/*
 * Local server for the SDE meeting toolkit.
 * Serves the static tool files.
 * Proxies AI draft requests to the Anthropic API, so the API key
 * stays on the server and never appears in the browser.
 * Identifies each caller by login and enforces a daily token quota per person.
 */
const http = require('http');
const fs = require('fs');
const path = require('path');

const ROOT = __dirname;
const PORT = process.env.PORT || 5173;
const ANTHROPIC_VERSION = '2023-06-01';

const MIME = {
  '.html': 'text/html; charset=utf-8',
  '.js': 'text/javascript; charset=utf-8',
  '.css': 'text/css; charset=utf-8',
  '.json': 'application/json; charset=utf-8',
  '.svg': 'image/svg+xml',
  '.png': 'image/png',
  '.skill': 'application/zip'
};

function loadEnvFile() {
  const envPath = path.join(ROOT, '.env');
  let content;
  try {
    content = fs.readFileSync(envPath, 'utf8');
  } catch (err) {
    return; // no .env file; that is allowed, the AI draft route will report it
  }
  content.split('\n').forEach((line) => {
    const trimmed = line.trim();
    if (!trimmed || trimmed.startsWith('#')) return;
    const idx = trimmed.indexOf('=');
    if (idx === -1) return;
    const key = trimmed.slice(0, idx).trim();
    const value = trimmed.slice(idx + 1).trim().replace(/^["']|["']$/g, '');
    if (key && !(key in process.env)) process.env[key] = value;
  });
}
loadEnvFile();

function sendJson(res, status, obj) {
  const body = JSON.stringify(obj);
  res.writeHead(status, { 'Content-Type': 'application/json; charset=utf-8' });
  res.end(body);
}

/* ===== Access control =====
 * Named users. Set APP_USERS as a comma-separated list of user:password
 * pairs, for example: APP_USERS=alice:pass1,bob:pass2
 * Each name is also the identity used for the daily token quota below.
 *
 * Legacy single-user mode: set APP_USERNAME and APP_PASSWORD instead. That
 * name becomes the one identity everyone shares (no per-person quota).
 *
 * Leave all of the above unset for solo local use: no login prompt, and
 * usage is tracked under the identity "local".
 *
 * This is a simple shared-credential gate, meant to sit behind the company
 * VPN and internal network, not to replace them. */
function loadUserMap() {
  const map = {};
  if (process.env.APP_USERS) {
    process.env.APP_USERS.split(',').forEach((pair) => {
      const idx = pair.indexOf(':');
      if (idx === -1) return;
      const name = pair.slice(0, idx).trim();
      const pass = pair.slice(idx + 1).trim();
      if (name && pass) map[name] = pass;
    });
  } else if (process.env.APP_USERNAME && process.env.APP_PASSWORD) {
    map[process.env.APP_USERNAME] = process.env.APP_PASSWORD;
  }
  return map;
}
const USER_MAP = loadUserMap();
const AUTH_REQUIRED = Object.keys(USER_MAP).length > 0;

// Returns the identified username on success, or null on failure.
function checkBasicAuth(req) {
  if (!AUTH_REQUIRED) return 'local';
  const header = req.headers['authorization'] || '';
  if (!header.startsWith('Basic ')) return null;
  let decoded;
  try {
    decoded = Buffer.from(header.slice(6), 'base64').toString('utf8');
  } catch (err) {
    return null;
  }
  const idx = decoded.indexOf(':');
  if (idx === -1) return null;
  const name = decoded.slice(0, idx);
  const pass = decoded.slice(idx + 1);
  return USER_MAP[name] === pass ? name : null;
}
function requireAuth(res) {
  res.writeHead(401, {
    'WWW-Authenticate': 'Basic realm="SDE Meeting Toolkit"',
    'Content-Type': 'text/plain'
  });
  res.end('Authentication required.');
}

/* ===== Rate limiting for the AI proxy =====
 * Caps AI draft calls per source IP, independent of the token quota below.
 * This catches a runaway script quickly, before it burns through a whole
 * day's token quota in a few seconds. Resets if the process restarts. */
const RATE_LIMIT_MAX = parseInt(process.env.RATE_LIMIT_MAX || '20', 10);
const RATE_LIMIT_WINDOW_MS = parseInt(process.env.RATE_LIMIT_WINDOW_MS || String(5 * 60 * 1000), 10);
const rateLimitHits = new Map();
function isRateLimited(ip) {
  const now = Date.now();
  const hits = (rateLimitHits.get(ip) || []).filter((t) => now - t < RATE_LIMIT_WINDOW_MS);
  hits.push(now);
  rateLimitHits.set(ip, hits);
  return hits.length > RATE_LIMIT_MAX;
}

/* ===== Per-user daily token quota (off by default) =====
 * On the back burner: real usage does not look large enough to justify
 * running this. Left in place, disabled, in case that changes. Set
 * TOKEN_LIMIT_PER_USER to a positive number to turn it back on; leave it
 * unset or 0 for unlimited, which skips the check and the usage file.
 *
 * TOKEN_LIMIT_PER_USER caps combined input+output tokens per identified user,
 * per UTC calendar day. Usage is written to TOKEN_USAGE_FILE after every AI
 * call, so it survives a container restart. Mount that file's folder as a
 * volume in Docker or it resets on every redeploy.
 *
 * The check runs before the API call using the day's tally so far: if the
 * user is already at or over the limit, the call is refused with no cost.
 * A single call in progress when the limit is reached can still push the
 * tally past the cap by that one call's tokens; the next call is blocked.
 * That is an accepted tradeoff, since real token cost of a call is only
 * known once its response returns. */
const TOKEN_LIMIT_PER_USER = parseInt(process.env.TOKEN_LIMIT_PER_USER || '0', 10);
const TOKEN_LIMIT_ENABLED = TOKEN_LIMIT_PER_USER > 0;
const TOKEN_USAGE_FILE = process.env.TOKEN_USAGE_FILE || path.join(ROOT, 'data', 'token-usage.json');

function todayUTC() {
  return new Date().toISOString().slice(0, 10); // "YYYY-MM-DD"
}
function loadUsage() {
  try {
    return JSON.parse(fs.readFileSync(TOKEN_USAGE_FILE, 'utf8'));
  } catch (err) {
    return {};
  }
}
function saveUsage(usage) {
  try {
    fs.mkdirSync(path.dirname(TOKEN_USAGE_FILE), { recursive: true });
    fs.writeFileSync(TOKEN_USAGE_FILE, JSON.stringify(usage));
  } catch (err) {
    console.error('Could not write token usage file:', err.message);
  }
}
function usedTokensToday(usage, user) {
  const rec = usage[user];
  if (!rec || rec.date !== todayUTC()) return 0;
  return rec.tokens;
}
function addTokens(user, tokens) {
  const usage = loadUsage();
  const today = todayUTC();
  const rec = usage[user] && usage[user].date === today ? usage[user] : { date: today, tokens: 0 };
  rec.tokens += tokens;
  usage[user] = rec;
  saveUsage(usage);
  return rec.tokens;
}
function secondsUntilUTCMidnight() {
  const now = new Date();
  const midnight = new Date(Date.UTC(now.getUTCFullYear(), now.getUTCMonth(), now.getUTCDate() + 1));
  return Math.round((midnight - now) / 1000);
}

/* ===== Mock mode =====
 * Set MOCK_AI=true to test the whole app, including the AI draft button and
 * the token quota above, with no API key and no real API call. Returns a
 * canned breadcrumb draft with a synthetic usage count, shaped like a real
 * Anthropic response, so the frontend parsing, gate checks, and quota
 * accounting all run exactly as they would against the live API. */
function mockClaudeResponse(res, user) {
  const draft = {
    domain: 'MOCK: Progress Visibility',
    driver: 'MOCK driver: schedule forecasts drift from field reality.',
    cap: 'MOCK capability: a rules-of-credit progress check against the field.',
    metric: 'MOCK metric: claiming accuracy, reported % vs field-verified %, by phase.',
    method: 'MOCK method: monthly spot audit of 30+ sampled assets.',
    baseline: 'MOCK baseline: first audit result.'
  };
  const usage = { input_tokens: 950, output_tokens: 280 };
  const body = {
    content: [{ type: 'text', text: JSON.stringify(draft) }],
    usage
  };
  if (TOKEN_LIMIT_ENABLED) addTokens(user, usage.input_tokens + usage.output_tokens);
  res.writeHead(200, { 'Content-Type': 'application/json; charset=utf-8' });
  res.end(JSON.stringify(body));
}

function proxyToClaude(req, res, user) {
  if (String(process.env.MOCK_AI).toLowerCase() === 'true') {
    mockClaudeResponse(res, user);
    return;
  }
  if (!process.env.ANTHROPIC_API_KEY) {
    sendJson(res, 500, {
      error: 'ANTHROPIC_API_KEY is not set. Add it to the .env file in this folder, then restart the server.'
    });
    return;
  }
  let body = '';
  req.on('data', (chunk) => { body += chunk; });
  req.on('end', async () => {
    try {
      const upstream = await fetch('https://api.anthropic.com/v1/messages', {
        method: 'POST',
        headers: {
          'Content-Type': 'application/json',
          'x-api-key': process.env.ANTHROPIC_API_KEY,
          'anthropic-version': ANTHROPIC_VERSION
        },
        body
      });
      const text = await upstream.text();
      res.writeHead(upstream.status, { 'Content-Type': 'application/json; charset=utf-8' });
      res.end(text);
      if (TOKEN_LIMIT_ENABLED) {
        try {
          const parsed = JSON.parse(text);
          if (parsed.usage) {
            addTokens(user, (parsed.usage.input_tokens || 0) + (parsed.usage.output_tokens || 0));
          }
        } catch (err) {
          // Response was not JSON, or had no usage field. Nothing to record.
        }
      }
    } catch (err) {
      sendJson(res, 502, { error: 'Could not reach the Anthropic API: ' + err.message });
    }
  });
}

function serveStatic(req, res) {
  const urlPath = decodeURIComponent(req.url.split('?')[0]);
  if (urlPath === '/') {
    const index = `<!doctype html><html><body style="font:14px system-ui;padding:2rem">
      <h1>SDE Meeting Toolkit</h1>
      <ul>
        <li><a href="/tools/field-problem-workshop.html">Field Problem Workshop</a></li>
        <li><a href="/tools/scope-lock-meeting-suite.html">Scope Lock Meeting Suite</a></li>
      </ul>
    </body></html>`;
    res.writeHead(200, { 'Content-Type': 'text/html; charset=utf-8' });
    res.end(index);
    return;
  }
  const filePath = path.normalize(path.join(ROOT, urlPath));
  if (!filePath.startsWith(ROOT)) {
    res.writeHead(403);
    res.end('Forbidden');
    return;
  }
  fs.readFile(filePath, (err, data) => {
    if (err) {
      res.writeHead(404, { 'Content-Type': 'text/plain' });
      res.end('Not found: ' + urlPath);
      return;
    }
    const ext = path.extname(filePath);
    res.writeHead(200, { 'Content-Type': MIME[ext] || 'application/octet-stream' });
    res.end(data);
  });
}

const server = http.createServer((req, res) => {
  const user = checkBasicAuth(req);
  if (!user) {
    requireAuth(res);
    return;
  }
  if (req.method === 'POST' && req.url === '/api/claude') {
    const ip = req.socket.remoteAddress || 'unknown';
    if (isRateLimited(ip)) {
      sendJson(res, 429, { error: `Rate limit reached (${RATE_LIMIT_MAX} AI drafts per ${Math.round(RATE_LIMIT_WINDOW_MS / 60000)} min). Wait a bit and try again.` });
      return;
    }
    if (TOKEN_LIMIT_ENABLED) {
      const usedToday = usedTokensToday(loadUsage(), user);
      if (usedToday >= TOKEN_LIMIT_PER_USER) {
        sendJson(res, 429, {
          error: `Daily token quota reached (${usedToday}/${TOKEN_LIMIT_PER_USER} tokens for "${user}"). Resets in ${secondsUntilUTCMidnight()}s, at UTC midnight.`
        });
        return;
      }
    }
    proxyToClaude(req, res, user);
    return;
  }
  if (req.method === 'GET') {
    serveStatic(req, res);
    return;
  }
  res.writeHead(405, { 'Content-Type': 'text/plain' });
  res.end('Method not allowed');
});

server.listen(PORT, () => {
  console.log(`SDE meeting toolkit running at http://localhost:${PORT}`);
  if (String(process.env.MOCK_AI).toLowerCase() === 'true') {
    console.log('MOCK_AI=true: AI draft button returns a canned response. No API key used or needed.');
  } else {
    console.log(process.env.ANTHROPIC_API_KEY ? 'ANTHROPIC_API_KEY loaded: AI draft button is live.' : 'No ANTHROPIC_API_KEY found: AI draft button will return an error until you add one to .env.');
  }
  console.log(AUTH_REQUIRED ? `Login required: ${Object.keys(USER_MAP).length} named user(s) configured.` : 'No login required: no APP_USERS or APP_USERNAME/APP_PASSWORD are set.');
  console.log(TOKEN_LIMIT_ENABLED ? `Per-user daily token quota: ${TOKEN_LIMIT_PER_USER} tokens. Usage file: ${TOKEN_USAGE_FILE}` : 'No per-user token quota: TOKEN_LIMIT_PER_USER is unset or 0 (unlimited, feature on the back burner).');
});