import { readdirSync, statSync, existsSync, openSync, readSync, closeSync } from 'node:fs';

import { homedir } from 'node:os';

import { join, resolve, sep } from 'node:path';

export function mungePath(absPath) {

  return absPath.replace(/[^A-Za-z0-9-]/g, '-');

}

const CWD_PROBE_BYTES = 65536;

const CWD_RE = /"cwd"\s*:\s*"((?:[^"\\]|\\.)*)"/;

export function recordedCwd(filePath) {

  let fd;

  try {

    fd = openSync(filePath, 'r');

    const buf = Buffer.alloc(CWD_PROBE_BYTES);

    const bytes = readSync(fd, buf, 0, CWD_PROBE_BYTES, 0);

    const head = buf.toString('utf8', 0, bytes);

    const m = head.match(CWD_RE);

    if (!m) return null;

    try {

      return JSON.parse(`"${m[1]}"`);

    } catch {

      return m[1];

    }

  } catch {

    return null;

  } finally {

    if (fd !== undefined) {

      try {

        closeSync(fd);

      } catch {

      }

    }

  }

}

export function claudeProjectsRoot() {

  return process.env.CLAUDE_CONFIG_DIR

    ? join(process.env.CLAUDE_CONFIG_DIR, 'projects')

    : join(homedir(), '.claude', 'projects');

}

export function discoverSessions(projectDir) {

  const root = claudeProjectsRoot();

  if (!existsSync(root)) return [];

  const abs = resolve(projectDir);

  const exact = mungePath(abs);

  const prefix = mungePath(abs + sep);

  const sessions = [];

  for (const entry of readdirSync(root, { withFileTypes: true })) {

    if (!entry.isDirectory()) continue;

    if (entry.name !== exact && !entry.name.startsWith(prefix)) continue;

    const dir = join(root, entry.name);

    for (const f of readdirSync(dir, { withFileTypes: true })) {

      if (!f.isFile() || !f.name.endsWith('.jsonl')) continue;

      const path = join(dir, f.name);

      let st;

      try {

        st = statSync(path);

      } catch {

        continue;

      }

      const cwd = recordedCwd(path);

      if (cwd && resolve(cwd) !== abs) continue;

      sessions.push({

        path,

        sessionId: f.name.replace(/\.jsonl$/, ''),

        sizeBytes: st.size,

        mtimeMs: st.mtimeMs,

        storageDir: entry.name,

      });

    }

  }

  sessions.sort((a, b) => a.mtimeMs - b.mtimeMs);

  return sessions;

}