import * as path from "path";
import type { DirEntry, FileStat, SkillFs } from "../src/types";

export interface FakeFsOptions {
  /** absolute file path -> content */
  files: Record<string, string | Buffer>;
  /** absolute path -> mtimeMs (files or directories). Default 1000. */
  mtimes?: Record<string, number>;
  /** symlink path -> target path. realpath resolves the longest matching prefix. */
  symlinks?: Record<string, string>;
}

export interface FakeFs extends SkillFs {
  /** Add or replace a file and bump its mtime. */
  write(file: string, content: string, mtimeMs?: number): void;
  calls: { readdir: number; stat: number; readFile: number };
}

export function fakeFs(opts: FakeFsOptions): FakeFs {
  const files = new Map<string, Buffer>();
  for (const [p, c] of Object.entries(opts.files)) files.set(p, Buffer.isBuffer(c) ? c : Buffer.from(c));
  const mtimes = new Map<string, number>(Object.entries(opts.mtimes ?? {}));
  const symlinks = opts.symlinks ?? {};
  const calls = { readdir: 0, stat: 0, readFile: 0 };

  const dirs = () => {
    const set = new Set<string>();
    for (const f of files.keys()) {
      let d = path.dirname(f);
      while (d !== "/" && !set.has(d)) {
        set.add(d);
        d = path.dirname(d);
      }
    }
    for (const d of mtimes.keys()) if (!files.has(d)) set.add(d);
    return set;
  };

  const enoent = (p: string) => Object.assign(new Error(`ENOENT: no such file or directory, '${p}'`), { code: "ENOENT" });

  /** Translates `p` through the longest matching symlink prefix, like the kernel following a link. */
  const resolve = (p: string): string => {
    const links = Object.keys(symlinks).sort((a, b) => b.length - a.length);
    for (const link of links) {
      if (p === link || p.startsWith(link + "/")) return symlinks[link] + p.slice(link.length);
    }
    return p;
  };

  return {
    calls,
    write(file, content, mtimeMs) {
      files.set(file, Buffer.from(content));
      mtimes.set(file, mtimeMs ?? (mtimes.get(file) ?? 1000) + 1);
    },
    async readdir(dir) {
      calls.readdir++;
      const real = resolve(dir);
      if (!dirs().has(real)) throw enoent(dir);
      const out = new Map<string, DirEntry>();
      for (const f of files.keys()) {
        if (path.dirname(f) === real) out.set(path.basename(f), { name: path.basename(f), isDirectory: false, isFile: true });
      }
      for (const d of dirs()) {
        if (path.dirname(d) === real) out.set(path.basename(d), { name: path.basename(d), isDirectory: true, isFile: false });
      }
      // A real Dirent for a symlink reports neither isDirectory() nor isFile().
      for (const link of Object.keys(symlinks)) {
        if (path.dirname(link) === real) out.set(path.basename(link), { name: path.basename(link), isDirectory: false, isFile: false });
      }
      return [...out.values()].sort((a, b) => a.name.localeCompare(b.name));
    },
    async stat(p): Promise<FileStat> {
      calls.stat++;
      const real = resolve(p);
      const mtimeMs = mtimes.get(real) ?? 1000;
      if (files.has(real)) return { mtimeMs, size: files.get(real)!.length, isDirectory: false, isFile: true };
      if (dirs().has(real)) return { mtimeMs, size: 0, isDirectory: true, isFile: false };
      throw enoent(p);
    },
    async readFile(p) {
      calls.readFile++;
      const c = files.get(resolve(p));
      if (!c) throw enoent(p);
      return c;
    },
    async realpath(p) {
      // Like realpath(3): every component must exist, including those behind a symlink.
      const real = resolve(p);
      if (!files.has(real) && !dirs().has(real)) throw enoent(p);
      return real;
    },
  };
}

import * as path from "path";
import type { DirEntry, FileStat, SkillFs } from "../src/types";

export interface FakeFsOptions {
  /** absolute file path -> content */
  files: Record<string, string | Buffer>;
  /** absolute path -> mtimeMs (files or directories). Default 1000. */
  mtimes?: Record<string, number>;
  /** symlink path -> target path. realpath resolves the longest matching prefix. */
  symlinks?: Record<string, string>;
}

export interface FakeFs extends SkillFs {
  /** Add or replace a file and bump its mtime. */
  write(file: string, content: string, mtimeMs?: number): void;
  calls: { readdir: number; stat: number; readFile: number };
}

export function fakeFs(opts: FakeFsOptions): FakeFs {
  const files = new Map<string, Buffer>();
  for (const [p, c] of Object.entries(opts.files)) files.set(p, Buffer.isBuffer(c) ? c : Buffer.from(c));
  const mtimes = new Map<string, number>(Object.entries(opts.mtimes ?? {}));
  const symlinks = opts.symlinks ?? {};
  const calls = { readdir: 0, stat: 0, readFile: 0 };

  const dirs = () => {
    const set = new Set<string>();
    for (const f of files.keys()) {
      let d = path.dirname(f);
      while (d !== "/" && !set.has(d)) {
        set.add(d);
        d = path.dirname(d);
      }
    }
    for (const d of mtimes.keys()) if (!files.has(d)) set.add(d);
    return set;
  };

  const enoent = (p: string) => Object.assign(new Error(`ENOENT: no such file or directory, '${p}'`), { code: "ENOENT" });

  /** Translates `p` through the longest matching symlink prefix, like the kernel following a link. */
  const resolve = (p: string): string => {
    const links = Object.keys(symlinks).sort((a, b) => b.length - a.length);
    for (const link of links) {
      if (p === link || p.startsWith(link + "/")) return symlinks[link] + p.slice(link.length);
    }
    return p;
  };

  return {
    calls,
    write(file, content, mtimeMs) {
      files.set(file, Buffer.from(content));
      mtimes.set(file, mtimeMs ?? (mtimes.get(file) ?? 1000) + 1);
    },
    async readdir(dir) {
      calls.readdir++;
      const real = resolve(dir);
      if (!dirs().has(real)) throw enoent(dir);
      const out = new Map<string, DirEntry>();
      for (const f of files.keys()) {
        if (path.dirname(f) === real) out.set(path.basename(f), { name: path.basename(f), isDirectory: false, isFile: true });
      }
      for (const d of dirs()) {
        if (path.dirname(d) === real) out.set(path.basename(d), { name: path.basename(d), isDirectory: true, isFile: false });
      }
      // A real Dirent for a symlink reports neither isDirectory() nor isFile().
      for (const link of Object.keys(symlinks)) {
        if (path.dirname(link) === real) out.set(path.basename(link), { name: path.basename(link), isDirectory: false, isFile: false });
      }
      return [...out.values()].sort((a, b) => a.name.localeCompare(b.name));
    },
    async stat(p): Promise<FileStat> {
      calls.stat++;
      const real = resolve(p);
      const mtimeMs = mtimes.get(real) ?? 1000;
      if (files.has(real)) return { mtimeMs, size: files.get(real)!.length, isDirectory: false, isFile: true };
      if (dirs().has(real)) return { mtimeMs, size: 0, isDirectory: true, isFile: false };
      throw enoent(p);
    },
    async readFile(p) {
      calls.readFile++;
      const c = files.get(resolve(p));
      if (!c) throw enoent(p);
      return c;
    },
    async realpath(p) {
      // Like realpath(3): every component must exist, including those behind a symlink.
      const real = resolve(p);
      if (!files.has(real) && !dirs().has(real)) throw enoent(p);
      return real;
    },
  };
}