#!/usr/bin/env node
/**
 * Token Checkpoint Monitor Hook
 *
 * Runs after tool execution to check if token usage has exceeded checkpoints.
 * Enforces inst_075: Token checkpoint monitoring is MANDATORY, not optional.
 *
 * This hook reads system context to extract current token count and compares
 * against checkpoints in .claude/token-checkpoints.json.
 */

const fs = require('fs');
const path = require('path');

const input = JSON.parse(process.argv[2] || '{}');

// Extract token usage from system warnings in context
// Claude Code provides token counts in <system_warning> tags
const contextText = JSON.stringify(input);
const tokenMatch = contextText.match(/Token usage: (\d+)\/(\d+)/);

if (!tokenMatch) {
  // No token info available - skip silently
  process.exit(0);
}

const currentTokens = parseInt(tokenMatch[1]);
const budgetTokens = parseInt(tokenMatch[2]);

// Read checkpoint configuration
const checkpointPath = path.join(__dirname, '../token-checkpoints.json');
let checkpoints;

try {
  checkpoints = JSON.parse(fs.readFileSync(checkpointPath, 'utf8'));
} catch (err) {
  console.error('\x1b[31m❌ Failed to read token-checkpoints.json\x1b[0m');
  process.exit(0);
}

const nextCheckpoint = checkpoints.next_checkpoint;

// Check if we've passed a checkpoint
if (currentTokens > nextCheckpoint) {
  console.log('\x1b[33m⚠️  TOKEN CHECKPOINT EXCEEDED\x1b[0m');
  console.log(`\x1b[36mCurrent: ${currentTokens.toLocaleString()} / ${budgetTokens.toLocaleString()} tokens (${((currentTokens/budgetTokens)*100).toFixed(1)}%)\x1b[0m`);
  console.log(`\x1b[36mCheckpoint: ${nextCheckpoint.toLocaleString()} tokens\x1b[0m`);
  console.log('\x1b[31m📊 MANDATORY: Run checkpoint analysis NOW\x1b[0m');
  console.log(`\x1b[36mnode scripts/check-token-checkpoint.js --tokens ${currentTokens}/${budgetTokens}\x1b[0m`);
  console.log('\x1b[36mSee inst_075 for checkpoint requirements\x1b[0m');
  process.exit(0);
}

// Approaching checkpoint - warn at 90%
const approachThreshold = nextCheckpoint * 0.9;
if (currentTokens > approachThreshold) {
  const remaining = nextCheckpoint - currentTokens;
  console.log(`\x1b[33m⚠️  Approaching ${(nextCheckpoint/budgetTokens*100)}% checkpoint: ${remaining.toLocaleString()} tokens remaining\x1b[0m`);
}

process.exit(0);