import { serve } from "https://deno.land/std@0.190.0/http/server.ts";
import { createClient } from "https://esm.sh/@supabase/supabase-js@2";

const corsHeaders = {
  "Access-Control-Allow-Origin": "*",
  "Access-Control-Allow-Headers": "authorization, x-client-info, apikey, content-type",
};

interface GoogleOAuthConfig {
  client_id: string;
  client_secret: string;
  refresh_token: string;
  access_token?: string;
  expires_at?: number;
}

interface UpdateEventRequest {
  session_id: string;
  date: string;
  start_time: string;
  end_time: string;
}

// Function to get access token from refresh token (OAuth2)
async function getGoogleAccessToken(oauthConfig: GoogleOAuthConfig): Promise<{ access_token: string; expires_in: number }> {
  try {
    console.log("Attempting to exchange refresh token for access token...");

    const tokenRequest = {
      client_id: oauthConfig.client_id,
      client_secret: oauthConfig.client_secret,
      refresh_token: oauthConfig.refresh_token,
      grant_type: "refresh_token",
    };

    const response = await fetch("https://oauth2.googleapis.com/token", {
      method: "POST",
      headers: { "Content-Type": "application/x-www-form-urlencoded" },
      body: new URLSearchParams(tokenRequest),
    });

    if (!response.ok) {
      const errorText = await response.text();
      console.error("Token response error:", errorText);
      throw new Error(`Token exchange failed: ${errorText}`);
    }

    const data = await response.json();

    if (!data.access_token) {
      throw new Error("No access token in response");
    }

    console.log("Successfully obtained access token");
    return {
      access_token: data.access_token,
      expires_in: data.expires_in || 3600
    };
  } catch (error: any) {
    console.error("Error getting Google access token:", error);
    throw error;
  }
}

serve(async (req: Request): Promise<Response> => {
  if (req.method === "OPTIONS") {
    return new Response(null, { headers: corsHeaders });
  }

  const logs: string[] = [];
  const log = (msg: string) => {
    console.log(msg);
    logs.push(msg);
  };

  try {
    const supabaseUrl = Deno.env.get("SUPABASE_URL")!;
    const supabaseServiceKey = Deno.env.get("SUPABASE_SERVICE_ROLE_KEY")!;
    const supabase = createClient(supabaseUrl, supabaseServiceKey);

    const body: UpdateEventRequest = await req.json();
    const { session_id, date, start_time, end_time } = body;

    log(`Updating calendar event for session: ${session_id}`);
    log(`New time: ${date} ${start_time} - ${end_time}`);

    // Get session details including calendar_event_id
    const { data: session, error: sessionError } = await supabase
      .from("consulting_sessions")
      .select("id, calendar_event_id, topic_category, profiles(name, email), notes, meet_link")
      .eq("id", session_id)
      .single();

    if (sessionError || !session) {
      log(`Session not found: ${sessionError?.message}`);
      return new Response(
        JSON.stringify({
          success: false,
          message: "Session not found",
          logs: logs
        }),
        { status: 404, headers: { ...corsHeaders, "Content-Type": "application/json" } }
      );
    }

    if (!session.calendar_event_id) {
      log("No calendar event ID found for this session");
      return new Response(
        JSON.stringify({
          success: false,
          message: "No calendar event linked to this session",
          logs: logs
        }),
        { status: 400, headers: { ...corsHeaders, "Content-Type": "application/json" } }
      );
    }

    // Get platform settings
    log("Fetching platform settings...");
    const { data: settings, error: settingsError } = await supabase
      .from("platform_settings")
      .select("integration_google_calendar_id, google_oauth_config")
      .single();

    if (settingsError || !settings) {
      log(`Error fetching settings: ${settingsError?.message}`);
      return new Response(
        JSON.stringify({
          success: false,
          message: "Error fetching settings",
          logs: logs
        }),
        { status: 500, headers: { ...corsHeaders, "Content-Type": "application/json" } }
      );
    }

    const calendarId = settings.integration_google_calendar_id;
    if (!calendarId) {
      log("Calendar ID not configured");
      return new Response(
        JSON.stringify({
          success: false,
          message: "Google Calendar ID not configured",
          logs: logs
        }),
        { status: 400, headers: { ...corsHeaders, "Content-Type": "application/json" } }
      );
    }

    // Get OAuth config
    const oauthConfigJson = settings.google_oauth_config;
    if (!oauthConfigJson) {
      log("OAuth config not found");
      return new Response(
        JSON.stringify({
          success: false,
          message: "Google OAuth Config not configured",
          logs: logs
        }),
        { status: 400, headers: { ...corsHeaders, "Content-Type": "application/json" } }
      );
    }

    let oauthConfig: GoogleOAuthConfig;
    try {
      oauthConfig = JSON.parse(oauthConfigJson);
    } catch (error: any) {
      log(`Failed to parse OAuth config: ${error.message}`);
      return new Response(
        JSON.stringify({
          success: false,
          message: "Invalid OAuth config format",
          logs: logs
        }),
        { status: 400, headers: { ...corsHeaders, "Content-Type": "application/json" } }
      );
    }

    // Get access token
    let accessToken: string;
    const now = Math.floor(Date.now() / 1000);

    if (oauthConfig.access_token && oauthConfig.expires_at && oauthConfig.expires_at > now + 60) {
      log(`Using cached access_token`);
      accessToken = oauthConfig.access_token;
    } else {
      log("Refreshing access token...");
      const tokenData = await getGoogleAccessToken(oauthConfig);
      accessToken = tokenData.access_token;

      const newExpiresAt = now + tokenData.expires_in;
      const updatedConfig = {
        ...oauthConfig,
        access_token: accessToken,
        expires_at: newExpiresAt
      };

      await supabase
        .from("platform_settings")
        .update({ google_oauth_config: JSON.stringify(updatedConfig) })
        .eq("id", settings.id);

      log("Updated cached access_token in database");
    }

    // Build event data for update
    const startDate = new Date(`${date}T${start_time}+07:00`);
    const endDate = new Date(`${date}T${end_time}+07:00`);

    log(`Event time: ${startDate.toISOString()} to ${endDate.toISOString()}`);

    const eventData = {
      start: {
        dateTime: startDate.toISOString(),
        timeZone: "Asia/Jakarta",
      },
      end: {
        dateTime: endDate.toISOString(),
        timeZone: "Asia/Jakarta",
      },
    };

    log(`Updating event ${session.calendar_event_id} in calendar ${calendarId}`);

    // Update event via Google Calendar API
    const calendarResponse = await fetch(
      `https://www.googleapis.com/calendar/v3/calendars/${encodeURIComponent(calendarId)}/events/${encodeURIComponent(session.calendar_event_id)}`,
      {
        method: "PATCH",
        headers: {
          "Authorization": `Bearer ${accessToken}`,
          "Content-Type": "application/json",
        },
        body: JSON.stringify(eventData),
      }
    );

    log(`Calendar API response status: ${calendarResponse.status}`);

    if (!calendarResponse.ok) {
      const errorText = await calendarResponse.text();
      log(`Google Calendar API error: ${errorText}`);
      return new Response(
        JSON.stringify({
          success: false,
          message: "Failed to update event in Google Calendar: " + errorText,
          logs: logs
        }),
        { status: 500, headers: { ...corsHeaders, "Content-Type": "application/json" } }
      );
    }

    const eventDataResult = await calendarResponse.json();
    log(`Event updated successfully: ${eventDataResult.id}`);

    return new Response(
      JSON.stringify({
        success: true,
        event_id: eventDataResult.id,
        html_link: eventDataResult.htmlLink,
        logs: logs
      }),
      { headers: { ...corsHeaders, "Content-Type": "application/json" } }
    );

  } catch (error: any) {
    log(`Error updating calendar event: ${error.message}`);
    log(`Stack: ${error.stack}`);
    return new Response(
      JSON.stringify({
        success: false,
        message: error.message || "Internal server error",
        logs: logs
      }),
      { status: 500, headers: { ...corsHeaders, "Content-Type": "application/json" } }
    );
  }
});