package main

import (
	"errors"
	"net/http"
	"strings"

	"github.com/jackc/pgx/v5"
)

type clearChatRequest struct {
	Scope string `json:"scope"`
}

func (s *Server) handleClearChat(w http.ResponseWriter, r *http.Request) {
	user, ok := userFromContext(r.Context())
	if !ok {
		writeError(w, http.StatusUnauthorized, "Unauthorized")
		return
	}

	conversationID := strings.TrimSpace(r.PathValue("id"))
	if !s.canAccessConversation(r.Context(), conversationID, user.ID) {
		writeError(w, http.StatusForbidden, "Kein Zugriff auf diesen Chat")
		return
	}
	if !s.isConversationMember(r.Context(), conversationID, user.ID) {
		writeError(w, http.StatusForbidden, "Nur Mitglieder können diesen Chat leeren")
		return
	}

	var input clearChatRequest
	if err := readJSON(r, &input); err != nil {
		writeError(w, http.StatusBadRequest, "Ungültige Anfrage")
		return
	}

	scope := strings.TrimSpace(input.Scope)
	if scope != "me" && scope != "all" {
		writeError(w, http.StatusBadRequest, "Ungültiger Löschumfang")
		return
	}

	var conversationType, ownerID, teamID string
	err := s.db.QueryRow(
		r.Context(),
		`
		SELECT type, COALESCE(created_by::TEXT, ''), COALESCE(team_id::TEXT, '')
		FROM conversations
		WHERE id = $1
		`,
		conversationID,
	).Scan(&conversationType, &ownerID, &teamID)
	if errors.Is(err, pgx.ErrNoRows) {
		writeError(w, http.StatusNotFound, "Chat wurde nicht gefunden")
		return
	}
	if err != nil {
		writeError(w, http.StatusInternalServerError, "Chat konnte nicht geladen werden")
		return
	}

	if scope == "all" {
		switch conversationType {
		case "direct":
		case "group":
			if teamID != "" {
				if !canManageTeamGroup(user) {
					writeError(w, http.StatusForbidden, "Keine Berechtigung zum Leeren dieses Team-Gruppenchats")
					return
				}
			} else if !canManageGroup(user, ownerID) {
				writeError(w, http.StatusForbidden, "Nur der Ersteller oder ein Administrator darf die Gruppe für alle leeren")
				return
			}
		default:
			writeError(w, http.StatusBadRequest, "Dieser Chat kann nicht für alle geleert werden")
			return
		}
	}

	if scope == "me" {
		if _, err := s.db.Exec(
			r.Context(),
			`
			UPDATE conversation_members
			SET last_cleared_at = now(), last_read_at = now()
			WHERE conversation_id = $1
			  AND user_id = $2
			`,
			conversationID,
			user.ID,
		); err != nil {
			writeError(w, http.StatusInternalServerError, "Chat konnte nicht geleert werden")
			return
		}

		conversation, err := s.getChatConversation(r.Context(), conversationID, user.ID, user.ShowLastSeen)
		if err != nil {
			writeError(w, http.StatusInternalServerError, "Chat konnte nicht geladen werden")
			return
		}

		writeJSON(w, http.StatusOK, map[string]any{
			"conversation": conversation,
		})
		return
	}

	tx, err := s.db.Begin(r.Context())
	if err != nil {
		writeError(w, http.StatusInternalServerError, "Chat konnte nicht geleert werden")
		return
	}
	defer tx.Rollback(r.Context())

	if _, err := tx.Exec(
		r.Context(),
		`
		UPDATE messages
		SET deleted_at = now()
		WHERE conversation_id = $1
		  AND deleted_at IS NULL
		`,
		conversationID,
	); err != nil {
		writeError(w, http.StatusInternalServerError, "Chat konnte nicht geleert werden")
		return
	}

	if _, err := tx.Exec(
		r.Context(),
		`
		UPDATE conversations
		SET
			last_message_at = (
				SELECT MAX(created_at)
				FROM messages
				WHERE conversation_id = $1
				  AND deleted_at IS NULL
				  AND (expires_at IS NULL OR expires_at > now())
			),
			updated_at = now()
		WHERE id = $1
		`,
		conversationID,
	); err != nil {
		writeError(w, http.StatusInternalServerError, "Chat konnte nicht geleert werden")
		return
	}

	if err := tx.Commit(r.Context()); err != nil {
		writeError(w, http.StatusInternalServerError, "Chat konnte nicht geleert werden")
		return
	}

	s.publishChatMessagesReload(r.Context(), conversationID)
	s.publishConversationUpdate(r.Context(), conversationID)

	conversation, err := s.getChatConversation(r.Context(), conversationID, user.ID, user.ShowLastSeen)
	if err != nil {
		writeError(w, http.StatusInternalServerError, "Chat konnte nicht geladen werden")
		return
	}

	writeJSON(w, http.StatusOK, map[string]any{
		"conversation": conversation,
	})
}