/**
 * @file The git WRITES the dashboard offers on a lane: fetch, pull, push,
 * stage/unstage a file, commit, discard a file, switch branch, and create or
 * delete a branch. Everything here is deliberately the boring half of git —
 * there is no merge, no rebase, no reset, no stash and no conflict
 * resolution, because a dashboard button is the wrong place to start an
 * operation whose recovery needs a terminal (`reset` stays where it was:
 * behind the three-check destroy guard in worktree.js).
 *
 * Four rules hold for every action:
 *   - argv only, via worktree.js's `git()` — never a shell string.
 *   - the lane's own working directory is the only cwd.
 *   - a caller-supplied path is never trusted as a path: it must be one
 *     `git status` is reporting as changed right now (`resolvePaths`), so no
 *     `..`, no absolute path and no untouched file is reachable.
 *   - `pull` is `--ff-only` and `switch` demands a clean tree, so neither can
 *     invent a merge commit or a conflict underneath a running agent.
 *
 * `discard` is the ONE irreversible action here — it throws away work git has
 * no copy of — so it additionally demands an explicit `confirm: true` in the
 * body. Do not add a second destructive action without the same gate.
 *
 * Network actions carry a timeout: a lane pointed at an unreachable remote
 * should fail in half a minute, not hold an HTTP request open.
 * @author Nguyễn Ngọc Trí Vĩ <vinnt@smartgift.vn>
 */

const {
  git,
  isValidBranchName,
  listBranches,
  branchCheckedOutAt,
  statusCounts,
} = require("./worktree");

/** How long a fetch/pull/push may run before it is killed. */
const NETWORK_TIMEOUT_MS = 60_000;
/** Longest commit message accepted — a subject+body, not a pasted file. */
const MAX_MESSAGE_LEN = 4000;

const ACTIONS = new Set([
  "fetch",
  "pull",
  "push",
  "commit",
  "switch",
  "stage",
  "unstage",
  "discard",
  "branch-create",
  "branch-delete",
]);

/** Branches this module refuses to delete, whatever the request says. */
const PROTECTED = new Set(["main", "master", "development", "develop"]);

function bad(code, message) {
  const err = new Error(message);
  err.code = code;
  return err;
}

/** Whether the working tree has anything uncommitted (tracked or not). */
async function isDirty(dir) {
  const { dirty, untracked } = await statusCounts(dir);
  return dirty + untracked > 0;
}

/**
 * The paths a per-file action may name — exactly the ones `git status` is
 * reporting as changed right now, keyed by their porcelain code.
 *
 * This is the whole authorization story for `stage`/`unstage`/`discard`: the
 * request cannot reach a path git is not already talking about, so no `..`,
 * no absolute path, and no untouched file can be deleted by a typo. A path
 * that is not in this map is a 400, never a silent no-op.
 */
async function changedPaths(dir) {
  const result = await git(dir, ["status", "--porcelain=v1", "--untracked-files=normal"]);
  const map = new Map();
  for (const line of result.stdout.split("\n")) {
    if (!line.trim()) continue;
    const code = line.slice(0, 2);
    const raw = line.slice(3).trimEnd();
    const file = raw.split(" -> ").pop().replace(/^"|"$/g, "");
    map.set(file, code);
  }
  return map;
}

/** Validate `body.paths` against what git reports as changed. */
async function resolvePaths(dir, body) {
  const wanted = Array.isArray(body.paths)
    ? body.paths
    : typeof body.path === "string"
      ? [body.path]
      : [];
  if (!wanted.length) throw bad("EBADPATH", "at least one path is required");
  if (wanted.some((p) => typeof p !== "string" || !p)) {
    throw bad("EBADPATH", "every path must be a non-empty string");
  }
  const changed = await changedPaths(dir);
  const unknown = wanted.filter((p) => !changed.has(p));
  if (unknown.length) {
    throw bad("EBADPATH", `not a changed path: ${unknown[0]}`);
  }
  return wanted.map((p) => ({ path: p, code: changed.get(p) }));
}

/**
 * Run one action against a lane's working directory.
 *
 * @param {string} dir The lane's cwd.
 * @param {string} action One of ACTIONS.
 * @param {object} [body] Action input: `{message}` for commit,
 *   `{branch, create}` for switch. Ignored otherwise.
 * @returns {Promise<{action, ok, output, branch?}>} `output` is git's own
 *   stdout+stderr, shown verbatim — a push rejection or a credential failure
 *   says more in git's words than in ours.
 */
async function runGitAction(dir, action, body = {}) {
  if (!ACTIONS.has(action)) throw bad("EBADACTION", `unknown git action ${action}`);

  if (action === "fetch") {
    return done(
      action,
      await git(dir, ["fetch", "--all", "--prune"], { timeout: NETWORK_TIMEOUT_MS })
    );
  }

  if (action === "pull") {
    // --ff-only on purpose: a divergent branch is reported, never merged. The
    // user (or the agent in the pane) decides how to reconcile it.
    return done(action, await git(dir, ["pull", "--ff-only"], { timeout: NETWORK_TIMEOUT_MS }));
  }

  if (action === "push") {
    // HEAD, not a branch name from the request: the lane pushes the branch it
    // is actually on, and -u makes the first push set the upstream the
    // ahead/behind counts then read.
    return done(
      action,
      await git(dir, ["push", "-u", "origin", "HEAD"], { timeout: NETWORK_TIMEOUT_MS })
    );
  }

  if (action === "stage") {
    const paths = await resolvePaths(dir, body);
    // `add` covers every case the panel can show: a modification, a new file
    // and a deletion all stage with the same verb.
    return done(action, await git(dir, ["add", "--", ...paths.map((p) => p.path)]));
  }

  if (action === "unstage") {
    const paths = await resolvePaths(dir, body);
    const untracked = paths.filter((p) => p.code === "A " || p.code === "AM");
    // An intent-to-add/new file has nothing in HEAD to restore from, so
    // `restore --staged` would fail on the very first commit of a repo.
    const args =
      untracked.length === paths.length && !(await hasHead(dir))
        ? ["rm", "--cached", "-r", "--", ...paths.map((p) => p.path)]
        : ["restore", "--staged", "--", ...paths.map((p) => p.path)];
    return done(action, await git(dir, args));
  }

  if (action === "discard") {
    if (body.confirm !== true) throw bad("ECONFIRM", "discard requires confirm: true");
    const paths = await resolvePaths(dir, body);
    const untracked = paths.filter((p) => p.code === "??").map((p) => p.path);
    const tracked = paths.filter((p) => p.code !== "??").map((p) => p.path);
    const out = [];
    // Untracked files are deleted (git has no copy to restore); tracked ones
    // go back to HEAD in both gutters, so a staged-then-edited file lands in
    // one state rather than half-reverted.
    if (untracked.length) out.push(await git(dir, ["clean", "-fd", "--", ...untracked]));
    if (tracked.length) {
      out.push(
        await git(dir, ["restore", "--source=HEAD", "--staged", "--worktree", "--", ...tracked])
      );
    }
    return done(action, mergeResults(out));
  }

  if (action === "commit") {
    const message = typeof body.message === "string" ? body.message.trim() : "";
    if (!message) throw bad("EBADMESSAGE", "commit message is required");
    if (message.length > MAX_MESSAGE_LEN) throw bad("EBADMESSAGE", "commit message is too long");
    if (body.only === "staged") {
      // The panel's per-file staging only means something if a commit can
      // take the index as it stands — no `add -A` sweeping in the rest.
      const staged = [...(await changedPaths(dir)).values()].some(
        (code) => code[0] !== " " && code[0] !== "?"
      );
      if (!staged) throw bad("ENOCHANGES", "nothing staged to commit");
    } else {
      if (!(await isDirty(dir))) throw bad("ENOCHANGES", "nothing to commit");
      await git(dir, ["add", "-A"]);
    }
    // -m takes the message as one argv element, so a message containing
    // newlines, quotes or a leading dash is content, never syntax.
    return done(action, await git(dir, ["commit", "-m", message]));
  }

  if (action === "branch-create" || action === "branch-delete") {
    return branchAction(dir, action, body);
  }

  // switch
  const branch = typeof body.branch === "string" ? body.branch.trim() : "";
  if (!branch) throw bad("EBADBRANCH", "branch is required");
  if (!(await isValidBranchName(dir, branch))) {
    throw bad("EBADBRANCH", "branch is not a valid git branch name");
  }
  if (await isDirty(dir)) {
    // git would refuse anyway for conflicting files, but it happily carries
    // unrelated edits across a switch — which silently moves an agent's
    // half-finished work onto another branch. Refuse the whole case.
    throw bad("EDIRTY", "working tree has uncommitted changes");
  }
  const { branches } = await listBranches(dir);
  const exists = branches.includes(branch);
  if (body.create) {
    if (exists) throw bad("EBRANCHEXISTS", `branch ${branch} already exists`);
    return done(action, await git(dir, ["switch", "-c", branch]), branch);
  }
  if (!exists) throw bad("ENOBRANCH", `branch ${branch} does not exist locally`);
  const busyAt = await branchCheckedOutAt(dir, branch);
  if (busyAt) throw bad("EBRANCHBUSY", `branch ${branch} is checked out at ${busyAt}`);
  return done(action, await git(dir, ["switch", branch]), branch);
}

/** Create or delete a branch WITHOUT touching the working tree. */
async function branchAction(dir, action, body) {
  const branch = typeof body.branch === "string" ? body.branch.trim() : "";
  if (!branch) throw bad("EBADBRANCH", "branch is required");
  if (!(await isValidBranchName(dir, branch))) {
    throw bad("EBADBRANCH", "branch is not a valid git branch name");
  }
  const { branches, current } = await listBranches(dir);
  const exists = branches.includes(branch);

  if (action === "branch-create") {
    if (exists) throw bad("EBRANCHEXISTS", `branch ${branch} already exists`);
    const base = typeof body.base === "string" ? body.base.trim() : "";
    if (base && !(await isValidBranchName(dir, base))) {
      throw bad("EBADBRANCH", "base is not a valid git ref name");
    }
    // No switch: creating a branch to spawn a sibling worktree lane from must
    // not move the branch the agent in this pane is standing on.
    return done(action, await git(dir, ["branch", branch, ...(base ? [base] : [])]), branch);
  }

  if (!exists) throw bad("ENOBRANCH", `branch ${branch} does not exist locally`);
  if (PROTECTED.has(branch)) throw bad("EPROTECTED", `branch ${branch} is protected`);
  if (branch === current) throw bad("EBRANCHBUSY", `branch ${branch} is the current branch`);
  const busyAt = await branchCheckedOutAt(dir, branch);
  if (busyAt) throw bad("EBRANCHBUSY", `branch ${branch} is checked out at ${busyAt}`);
  // -d, never -D: git refuses to drop unmerged commits, and that refusal is
  // exactly the safety net a dashboard button needs. Force-deleting is a
  // terminal operation.
  return done(action, await git(dir, ["branch", "-d", branch]), branch);
}

/** Whether the repo has any commit yet. */
async function hasHead(dir) {
  try {
    await git(dir, ["rev-parse", "--verify", "HEAD"]);
    return true;
  } catch {
    return false;
  }
}

function mergeResults(results) {
  return {
    stdout: results.map((r) => r.stdout).join(""),
    stderr: results.map((r) => r.stderr).join(""),
  };
}

function done(action, result, branch) {
  const output = [result.stdout, result.stderr].filter(Boolean).join("").trim();
  return { action, ok: true, output, ...(branch ? { branch } : {}) };
}

module.exports = { runGitAction, ACTIONS, PROTECTED, NETWORK_TIMEOUT_MS };