import { execFile } from "node:child_process";
import { promisify } from "node:util";
import { join } from "node:path";
import type { PomConfig, PomState } from "./domain";
import { stage } from "./domain";
import { pathExists } from "./persistence";

const execFileAsync = promisify(execFile);

async function git(root: string, args: string[]): Promise<string> {
  const result = await execFileAsync("git", ["-C", root, ...args], { maxBuffer: 4 * 1024 * 1024 });
  return result.stdout.trim();
}

export async function ensureGit(state: PomState, config: PomConfig): Promise<void> {
  if (config.gitMode === "off") return;
  if (!(await pathExists(join(state.projectRoot, ".git")))) {
    await git(state.projectRoot, ["init"]);
    await git(state.projectRoot, ["config", "user.name", "POM Production Kernel"]);
    await git(state.projectRoot, ["config", "user.email", "pom@local.invalid"]);
  }
}

export async function enterStageBranch(state: PomState, config: PomConfig): Promise<string | undefined> {
  if (config.gitMode !== "branch-per-stage") return undefined;
  await ensureGit(state, config);
  const spec = stage(state.currentStage);
  const branch = `pom/stage-${spec.id}-${spec.slug}`;
  const branches = await git(state.projectRoot, ["branch", "--format=%(refname:short)"]);
  if (branches.split("\n").includes(branch)) await git(state.projectRoot, ["switch", branch]);
  else await git(state.projectRoot, ["switch", "-c", branch]);
  return branch;
}

export async function checkpointStage(state: PomState, config: PomConfig, label: string): Promise<string | undefined> {
  if (config.gitMode === "off") return undefined;
  await ensureGit(state, config);
  await git(state.projectRoot, ["add", "-A"]);
  const status = await git(state.projectRoot, ["status", "--porcelain"]);
  if (!status) return undefined;
  await git(state.projectRoot, ["commit", "-m", label]);
  return git(state.projectRoot, ["rev-parse", "--short", "HEAD"]);
}