import { $ } from "bun";

export interface Identity { name: string; email: string }
export interface GitResult { code: number; stdout: string; stderr: string }

/** Settings that make studio git runs deterministic, whatever the machine's global config says. */
const BASE = [
  "-c", "core.hooksPath=/dev/null",
  "-c", "commit.gpgsign=false",
  "-c", "core.quotepath=false",
  "-c", "merge.conflictstyle=merge",
  "-c", "pull.rebase=false",
  "-c", "init.defaultBranch=main",
  "-c", "protocol.ext.allow=never", // author-supplied remote URLs must never run commands
];

function env(who?: Identity): Record<string, string> {
  const e: Record<string, string> = {};
  for (const [k, v] of Object.entries(process.env)) {
    if (v !== undefined && !k.startsWith("GIT_")) e[k] = v; // never inherit GIT_DIR, GIT_INDEX_FILE, ...
  }
  e.GIT_TERMINAL_PROMPT = "0";
  // Ignore the machine's global/system git config (url.*.insteadOf, credential helpers, ...).
  e.GIT_CONFIG_GLOBAL = "/dev/null";
  e.GIT_CONFIG_NOSYSTEM = "1";
  e.GIT_SSH_COMMAND = "ssh -o BatchMode=yes";
  // A fallback identity so git never refuses a merge/commit; real saves always pass `who`.
  const id = who ?? { name: "STCourses", email: "studio@stcourses.invalid" };
  e.GIT_AUTHOR_NAME = id.name;
  e.GIT_AUTHOR_EMAIL = id.email;
  e.GIT_COMMITTER_NAME = id.name;
  e.GIT_COMMITTER_EMAIL = id.email;
  return e;
}

/** Runs `git <args>` in `cwd`. Never throws on a non-zero exit; use `gitOk` for that. */
export async function git(cwd: string, args: string[], who?: Identity): Promise<GitResult> {
  const r = await $`git ${BASE} ${args}`.cwd(cwd).env(env(who)).quiet().nothrow();
  return { code: r.exitCode, stdout: r.stdout.toString(), stderr: r.stderr.toString() };
}

export class GitError extends Error {
  constructor(public args: string[], public result: GitResult) {
    super(`git ${args.join(" ")} failed (${result.code}): ${result.stderr.trim() || result.stdout.trim()}`);
  }
}

export async function gitOk(cwd: string, args: string[], who?: Identity): Promise<string> {
  const r = await git(cwd, args, who);
  if (r.code !== 0) throw new GitError(args, r);
  return r.stdout;
}

/** NUL-separated output (`-z`) to a list, so paths with spaces or newlines survive. */
export function splitZ(out: string): string[] {
  return out.split("\0").filter(Boolean);
}