#!/usr/bin/env node
/**
 * ECC Context Monitor — PostToolUse hook
 *
 * Reads bridge file from ecc-metrics-bridge.js and injects agent-facing
 * warnings when thresholds are crossed: context exhaustion, high cost,
 * scope creep, or tool loops.
 */

'use strict';

const fs = require('fs');
const os = require('os');
const path = require('path');
const { sanitizeSessionId, readBridge } = require('../lib/session-bridge');

const CONTEXT_WARNING_PCT = 35;
const CONTEXT_CRITICAL_PCT = 25;
const COST_NOTICE_USD = 5;
const COST_WARNING_USD = 10;
const COST_CRITICAL_USD = 50;
const FILES_WARNING_COUNT = 20;
const LOOP_THRESHOLD = 3;
const STALE_SECONDS = 60;
const DEBOUNCE_CALLS = 5;

/**
 * Get debounce state file path.
 * @param {string} sessionId
 * @returns {string}
 */
function getWarnPath(sessionId) {
  return path.join(os.tmpdir(), `ecc-ctx-warn-${sessionId}.json`);
}

/**
 * Read debounce state.
 * @param {string} sessionId
 * @returns {object}
 */
function readWarnState(sessionId) {
  try {
    return JSON.parse(fs.readFileSync(getWarnPath(sessionId), 'utf8'));
  } catch {
    return { callsSinceWarn: 0, lastSeverity: null };
  }
}

/**
 * Write debounce state.
 * @param {string} sessionId
 * @param {object} state
 */
function writeWarnState(sessionId, state) {
  const target = getWarnPath(sessionId);
  const tmp = `${target}.tmp`;
  fs.writeFileSync(tmp, JSON.stringify(state), 'utf8');
  fs.renameSync(tmp, target);
}

/**
 * Detect tool loops from recent_tools ring buffer.
 * @param {Array} recentTools
 * @returns {{detected: boolean, tool: string, count: number}}
 */
function detectLoop(recentTools) {
  if (!Array.isArray(recentTools) || recentTools.length < LOOP_THRESHOLD) {
    return { detected: false, tool: '', count: 0 };
  }
  const counts = {};
  for (const entry of recentTools) {
    const key = `${entry.tool}:${entry.hash}`;
    counts[key] = (counts[key] || 0) + 1;
  }
  for (const [key, count] of Object.entries(counts)) {
    if (count >= LOOP_THRESHOLD) {
      return { detected: true, tool: key.split(':')[0], count };
    }
  }
  return { detected: false, tool: '', count: 0 };
}

/**
 * Evaluate all warning conditions against bridge data.
 * Returns array of {severity, type, message} sorted by severity desc.
 */
function evaluateConditions(bridge) {
  const warnings = [];
  const remaining = bridge.context_remaining_pct;

  // Context warnings (skip if no context data)
  if (remaining !== null && remaining !== undefined) {
    if (remaining <= CONTEXT_CRITICAL_PCT) {
      warnings.push({
        severity: 3,
        type: 'context',
        message:
          `CONTEXT CRITICAL: ${remaining}% remaining. Context nearly exhausted. ` +
          'Inform the user that context is low and ask how they want to proceed. ' +
          'Do NOT autonomously save state or write handoff files unless the user asks.'
      });
    } else if (remaining <= CONTEXT_WARNING_PCT) {
      warnings.push({
        severity: 2,
        type: 'context',
        message: `CONTEXT WARNING: ${remaining}% remaining. ` + 'Be aware that context is getting limited. Avoid starting new complex work.'
      });
    }
  }

  // Cost warnings
  const cost = bridge.total_cost_usd || 0;
  if (cost > COST_CRITICAL_USD) {
    warnings.push({
      severity: 3,
      type: 'cost',
      message: `COST CRITICAL: Session cost is $${cost.toFixed(2)}. ` + 'Stop and inform the user about high cost before continuing.'
    });
  } else if (cost > COST_WARNING_USD) {
    warnings.push({
      severity: 2,
      type: 'cost',
      message: `COST WARNING: Session cost is $${cost.toFixed(2)}. ` + 'Review whether the current approach justifies the expense.'
    });
  } else if (cost > COST_NOTICE_USD) {
    warnings.push({
      severity: 1,
      type: 'cost',
      message: `COST NOTICE: Session cost is $${cost.toFixed(2)}. ` + 'Consider whether the current approach is efficient.'
    });
  }

  // File scope warning
  const fileCount = bridge.files_modified_count || 0;
  if (fileCount > FILES_WARNING_COUNT) {
    warnings.push({
      severity: 2,
      type: 'scope',
      message: `SCOPE WARNING: ${fileCount} files modified this session. ` + 'Consider whether changes are too scattered.'
    });
  }

  // Loop detection
  const loop = detectLoop(bridge.recent_tools);
  if (loop.detected) {
    warnings.push({
      severity: 2,
      type: 'loop',
      message: `LOOP WARNING: Tool '${loop.tool}' called ${loop.count} times ` + 'with same parameters in last 5 calls. This may indicate a stuck loop.'
    });
  }

  return warnings.sort((a, b) => b.severity - a.severity);
}

/**
 * Map numeric severity to label.
 */
function severityLabel(n) {
  if (n >= 3) return 'critical';
  if (n >= 2) return 'warning';
  return 'notice';
}

/**
 * @param {string} rawInput - Raw JSON string from stdin
 * @returns {string} JSON output with additionalContext or pass-through
 */
function run(rawInput) {
  try {
    const input = rawInput.trim() ? JSON.parse(rawInput) : {};

    const sessionId = sanitizeSessionId(input.session_id) || sanitizeSessionId(process.env.ECC_SESSION_ID) || sanitizeSessionId(process.env.CLAUDE_SESSION_ID);

    if (!sessionId) return rawInput;

    const bridge = readBridge(sessionId);
    if (!bridge) return rawInput;

    // Stale check for context warnings
    const now = Math.floor(Date.now() / 1000);
    const lastTs = bridge.last_timestamp ? Math.floor(new Date(bridge.last_timestamp).getTime() / 1000) : 0;
    const isStale = lastTs > 0 && now - lastTs > STALE_SECONDS;

    // If bridge is stale, null out context data (still check cost/scope/loop)
    const evalBridge = isStale ? { ...bridge, context_remaining_pct: null } : bridge;

    const warnings = evaluateConditions(evalBridge);
    if (warnings.length === 0) return rawInput;

    // Debounce logic
    const warnState = readWarnState(sessionId);
    warnState.callsSinceWarn = (warnState.callsSinceWarn || 0) + 1;

    const topSeverity = severityLabel(warnings[0].severity);
    const severityEscalated = topSeverity === 'critical' && warnState.lastSeverity !== 'critical';

    const isFirst = !warnState.lastSeverity;
    if (!isFirst && warnState.callsSinceWarn < DEBOUNCE_CALLS && !severityEscalated) {
      writeWarnState(sessionId, warnState);
      return rawInput;
    }

    // Reset debounce, emit warning
    warnState.callsSinceWarn = 0;
    warnState.lastSeverity = topSeverity;
    writeWarnState(sessionId, warnState);

    // Combine top 2 warnings
    const message = warnings
      .slice(0, 2)
      .map(w => w.message)
      .join('\n');

    const output = {
      hookSpecificOutput: {
        hookEventName: 'PostToolUse',
        additionalContext: message
      }
    };

    return JSON.stringify(output);
  } catch {
    // Never block tool execution
    return rawInput;
  }
}

if (require.main === module) {
  let data = '';
  const MAX_STDIN = 1024 * 1024;
  process.stdin.setEncoding('utf8');
  process.stdin.on('data', chunk => {
    if (data.length < MAX_STDIN) data += chunk.substring(0, MAX_STDIN - data.length);
  });
  process.stdin.on('end', () => {
    process.stdout.write(run(data));
    process.exit(0);
  });
}

module.exports = { run, evaluateConditions, detectLoop, severityLabel };