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';

// CORS - Production domain only
const ALLOWED_ORIGINS = [
  'https://telegram.pezkuwichain.io',
  'https://telegram.pezkiwi.app',
  'https://t.me',
];

function getCorsHeaders(origin: string | null): Record<string, string> {
  const allowedOrigin =
    origin && ALLOWED_ORIGINS.some((o) => origin.startsWith(o)) ? origin : ALLOWED_ORIGINS[0];

  return {
    'Access-Control-Allow-Origin': allowedOrigin,
    'Access-Control-Allow-Headers':
      'authorization, x-client-info, apikey, content-type, x-supabase-client-platform',
    'Access-Control-Allow-Methods': 'POST, OPTIONS',
  };
}

interface P2PMessagesRequest {
  sessionToken: string;
  action: 'send' | 'list';
  tradeId: string;
  message?: string;
}

// Session token secret (derived from bot token)
function getSessionSecret(botToken: string): Uint8Array {
  return createHmac('sha256', 'SessionTokenSecret').update(botToken).digest();
}

// Verify HMAC-signed session token
function verifySessionToken(token: string, botToken: string): number | null {
  try {
    const parts = token.split('.');
    if (parts.length !== 2) {
      // Try legacy format for backwards compatibility
      return verifyLegacyToken(token);
    }

    const [payloadB64, signature] = parts;

    // Verify signature
    const secret = getSessionSecret(botToken);
    const expectedSig = createHmac('sha256', secret).update(payloadB64).digest('hex');

    if (signature !== expectedSig) {
      return null;
    }

    // Parse payload
    const payload = JSON.parse(atob(payloadB64));

    // Check expiration
    if (Date.now() > payload.exp) {
      return null;
    }

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

// Legacy token format (Base64 only) - for backwards compatibility
function verifyLegacyToken(token: string): number | null {
  try {
    const decoded = atob(token);
    const [telegramId, timestamp] = decoded.split(':');
    const ts = parseInt(timestamp);
    // Token valid for 7 days
    if (Date.now() - ts > 7 * 24 * 60 * 60 * 1000) {
      return null;
    }
    return parseInt(telegramId);
  } catch {
    return null;
  }
}

serve(async (req) => {
  const origin = req.headers.get('origin');
  const corsHeaders = getCorsHeaders(origin);

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

  try {
    const body: P2PMessagesRequest = await req.json();
    const { sessionToken, action, tradeId, message } = body;

    // Get bot tokens for session verification (dual bot support)
    const botTokens: string[] = [];
    const _mainToken = Deno.env.get('TELEGRAM_BOT_TOKEN');
    const _krdToken = Deno.env.get('TELEGRAM_BOT_TOKEN_KRD');
    if (_mainToken) botTokens.push(_mainToken);
    if (_krdToken) botTokens.push(_krdToken);
    if (botTokens.length === 0) {
      return new Response(JSON.stringify({ error: 'Server configuration error' }), {
        status: 500,
        headers: { ...corsHeaders, 'Content-Type': 'application/json' },
      });
    }

    // Validate session token
    if (!sessionToken) {
      return new Response(JSON.stringify({ error: 'Missing session token' }), {
        status: 401,
        headers: { ...corsHeaders, 'Content-Type': 'application/json' },
      });
    }

    let telegramId: number | null = null;
    for (const bt of botTokens) {
      telegramId = verifySessionToken(sessionToken, bt);
      if (telegramId) break;
    }
    if (!telegramId) {
      return new Response(JSON.stringify({ error: 'Invalid or expired session' }), {
        status: 401,
        headers: { ...corsHeaders, 'Content-Type': 'application/json' },
      });
    }

    // Validate required fields
    if (!action || !tradeId) {
      return new Response(JSON.stringify({ error: 'Missing required fields: action, tradeId' }), {
        status: 400,
        headers: { ...corsHeaders, 'Content-Type': 'application/json' },
      });
    }

    if (!['send', 'list'].includes(action)) {
      return new Response(JSON.stringify({ error: 'Invalid action. Must be "send" or "list"' }), {
        status: 400,
        headers: { ...corsHeaders, 'Content-Type': 'application/json' },
      });
    }

    // Create Supabase admin client (bypasses RLS)
    const supabaseUrl = Deno.env.get('SUPABASE_URL')!;
    const supabaseServiceKey = Deno.env.get('SUPABASE_SERVICE_ROLE_KEY')!;
    const supabase = createClient(supabaseUrl, supabaseServiceKey);

    // Get auth user ID for this telegram user
    const telegramEmail = `telegram_${telegramId}@pezkuwichain.io`;
    const {
      data: { users: authUsers },
    } = await supabase.auth.admin.listUsers({ perPage: 1000 });
    const authUser = authUsers?.find((u: { email?: string }) => u.email === telegramEmail);

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

    const userId = authUser.id;

    // Verify user is a party to this trade
    const { data: trade, error: tradeError } = await supabase
      .from('p2p_fiat_trades')
      .select('seller_id, buyer_id')
      .eq('id', tradeId)
      .single();

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

    if (trade.seller_id !== userId && trade.buyer_id !== userId) {
      return new Response(JSON.stringify({ error: 'You are not a party to this trade' }), {
        status: 403,
        headers: { ...corsHeaders, 'Content-Type': 'application/json' },
      });
    }

    // ==================== SEND ====================
    if (action === 'send') {
      if (!message || message.trim().length === 0) {
        return new Response(JSON.stringify({ error: 'Message cannot be empty' }), {
          status: 400,
          headers: { ...corsHeaders, 'Content-Type': 'application/json' },
        });
      }

      const { data: newMessage, error: insertError } = await supabase
        .from('p2p_messages')
        .insert({
          trade_id: tradeId,
          sender_id: userId,
          message: message.trim(),
          message_type: 'text',
        })
        .select()
        .single();

      if (insertError) {
        console.error('Send message error:', insertError);
        return new Response(
          JSON.stringify({ error: 'Failed to send message: ' + insertError.message }),
          {
            status: 500,
            headers: { ...corsHeaders, 'Content-Type': 'application/json' },
          }
        );
      }

      return new Response(
        JSON.stringify({
          success: true,
          messageId: newMessage.id,
        }),
        { headers: { ...corsHeaders, 'Content-Type': 'application/json' } }
      );
    }

    // ==================== LIST ====================
    if (action === 'list') {
      // Fetch all messages for this trade ordered by created_at ASC
      const { data: messages, error: messagesError } = await supabase
        .from('p2p_messages')
        .select('*')
        .eq('trade_id', tradeId)
        .order('created_at', { ascending: true });

      if (messagesError) {
        console.error('List messages error:', messagesError);
        return new Response(
          JSON.stringify({ error: 'Failed to fetch messages: ' + messagesError.message }),
          {
            status: 500,
            headers: { ...corsHeaders, 'Content-Type': 'application/json' },
          }
        );
      }

      // Mark unread messages as read for this user
      // (messages sent by the OTHER party that haven't been read yet)
      const unreadMessageIds = (messages || [])
        .filter((m: { sender_id: string; is_read: boolean; id: string }) => m.sender_id !== userId && !m.is_read)
        .map((m: { id: string }) => m.id);

      if (unreadMessageIds.length > 0) {
        await supabase
          .from('p2p_messages')
          .update({ is_read: true, read_at: new Date().toISOString() })
          .in('id', unreadMessageIds);
      }

      return new Response(
        JSON.stringify({
          success: true,
          messages: messages || [],
        }),
        { headers: { ...corsHeaders, 'Content-Type': 'application/json' } }
      );
    }

    // Should not reach here
    return new Response(JSON.stringify({ error: 'Invalid action' }), {
      status: 400,
      headers: { ...corsHeaders, 'Content-Type': 'application/json' },
    });
  } catch (error) {
    console.error('Error:', error);
    const origin = req.headers.get('origin');
    return new Response(
      JSON.stringify({ error: error instanceof Error ? error.message : 'Internal server error' }),
      {
        status: 500,
        headers: { ...getCorsHeaders(origin), 'Content-Type': 'application/json' },
      }
    );
  }
});