/**
 * @file Better conflicts and history reads for the Changes panel: the three
 * git stages of ONE conflicted file for the 3-way merge editor (`readConflict`,
 * base `:1`, current `:2`, incoming `:3`, plus the working file it saves over),
 * the editor's save (`conflict-save`: the whole-file editor's own write path,
 * lane-file-write.js, then `git add` exactly like `resolve done`, refused while
 * a conflict marker is left), and the read-only reflog (`readReflog`).
 *
 * A path is never trusted as a path: the conflict read accepts only a file
 * `git ls-files -u` lists as unmerged right now (cwd-relative, so a
 * subdirectory lane cannot name a file outside itself), keeps the read path's
 * guards (`lanePath`, ESECRET, a size cap) and reads each stage by its BLOB id,
 * never by a revision expression from the request. A reflog's ref is `HEAD` or
 * a local branch that exists, looked up — never passed through.
 * @author Nguyễn Ngọc Trí Vĩ <vinnt@smartgift.vn>
 */

const { git: rawGit, isValidBranchName, operationInProgress } = require("./worktree");
const {
  contentSha,
  isSecretOnDisk,
  lanePath,
  looksBinary,
  resolveInLane,
  MAX_FILE_VIEW_BYTES,
  CONFLICT_CODES,
} = require("./git-diff");

const git = (dir, args, opts) => rawGit(dir, args, { literal: true, ...opts });

/** A line git writes to open or close a conflict block (git-ops.js's own). */
const MARKER_RE = /^(<{7} |>{7} |={7}$)/m;
/** Most reflog entries one page answers with. */
const MAX_REFLOG_PAGE = 200;

function bad(code, message) {
  return Object.assign(new Error(message), { code });
}

/** `ls-files -u` as path → {1?: blob, 2?: blob, 3?: blob}; cwd-relative paths. */
async function unmergedStages(dir) {
  const out = (await git(dir, ["ls-files", "-u", "-z"])).stdout;
  const map = new Map();
  for (const rec of out.split("\0").filter(Boolean)) {
    const tab = rec.indexOf("\t");
    const [, blob, stage] = rec.slice(0, tab).split(" ");
    const p = rec.slice(tab + 1);
    if (!map.has(p)) map.set(p, {});
    map.get(p)[stage] = blob;
  }
  return map;
}

/** One stage's text, or `{missing}` / `{binary}` / `{tooBig}`. */
async function blobText(dir, blob) {
  if (!blob) return { missing: true, text: null };
  const size = Number((await git(dir, ["cat-file", "-s", blob])).stdout.trim());
  if (size > MAX_FILE_VIEW_BYTES) return { tooBig: true, text: null };
  const buf = (await git(dir, ["cat-file", "blob", blob], { encoding: "buffer" })).stdout;
  if (looksBinary(buf)) return { binary: true, text: null };
  return { text: buf.toString("utf8") };
}

/** The head file of the open operation, for "Incoming: <sha> <subject>". */
const INCOMING_HEAD = {
  merge: "MERGE_HEAD",
  "cherry-pick": "CHERRY_PICK_HEAD",
  revert: "REVERT_HEAD",
  rebase: "REBASE_HEAD",
};

/**
 * The merge editor's input for `requested`: base/ours/theirs text, the working
 * file (with its markers) and its `sha` — the `baseSha` a save must name.
 * Throws EBADPATH (not unmerged), ESECRET, or answers a side as null when git
 * has none (added on one side, deleted on the other).
 */
async function readConflict(dir, requested) {
  const file = lanePath(requested);
  if (await isSecretOnDisk(dir, file)) {
    throw bad("ESECRET", "that file holds secrets and is not readable here");
  }
  const stages = (await unmergedStages(dir)).get(file);
  if (!stages) throw bad("EBADPATH", `not a conflicted path: ${file}`);
  const [base, ours, theirs] = await Promise.all(
    ["1", "2", "3"].map((s) => blobText(dir, stages[s]))
  );
  let working = { text: null, sha: null, binary: false, tooBig: false, missing: true };
  try {
    const abs = await resolveInLane(dir, file);
    const fs = require("node:fs");
    const st = await fs.promises.stat(abs);
    if (st.isFile()) {
      if (st.size > MAX_FILE_VIEW_BYTES) working = { ...working, missing: false, tooBig: true };
      else {
        const buf = await require("./run-as").readFileSafeAsync(abs);
        working = looksBinary(buf)
          ? { ...working, missing: false, binary: true }
          : { text: buf.toString("utf8"), sha: contentSha(buf), missing: false };
      }
    }
  } catch (err) {
    if (err.code === "ESECRET" || err.code === "EFOREIGN") throw err;
    /* gone from the tree: one side deleted it */
  }
  const operation = await operationInProgress(dir);
  let incoming = null;
  const head = operation && INCOMING_HEAD[operation];
  if (head) {
    const line = await git(dir, ["log", "-1", "--format=%H%x00%h%x00%s", head, "--"]).then(
      (r) => r.stdout.trim(),
      () => ""
    );
    if (line) {
      const [sha, short, subject] = line.split("\0");
      incoming = { sha, short, subject };
    }
  }
  const branch = (
    await git(dir, ["branch", "--show-current"]).catch(() => ({ stdout: "" }))
  ).stdout.trim();
  // Editable only when every side that exists is text under the cap and the
  // working file is there to save over.
  const sides = [base, ours, theirs];
  const usable =
    working.text != null && !working.binary && !sides.some((s) => s.binary || s.tooBig);
  return {
    path: file,
    operation,
    branch: branch || null,
    incoming,
    base: base.text,
    ours: ours.text,
    theirs: theirs.text,
    working: working.text,
    sha: working.sha,
    usable,
    binary: working.binary || sides.some((s) => s.binary),
    tooBig: working.tooBig || sides.some((s) => s.tooBig),
  };
}

/**
 * `conflict-save {path, content, baseSha, resolve?}`: the merge editor's
 * result over the working file — through lane-file-write.js (lanePath,
 * resolveInLane, ESECRET, existing text file only, `baseSha` → ESTALE) — then
 * `git add`, the same step `resolve done` takes. With `resolve` (default) a
 * result that still holds a marker is refused BEFORE anything is written
 * (EMARKERS); `resolve: false` saves the half-done result and leaves the file
 * in conflict.
 */
async function saveConflict(dir, body) {
  const { resolvePaths } = require("./git-ops")._internal;
  const [target] = await resolvePaths(dir, { path: body.path });
  if (!CONFLICT_CODES.has(target.code)) {
    throw bad("EBADPATH", `not a conflicted path: ${target.path}`);
  }
  const resolve = body.resolve !== false;
  if (typeof body.content !== "string") throw bad("EBADCONTENT", "content must be a string");
  if (resolve && MARKER_RE.test(body.content)) {
    throw bad("EMARKERS", `${target.path} still has conflict markers`);
  }
  await require("./lane-file-write").writeLaneFile(dir, target.path, body.content, body.baseSha);
  const out = resolve ? await git(dir, ["add", "--", target.path]) : { stdout: "", stderr: "" };
  const output = [out.stdout, out.stderr].filter(Boolean).join("").trim();
  return { action: "conflict-save", ok: true, output, resolved: resolve };
}

/**
 * One page of a reflog, newest first: `ref` is `HEAD` (default) or a local
 * branch that exists. Each entry: `{index, selector, sha, short, action,
 * message, time, subject}` — `action`/`message` split git's own reflog
 * subject ("commit: fix"), `subject` is the commit's. `more` says another page
 * exists. A ref with no reflog (never moved here) is an empty list.
 */
async function readReflog(dir, { ref, skip, limit } = {}) {
  let name = "HEAD";
  if (typeof ref === "string" && ref && ref !== "HEAD") {
    if (!(await isValidBranchName(dir, ref))) throw bad("EBADBRANCH", "not a branch name");
    const exists = await git(dir, ["show-ref", "--verify", "-q", `refs/heads/${ref}`]).then(
      () => true,
      () => false
    );
    if (!exists) throw bad("ENOBRANCH", `no local branch ${ref}`);
    name = `refs/heads/${ref}`;
  }
  const from = Math.max(0, Number.parseInt(skip, 10) || 0);
  const n = Math.min(MAX_REFLOG_PAGE, Math.max(1, Number.parseInt(limit, 10) || 50));
  const out = await git(dir, [
    "log",
    "-g",
    "--date=unix",
    "--format=%H%x00%h%x00%gd%x00%gs%x00%s",
    `--skip=${from}`,
    "-n",
    String(n + 1),
    name,
    "--",
  ]).then(
    (r) => r.stdout,
    () => ""
  );
  const rows = out.split("\n").filter(Boolean);
  const label = name === "HEAD" ? "HEAD" : ref;
  const entries = rows.slice(0, n).map((line, i) => {
    const [sha, short, sel, gs, subject] = line.split("\0");
    const time = Number((sel.match(/@\{(\d+)\}$/) || [])[1]) || null;
    const colon = gs.indexOf(": ");
    return {
      index: from + i,
      selector: `${label}@{${from + i}}`,
      sha,
      short,
      action: colon > 0 ? gs.slice(0, colon) : gs,
      message: colon > 0 ? gs.slice(colon + 2) : "",
      time,
      subject,
    };
  });
  return { ref: label, entries, more: rows.length > n };
}

module.exports = { readConflict, saveConflict, readReflog, unmergedStages, MARKER_RE };