#!/usr/bin/env node
/**
 * Capture an overview using an available non-managed backend.
 * Managed browser preview remains the preferred platform-level path; this CLI handles
 * Firefox and deterministic SVG rasterization when those binaries are installed.
 */
import { execFileSync, spawnSync } from 'node:child_process';
import { existsSync, mkdirSync } from 'node:fs';
import { dirname, resolve } from 'node:path';
import { ScriptError, main, parseFlags } from './lib.js';

main(async () => {
  const flags = parseFlags(process.argv.slice(2), {
    required: ['output'],
    optional: ['url', 'svg', 'backend', 'width', 'height'],
  });
  const output = resolve(flags.output);
  mkdirSync(dirname(output), { recursive: true });
  const backend = chooseBackend(flags.backend, flags.url, flags.svg);
  if (backend === 'firefox') captureFirefox(flags.url, output, flags.width, flags.height);
  else captureSvg(flags.svg, output, flags.width, flags.height);
  return { backend, output };
});

function chooseBackend(requested, url, svg) {
  if (requested && requested !== 'auto' && requested !== 'firefox' && requested !== 'svg') {
    throw new ScriptError('BACKEND_UNKNOWN', `不支援的 capture backend：${requested}`);
  }
  if (requested === 'firefox') {
    requireBinary('firefox');
    if (!url) throw new ScriptError('URL_REQUIRED', 'Firefox backend 需要 --url');
    return 'firefox';
  }
  if (requested === 'svg') {
    requireSvgInput(svg);
    requireAnyBinary(['rsvg-convert', 'resvg']);
    return 'svg';
  }
  if (url && hasBinary('firefox')) return 'firefox';
  if (svg && (hasBinary('rsvg-convert') || hasBinary('resvg'))) return 'svg';
  throw new ScriptError('NO_CAPTURE_BACKEND', '沒有可用的 Firefox 或 SVG rasterizer；請使用平台 preview，或安裝 firefox、rsvg-convert、resvg');
}

function captureFirefox(url, output, width, height) {
  const args = ['--headless'];
  if (width) args.push('--window-size', `${width}${height ? `,${height}` : ''}`);
  args.push('--screenshot', output, url);
  const result = spawnSync('firefox', args, { encoding: 'utf8' });
  if (result.status !== 0 || !existsSync(output)) throw new ScriptError('CAPTURE_FAILED', `Firefox 截圖失敗：${result.stderr || result.stdout || '沒有輸出檔案'}`);
}

function captureSvg(svg, output, width, height) {
  requireSvgInput(svg);
  if (hasBinary('rsvg-convert')) {
    const args = [`--output=${output}`];
    if (width) args.push(`--width=${width}`);
    if (height) args.push(`--height=${height}`);
    args.push(resolve(svg));
    const result = spawnSync('rsvg-convert', args, { encoding: 'utf8' });
    if (result.status !== 0) throw new ScriptError('CAPTURE_FAILED', `rsvg-convert 失敗：${result.stderr || result.stdout}`);
  } else {
    const args = [];
    if (width) args.push('-w', String(width));
    args.push(resolve(svg), output);
    const result = spawnSync('resvg', args, { encoding: 'utf8' });
    if (result.status !== 0) throw new ScriptError('CAPTURE_FAILED', `resvg 失敗：${result.stderr || result.stdout}`);
  }
  if (!existsSync(output)) throw new ScriptError('CAPTURE_FAILED', 'rasterizer 沒有產生輸出檔案');
}

function requireSvgInput(svg) {
  if (!svg || !existsSync(resolve(svg))) throw new ScriptError('SVG_REQUIRED', 'SVG backend 需要存在的 --svg');
}
function requireBinary(binary) { if (!hasBinary(binary)) throw new ScriptError('BINARY_NOT_FOUND', `找不到 ${binary}`); }
function requireAnyBinary(binaries) { if (!binaries.some(hasBinary)) throw new ScriptError('BINARY_NOT_FOUND', `找不到 ${binaries.join(' 或 ')}`); }
function hasBinary(binary) { try { execFileSync('sh', ['-c', `command -v ${binary}`], { stdio: 'ignore' }); return true; } catch { return false; } }