// 文件系统与会话基元。刻意不引任何第三方依赖：构建脚本要能在一台只有 Node 的机器上跑起来。

import { createHash } from "node:crypto";
import { cp, mkdir, readFile, readdir, rm, stat, writeFile } from "node:fs/promises";
import { existsSync } from "node:fs";
import { dirname, join, relative, resolve, sep } from "node:path";

/** 仓库根（tools/lib/fs.ts → ../..）。所有路径都相对它解析，脚本可从任意 cwd 调用。 */
export const repoRoot = resolve(import.meta.dirname, "..", "..");

/** 把仓库相对路径解析成绝对路径。 */
export function abs(rel: string): string {
  return join(repoRoot, rel);
}

/** 统一成以 / 分隔的仓库相对路径，便于打印与写进 dist-map.json。 */
export function rel(absPath: string): string {
  return relative(repoRoot, absPath).split(sep).join("/");
}

export async function readJson<T>(path: string): Promise<T> {
  return JSON.parse(await readFile(path, "utf8")) as T;
}

export async function writeJson(path: string, value: unknown): Promise<void> {
  await mkdir(dirname(path), { recursive: true });
  await writeFile(path, JSON.stringify(value, null, "\t") + "\n", "utf8");
}

export async function writeText(path: string, value: string): Promise<void> {
  await mkdir(dirname(path), { recursive: true });
  await writeFile(path, value.endsWith("\n") ? value : value + "\n", "utf8");
}

export async function exists(path: string): Promise<boolean> {
  return existsSync(path);
}

export async function isDir(path: string): Promise<boolean> {
  try {
    return (await stat(path)).isDirectory();
  } catch {
    return false;
  }
}

export async function isFile(path: string): Promise<boolean> {
  try {
    return (await stat(path)).isFile();
  } catch {
    return false;
  }
}

/** 列目录，只返回目录名，跳过以 . 开头的条目与显式排除的名字。 */
export async function listDirs(path: string, exclude: string[] = []): Promise<string[]> {
  if (!(await isDir(path))) return [];
  const entries = await readdir(path, { withFileTypes: true });
  return entries
    .filter((e) => e.isDirectory() && !e.name.startsWith(".") && !exclude.includes(e.name))
    .map((e) => e.name)
    .sort();
}

/**
 * 拷贝目录树。
 *
 * 刻意用真拷贝而不是链接（hardlink / junction）：分发目录要能被整体搬到别的机器上传，
 * 链接会让"目录可整体搬走"这条不变式在某些工具下失效（见 docs/adr/0005）。
 */
export async function copyTree(src: string, dest: string): Promise<void> {
  if (!(await exists(src))) return;
  await mkdir(dirname(dest), { recursive: true });
  await cp(src, dest, { recursive: true, force: true });
}

/** 拷贝单个文件，自动建父目录。 */
export async function copyFileTo(src: string, dest: string): Promise<void> {
  await mkdir(dirname(dest), { recursive: true });
  await cp(src, dest, { force: true });
}

/** 目录内所有文件的相对路径（以 / 分隔）。 */
export async function walkFiles(root: string, base = root): Promise<string[]> {
  if (!(await isDir(base))) return [];
  const out: string[] = [];
  for (const entry of await readdir(base, { withFileTypes: true })) {
    const full = join(base, entry.name);
    if (entry.isDirectory()) out.push(...(await walkFiles(root, full)));
    else if (entry.isFile()) out.push(relative(root, full).split(sep).join("/"));
  }
  return out.sort();
}

/** 目录内所有文件的总字节数。 */
export async function dirBytes(root: string): Promise<number> {
  if (!(await isDir(root))) return 0;
  let total = 0;
  for (const f of await walkFiles(root)) total += (await stat(join(root, f))).size;
  return total;
}

export async function sizeOf(path: string): Promise<number> {
  try {
    return (await stat(path)).size;
  } catch {
    return 0;
  }
}

/** 一个长任务的耗时统计与人性化打印。 */
export function mb(bytes: number): string {
  return (bytes / 1024 / 1024).toFixed(1) + " MB";
}

export function sha1(text: string): string {
  return createHash("sha1").update(text).digest("hex");
}

/** 清空目录后重建（用于"分发目录绝不残留脏文件"这条保证）。 */
export async function resetDir(path: string): Promise<void> {
  await rm(path, { recursive: true, force: true });
  await mkdir(path, { recursive: true });
}

/** 单行进度输出，避免几十个分发目录刷屏。 */
export function log(message: string): void {
  process.stdout.write(message + "\n");
}