package server

import (
	"fmt"
	"net/http"
	"strconv"
	"strings"

	"chat-agent-system/internal/replyexport"
)

// handleGetExportCapability 获取单条消息权威导出能力
// GET /api/v1/chat/messages/{message_id}/export-capability
func (s *Server) handleGetExportCapability(w http.ResponseWriter, r *http.Request) {
	user, ok := s.requireAuthenticatedUser(w, r)
	if !ok {
		return
	}

	if s.ctxMgr == nil {
		writeSafeError(w, r, http.StatusServiceUnavailable, "context manager not initialized")
		return
	}

	msgID := extractMessageIDFromPath(r, "export-capability")
	if msgID <= 0 {
		writeJSONResponse(w, http.StatusBadRequest, map[string]string{
			"error_code": "INVALID_MESSAGE_ID",
			"message":    "无效的消息ID",
		})
		return
	}

	msg, err := s.ctxMgr.GetMessageByID(r.Context(), msgID)
	if err != nil || msg == nil {
		writeJSONResponse(w, http.StatusNotFound, map[string]string{
			"error_code": "MESSAGE_NOT_FOUND",
			"message":    "指定消息不存在或已被删除",
		})
		return
	}
	if !s.assertMessageOwnedByUser(w, r, msg, user.ID) {
		return
	}

	cap, ok := msg.ExportCapability.(replyexport.MessageExportCapability)
	if !ok {
		// 动态降级重新评估
		hasCard := false
		if msg.Metadata != nil {
			if _, exists := msg.Metadata["interactive_card"]; exists {
				hasCard = true
			}
		}
		_, cap = replyexport.EvaluatePolicy(replyexport.PolicyOptions{
			Role:               msg.Role,
			Status:             "completed",
			Content:            msg.Content,
			HasInteractiveCard: hasCard,
			Revision:           msg.ContentRevision,
		})
	}

	resp := map[string]any{
		"message_id":       msg.ID,
		"policy":           cap.Policy,
		"formats":          cap.Formats,
		"body_selector":    "content_only",
		"content_revision": cap.ContentRevision,
		"content_sha256":   cap.ContentSha256,
	}
	if cap.ReasonCode != "" {
		resp["reason_code"] = cap.ReasonCode
	}

	writeJSONResponse(w, http.StatusOK, resp)
}

// handleGetExportSource 获取单条消息受控不可变正文快照
// GET /api/v1/chat/messages/{message_id}/export-source?content_revision=
func (s *Server) handleGetExportSource(w http.ResponseWriter, r *http.Request) {
	user, ok := s.requireAuthenticatedUser(w, r)
	if !ok {
		return
	}

	if s.ctxMgr == nil {
		writeSafeError(w, r, http.StatusServiceUnavailable, "context manager not initialized")
		return
	}

	msgID := extractMessageIDFromPath(r, "export-source")
	if msgID <= 0 {
		writeJSONResponse(w, http.StatusBadRequest, map[string]string{
			"error_code": "INVALID_MESSAGE_ID",
			"message":    "无效的消息ID",
		})
		return
	}

	msg, err := s.ctxMgr.GetMessageByID(r.Context(), msgID)
	if err != nil || msg == nil {
		writeJSONResponse(w, http.StatusNotFound, map[string]string{
			"error_code": "MESSAGE_NOT_FOUND",
			"message":    "指定消息不存在或已被删除",
		})
		return
	}
	if !s.assertMessageOwnedByUser(w, r, msg, user.ID) {
		return
	}

	cap, ok := msg.ExportCapability.(replyexport.MessageExportCapability)
	if !ok {
		hasCard := false
		if msg.Metadata != nil {
			if _, exists := msg.Metadata["interactive_card"]; exists {
				hasCard = true
			}
		}
		_, cap = replyexport.EvaluatePolicy(replyexport.PolicyOptions{
			Role:               msg.Role,
			Status:             "completed",
			Content:            msg.Content,
			HasInteractiveCard: hasCard,
			Revision:           msg.ContentRevision,
		})
	}

	if cap.Policy == replyexport.PolicyNone {
		writeJSONResponse(w, http.StatusBadRequest, map[string]string{
			"error_code": "MESSAGE_NOT_EXPORTABLE",
			"message":    "该消息不支持导出为文档",
		})
		return
	}

	// 校验 revision（若客户端传入了指定版本）
	if reqRevStr := r.URL.Query().Get("content_revision"); reqRevStr != "" {
		if reqRev, err := strconv.Atoi(reqRevStr); err == nil && reqRev > 0 {
			if reqRev != cap.ContentRevision {
				writeJSONResponse(w, http.StatusConflict, map[string]string{
					"error_code": "MESSAGE_REVISION_CHANGED",
					"message":    "消息内容版本已更新，请重新加载最新快照",
				})
				return
			}
		}
	}

	title := replyexport.DeriveTitle(msg.Content, msg.CreatedAt)
	snapshotID := fmt.Sprintf("msg:%d:rev:%d", msg.ID, cap.ContentRevision)

	w.Header().Set("Cache-Control", "private, no-store")
	writeJSONResponse(w, http.StatusOK, map[string]any{
		"snapshot_id":      snapshotID,
		"message_id":       msg.ID,
		"content_revision": cap.ContentRevision,
		"content_sha256":   cap.ContentSha256,
		"title":            title,
		"markdown":         msg.Content,
		"capability":       cap,
	})
}

// extractMessageIDFromPath 从路由参数或 URL 路径中提取 message_id
func extractMessageIDFromPath(r *http.Request, actionName string) int64 {
	// 优先尝试 Go 1.22 PathValue
	val := r.PathValue("message_id")
	if val != "" {
		id, err := strconv.ParseInt(val, 10, 64)
		if err == nil && id > 0 {
			return id
		}
	}

	// 降级：从路径分割提取 /api/v1/chat/messages/{id}/{action}
	parts := strings.Split(strings.Trim(r.URL.Path, "/"), "/")
	for i, p := range parts {
		if p == "messages" && i+1 < len(parts) {
			id, err := strconv.ParseInt(parts[i+1], 10, 64)
			if err == nil && id > 0 {
				return id
			}
		}
	}

	return 0
}