import { serve } from 'https://deno.land/std@0.190.0/http/server.ts';
import { createEdgeFunction } from '../_shared/edgeFunctionWrapper.ts';
import { corsHeadersWithTracing } from '../_shared/cors.ts';
import { 
  addSpanEvent, 
  setSpanAttributes, 
  getSpanContext, 
  startSpan,
  endSpan,
} from '../_shared/logger.ts';
import { toError } from '../_shared/errorFormatter.ts';
import { 
  validateApprovalRequest,
} from '../_shared/submissionValidation.ts';
import { ValidationError } from '../_shared/typeValidation.ts';

// Main handler function
const handler = async (req: Request, context: { supabase: any; user: any; span: any; requestId: string }) => {
  const { supabase, user, span: rootSpan, requestId } = context;

  // Early logging - confirms request reached handler
  addSpanEvent(rootSpan, 'handler_entry', { 
    requestId, 
    userId: user.id,
    timestamp: Date.now() 
  });

  setSpanAttributes(rootSpan, { 
    'user.id': user.id,
    'function.name': 'process-selective-approval' 
  });

  // Health check endpoint
  if (req.url.includes('/health')) {
    addSpanEvent(rootSpan, 'health_check_start');
    const { data, error } = await supabase
      .from('content_submissions')
      .select('count')
      .limit(1);
    
    addSpanEvent(rootSpan, 'health_check_complete', { 
      dbConnected: !error,
      error: error?.message 
    });

    return new Response(JSON.stringify({ 
      status: 'ok', 
      dbConnected: !error,
      timestamp: Date.now(),
      error: error?.message
    }), { 
      headers: { 'Content-Type': 'application/json' },
      status: error ? 500 : 200
    });
  }

  // STEP 1: Parse and validate request
  addSpanEvent(rootSpan, 'validation_start');
  
  let submissionId: string;
  let itemIds: string[];
  
  try {
    const body = await req.json();
    const validated = validateApprovalRequest(body, requestId);
    submissionId = validated.submissionId;
    itemIds = validated.itemIds;
  } catch (error) {
    if (error instanceof ValidationError) {
      addSpanEvent(rootSpan, 'validation_failed', {
        field: error.field,
        expected: error.expected,
        received: error.received,
      });
      throw error; // Will be caught by wrapper
    }
    throw error;
  }
  
  const idempotencyKey = req.headers.get('x-idempotency-key');
  if (!idempotencyKey) {
    addSpanEvent(rootSpan, 'validation_failed', { reason: 'missing_idempotency_key' });
    throw new ValidationError('idempotency_key', 'Missing X-Idempotency-Key header', 'string', 'undefined');
  }

  setSpanAttributes(rootSpan, {
    'submission.id': submissionId,
    'submission.item_count': itemIds.length,
    'idempotency.key': idempotencyKey,
  });
  addSpanEvent(rootSpan, 'validation_complete');

  // STEP 2: Idempotency check with timeout
  addSpanEvent(rootSpan, 'idempotency_check_start');
  
  const idempotencyCheckPromise = supabase
    .from('submission_idempotency_keys')
    .select('*')
    .eq('idempotency_key', idempotencyKey)
    .single();

  // Add 5 second timeout for idempotency check
  const timeoutPromise = new Promise((_, reject) => 
    setTimeout(() => reject(new Error('Idempotency check timed out after 5s')), 5000)
  );

  let existingKey;
  try {
    const result = await Promise.race([
      idempotencyCheckPromise,
      timeoutPromise
    ]) as any;
    existingKey = result.data;
  } catch (timeoutError: any) {
    addSpanEvent(rootSpan, 'idempotency_check_timeout', { error: timeoutError.message });
    throw new Error(`Database query timeout: ${timeoutError.message}`);
  }
  
  addSpanEvent(rootSpan, 'idempotency_check_complete', { 
    foundKey: !!existingKey,
    status: existingKey?.status 
  });

  if (existingKey?.status === 'completed') {
    addSpanEvent(rootSpan, 'idempotency_cache_hit');
    setSpanAttributes(rootSpan, { 'cache.hit': true });
    return new Response(
      JSON.stringify(existingKey.result_data),
      {
        status: 200,
        headers: { 'X-Cache-Status': 'HIT' }
      }
    );
  }

  // STEP 3: 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 });
    throw new Error('Submission not found');
  }

  // STEP 4: Verify moderator can approve this submission
  if (submission.assigned_to && submission.assigned_to !== user.id) {
    throw new Error('Submission is locked by another moderator');
  }

  if (!['pending', 'partially_approved'].includes(submission.status)) {
    throw new Error('Submission already processed');
  }

  // STEP 5: Register idempotency key as processing (atomic upsert)
  if (!existingKey) {
    const { data: insertedKey, error: idempotencyError } = await supabase
      .from('submission_idempotency_keys')
      .insert({
        idempotency_key: idempotencyKey,
        submission_id: submissionId,
        moderator_id: user.id,
        item_ids: itemIds,
        status: 'processing'
      })
      .select()
      .single();

    if (idempotencyError && idempotencyError.code === '23505') {
      throw new Error('Another moderator is processing this submission');
    }

    if (idempotencyError) {
      throw toError(idempotencyError);
    }
  }

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

  addSpanEvent(rpcSpan, 'rpc_call_start');

  // STEP 6: 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_approval_transaction',
      {
        p_submission_id: submissionId,
        p_item_ids: itemIds,
        p_moderator_id: user.id,
        p_submitter_id: submission.user_id,
        p_request_id: requestId,
        p_trace_id: rootSpan.traceId,
        p_parent_span_id: rpcSpan.spanId
      }
    );

    result = data;
    rpcError = error;

    if (!rpcError) {
      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 });
        break;
      }

      const backoffMs = 100 * Math.pow(2, retryCount);
      addSpanEvent(rpcSpan, 'deadlock_retry', { attempt: retryCount, backoffMs });
      await new Promise(r => setTimeout(r, backoffMs));
      continue;
    }

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

  if (rpcError) {
    endSpan(rpcSpan, 'error', rpcError);
    
    // 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) {
      // Non-blocking
    }
    throw toError(rpcError);
  }

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

  setSpanAttributes(rootSpan, {
    'result.status': result?.status,
    'result.final_status': result?.status,
    'retries': retryCount,
  });

  // STEP 7: 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) {
    // Non-blocking - transaction succeeded, so continue with success response
  }

  return result;
};

// Create edge function with automatic error handling, CORS, auth, and logging
serve(createEdgeFunction(
  {
    name: 'process-selective-approval',
    requireAuth: true,
    corsHeaders: corsHeadersWithTracing,
  },
  handler
));