// The session side of the host's git socket (#1587,
// packages/cli/src/git-socket.mjs). The runner calls these for the
// push_working and fetch_review tools, inside the sandbox, in the session's
// own clones under its workspace. Commits leave and arrive only as bundles:
//
//   push   `git bundle create` of the named branch, leaving out what the
//          clone's origin and working remotes already have, written to the
//          run's /tmp; the host takes it once the broker authorized the push.
//   fetch  the host sends a bundle of the commit the review request names;
//          the runner fetches it with fsck on into
//          refs/remotes/working/<work ref> of that project's clone.
//
// The bundle files are deleted on every path. git runs with no system or
// global config and no hooks, as the host's does.

import { spawn } from "node:child_process";
import { randomBytes } from "node:crypto";
import { closeSync, createReadStream, existsSync, openSync, readdirSync, rmSync, statSync, writeSync } from "node:fs";
import { connect } from "node:net";
import { join } from "node:path";
import { once } from "node:events";

// The host's cap (BUNDLE_MAX and HAVE_MAX in packages/seat/src/working.mjs;
// a test holds them equal). Kept here so the runner doesn't load the host's module.
export const BUNDLE_MAX = 32 * 1024 * 1024;
export const HAVE_MAX = 32;
const PROJECT = /^[a-z0-9][a-z0-9._-]{0,63}$/;
const WORK_REF = /^work\/vikunja-[1-9][0-9]*-[1-9][0-9]*$/;
const OID = /^[0-9a-f]{40}([0-9a-f]{24})?$/;
const TIMEOUT_MS = 300_000;
// How long a git has after SIGTERM before SIGKILL, as on the host.
const GRACE_MS = 5000;
const LIMITS = { timeoutMs: TIMEOUT_MS, graceMs: GRACE_MS };
const SAFE = [
  "-c", "core.hooksPath=/dev/null",
  "-c", "core.fsmonitor=false",
  "-c", "protocol.allow=never",
  "-c", "protocol.file.allow=always",
  "-c", "submodule.recurse=false",
];

const failure = (code, message = code) => Object.assign(new Error(message), { code });

// The same rule as validBranch in packages/seat/src/working.mjs.
export const validBranch = (branch) =>
  typeof branch === "string" && /^[A-Za-z0-9][A-Za-z0-9._\/-]{0,199}$/.test(branch) && !/\.\.|\/\/|\/\.|@\{|\.lock(\/|$)|[./]$/.test(branch);

// git with SAFE first, in its own process group (detached). Past
// limits.timeoutMs the group gets SIGTERM, on which git removes its
// lockfiles, then SIGKILL limits.graceMs later; once a signalled git has
// closed, the group gets SIGKILL again. The same sequence as the host's
// runGit in packages/seat/src/checkout.mjs, kept here so the runner doesn't
// load the host's module. Exported for the tests, which shorten `limits`.
export function git(args, env = process.env, limits = LIMITS) {
  return new Promise((resolve) => {
    const child = spawn("git", [...SAFE, ...args], {
      env: { PATH: env.PATH ?? "/usr/bin:/bin", HOME: "/nonexistent", GIT_CONFIG_NOSYSTEM: "1", GIT_CONFIG_GLOBAL: "/dev/null", GIT_TERMINAL_PROMPT: "0", LC_ALL: "C" },
      detached: true,
      stdio: ["ignore", "pipe", "pipe"],
    });
    let out = "";
    let err = "";
    let signalled = false;
    let kill = null;
    // A git that never started has no pid; an empty group is ESRCH.
    const group = (signal) => {
      try {
        process.kill(-child.pid, signal);
      } catch {}
    };
    const term = setTimeout(() => {
      signalled = true;
      group("SIGTERM");
      kill = setTimeout(() => group("SIGKILL"), limits.graceMs);
    }, limits.timeoutMs);
    const settle = (r) => {
      clearTimeout(term);
      clearTimeout(kill);
      if (signalled) group("SIGKILL");
      resolve(r);
    };
    child.stdout.setEncoding("utf8").on("data", (d) => (out += d));
    child.stderr.setEncoding("utf8").on("data", (d) => (err += d));
    child.on("error", (e) => settle({ ok: false, out, err, why: e.code ?? e.message }));
    child.on("close", (code, signal) => settle({ ok: code === 0, out, err, why: signal ? `killed by ${signal}` : err.trim().split("\n").pop() || `exit ${code}` }));
  });
}

function clone(workspace, project) {
  if (!PROJECT.test(project ?? "")) throw failure("invalid-request", "not a project id");
  const dir = join(workspace, project);
  if (!existsSync(join(dir, ".git"))) throw failure("no-clone", `no clone of ${project} in the workspace`);
  return dir;
}

// One connection to the git socket: JSON lines and raw bytes, read in order.
function open(path) {
  if (typeof path !== "string" || !path) throw failure("not-authorized", "this session has no git socket");
  const socket = connect(path);
  let buf = Buffer.alloc(0);
  let gone = null;
  let wake = null;
  const poke = () => wake?.();
  socket.on("data", (c) => {
    buf = buf.length ? Buffer.concat([buf, c]) : c;
    poke();
  });
  socket.on("end", () => {
    gone ??= "the host closed the connection";
    poke();
  });
  socket.on("error", (e) => {
    gone ??= `git socket: ${e.code ?? e.message}`;
    poke();
  });
  socket.setTimeout(TIMEOUT_MS, () => {
    gone ??= "git socket timed out";
    socket.destroy();
    poke();
  });
  const wait = () => new Promise((r) => (wake = () => ((wake = null), r())));
  return {
    socket,
    async line() {
      for (;;) {
        const nl = buf.indexOf(0x0a);
        if (nl >= 0) {
          const text = buf.subarray(0, nl).toString("utf8");
          buf = buf.subarray(nl + 1);
          try {
            return JSON.parse(text);
          } catch {
            throw failure("invalid-response", "the host's reply isn't JSON");
          }
        }
        if (buf.length > 65536) throw failure("invalid-response", "the host's reply line is too long");
        if (gone) throw failure("outcome-unknown", gone);
        await wait();
      }
    },
    async bytes(size, fd) {
      let got = 0;
      for (;;) {
        if (buf.length) {
          const take = buf.subarray(0, size - got);
          writeSync(fd, take);
          got += take.length;
          buf = buf.subarray(take.length);
        }
        if (got === size) return;
        if (gone) throw failure("outcome-unknown", gone);
        await wait();
      }
    },
    close: () => socket.destroy(),
  };
}

const refused = (r) => {
  if (r?.ok === false) throw failure(/^[a-z-]{1,64}$/.test(r.error ?? "") ? r.error : "refused");
  if (r?.ok !== true) throw failure("invalid-response");
  return r;
};

// await pushWorking({ path, cap, workspace, task_ref, project, branch, tmp })
// Resolves the host's { ref, commit, previous }.
export async function pushWorking({ path, cap, workspace, task_ref, project, branch, tmp = "/tmp", env = process.env }) {
  const dir = clone(workspace, project);
  if (!validBranch(branch)) throw failure("invalid-request", "not a branch name");
  if (!(await git(["-C", dir, "rev-parse", "-q", "--verify", `refs/heads/${branch}^{commit}`], env)).ok) throw failure("no-such-branch", `no branch ${branch} in the ${project} clone`);
  const file = join(tmp, `push-${randomBytes(8).toString("hex")}.bundle`);
  try {
    const made = await git(["-C", dir, "bundle", "create", "-q", file, `refs/heads/${branch}`, "--not", "--remotes=origin", "--remotes=working"], env);
    if (!made.ok) throw failure(/empty bundle/.test(made.err) ? "nothing-to-push" : "bundle-failed", made.why);
    const size = statSync(file).size;
    if (size > BUNDLE_MAX) throw failure("bundle-too-large", `${size} bytes, over ${BUNDLE_MAX}`);
    const conn = open(path);
    try {
      conn.socket.write(`${JSON.stringify({ cap, op: "push", task_ref, project, branch, size })}\n`);
      refused(await conn.line());
      for await (const chunk of createReadStream(file)) if (!conn.socket.write(chunk)) await once(conn.socket, "drain");
      const result = refused(await conn.line()).result;
      // The clone remembers what the working repository has, so the next
      // push sends only what is new. Best effort: the push already landed.
      if (WORK_REF.test(result?.ref ?? "") && OID.test(result.commit ?? "")) await git(["-C", dir, "update-ref", `refs/remotes/working/${result.ref}`, result.commit], env);
      return result;
    } finally {
      conn.close();
    }
  } finally {
    rmSync(file, { force: true });
  }
}

// await fetchReview({ path, cap, workspace, task_ref, request, tmp })
// Resolves { project, ref, commit, clone }; ref is the clone's remote ref.
export async function fetchReview({ path, cap, workspace, task_ref, request, tmp = "/tmp", env = process.env }) {
  // Commits the host may leave out: what the clones' remotes already hold.
  // The working refs come first, since a review is most often of a commit
  // built on one; origin's fill what is left of HAVE_MAX. The order is per
  // clone, not across clones: each clone's refs newest first, one clone
  // after another in the workspace's directory order. So past HAVE_MAX, a
  // later clone's newer refs can lose to an earlier clone's older ones.
  const have = new Set();
  const projects = projectsIn(workspace);
  for (const remote of ["refs/remotes/working", "refs/remotes/origin"])
    for (const project of projects) {
      if (have.size >= HAVE_MAX) break;
      const r = await git(["-C", join(workspace, project), "for-each-ref", "--sort=-committerdate", "--format=%(objectname)", remote], env);
      if (r.ok) for (const oid of r.out.split("\n")) if (OID.test(oid) && have.size < HAVE_MAX) have.add(oid);
    }
  const file = join(tmp, `fetch-${randomBytes(8).toString("hex")}.bundle`);
  try {
    const conn = open(path);
    let result;
    try {
      conn.socket.write(`${JSON.stringify({ cap, op: "fetch", task_ref, request, have: [...have] })}\n`);
      result = refused(await conn.line()).result;
      if (!PROJECT.test(result?.project ?? "") || !WORK_REF.test(result.ref ?? "") || !OID.test(result.commit ?? "") || !Number.isSafeInteger(result.size) || result.size < 1 || result.size > BUNDLE_MAX)
        throw failure("invalid-response");
      const fd = openSync(file, "wx", 0o600);
      try {
        await conn.bytes(result.size, fd);
      } finally {
        closeSync(fd);
      }
    } finally {
      conn.close();
    }
    const dir = clone(workspace, result.project);
    const into = `refs/remotes/working/${result.ref}`;
    const fetched = await git(["-c", "transfer.fsckObjects=true", "-C", dir, "fetch", "-q", "--no-tags", "--no-write-fetch-head", "--no-recurse-submodules", "--no-auto-maintenance", file, `+refs/mosaic/review:${into}`], env);
    if (!fetched.ok) throw failure("fetch-failed", fetched.why);
    const tip = await git(["-C", dir, "rev-parse", "-q", "--verify", `${into}^{commit}`], env);
    if (tip.out.trim() !== result.commit) throw failure("fetch-failed", "the fetched commit isn't the one the host named");
    return { project: result.project, ref: `working/${result.ref}`, commit: result.commit, clone: dir };
  } finally {
    rmSync(file, { force: true });
  }
}

// The project clones in a workspace: each directory with a project id's
// name and a .git.
const projectsIn = (workspace) => readdirSync(workspace).filter((name) => PROJECT.test(name) && existsSync(join(workspace, name, ".git")));