/** 版本号解析 vX.Y.Z-dav-{client}-{build} */
export interface GcaVersion {
  major: number;
  minor: number;
  patch: number;
  client: 'desktop' | 'android' | 'cli';
  build: number;
  raw: string;
}

export interface Manifest {
  version: string;
  builds: Record<string, ManifestBuild>;
}

export interface ManifestBuild {
  tag: string;
  url: string;
  sha256: string;
  size: number;
  minVersion?: string;
}

const MANIFEST_URL = 'https://git.childish-ghost.com/LukeMackin/Yuzu-GCA/releases/download/manifest/manifest.json';

const VERSION_RE = /^v(\d+)\.(\d+)\.(\d+)-dav-(desktop|android|cli)-(\d+)$/;

export function parseVersion(raw: string): GcaVersion | null {
  const m = raw.trim().match(VERSION_RE);
  if (!m) return null;
  return {
    major: parseInt(m[1], 10),
    minor: parseInt(m[2], 10),
    patch: parseInt(m[3], 10),
    client: m[4] as GcaVersion['client'],
    build: parseInt(m[5], 10),
    raw,
  };
}

export function compareVersion(a: GcaVersion, b: GcaVersion): number {
  if (a.major !== b.major) return a.major - b.major;
  if (a.minor !== b.minor) return a.minor - b.minor;
  if (a.patch !== b.patch) return a.patch - b.patch;
  return a.build - b.build;
}

/** 调用方传入本地版本号，返回是否需要更新以及目标 manifest entry */
export async function checkUpdate(
  client: GcaVersion['client'],
  localVersion: GcaVersion,
  manifestUrl = MANIFEST_URL,
): Promise<{ shouldUpdate: boolean; build: ManifestBuild | null; remoteVersion: GcaVersion | null }> {
  try {
    const resp = await fetch(manifestUrl);
    if (!resp.ok) return { shouldUpdate: false, build: null, remoteVersion: null };

    const manifest: Manifest = await resp.json();
    const build = manifest.builds[client];
    if (!build) return { shouldUpdate: false, build: null, remoteVersion: null };

    const remoteVersion = parseVersion(build.tag);
    if (!remoteVersion) return { shouldUpdate: false, build: null, remoteVersion: null };

    return {
      shouldUpdate: compareVersion(remoteVersion, localVersion) > 0,
      build,
      remoteVersion,
    };
  } catch {
    return { shouldUpdate: false, build: null, remoteVersion: null };
  }
}

/** SemVer 比较（用于 expo-updates manifest） */
export function semverGt(a: string, b: string): boolean {
  const [aM, am, aP] = a.split('.').map(Number);
  const [bM, bm, bP] = b.split('.').map(Number);
  if (aM !== bM) return aM > bM;
  if (am !== bm) return am > bm;
  return aP > bP;
}