/**
 * @file codex-mutate.js
 * @description Mutation helpers for the Codex Config panel. Handles
 * create / overwrite / delete on Codex's text-file surfaces: skills, agents,
 * rules, memory (AGENTS.md), and config (config.toml). Mirrors cc-mutate.js's
 * structure (single `resolveTarget` chokepoint, regex-validated names,
 * containment re-check, backup-before-mutation, atomic write) so the two
 * panels share the same safety shape and error-code vocabulary.
 *
 * Hard constraints (do not relax without a follow-up review):
 *   - `memory` and `config` are fixed filenames (AGENTS.md / config.toml) —
 *     they take NO `name`. Passing one is a caller error (EBADNAME).
 *   - Every write/delete of an existing file creates a timestamped backup
 *     BEFORE the mutation. Backups land under
 *     <root>/codex-config-backups/<type>/, a directory Codex never scans, so
 *     a deleted skill can never come back as a discoverable skill named
 *     after its backup.
 *   - Writes are atomic via temp file + fs.renameSync (see config-write.js).
 *   - Names are validated against a strict allowlist regex; resolved paths
 *     are double-checked to live under the expected containment root before
 *     any I/O.
 *   - Codex has no `project-local` scope and no auto-memory: only "user" and
 *     "project" are valid scopes.
 * @author Nguyễn Ngọc Trí Vĩ <vinnt@smartgift.vn>
 */

const fs = require("node:fs");
const path = require("node:path");
const { getCodexHome, getProjectCodexDir, getProjectRoot } = require("./codex-home");
const { MAX_FILE_BYTES } = require("./cc-discovery");
const { createBackup, atomicWriteFile, assertUnder } = require("./config-write");

const NAME_RE = /^[A-Za-z0-9][A-Za-z0-9._-]{0,63}$/;

const TYPES = {
  skills: { kind: "dir", subdir: "skills", filename: "SKILL.md" },
  agents: { kind: "file", subdir: "agents", ext: ".toml" },
  rules: { kind: "file", subdir: "rules", ext: ".rules" },
  memory: { kind: "fixed", file: "AGENTS.md" }, // AGENTS.md, no `name`
  config: { kind: "fixed", file: "config.toml" }, // config.toml, no `name`
};

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

function assertScope(scope) {
  if (scope !== "user" && scope !== "project") {
    throw makeError("EBADSCOPE", `unknown scope: ${scope}`);
  }
}

/** The <root> a (scope) resolves under for skills/agents/rules subdirs. */
function rootForScope(scope, opts = {}) {
  return scope === "user" ? getCodexHome() : getProjectCodexDir(opts.cwd);
}

/** Fixed-filename path for memory/config, per scope's own layout rule. */
function fixedPathFor(type, scope, opts = {}) {
  if (type === "memory") {
    return scope === "user"
      ? path.join(getCodexHome(), "AGENTS.md")
      : path.join(getProjectRoot(opts.cwd), "AGENTS.md");
  }
  // config
  return scope === "user"
    ? path.join(getCodexHome(), "config.toml")
    : path.join(getProjectCodexDir(opts.cwd), "config.toml");
}

/**
 * Resolve the on-disk target for a (scope, type, name) tuple AND the
 * containment root used for path-traversal checks.
 *
 * Returns: { kind: "file" | "dir", target, filePath, containmentRoot }
 */
function resolveTarget(scope, type, name, opts = {}) {
  const spec = TYPES[type];
  if (!spec) throw makeError("EBADTYPE", `unknown type: ${type}`);
  assertScope(scope);

  if (spec.kind === "fixed") {
    if (name !== undefined && name !== null) {
      throw makeError("EBADNAME", `${type} is a fixed file and takes no name`);
    }
    const filePath = fixedPathFor(type, scope, opts);
    return { kind: "file", target: filePath, filePath, containmentRoot: path.dirname(filePath) };
  }

  if (typeof name !== "string" || !NAME_RE.test(name)) {
    throw makeError("EBADNAME", `name must match ${NAME_RE}`);
  }

  const subdirAbs = path.join(rootForScope(scope, opts), spec.subdir);

  if (spec.kind === "dir") {
    const target = path.join(subdirAbs, name);
    return {
      kind: "dir",
      target,
      filePath: path.join(target, spec.filename),
      containmentRoot: subdirAbs,
    };
  }

  const target = path.join(subdirAbs, name + spec.ext);
  return { kind: "file", target, filePath: target, containmentRoot: subdirAbs };
}

/** <root>/codex-config-backups/<type>/, always rooted the same way as the read side's <root>. */
function backupRootFor(scope, type, opts = {}) {
  return path.join(rootForScope(scope, opts), "codex-config-backups", type);
}

function rmTreeSync(p) {
  fs.rmSync(p, { recursive: true, force: true });
}

// ── Public API ─────────────────────────────────────────────────────────

/**
 * Create or overwrite a single text artifact. `name` is required for
 * skills/agents/rules and forbidden for memory/config.
 *
 * @param {{scope:string, type:string, name?:string, content:string, cwd?:string}} args
 */
function writeArtifact(args) {
  const { scope, type, name, content, cwd } = args;
  if (typeof content !== "string") throw makeError("EBADCONTENT", "content must be a string");
  if (Buffer.byteLength(content, "utf8") > MAX_FILE_BYTES) {
    throw makeError("ETOOLARGE", `content exceeds ${MAX_FILE_BYTES} bytes`);
  }

  const r = resolveTarget(scope, type, name, { cwd });
  assertUnder(r.containmentRoot, r.target);

  const existedBefore = fs.existsSync(r.filePath);
  const backup = existedBefore
    ? createBackup({
        source: r.kind === "dir" ? r.target : r.filePath,
        backupRoot: backupRootFor(scope, type, { cwd }),
        type,
        name: path.basename(r.target),
      })
    : null;

  if (r.kind === "dir") {
    fs.mkdirSync(r.target, { recursive: true });
  }
  atomicWriteFile(r.filePath, content);

  return { file: r.filePath, created: !existedBefore, backup };
}

/**
 * Delete a single text artifact. Backup is mandatory and runs first; if
 * the target does not exist, no backup is attempted.
 */
function deleteArtifact(args) {
  const { scope, type, name, cwd } = args;
  const r = resolveTarget(scope, type, name, { cwd });
  assertUnder(r.containmentRoot, r.target);

  if (!fs.existsSync(r.target)) {
    throw makeError("ENOTFOUND", `${type}/${name || TYPES[type].file} does not exist`);
  }

  const backup = createBackup({
    source: r.target,
    backupRoot: backupRootFor(scope, type, { cwd }),
    type,
    name: path.basename(r.target),
  });

  if (r.kind === "dir") {
    rmTreeSync(r.target);
  } else {
    fs.unlinkSync(r.target);
  }

  return { file: r.filePath, backup };
}

/**
 * List backups for either all types or a specific (scope, type) bucket.
 * Returns [{ type, name, file, mtime, size }].
 */
function listBackups(opts = {}) {
  const out = [];
  const scopes = opts.scope ? [opts.scope] : ["user", "project"];
  const types = opts.type ? [opts.type] : Object.keys(TYPES);
  for (const scope of scopes) {
    for (const type of types) {
      const root = backupRootFor(scope, type, opts);
      let entries = [];
      try {
        entries = fs.readdirSync(root, { withFileTypes: true });
      } catch {
        continue;
      }
      for (const ent of entries) {
        const full = path.join(root, ent.name);
        let stat;
        try {
          stat = fs.statSync(full);
        } catch {
          continue;
        }
        out.push({
          type,
          name: ent.name,
          file: full,
          mtime: stat.mtimeMs,
          size: ent.isDirectory() ? null : stat.size,
        });
      }
    }
  }
  return out.sort((a, b) => b.mtime - a.mtime);
}

module.exports = {
  writeArtifact,
  deleteArtifact,
  listBackups,
  resolveTarget, // exported for tests
  TYPES,
  NAME_RE,
};