import { serve } from 'https://deno.land/std@0.168.0/http/server.ts';
import { createClient } from 'https://esm.sh/@supabase/supabase-js@2.57.4';
import { corsHeaders } from './cors.ts';
import { rateLimiters, withRateLimit } from '../_shared/rateLimiter.ts';
import { 
  edgeLogger, 
  startSpan, 
  endSpan, 
  addSpanEvent, 
  setSpanAttributes, 
  getSpanContext, 
  logSpan,
  extractSpanContextFromHeaders,
  type Span 
} from '../_shared/logger.ts';

const SUPABASE_URL = Deno.env.get('SUPABASE_URL') || 'https://api.thrillwiki.com';
const SUPABASE_ANON_KEY = Deno.env.get('SUPABASE_ANON_KEY')!;

interface RejectionRequest {
  submissionId: string;
  itemIds: string[];
  rejectionReason: string;
  idempotencyKey: string;
}

// Main handler function
const handler = async (req: Request) => {
  // Handle CORS preflight requests
  if (req.method === 'OPTIONS') {
    return new Response(null, { 
      status: 204,
      headers: corsHeaders 
    });
  }

  // Extract parent span context from headers (if present)
  const parentSpanContext = extractSpanContextFromHeaders(req.headers);

  // Create root span for this edge function invocation
  const rootSpan = startSpan(
    'process-selective-rejection',
    'SERVER',
    parentSpanContext,
    {
      'http.method': 'POST',
      'function.name': 'process-selective-rejection',
    }
  );
  const requestId = rootSpan.spanId;
  
  try {
    // STEP 1: Authentication
    addSpanEvent(rootSpan, 'authentication_start');
    const authHeader = req.headers.get('Authorization');
    if (!authHeader) {
      addSpanEvent(rootSpan, 'authentication_failed', { reason: 'missing_header' });
      endSpan(rootSpan, 'error');
      logSpan(rootSpan);
      return new Response(
        JSON.stringify({ error: 'Missing Authorization header' }),
        { 
          status: 401, 
          headers: { 
            ...corsHeaders,
            'Content-Type': 'application/json' 
          } 
        }
      );
    }

    const supabase = createClient(SUPABASE_URL, SUPABASE_ANON_KEY, {
      global: { headers: { Authorization: authHeader } }
    });

    const { data: { user }, error: authError } = await supabase.auth.getUser();
    if (authError || !user) {
      addSpanEvent(rootSpan, 'authentication_failed', { error: authError?.message });
      edgeLogger.warn('Authentication failed', { 
        requestId,
        error: authError?.message,
        action: 'process_rejection'
      });
      endSpan(rootSpan, 'error', authError || new Error('Unauthorized'));
      logSpan(rootSpan);
      return new Response(
        JSON.stringify({ error: 'Unauthorized' }),
        { 
          status: 401, 
          headers: { 
            ...corsHeaders,
            'Content-Type': 'application/json' 
          } 
        }
      );
    }

    setSpanAttributes(rootSpan, { 'user.id': user.id });
    addSpanEvent(rootSpan, 'authentication_success');
    edgeLogger.info('Rejection request received', { 
      requestId, 
      moderatorId: user.id,
      action: 'process_rejection'
    });

    // STEP 2: Parse request
    addSpanEvent(rootSpan, 'validation_start');
    const body: RejectionRequest = await req.json();
    const { submissionId, itemIds, rejectionReason, idempotencyKey } = body;

    if (!submissionId || !itemIds || itemIds.length === 0 || !rejectionReason) {
      addSpanEvent(rootSpan, 'validation_failed', {
        hasSubmissionId: !!submissionId,
        hasItemIds: !!itemIds,
        itemCount: itemIds?.length || 0,
        hasReason: !!rejectionReason,
      });
      edgeLogger.warn('Invalid request payload', { 
        requestId,
        hasSubmissionId: !!submissionId,
        hasItemIds: !!itemIds,
        itemCount: itemIds?.length || 0,
        hasReason: !!rejectionReason,
        action: 'process_rejection'
      });
      endSpan(rootSpan, 'error');
      logSpan(rootSpan);
      return new Response(
        JSON.stringify({ error: 'Missing required fields: submissionId, itemIds, rejectionReason' }),
        { 
          status: 400, 
          headers: { 
            ...corsHeaders,
            'Content-Type': 'application/json' 
          } 
        }
      );
    }

    setSpanAttributes(rootSpan, {
      'submission.id': submissionId,
      'submission.item_count': itemIds.length,
      'idempotency.key': idempotencyKey,
    });
    addSpanEvent(rootSpan, 'validation_complete');
    edgeLogger.info('Request validated', {
      requestId,
      submissionId,
      itemCount: itemIds.length,
      action: 'process_rejection'
    });

    // STEP 3: Idempotency check
    addSpanEvent(rootSpan, 'idempotency_check_start');
    const { data: existingKey } = await supabase
      .from('submission_idempotency_keys')
      .select('*')
      .eq('idempotency_key', idempotencyKey)
      .single();

    if (existingKey?.status === 'completed') {
      addSpanEvent(rootSpan, 'idempotency_cache_hit');
      setSpanAttributes(rootSpan, { 'cache.hit': true });
      edgeLogger.info('Idempotency cache hit', { 
        requestId, 
        idempotencyKey,
        cached: true,
        action: 'process_rejection'
      });
      endSpan(rootSpan, 'ok');
      logSpan(rootSpan);
      return new Response(
        JSON.stringify(existingKey.result_data),
        {
          status: 200,
          headers: {
            ...corsHeaders,
            'Content-Type': 'application/json',
            'X-Cache-Status': 'HIT'
          }
        }
      );
    }

    // STEP 4: Fetch submission to get submitter_id
    const { data: submission, error: submissionError } = await supabase
      .from('content_submissions')
      .select('user_id, status, assigned_to')
      .eq('id', submissionId)
      .single();

    if (submissionError || !submission) {
      addSpanEvent(rootSpan, 'submission_fetch_failed', { error: submissionError?.message });
      edgeLogger.error('Submission not found', { 
        requestId, 
        submissionId,
        error: submissionError?.message,
        action: 'process_rejection'
      });
      endSpan(rootSpan, 'error', submissionError || new Error('Submission not found'));
      logSpan(rootSpan);
      return new Response(
        JSON.stringify({ error: 'Submission not found' }),
        { 
          status: 404, 
          headers: { 
            ...corsHeaders,
            'Content-Type': 'application/json' 
          } 
        }
      );
    }

    // STEP 5: Verify moderator can reject this submission
    if (submission.assigned_to && submission.assigned_to !== user.id) {
      edgeLogger.warn('Lock conflict', { 
        requestId,
        submissionId,
        lockedBy: submission.assigned_to,
        attemptedBy: user.id,
        action: 'process_rejection'
      });
      return new Response(
        JSON.stringify({ error: 'Submission is locked by another moderator' }),
        { 
          status: 409, 
          headers: { 
            ...corsHeaders,
            'Content-Type': 'application/json' 
          } 
        }
      );
    }

    if (!['pending', 'partially_approved'].includes(submission.status)) {
      edgeLogger.warn('Invalid submission status', { 
        requestId,
        submissionId,
        currentStatus: submission.status,
        expectedStatuses: ['pending', 'partially_approved'],
        action: 'process_rejection'
      });
      return new Response(
        JSON.stringify({ error: 'Submission already processed' }),
        { 
          status: 400, 
          headers: { 
            ...corsHeaders,
            'Content-Type': 'application/json' 
          } 
        }
      );
    }

    // STEP 6: Register idempotency key as processing
    if (!existingKey) {
      await supabase.from('submission_idempotency_keys').insert({
        idempotency_key: idempotencyKey,
        submission_id: submissionId,
        moderator_id: user.id,
        status: 'processing'
      });
    }

    // Create child span for RPC transaction
    const rpcSpan = startSpan(
      'process_rejection_transaction',
      'DATABASE',
      getSpanContext(rootSpan),
      {
        'db.operation': 'rpc',
        'db.function': 'process_rejection_transaction',
        'submission.id': submissionId,
        'submission.item_count': itemIds.length,
      }
    );

    addSpanEvent(rpcSpan, 'rpc_call_start');
    edgeLogger.info('Calling rejection transaction RPC', { 
      requestId, 
      submissionId,
      itemCount: itemIds.length,
      action: 'process_rejection'
    });

    // ============================================================================
    // STEP 7: Call RPC function with deadlock retry logic
    // ============================================================================
    let retryCount = 0;
    const MAX_DEADLOCK_RETRIES = 3;
    let result: any = null;
    let rpcError: any = null;

    while (retryCount <= MAX_DEADLOCK_RETRIES) {
      const { data, error } = await supabase.rpc(
        'process_rejection_transaction',
        {
          p_submission_id: submissionId,
          p_item_ids: itemIds,
          p_moderator_id: user.id,
          p_rejection_reason: rejectionReason,
          p_request_id: requestId,
          p_trace_id: rootSpan.traceId,
          p_parent_span_id: rpcSpan.spanId
        }
      );

      result = data;
      rpcError = error;

      if (!rpcError) {
        // Success!
        addSpanEvent(rpcSpan, 'rpc_call_success', {
          'result.status': data?.status,
          'items.processed': itemIds.length,
        });
        break;
      }

      // Check for deadlock (40P01) or serialization failure (40001)
      if (rpcError.code === '40P01' || rpcError.code === '40001') {
        retryCount++;
        if (retryCount > MAX_DEADLOCK_RETRIES) {
          addSpanEvent(rpcSpan, 'max_retries_exceeded', { attempt: retryCount });
          edgeLogger.error('Max deadlock retries exceeded', { 
            requestId,
            submissionId,
            attempt: retryCount,
            action: 'process_rejection'
          });
          break;
        }

        const backoffMs = 100 * Math.pow(2, retryCount);
        addSpanEvent(rpcSpan, 'deadlock_retry', { attempt: retryCount, backoffMs });
        edgeLogger.warn('Deadlock detected, retrying', { 
          requestId, 
          attempt: retryCount,
          maxAttempts: MAX_DEADLOCK_RETRIES,
          backoffMs,
          action: 'process_rejection'
        });
        await new Promise(r => setTimeout(r, backoffMs));
        continue;
      }

      // Non-retryable error, break immediately
      addSpanEvent(rpcSpan, 'rpc_call_failed', { 
        error: rpcError.message,
        errorCode: rpcError.code 
      });
      break;
    }

    if (rpcError) {
      // Transaction failed - EVERYTHING rolled back automatically by PostgreSQL
      endSpan(rpcSpan, 'error', rpcError);
      logSpan(rpcSpan);
      
      edgeLogger.error('Transaction failed', { 
        requestId, 
        duration: rpcSpan.duration,
        submissionId,
        error: rpcError.message,
        errorCode: rpcError.code,
        retries: retryCount,
        action: 'process_rejection'
      });

      // Update idempotency key to failed
      try {
        await supabase
          .from('submission_idempotency_keys')
          .update({
            status: 'failed',
            error_message: rpcError.message,
            completed_at: new Date().toISOString()
          })
          .eq('idempotency_key', idempotencyKey);
      } catch (updateError) {
        edgeLogger.warn('Failed to update idempotency key', { 
          requestId, 
          idempotencyKey,
          status: 'failed',
          error: updateError instanceof Error ? updateError.message : String(updateError),
          action: 'process_rejection'
        });
        // Non-blocking - continue with error response even if idempotency update fails
      }

      endSpan(rootSpan, 'error', rpcError);
      logSpan(rootSpan);

      return new Response(
        JSON.stringify({
          error: 'Rejection transaction failed',
          message: rpcError.message,
          details: rpcError.details,
          retries: retryCount
        }),
        {
          status: 500,
          headers: {
            ...corsHeaders,
            'Content-Type': 'application/json'
          }
        }
      );
    }

    // RPC succeeded
    endSpan(rpcSpan, 'ok');
    logSpan(rpcSpan);

    setSpanAttributes(rootSpan, {
      'result.status': result?.status,
      'result.final_status': result?.status,
      'retries': retryCount,
    });
    edgeLogger.info('Transaction completed successfully', { 
      requestId, 
      duration: rpcSpan.duration,
      submissionId,
      itemCount: itemIds.length,
      retries: retryCount,
      newStatus: result?.status,
      action: 'process_rejection'
    });

    // STEP 8: Success - update idempotency key
    try {
      await supabase
        .from('submission_idempotency_keys')
        .update({
          status: 'completed',
          result_data: result,
          completed_at: new Date().toISOString()
        })
        .eq('idempotency_key', idempotencyKey);
    } catch (updateError) {
      edgeLogger.warn('Failed to update idempotency key', { 
        requestId, 
        idempotencyKey,
        status: 'completed',
        error: updateError instanceof Error ? updateError.message : String(updateError),
        action: 'process_rejection'
      });
      // Non-blocking - transaction succeeded, so continue with success response
    }

    endSpan(rootSpan, 'ok');
    logSpan(rootSpan);

    return new Response(
      JSON.stringify(result),
      {
        status: 200,
        headers: {
          ...corsHeaders,
          'Content-Type': 'application/json',
          'X-Request-Id': requestId
        }
      }
    );

  } catch (error) {
    endSpan(rootSpan, 'error', error instanceof Error ? error : new Error(String(error)));
    logSpan(rootSpan);
    
    edgeLogger.error('Unexpected error', { 
      requestId, 
      duration: rootSpan.duration,
      error: error instanceof Error ? error.message : String(error),
      stack: error instanceof Error ? error.stack : undefined,
      action: 'process_rejection'
    });
    return new Response(
      JSON.stringify({
        error: 'Internal server error',
        message: error instanceof Error ? error.message : 'Unknown error'
      }),
      { 
        status: 500, 
        headers: { 
          ...corsHeaders,
          'Content-Type': 'application/json' 
        } 
      }
    );
  }
};

// Apply rate limiting: 10 requests per minute per IP (standard tier)
serve(withRateLimit(handler, rateLimiters.standard, corsHeaders));