import { spawn } from 'node:child_process';
import type { FastifyBaseLogger } from 'fastify';

// UUIDs already match [0-9a-f-]; allow uppercase and longer just in case.
const ID_RE = /^[a-zA-Z0-9_-]{1,64}$/;

export function sanitizeId(raw: string): string | null {
  if (!ID_RE.test(raw)) return null;
  return raw.toLowerCase();
}

export function tmuxSessionName(sessionId: string): string {
  return `bc-${sessionId}`;
}

export function tmuxWindowName(paneId: string): string {
  return `term-${paneId}`;
}

interface CmdResult {
  stdout: string;
  stderr: string;
  code: number;
}

// Wrap child_process.spawn with shell:false so each argv element is passed
// as a separate argument — no shell interpolation, no injection surface.
function runTmux(tmuxConfPath: string, args: string[]): Promise<CmdResult> {
  return new Promise((resolve) => {
    const child = spawn('tmux', ['-f', tmuxConfPath, ...args], { shell: false });
    let stdout = '';
    let stderr = '';
    child.stdout.on('data', (chunk: Buffer) => { stdout += chunk.toString('utf8'); });
    child.stderr.on('data', (chunk: Buffer) => { stderr += chunk.toString('utf8'); });
    child.on('error', (err) => {
      resolve({ stdout, stderr: stderr + String(err), code: 1 });
    });
    child.on('close', (code) => {
      resolve({ stdout, stderr, code: code ?? 0 });
    });
  });
}

export async function hasSession(tmuxConfPath: string, sessionName: string): Promise<boolean> {
  const res = await runTmux(tmuxConfPath, ['has-session', '-t', `=${sessionName}`]);
  return res.code === 0;
}

export async function listWindows(tmuxConfPath: string, sessionName: string): Promise<string[]> {
  const res = await runTmux(tmuxConfPath, ['list-windows', '-t', sessionName, '-F', '#{window_name}']);
  if (res.code !== 0) return [];
  return res.stdout.trim().split('\n').filter(Boolean);
}

export async function killWindow(
  tmuxConfPath: string,
  sessionName: string,
  windowName: string,
): Promise<boolean> {
  const res = await runTmux(tmuxConfPath, ['kill-window', '-t', `${sessionName}:${windowName}`]);
  return res.code === 0;
}

// Idempotent. Creates the tmux session if it doesn't exist, then ensures the
// named window is present. The session's initial window is created with the
// target name (via `-n`) so we don't need a separate rename step.
export async function ensureWindow(
  tmuxConfPath: string,
  sessionName: string,
  windowName: string,
  projectRoot: string,
  log: FastifyBaseLogger,
): Promise<void> {
  if (!(await hasSession(tmuxConfPath, sessionName))) {
    log.info({ sessionName, windowName, projectRoot }, 'creating tmux session');
    const res = await runTmux(tmuxConfPath, [
      'new-session', '-d',
      '-s', sessionName,
      '-n', windowName,
      '-c', projectRoot,
    ]);
    if (res.code !== 0) {
      log.error({ res }, 'tmux new-session failed');
      throw new Error(`tmux new-session failed: ${res.stderr}`);
    }
    return;
  }

  const windows = await listWindows(tmuxConfPath, sessionName);
  if (windows.includes(windowName)) return;

  const res = await runTmux(tmuxConfPath, [
    'new-window',
    '-t', sessionName,
    '-n', windowName,
    '-c', projectRoot,
  ]);
  if (res.code !== 0) {
    log.error({ res }, 'tmux new-window failed');
    throw new Error(`tmux new-window failed: ${res.stderr}`);
  }
}