeywordHit(ctx, item.ID)
				break
			}
		}
	}
	return hit, action
}

// 命中次数是运营调词库的依据：一个从来不命中的词和一个天天命中的词，价值不一样。
func (a *App) countKeywordHit(ctx context.Context, id int64) {
	go func() {
		background, cancel := context.WithTimeout(context.Background(), 3*time.Second)
		defer cancel()
		_, _ = a.db.ExecContext(background, `UPDATE content_keywords SET hit_count=hit_count+1,last_hit_at=NOW(3) WHERE id=?`, id)
	}()
}

// --- 管理端 ---------------------------------------------------------------

func (a *App) adminKeywords(w http.ResponseWriter, r *http.Request) {
	page, size, offset := pagination(r)
	where := " WHERE 1=1"
	args := []any{}
	if scope := strings.TrimSpace(r.URL.Query().Get("scope")); scope != "" {
		where += " AND scope=?"
		args = append(args, scope)
	}
	if action := strings.TrimSpace(r.URL.Query().Get("action")); action != "" {
		where += " AND action=?"
		args = append(args, action)
	}
	if keyword := strings.TrimSpace(r.URL.Query().Get("keyword")); keyword != "" {
		where += " AND (word LIKE ? OR category LIKE ?)"
		like := "%" + keyword + "%"
		args = append(args, like, like)
	}
	var total int64
	_ = a.db.QueryRowContext(r.Context(), `SELECT COUNT(*) FROM content_keywords`+where, args...).Scan(&total)
	rows, err := a.db.QueryContext(r.Context(), `SELECT id,word,scope,action,category,note,status,hit_count,last_hit_at,created_at
		FROM content_keywords`+where+` ORDER BY hit_count DESC,id DESC LIMIT ? OFFSET ?`, append(args, size, offset)...)
	if err != nil {
		fail(w, http.StatusInternalServerError, 50001, "查询词库失败")
		return
	}
	defer rows.Close()
	items := []map[string]any{}
	for rows.Next() {
		var id int64
		var word, scope, action, category, note string
		var status, hits int
		var lastHit any
		var created time.Time
		if rows.Scan(&id, &word, &scope, &action, &category, &note, &status, &hits, &lastHit, &created) != nil {
			continue
		}
		items = append(items, map[string]any{
			"id": id, "word": word, "scope": scope, "action": action, "category": category,
			"note": note, "status": status, "hitCount": hits, "lastHitAt": lastHit,
			"createdAt": created.Format(time.RFC3339),
		})
	}
	reply(w, map[string]any{"items": items, "total": total, "page": page, "size": size})
}

type keywordRequest struct {
	Word     string `json:"word"`
	Scope    string `json:"scope"`
	Action   string `json:"action"`
	Category string `json:"category"`
	Note     string `json:"note"`
	Status   int    `json:"status"`
}

var keywordScopes = map[string]bool{"all": true, "message": true, "post": true, "adoption": true, "nickname": true}

func validKeyword(req *keywordRequest) string {
	req.Word = strings.TrimSpace(req.Word)
	req.Category = strings.TrimSpace(req.Category)
	req.Note = strings.TrimSpace(req.Note)
	if req.Scope == "" {
		req.Scope = "all"
	}
	if req.Action == "" {
		req.Action = "review"
	}
	if len([]rune(req.Word)) < 1 || len([]rune(req.Word)) > 30 {
		return "关键词为 1 到 30 个字"
	}
	if !keywordScopes[req.Scope] {
		return "适用范围无效"
	}
	if req.Action != "block" && req.Action != "review" {
		return "命中动作只能是拦截或转人工"
	}
	if len([]rune(req.Category)) > 20 || len([]rune(req.Note)) > 100 {
		return "分类或备注过长"
	}
	return ""
}

func (a *App) adminCreateKeyword(w http.ResponseWriter, r *http.Request) {
	var req keywordRequest
	if decode(r, &req) != nil {
		fail(w, http.StatusBadRequest, 20001, "格式错误")
		return
	}
	if message := validKeyword(&req); message != "" {
		fail(w, http.StatusBadRequest, 20001, message)
		return
	}
	result, err := a.db.ExecContext(r.Context(), `INSERT INTO content_keywords(word,scope,action,category,note,status,created_by)
		VALUES(?,?,?,?,?,1,?)`, req.Word, req.Scope, req.Action, req.Category, req.Note, current(r).ID)
	if err != nil {
		fail(w, http.StatusBadRequest, 20001, "这个词在该范围下已经存在")
		return
	}
	id, _ := result.LastInsertId()
	invalidateKeywordCache()
	a.audit(r, "create", "content_keyword", id, map[string]any{"word": req.Word, "scope": req.Scope, "action": req.Action})
	reply(w, map[string]any{"id": id})
}

func (a *App) adminUpdateKeyword(w http.ResponseWriter, r *http.Request) {
	id, err := pathID(r)
	if err != nil {
		fail(w, http.StatusBadRequest, 20001, "编号无效")
		return
	}
	var req keywordRequest
	if decode(r, &req) != nil {
		fail(w, http.StatusBadRequest, 20001, "格式错误")
		return
	}
	if message := validKeyword(&req); message != "" {
		fail(w, http.StatusBadRequest, 20001, message)
		return
	}
	status := 1
	if req.Status == 0 {
		status = 0
	}
	result, err := a.db.ExecContext(r.Context(), `UPDATE content_keywords SET word=?,scope=?,action=?,category=?,note=?,status=? WHERE id=?`,
		req.Word, req.Scope, req.Action, req.Category, req.Note, status, id)
	if err != nil {
		fail(w, http.StatusBadRequest, 20001, "保存失败，可能与已有词重复")
		return
	}
	if affected, _ := result.RowsAffected(); affected == 0 {
		fail(w, http.StatusNotFound, 30001, "词条不存在")
		return
	}
	invalidateKeywordCache()
	a.audit(r, "update", "content_keyword", id, map[string]any{"word": req.Word, "status": status})
	reply(w, map[string]bool{"success": true})
}

func (a *App) adminDeleteKeyword(w http.ResponseWriter, r *http.Request) {
	id, err := pathID(r)
	if err != nil {
		fail(w, http.StatusBadRequest, 20001, "编号无效")
		return
	}
	result, err := a.db.ExecContext(r.Context(), `DELETE FROM content_keywords WHERE id=?`, id)
	if err != nil {
		fail(w, http.StatusInternalServerError, 50001, "删除失败")
		return
	}
	if affected, _ := result.RowsAffected(); affected == 0 {
		fail(w, http.StatusNotFound, 30001, "词条不存在")
		return
	}
	invalidateKeywordCache()
	a.audit(r, "delete", "content_keyword", id, nil)
	reply(w, map[string]bool{"success": true})
}

// adminTestKeyword lets an operator paste a real message and see what the list
// would do with it, instead of finding out from a complaint.
func (a *App) adminTestKeyword(w http.ResponseWriter, r *http.Request) {
	var req struct {
		Scope string `json:"scope"`
		Text  string `json:"text"`
	}
	if decode(r, &req) != nil {
		fail(w, http.StatusBadRequest, 20001, "格式错误")
		return
	}
	if req.Scope == "" {
		req.Scope = "message"
	}
	word, action := a.matchKeyword(r.Context(), req.Scope, req.Text)
	reply(w, map[string]any{"word": word, "action": action, "matched": word != ""})
}

// recordKeywordRisk turns a soft keyword hit into something visible: the risk
// centre is where a moderator would look, so that is where it goes.
func (a *App) recordKeywordRisk(ctx context.Context, userID int64, scope, word string) {
	if userID <= 0 {
		return
	}
	_, _ = a.db.ExecContext(ctx, `INSERT INTO risk_events(user_id,event_type,score_delta,metadata)
		VALUES(?,?,?,JSON_OBJECT('scope',?,'word',?))`, userID, "keyword_"+scope, 2, scope, word)
	_, _ = a.db.ExecContext(ctx, `INSERT INTO user_risk_profiles(user_id,risk_score,message_score)
		VALUES(?,2,2) ON DUPLICATE KEY UPDATE risk_score=risk_score+2,message_score=message_score+2`, userID)
}