#!/usr/bin/env ts-node

/**
 * Phase 0.5 Spike — tmux Control Mode
 * 
 * This is a throwaway PoC to evaluate tmux control mode as an alternative
 * to pipe-pane for streaming pi output.
 * 
 * Usage:
 *   npm run spike-cc
 *   
 * Then in another terminal:
 *   tmux attach -t pi-cc  # Verify parallel attach works
 */

import { spawn, ChildProcess } from 'child_process';
import * as readline from 'readline';

const SESSION_NAME = 'pi-cc';

interface Stats {
  outputEvents: number;
  bytesReceived: number;
  otherEvents: number;
  startTime: number;
}

const stats: Stats = {
  outputEvents: 0,
  bytesReceived: 0,
  otherEvents: 0,
  startTime: Date.now(),
};

/**
 * Decode tmux's octal-escaped output format.
 * Example: "hello\\012world" -> "hello\nworld"
 */
function decodeOctalEscapes(input: string): Buffer {
  const chunks: number[] = [];
  let i = 0;
  
  while (i < input.length) {
    if (input[i] === '\\' && i + 3 < input.length) {
      // Check if next 3 chars are octal digits
      const octalStr = input.substring(i + 1, i + 4);
      if (/^[0-7]{3}$/.test(octalStr)) {
        const charCode = parseInt(octalStr, 8);
        chunks.push(charCode);
        i += 4;
        continue;
      }
    }
    
    // Regular character
    chunks.push(input.charCodeAt(i));
    i++;
  }
  
  return Buffer.from(chunks);
}

/**
 * Parse a control mode notification line.
 */
function parseNotification(line: string): { type: string; data: string } | null {
  if (!line.startsWith('%')) {
    return null;
  }
  
  const spaceIdx = line.indexOf(' ');
  if (spaceIdx === -1) {
    return { type: line.substring(1), data: '' };
  }
  
  return {
    type: line.substring(1, spaceIdx),
    data: line.substring(spaceIdx + 1),
  };
}

/**
 * Handle a %output notification.
 */
function handleOutputEvent(data: string): void {
  // Format: %output %<pane-id> <value>
  const parts = data.split(' ', 2);
  if (parts.length < 2) {
    console.error('[spike-cc] Invalid %output format:', data);
    return;
  }
  
  const paneId = parts[0]; // e.g., "%1"
  const escapedValue = parts[1];
  
  // Decode octal escapes and write to stdout
  const decoded = decodeOctalEscapes(escapedValue);
  
  stats.outputEvents++;
  stats.bytesReceived += decoded.length;
  
  // Write to stdout (this is our streaming output)
  process.stdout.write(decoded);
}

/**
 * Main control mode loop.
 */
function runControlMode(): void {
  console.error('[spike-cc] Starting tmux control mode spike...');
  console.error('[spike-cc] Session name:', SESSION_NAME);
  console.error('[spike-cc] Creating detached session first...');
  
  // Step 1: Create detached session with pi
  const createSession = spawn('tmux', [
    'new-session',
    '-d',
    '-s', SESSION_NAME,
    '-x', '120',
    '-y', '40',
    'pi'
  ]);
  
  createSession.on('close', (code) => {
    if (code !== 0) {
      console.error('[spike-cc] Failed to create session, code:', code);
      console.error('[spike-cc] (This is OK if session already exists)');
    }
    
    // Step 2: Attach in control mode
    console.error('[spike-cc] Attaching in control mode...');
    console.error('[spike-cc] ---------------------------------------------');
    console.error('[spike-cc] Pi output will stream below (raw bytes).');
    console.error('[spike-cc] Stats will be written to stderr every 10s.');
    console.error('[spike-cc] To attach normally: tmux attach -t', SESSION_NAME);
    console.error('[spike-cc] ---------------------------------------------');
    
    const tmuxControl = spawn('tmux', ['-C', 'attach', '-t', SESSION_NAME], {
      stdio: ['pipe', 'pipe', 'pipe'],
    });
    
    // Keep stdin open (don't send EOF)
    // This prevents tmux from thinking the control client disconnected
    
    // Read control mode output line by line
    const rl = readline.createInterface({
      input: tmuxControl.stdout,
      crlfDelay: Infinity,
    });
    
    rl.on('line', (line) => {
      const notification = parseNotification(line);
      
      if (!notification) {
        // Not a notification, probably command response
        return;
      }
      
      if (notification.type === 'output') {
        handleOutputEvent(notification.data);
      } else if (notification.type === 'exit') {
        console.error('\n[spike-cc] Received %exit, shutting down...');
        process.exit(0);
      } else {
        // Other events (layout-change, window-add, etc.)
        stats.otherEvents++;
        // Log first few for debugging
        if (stats.otherEvents <= 5) {
          console.error(`[spike-cc] Event: %${notification.type}`);
        }
      }
    });
    
    tmuxControl.stderr.on('data', (data) => {
      console.error('[spike-cc] tmux stderr:', data.toString());
    });
    
    tmuxControl.on('close', (code) => {
      console.error('\n[spike-cc] tmux process exited, code:', code);
      printFinalStats();
      process.exit(code || 0);
    });
    
    // Stats reporter
    const statsInterval = setInterval(() => {
      printStats();
    }, 10000);
    
    // Cleanup on exit
    process.on('SIGINT', () => {
      console.error('\n[spike-cc] Caught SIGINT, cleaning up...');
      clearInterval(statsInterval);
      tmuxControl.kill();
      printFinalStats();
      process.exit(0);
    });
  });
}

function printStats(): void {
  const elapsed = ((Date.now() - stats.startTime) / 1000).toFixed(1);
  console.error(`\n[spike-cc] === Stats @ ${elapsed}s ===`);
  console.error(`[spike-cc]   Output events: ${stats.outputEvents}`);
  console.error(`[spike-cc]   Bytes received: ${stats.bytesReceived}`);
  console.error(`[spike-cc]   Other events: ${stats.otherEvents}`);
  console.error(`[spike-cc]   Rate: ${(stats.outputEvents / parseFloat(elapsed)).toFixed(2)} events/s`);
}

function printFinalStats(): void {
  const elapsed = ((Date.now() - stats.startTime) / 1000).toFixed(1);
  console.error('\n[spike-cc] === Final Stats ===');
  console.error(`[spike-cc]   Total time: ${elapsed}s`);
  console.error(`[spike-cc]   Output events: ${stats.outputEvents}`);
  console.error(`[spike-cc]   Bytes received: ${stats.bytesReceived}`);
  console.error(`[spike-cc]   Other events: ${stats.otherEvents}`);
}

// Run
runControlMode();