import { serve } from 'https://deno.land/std@0.177.0/http/server.ts';
import { createClient } from 'https://esm.sh/@supabase/supabase-js@2';
import { createHmac } from 'https://deno.land/std@0.177.0/node/crypto.ts';

const ALLOWED_ORIGIN = 'https://telegram.pezkuwichain.io';

function getCorsHeaders(): Record<string, string> {
  return {
    'Access-Control-Allow-Origin': ALLOWED_ORIGIN,
    'Access-Control-Allow-Headers':
      'authorization, x-client-info, apikey, content-type, x-supabase-client-platform',
    'Access-Control-Allow-Methods': 'POST, OPTIONS',
  };
}

interface TelegramUser {
  id: number;
  first_name: string;
  last_name?: string;
  username?: string;
  photo_url?: string;
  language_code?: string;
}

function validateInitData(initData: string, botToken: string): TelegramUser | null {
  try {
    const params = new URLSearchParams(initData);
    const hash = params.get('hash');
    if (!hash) return null;

    params.delete('hash');

    const sortedParams = Array.from(params.entries())
      .sort(([a], [b]) => a.localeCompare(b))
      .map(([key, value]) => `${key}=${value}`)
      .join('\n');

    const secretKey = createHmac('sha256', 'WebAppData').update(botToken).digest();
    const calculatedHash = createHmac('sha256', secretKey).update(sortedParams).digest('hex');

    if (calculatedHash !== hash) return null;

    const authDate = parseInt(params.get('auth_date') || '0');
    const now = Math.floor(Date.now() / 1000);
    if (now - authDate > 86400) return null;

    const userStr = params.get('user');
    if (!userStr) return null;

    return JSON.parse(userStr) as TelegramUser;
  } catch {
    return null;
  }
}

function getSessionSecret(botToken: string): Uint8Array {
  return createHmac('sha256', 'SessionTokenSecret').update(botToken).digest();
}

function generateSessionToken(telegramId: number, botToken: string): string {
  const payload = {
    tgId: telegramId,
    iat: Date.now(),
    exp: Date.now() + 24 * 60 * 60 * 1000,
    jti: crypto.randomUUID(),
  };

  const payloadB64 = btoa(JSON.stringify(payload));
  const secret = getSessionSecret(botToken);
  const signature = createHmac('sha256', secret).update(payloadB64).digest('hex');

  return `${payloadB64}.${signature}`;
}

function verifySessionToken(token: string, botToken: string): number | null {
  try {
    const parts = token.split('.');
    if (parts.length !== 2) return null;

    const [payloadB64, signature] = parts;
    const secret = getSessionSecret(botToken);
    const expectedSig = createHmac('sha256', secret).update(payloadB64).digest('hex');

    if (signature !== expectedSig) return null;

    const payload = JSON.parse(atob(payloadB64));
    if (Date.now() > payload.exp) return null;

    return payload.tgId;
  } catch {
    return null;
  }
}

serve(async (req) => {
  const corsHeaders = getCorsHeaders();

  if (req.method === 'OPTIONS') {
    return new Response('ok', { headers: corsHeaders });
  }

  try {
    const body = await req.json();
    const { initData, sessionToken } = body;

    const supabaseUrl = Deno.env.get('SUPABASE_URL')!;
    const supabaseServiceKey = Deno.env.get('SUPABASE_SERVICE_ROLE_KEY')!;
    const botToken = Deno.env.get('TELEGRAM_BOT_TOKEN');

    if (!botToken) {
      return new Response(JSON.stringify({ error: 'Server configuration error' }), {
        status: 500,
        headers: { ...corsHeaders, 'Content-Type': 'application/json' },
      });
    }

    const supabase = createClient(supabaseUrl, supabaseServiceKey);

    // Method 1: Session token verification
    if (sessionToken) {
      const tgId = verifySessionToken(sessionToken, botToken);
      if (!tgId) {
        return new Response(JSON.stringify({ error: 'Invalid or expired session' }), {
          status: 401,
          headers: { ...corsHeaders, 'Content-Type': 'application/json' },
        });
      }

      const { data: userData, error: userError } = await supabase
        .from('users')
        .select('*')
        .eq('telegram_id', tgId)
        .single();

      if (userError || !userData) {
        return new Response(JSON.stringify({ error: 'User not found' }), {
          status: 404,
          headers: { ...corsHeaders, 'Content-Type': 'application/json' },
        });
      }

      return new Response(
        JSON.stringify({
          user: userData,
          session_token: generateSessionToken(tgId, botToken),
        }),
        { headers: { ...corsHeaders, 'Content-Type': 'application/json' } }
      );
    }

    // Method 2: initData verification
    if (!initData) {
      return new Response(JSON.stringify({ error: 'Missing authentication data' }), {
        status: 400,
        headers: { ...corsHeaders, 'Content-Type': 'application/json' },
      });
    }

    const telegramUser = validateInitData(initData, botToken);
    if (!telegramUser) {
      return new Response(JSON.stringify({ error: 'Invalid Telegram data' }), {
        status: 401,
        headers: { ...corsHeaders, 'Content-Type': 'application/json' },
      });
    }

    // Get or create user
    const { data: existingUser } = await supabase
      .from('users')
      .select('id')
      .eq('telegram_id', telegramUser.id)
      .single();

    let userId: string;

    if (existingUser) {
      userId = existingUser.id;
      await supabase
        .from('users')
        .update({
          username: telegramUser.username,
          first_name: telegramUser.first_name,
          last_name: telegramUser.last_name,
          photo_url: telegramUser.photo_url,
          language_code: telegramUser.language_code,
          updated_at: new Date().toISOString(),
        })
        .eq('id', userId);
    } else {
      const { data: newUser, error: createError } = await supabase
        .from('users')
        .insert({
          telegram_id: telegramUser.id,
          username: telegramUser.username,
          first_name: telegramUser.first_name,
          last_name: telegramUser.last_name,
          photo_url: telegramUser.photo_url,
          language_code: telegramUser.language_code || 'ku',
        })
        .select('id')
        .single();

      if (createError) {
        return new Response(JSON.stringify({ error: 'Failed to create user' }), {
          status: 500,
          headers: { ...corsHeaders, 'Content-Type': 'application/json' },
        });
      }

      userId = newUser.id;
    }

    const { data: userData } = await supabase.from('users').select('*').eq('id', userId).single();

    return new Response(
      JSON.stringify({
        user: userData,
        telegram_user: telegramUser,
        session_token: generateSessionToken(telegramUser.id, botToken),
      }),
      { headers: { ...corsHeaders, 'Content-Type': 'application/json' } }
    );
  } catch {
    return new Response(JSON.stringify({ error: 'Internal server error' }), {
      status: 500,
      headers: { ...corsHeaders, 'Content-Type': 'application/json' },
    });
  }
});