export const utf8 = new TextDecoder();
export const looksBinary = (data: Uint8Array) => data.subarray(0, 8192).includes(0);

// mirrors excluded_directory / excluded_file in src/languages.rs; keep them in sync
const GENERATED_DIRECTORIES = new Set([
  "node_modules", "vendor", "third_party", "third-party", "target", "dist", "build",
  "coverage", ".next", ".nuxt", ".output", ".yarn", ".gradle", ".terraform", ".dart_tool",
  ".direnv", ".venv", "venv", "__pycache__", "pods", "carthage", "generated",
]);
const GENERATED_FILES = new Set([
  "cargo.lock", "package-lock.json", "npm-shrinkwrap.json", "yarn.lock", "pnpm-lock.yaml",
  "bun.lock", "bun.lockb", "deno.lock", "composer.lock", "gemfile.lock", "go.sum", "poetry.lock",
  "uv.lock", "pipfile.lock", "pdm.lock", "flake.lock", "mix.lock", "pubspec.lock",
  "package.resolved", "packages.lock.json", "gradle.lockfile", "podfile.lock", "cartfile.resolved",
]);
const GENERATED_SUFFIXES = [
  ".lock", ".min.js", ".min.css", ".g.dart", ".pb.go", ".pb.rs", ".pb.cc", ".pb.h", "_pb2.py",
  ".designer.cs",
];

export function looksGenerated(path: string): boolean {
  const segments = path.toLowerCase().split("/");
  const name = segments.pop()!;
  return segments.some(dir => GENERATED_DIRECTORIES.has(dir))
    || GENERATED_FILES.has(name)
    || GENERATED_SUFFIXES.some(suffix => name.endsWith(suffix))
    || name.includes(".generated.")
    || name.includes("_generated.");
}

/** mirrors human_size in src/render.rs */
export function humanSize(bytes: number): string {
  if (bytes < 1024) return `${bytes} B`;
  if (bytes < 1 << 20) return `${(bytes / 1024).toFixed(1)} KiB`;
  return `${(bytes / (1 << 20)).toFixed(1)} MiB`;
}

export const plural = (n: number, noun: string) => `${n} ${noun}${n === 1 ? "" : "s"}`;

/** the identity's own timezone, like git log */
export function identityDate(id: { time: number; tz: string }): string {
  const offset = (Number(id.tz.slice(0, 3)) * 60 + Number(id.tz[0] + id.tz.slice(3))) * 60000;
  const local = new Date(id.time * 1000 + offset).toISOString();
  return `${local.slice(0, 10)} ${local.slice(11, 16)} ${id.tz}`;
}