#!/usr/bin/env node

/**
 * Hook Validator: Token Checkpoint Enforcement
 *
 * Runs BEFORE any tool execution to enforce token checkpoint reporting.
 * Prevents "framework fade" where pressure checks are skipped.
 *
 * This is architectural enforcement - AI cannot bypass this check.
 *
 * Checks:
 * - Current token estimate vs next checkpoint
 * - If checkpoint overdue: BLOCK and force pressure check
 *
 * Exit codes:
 * 0 = PASS (allow tool execution)
 * 1 = FAIL (block - checkpoint overdue)
 *
 * Copyright 2025 Tractatus Project
 * Licensed under Apache License 2.0
 */

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

const SESSION_STATE_PATH = path.join(__dirname, '../../.claude/session-state.json');
const TOKEN_CHECKPOINTS_PATH = path.join(__dirname, '../../.claude/token-checkpoints.json');

/**
 * Color output
 */
const colors = {
  reset: '\x1b[0m',
  green: '\x1b[32m',
  yellow: '\x1b[33m',
  red: '\x1b[31m',
  cyan: '\x1b[36m'
};

function log(message, color = 'reset') {
  console.log(`${colors[color]}${message}${colors.reset}`);
}

function error(message) {
  log(`  ✗ ${message}`, 'red');
}

function success(message) {
  log(`  ✓ ${message}`, 'green');
}

/**
 * Estimate current token usage
 */
function estimateTokens() {
  try {
    if (!fs.existsSync(SESSION_STATE_PATH)) {
      return 0;
    }

    const sessionState = JSON.parse(fs.readFileSync(SESSION_STATE_PATH, 'utf8'));

    // If token_estimate exists in session state, use it
    if (sessionState.token_estimate && sessionState.token_estimate > 0) {
      return sessionState.token_estimate;
    }

    // Otherwise estimate from message count
    // Rough approximation: 1500 tokens per message (conservative)
    const messageCount = sessionState.message_count || 0;
    return messageCount * 1500;

  } catch (err) {
    // If we can't read session state, assume 0 (fail safe)
    return 0;
  }
}

/**
 * Load checkpoint configuration
 */
function loadCheckpoints() {
  try {
    if (!fs.existsSync(TOKEN_CHECKPOINTS_PATH)) {
      // No checkpoints file = no enforcement
      return null;
    }

    return JSON.parse(fs.readFileSync(TOKEN_CHECKPOINTS_PATH, 'utf8'));
  } catch (err) {
    return null;
  }
}

/**
 * Check if checkpoint is overdue
 */
function checkOverdue(currentTokens, checkpoints) {
  if (!checkpoints) {
    return { overdue: false };
  }

  // Find next incomplete checkpoint
  const nextCheckpoint = checkpoints.checkpoints.find(c => !c.completed);

  if (!nextCheckpoint) {
    // All checkpoints completed
    return { overdue: false };
  }

  // Check if we've passed the checkpoint threshold
  const overdueThreshold = nextCheckpoint.tokens;
  const isOverdue = currentTokens >= overdueThreshold;

  return {
    overdue: isOverdue,
    checkpoint: nextCheckpoint,
    currentTokens: currentTokens,
    threshold: overdueThreshold,
    percentage: nextCheckpoint.percentage
  };
}

/**
 * Main validation
 */
async function main() {
  // Estimate current token usage
  const currentTokens = estimateTokens();

  // Load checkpoints
  const checkpoints = loadCheckpoints();

  if (!checkpoints) {
    // No checkpoints configured - pass
    process.exit(0);
  }

  // Check if checkpoint overdue
  const status = checkOverdue(currentTokens, checkpoints);

  if (status.overdue) {
    log(`\n⚠️  TOKEN CHECKPOINT OVERDUE`, 'yellow');
    log(``, 'reset');
    error(`Current tokens: ~${status.currentTokens.toLocaleString()}`);
    error(`Checkpoint: ${status.threshold.toLocaleString()} tokens (${status.percentage}%)`);
    log(``, 'reset');
    log(`  📊 MANDATORY: Run pressure check before continuing`, 'red');
    log(``, 'reset');
    log(`  Command:`, 'cyan');
    log(`    node scripts/check-session-pressure.js --tokens ${currentTokens}/200000 --messages auto`, 'cyan');
    log(``, 'reset');
    log(`  This checkpoint enforces framework discipline and prevents fade.`, 'yellow');
    log(``, 'reset');

    // Update checkpoints to mark as overdue
    try {
      checkpoints.overdue = true;
      checkpoints.last_check = new Date().toISOString();
      fs.writeFileSync(TOKEN_CHECKPOINTS_PATH, JSON.stringify(checkpoints, null, 2));
    } catch (err) {
      // Non-critical
    }

    process.exit(1);  // BLOCK tool execution
  }

  // Checkpoint not overdue - allow execution
  process.exit(0);
}

main().catch(err => {
  error(`Checkpoint validation error: ${err.message}`);
  process.exit(1);
});