import { spawn } from 'child_process';
import { db } from '../../src/db'; // Placeholder local DB reference based on standard structure
// Assuming Drizzle-style schemas
import { mergeQueue, pullRequests, stackedPrs, commits } from '../../src/db/schema';
import { eq, asc, and } from 'drizzle-orm';

/**
 * OpenCodeHub Merge Queue Worker
 *
 * Runs as a separate Node daemon. Constantly polls the merge_queue table.
 * Takes the top item, uses the git-rpc-daemon to attempt a merge / run CI,
 * and if successful, applies to main.
 */

async function processQueue() {
  console.log('[MergeQueue] Polling for next available PR...');

  try {
    // Wrap in transaction to avoid race conditions with multiple queue workers
    await db.transaction(async (tx) => {
      // 1. Get highest-priority pending item
      const nextItem = await tx.select()
        .from(mergeQueue)
        .where(eq(mergeQueue.status, 'QUEUED'))
        .orderBy(asc(mergeQueue.position))
        .limit(1)
        .execute();

      if (nextItem.length === 0) return;

      const item = nextItem[0];
      console.log(`[MergeQueue] Processing PR #${item.prId} (Position: ${item.position})`);

      // 2. Mark as processing (lock)
      await tx.update(mergeQueue)
        .set({ status: 'PROCESSING', startedAt: new Date() })
        .where(eq(mergeQueue.id, item.id));

      // 3. Create speculative temporary branch (Via RPC call theoretically)
      // Here we simulate the RPC spawn since we're in the same repository monorepo.
      // git checkout main && git checkout -b merge-test-<pr_id>
      // git merge current-pr
      console.log(`[MergeQueue] Simulating speculative merge for PR #${item.prId}...`);
      
      // Assume success for simulation...
      const testsPass = true; 
      
      if (testsPass) {
        console.log(`[MergeQueue] PR #${item.prId} tests pass. Merging into main.`);
        
        // Finalize merge
        await tx.update(mergeQueue).set({ status: 'MERGED', completedAt: new Date() }).where(eq(mergeQueue.id, item.id));
        await tx.update(pullRequests).set({ status: 'MERGED' }).where(eq(pullRequests.id, item.prId));
        
        // 4. Graphite Parity: Auto-Rebase Dependents
        // Trigger webhooks or internal queue jobs that look for PRs stacked ON TOP of this PR,
        // and rebase them to the new main hash automatically.
        console.log(`[MergeQueue] Emitting auto-rebase events for dependents of PR #${item.prId}`);
      } else {
        console.log(`[MergeQueue] PR #${item.prId} tests failed. Evicting from queue.`);
        await tx.update(mergeQueue).set({ status: 'FAILED', completedAt: new Date() }).where(eq(mergeQueue.id, item.id));
        // Push all others behind it back to re-evaluate against base main
      }
    });
  } catch (err) {
    console.error('[MergeQueue] Error processing queue:', err);
  }

  // Poll again after delay
  setTimeout(processQueue, 5000);
}

// Start polling
processQueue();