import { assert } from "@std/assert";

export const SHOW = [
  "commit 0123456789abcdef0123456789abcdef01234567",
  "Author: A B <a@b.example>",
  "Date:   Wed Jul 1 12:00:00 2026 -0700",
  "",
  "    Subject line",
  "    ",
  "    Body paragraph.",
  "",
  "diff --git a/f b/f",
  "@@ -1 +1 @@",
  "-old",
  "+new",
].join("\n").split("\n");

export async function git(
  root: string,
  args: string[],
  stdin?: string,
  env?: Record<string, string>,
): Promise<string> {
  const cmd = new Deno.Command("git", {
    args,
    cwd: root,
    env,
    stdin: stdin !== undefined ? "piped" : "null",
    stdout: "piped",
    stderr: "piped",
  });
  const p = cmd.spawn();
  if (stdin !== undefined) {
    const w = p.stdin.getWriter();
    await w.write(new TextEncoder().encode(stdin));
    await w.close();
  }
  const o = await p.output();
  return new TextDecoder().decode(o.stdout);
}

export async function installHook(
  root: string,
  name: string,
  script: string,
) {
  const path = `${root}/.git/hooks/${name}`;
  await Deno.writeTextFile(path, `#!/bin/sh\n${script}\n`);
  await Deno.chmod(path, 0o755);
}

export function shellQuote(value: string): string {
  return `'${value.replaceAll("'", `'\\''`)}'`;
}

export async function initReftable(root: string): Promise<boolean> {
  const initialized = await new Deno.Command("git", {
    args: ["init", "-q", "--ref-format=reftable"],
    cwd: root,
    stdout: "null",
    stderr: "null",
  }).output();
  return initialized.success;
}

export async function withGitShim<T>(
  body: string,
  callback: () => T | Promise<T>,
): Promise<T> {
  const lookup = await new Deno.Command("which", {
    args: ["git"],
    stdout: "piped",
    stderr: "piped",
  }).output();
  assert(lookup.success, "the real Git executable is available");
  const realGitPath = new TextDecoder().decode(lookup.stdout).trim();
  const shimDir = await Deno.makeTempDir();
  const shim = `${shimDir}/git`;
  await Deno.writeTextFile(
    shim,
    `#!/bin/sh
${body}
exec ${shellQuote(realGitPath)} "$@"
`,
  );
  await Deno.chmod(shim, 0o755);
  const originalPath = Deno.env.get("PATH");
  Deno.env.set("PATH", `${shimDir}:${originalPath ?? ""}`);
  try {
    return await callback();
  } finally {
    if (originalPath === undefined) Deno.env.delete("PATH");
    else Deno.env.set("PATH", originalPath);
    await Deno.remove(shimDir, { recursive: true });
  }
}