package server

// chat_unread_api.go — P3 / Step 2 双轨制未读消息与位点推进 API
//
// GET  /api/v1/chat/unread?session_id=...&user_id=...&since_message_id=...
// POST /api/v1/chat/read

import (
	"encoding/json"
	"net/http"
	"strconv"

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

func (s *Server) handleChatUnread(w http.ResponseWriter, r *http.Request) {
	user, ok := s.requireAuthenticatedUser(w, r)
	if !ok {
		return
	}

	sessionID := r.URL.Query().Get("session_id")
	if sessionID == "" {
		http.Error(w, "missing session_id", http.StatusBadRequest)
		return
	}

	authCtx, ok := s.authorizeSessionRead(w, r, sessionID, user)
	if !ok {
		return
	}

	var userID int64
	if uStr := r.URL.Query().Get("user_id"); uStr != "" {
		if uid, err := strconv.ParseInt(uStr, 10, 64); err == nil {
			userID = uid
		}
	}

	var sinceID int64
	if sinceStr := r.URL.Query().Get("since_message_id"); sinceStr != "" {
		if id, err := strconv.ParseInt(sinceStr, 10, 64); err == nil {
			sinceID = id
		}
	}

	if s.svc == nil || s.svc.ContextManager() == nil {
		writeJSONResponse(w, http.StatusOK, ctxmgr.ChatUnreadSummary{
			Total:            0,
			NextMessageID:    0,
			UnreadMessageIDs: []int64{},
			Items:            []ctxmgr.UnreadDayItem{},
		})
		return
	}

	summary, err := s.svc.ContextManager().GetChatUnreadSummary(r.Context(), sessionID, userID, sinceID)
	if err != nil {
		writeJSONResponse(w, http.StatusOK, ctxmgr.ChatUnreadSummary{
			Total:            0,
			NextMessageID:    0,
			UnreadMessageIDs: []int64{},
			Items:            []ctxmgr.UnreadDayItem{},
		})
		return
	}

	if authCtx.StageAccess != nil && authCtx.StageAccess.Restricted {
		visible, err := s.listVisibleSessionMessages(r.Context(), authCtx)
		if err == nil {
			allowed := make(map[int64]bool, len(visible))
			for _, msg := range visible {
				allowed[msg.ID] = true
			}
			filteredIDs := make([]int64, 0, len(summary.UnreadMessageIDs))
			for _, id := range summary.UnreadMessageIDs {
				if allowed[id] {
					filteredIDs = append(filteredIDs, id)
				}
			}
			summary.UnreadMessageIDs = filteredIDs
			summary.Total = len(filteredIDs)
		}
	}

	writeJSONResponse(w, http.StatusOK, summary)
}

func (s *Server) handleChatRead(w http.ResponseWriter, r *http.Request) {
	if r.Method != http.MethodPost {
		http.Error(w, "method not allowed", http.StatusMethodNotAllowed)
		return
	}

	user, ok := s.requireAuthenticatedUser(w, r)
	if !ok {
		return
	}

	var req ctxmgr.MarkChatReadRequest
	if err := json.NewDecoder(r.Body).Decode(&req); err != nil {
		http.Error(w, "invalid request body: "+err.Error(), http.StatusBadRequest)
		return
	}
	if req.SessionID == "" {
		http.Error(w, "missing session_id", http.StatusBadRequest)
		return
	}

	if _, ok := s.authorizeSessionRead(w, r, req.SessionID, user); !ok {
		return
	}

	if s.svc == nil || s.svc.ContextManager() == nil {
		http.Error(w, "context manager not initialized", http.StatusInternalServerError)
		return
	}

	pos, err := s.svc.ContextManager().MarkChatRead(r.Context(), req)
	if err != nil {
		http.Error(w, "mark chat read failed: "+err.Error(), http.StatusInternalServerError)
		return
	}

	writeJSONResponse(w, http.StatusOK, map[string]any{
		"ok":                   true,
		"session_id":           pos.SessionID,
		"user_id":              pos.UserID,
		"last_read_message_id": pos.LastReadMessageID,
		"dismissed_unread_ids": pos.DismissedUnreadIDs,
		"updated_at":           pos.UpdatedAt,
	})
}