import type { ProjectManifest } from './types';

const TEXT_EXTENSIONS = /\.(?:xml|urdf|txt|obj|mtl|csv|json|yaml|yml)$/i;
const decoder = new TextDecoder('utf-8', { fatal: false });
const encoder = new TextEncoder();

export function isEditableSource(path: string): boolean {
  return TEXT_EXTENSIONS.test(path);
}

export function editableSourcePaths(manifest: ProjectManifest): string[] {
  return manifest.files
    .filter((file) => isEditableSource(file.path))
    .map((file) => file.path)
    .sort((a, b) => a.localeCompare(b));
}

export function readCachedText(manifest: ProjectManifest, path: string): string {
  const file = manifest.files.find((candidate) => candidate.path === path);
  if (!file) throw new Error(`缓存中找不到文件：${path}`);
  if (!isEditableSource(path)) throw new Error(`不支持编辑二进制文件：${path}`);
  return decoder.decode(file.data);
}

/** 返回只更新浏览器会话内存的新工程清单，不接触用户本地文件系统。 */
export function mergeCachedFiles(
  manifest: ProjectManifest,
  additional: ProjectManifest['files'],
): ProjectManifest {
  if (!additional.length) return manifest;
  const byPath = new Map(manifest.files.map((file) => [file.path, file]));
  for (const file of additional) byPath.set(file.path, file);
  const files = Array.from(byPath.values());
  return { ...manifest, files, totalBytes: files.reduce((total, item) => total + item.size, 0) };
}

export function upsertCachedMjcf(
  manifest: ProjectManifest,
  path: string,
  text: string,
): ProjectManifest {
  const data = encoder.encode(text),
    index = manifest.files.findIndex((candidate) => candidate.path === path);
  const files = manifest.files.slice();
  const file = {
    path,
    data,
    size: data.byteLength,
    source: 'file' as const,
    mimeType: 'application/xml',
  };
  if (index < 0) files.push(file);
  else files[index] = { ...files[index], ...file };
  const entries = manifest.entries.some((entry) => entry.path === path)
    ? manifest.entries
    : [...manifest.entries, { path, format: 'mjcf' as const, label: `${path} (MJCF 缓存)` }];
  return {
    ...manifest,
    files,
    entries,
    totalBytes: files.reduce((total, item) => total + item.size, 0),
  };
}

export function updateCachedText(
  manifest: ProjectManifest,
  path: string,
  text: string,
): ProjectManifest {
  const index = manifest.files.findIndex((candidate) => candidate.path === path);
  if (index < 0) throw new Error(`缓存中找不到文件：${path}`);
  if (!isEditableSource(path)) throw new Error(`不支持编辑二进制文件：${path}`);
  const data = encoder.encode(text),
    files = manifest.files.slice();
  files[index] = {
    ...files[index],
    data,
    size: data.byteLength,
    mimeType: files[index].mimeType || 'text/plain',
  };
  return { ...manifest, files, totalBytes: files.reduce((total, file) => total + file.size, 0) };
}

export function downloadBytes(
  data: Uint8Array,
  fileName: string,
  mimeType = 'application/xml',
): void {
  const blob = new Blob([data as BlobPart], { type: `${mimeType};charset=utf-8` });
  const url = URL.createObjectURL(blob),
    anchor = document.createElement('a');
  anchor.href = url;
  anchor.download = fileName;
  anchor.style.display = 'none';
  document.body.append(anchor);
  anchor.click();
  anchor.remove();
  setTimeout(() => URL.revokeObjectURL(url), 0);
}

export function exportedFileName(projectName: string, extension: 'urdf' | 'xml'): string {
  const stem =
    projectName.replace(/\.(?:zip|xml|urdf)$/i, '').replace(/[^\p{L}\p{N}._-]+/gu, '_') || 'model';
  return `${stem}.${extension}`;
}