/**
 * Credential bundles under `~/.mosaic/auth/<harness>/<bundle>/`.
 *
 * A bundle is one account's credentials for one harness. Seats point at a bundle by name in
 * their `profile.json`, so two seats can hold genuinely different principals on one host --
 * which is the whole reason the fleet can run an author seat and a reviewer seat without the
 * review being self-review wearing two hats.
 *
 * Enrolling does not reimplement any harness's login. It creates the bundle directory, points
 * the harness at it by environment, and runs the harness's own login. What this module owns is
 * everything around that: that the directory is a real directory nobody can read but its owner,
 * that the credential actually landed, and that the account you logged in as is the account the
 * bundle claims to hold.
 *
 * Composition-side reader: commands/fleet-launch-command.ts resolveCredential().
 */

import {
  chmodSync,
  lstatSync,
  mkdirSync,
  readFileSync,
  readdirSync,
  realpathSync,
  rmSync,
  symlinkSync,
  writeFileSync,
  type Stats,
} from 'node:fs';
import { isAbsolute, join, relative, resolve, sep } from 'node:path';
import {
  CREDENTIAL_DIR_ENV,
  CREDENTIAL_FILE_NAMES,
  type CredentialHarness,
} from './credential-sharing.js';

/** Mirrors BUNDLE_NAME in commands/fleet-launch-command.ts; drift here is a launch failure. */
const BUNDLE_NAME = /^[A-Za-z0-9][A-Za-z0-9_.@-]*$/;

/**
 * The movable alias. `"bundle": "primary"` in a profile follows whatever this points at; a
 * named bundle stays pinned. It is the only symlink launch tolerates in an auth root.
 */
export const PRIMARY_ALIAS = 'primary';

/** Where each harness expects its own home, so login writes into the bundle we just made. */
const HOME_ENV_NAME: Record<CredentialHarness, string> = {
  claude: 'CLAUDE_CONFIG_DIR',
  pi: 'PI_CODING_AGENT_DIR',
  codex: 'CODEX_HOME',
  opencode: 'XDG_CONFIG_HOME',
};

/**
 * Files a harness writes that carry the logged-in account's identity, and the paths within
 * them to try. Best effort by design: a harness we cannot read an identity from still enrolls,
 * it just cannot be checked against its bundle name.
 */
const IDENTITY_SOURCES: Record<CredentialHarness, ReadonlyArray<readonly [string, string[]]>> = {
  claude: [
    ['.claude.json', ['oauthAccount.emailAddress', 'oauthAccount.email']],
    ['.credentials.json', ['claudeAiOauth.emailAddress']],
  ],
  pi: [['auth.json', ['account.email', 'email', 'user.email']]],
  codex: [['auth.json', ['tokens.id_token.email', 'account.email', 'email']]],
  opencode: [['auth.json', ['account.email', 'email']]],
};

export type AuthBundleErrorCode =
  | 'invalid-request'
  | 'bundle-not-found'
  | 'bundle-exists'
  | 'credential-missing'
  | 'unsafe-shape';

export class AuthBundleError extends Error {
  readonly code: AuthBundleErrorCode;

  constructor(code: AuthBundleErrorCode, message: string) {
    super(message);
    this.name = 'AuthBundleError';
    this.code = code;
  }
}

export interface BundleInfo {
  readonly name: string;
  /** Absolute path of the entry as named, before alias resolution. */
  readonly path: string;
  /** Where it actually lives. Differs from `path` only for the primary alias. */
  readonly resolved: string;
  /** True when this entry is the movable primary alias rather than a real bundle. */
  readonly alias: boolean;
  /** Alias target's bundle name, when this is the alias. */
  readonly target?: string;
  /** True when the harness's credential file is present in the resolved bundle. */
  readonly enrolled: boolean;
  /** Account identity recorded at enrollment, when one could be determined. */
  readonly email?: string;
}

export interface EnrollmentPlan {
  readonly harness: CredentialHarness;
  readonly bundle: string;
  readonly bundleDir: string;
  /** Absolute path the harness must end up writing its credential to. */
  readonly credentialPath: string;
  /** True when the directory did not exist before this call. */
  readonly created: boolean;
  /** True when a credential was already present -- a re-login, not a first enrollment. */
  readonly hadCredential: boolean;
  /**
   * Environment the harness login must run under. Every value is an absolute path; Claude
   * reads an empty credential-dir value as ~/.claude, the operator's own account, so an
   * empty value is never produced here.
   */
  readonly env: Readonly<Record<string, string>>;
}

export interface EnrollmentResult {
  readonly harness: CredentialHarness;
  readonly bundle: string;
  readonly bundleDir: string;
  readonly credentialPath: string;
  /** Identity read back out of what the harness wrote, when it could be determined. */
  readonly email?: string;
  /**
   * Set when an identity was found and it does not match the bundle name. Logging into the
   * wrong account is silent otherwise, and it is the failure that quietly collapses two
   * principals back into one.
   */
  readonly identityMismatch?: string;
  /** True when the credential file's permissions had to be tightened to owner-only. */
  readonly tightened: boolean;
}

function lstatIfPresent(path: string): Stats | undefined {
  try {
    return lstatSync(path);
  } catch (error: unknown) {
    if ((error as NodeJS.ErrnoException).code === 'ENOENT') return undefined;
    throw error;
  }
}

function assertContained(root: string, candidate: string, label: string): void {
  const rel = relative(resolve(root), resolve(candidate));
  if (rel === '..' || rel.startsWith(`..${sep}`) || isAbsolute(rel)) {
    throw new AuthBundleError('unsafe-shape', `${label} resolves outside ${root}: ${candidate}`);
  }
}

/** Reject a name before it is ever joined onto a path. */
export function assertSafeBundleName(bundle: string): void {
  if (!BUNDLE_NAME.test(bundle)) {
    throw new AuthBundleError(
      'invalid-request',
      `"${bundle}" is not a safe bundle name; use letters, digits, and . _ @ -`,
    );
  }
}

/** `~/.mosaic/auth/<harness>`. */
export function authRoot(userHome: string, harness: CredentialHarness): string {
  return join(userHome, 'auth', harness);
}

/**
 * Create the auth root chain with owner-only permissions, refusing anything that is not a
 * real directory. An explicit mode on mkdir is not enough on its own -- it is masked by the
 * ambient umask -- so each level is chmod'ed after creation.
 */
function ensurePrivateDirectory(path: string, label: string): boolean {
  const info = lstatIfPresent(path);
  if (info) {
    if (!info.isDirectory() || info.isSymbolicLink()) {
      throw new AuthBundleError(
        'unsafe-shape',
        `${label} must be a real, non-symlink directory: ${path}`,
      );
    }
    if ((info.mode & 0o077) !== 0) chmodSync(path, 0o700);
    return false;
  }
  mkdirSync(path, { recursive: true, mode: 0o700 });
  chmodSync(path, 0o700);
  return true;
}

function readJson(path: string): Record<string, unknown> | undefined {
  const info = lstatIfPresent(path);
  if (!info?.isFile() || info.isSymbolicLink()) return undefined;
  try {
    const value: unknown = JSON.parse(readFileSync(path, 'utf8'));
    if (typeof value !== 'object' || value === null || Array.isArray(value)) return undefined;
    return value as Record<string, unknown>;
  } catch {
    return undefined;
  }
}

function dig(source: Record<string, unknown>, dotted: string): string | undefined {
  let cursor: unknown = source;
  for (const key of dotted.split('.')) {
    if (typeof cursor !== 'object' || cursor === null || Array.isArray(cursor)) return undefined;
    cursor = (cursor as Record<string, unknown>)[key];
  }
  return typeof cursor === 'string' && cursor.trim() !== '' ? cursor.trim() : undefined;
}

/** Best-effort account identity from whatever the harness wrote into the bundle. */
export function readBundleIdentity(
  bundleDir: string,
  harness: CredentialHarness,
): string | undefined {
  const recorded = readJson(join(bundleDir, 'account.json'));
  if (recorded) {
    for (const path of ['emailAddress', 'email', 'oauthAccount.emailAddress']) {
      const found = dig(recorded, path);
      if (found) return found;
    }
  }
  for (const [file, paths] of IDENTITY_SOURCES[harness]) {
    const source = readJson(join(bundleDir, file));
    if (!source) continue;
    for (const path of paths) {
      const found = dig(source, path);
      if (found) return found;
    }
  }
  return undefined;
}

/**
 * The bundle name an email implies. Bundles are named by account identity so that a roster
 * row's `"bundle"` says who the seat is, not merely which slot it uses.
 */
export function bundleNameForEmail(email: string): string {
  return email.trim().toLowerCase().replace(/@/gu, '_');
}

/**
 * Create the bundle directory and describe the environment its login must run under.
 *
 * This deliberately stops short of running anything. The caller runs the harness's own login
 * under `plan.env`, then calls completeEnrollment() to check what landed.
 */
export function prepareEnrollment(
  userHome: string,
  harness: CredentialHarness,
  bundle: string,
): EnrollmentPlan {
  assertSafeBundleName(bundle);
  if (bundle === PRIMARY_ALIAS) {
    throw new AuthBundleError(
      'invalid-request',
      `"${PRIMARY_ALIAS}" is a movable alias, not a bundle. Enroll a bundle named for the account (for example: mosaic auth enroll --harness ${harness} --bundle jason_woltje.com), then point the alias at it with: mosaic auth default --harness ${harness} <bundle>`,
    );
  }

  ensurePrivateDirectory(userHome, 'user Mosaic root');
  ensurePrivateDirectory(join(userHome, 'auth'), 'auth directory');
  const root = authRoot(userHome, harness);
  ensurePrivateDirectory(root, `${harness} auth root`);

  const bundleDir = join(root, bundle);
  assertContained(realpathSync(root), resolve(bundleDir), 'credential bundle');
  const created = ensurePrivateDirectory(bundleDir, 'credential bundle');

  const credentialPath = join(bundleDir, CREDENTIAL_FILE_NAMES[harness]);
  const credentialDirEnvName = CREDENTIAL_DIR_ENV[harness];
  return {
    harness,
    bundle,
    bundleDir,
    credentialPath,
    created,
    hadCredential: lstatIfPresent(credentialPath)?.isFile() === true,
    env: {
      [HOME_ENV_NAME[harness]]: bundleDir,
      ...(credentialDirEnvName === undefined ? {} : { [credentialDirEnvName]: bundleDir }),
    },
  };
}

/**
 * Check what the harness login actually left behind, tighten it, and record the identity.
 *
 * A login that exits zero having written nothing is the failure worth catching here: the seat
 * would then fail much later, at composition, with a message about a missing credential and no
 * hint that the login was the thing that did not work.
 */
export function completeEnrollment(plan: EnrollmentPlan): EnrollmentResult {
  const info = lstatIfPresent(plan.credentialPath);
  if (!info?.isFile() || info.isSymbolicLink()) {
    throw new AuthBundleError(
      'credential-missing',
      `login left no credential at ${plan.credentialPath}. The bundle directory exists but is not enrolled; nothing was assigned.`,
    );
  }
  let tightened = false;
  if ((info.mode & 0o077) !== 0) {
    chmodSync(plan.credentialPath, 0o600);
    tightened = true;
  }

  const email = readBundleIdentity(plan.bundleDir, plan.harness);
  if (email !== undefined) {
    writeFileSync(
      join(plan.bundleDir, 'account.json'),
      `${JSON.stringify({ emailAddress: email, harness: plan.harness }, null, 2)}\n`,
      { mode: 0o600 },
    );
    chmodSync(join(plan.bundleDir, 'account.json'), 0o600);
  }

  const expected = email === undefined ? undefined : bundleNameForEmail(email);
  return {
    harness: plan.harness,
    bundle: plan.bundle,
    bundleDir: plan.bundleDir,
    credentialPath: plan.credentialPath,
    ...(email === undefined ? {} : { email }),
    ...(expected === undefined || expected === plan.bundle.toLowerCase()
      ? {}
      : { identityMismatch: expected }),
    tightened,
  };
}

/** Every entry in a harness's auth root, alias included, with enrollment state. */
export function listBundles(userHome: string, harness: CredentialHarness): BundleInfo[] {
  const root = authRoot(userHome, harness);
  const info = lstatIfPresent(root);
  if (!info) return [];
  if (!info.isDirectory() || info.isSymbolicLink()) {
    throw new AuthBundleError(
      'unsafe-shape',
      `${harness} auth root must be a real, non-symlink directory: ${root}`,
    );
  }

  const entries: BundleInfo[] = [];
  for (const entry of readdirSync(root, { withFileTypes: true }).sort((a, b) =>
    a.name < b.name ? -1 : a.name > b.name ? 1 : 0,
  )) {
    if (!entry.isDirectory() && !entry.isSymbolicLink()) continue;
    const path = join(root, entry.name);
    let resolved: string;
    try {
      resolved = realpathSync(path);
    } catch {
      // A dangling alias is real state worth showing rather than a reason to fail the listing.
      entries.push({ name: entry.name, path, resolved: path, alias: true, enrolled: false });
      continue;
    }
    const alias = entry.isSymbolicLink();
    const credential = join(resolved, CREDENTIAL_FILE_NAMES[harness]);
    const email = readBundleIdentity(resolved, harness);
    entries.push({
      name: entry.name,
      path,
      resolved,
      alias,
      ...(alias ? { target: resolved.slice(resolved.lastIndexOf(sep) + 1) } : {}),
      enrolled: lstatIfPresent(credential)?.isFile() === true,
      ...(email === undefined ? {} : { email }),
    });
  }
  return entries;
}

/**
 * Point the movable `primary` alias at a real bundle.
 *
 * Relative so the whole `~/.mosaic` tree stays relocatable, and replaced rather than followed
 * so retargeting never writes through into the old bundle.
 */
export function setDefaultBundle(
  userHome: string,
  harness: CredentialHarness,
  bundle: string,
): string {
  assertSafeBundleName(bundle);
  if (bundle === PRIMARY_ALIAS) {
    throw new AuthBundleError('invalid-request', `the ${PRIMARY_ALIAS} alias cannot target itself`);
  }
  const root = authRoot(userHome, harness);
  const target = join(root, bundle);
  const info = lstatIfPresent(target);
  if (!info) {
    throw new AuthBundleError(
      'bundle-not-found',
      `no such bundle: ${target} — enroll it first: mosaic auth enroll --harness ${harness} --bundle ${bundle}`,
    );
  }
  if (!info.isDirectory() || info.isSymbolicLink()) {
    throw new AuthBundleError(
      'unsafe-shape',
      `the ${PRIMARY_ALIAS} alias may only target a real bundle directory: ${target}`,
    );
  }

  const alias = join(root, PRIMARY_ALIAS);
  const existing = lstatIfPresent(alias);
  if (existing && !existing.isSymbolicLink()) {
    throw new AuthBundleError(
      'unsafe-shape',
      `a real directory occupies the ${PRIMARY_ALIAS} alias path and will not be deleted: ${alias}. Move it aside, or enroll under its own name.`,
    );
  }
  if (existing) rmSync(alias);
  symlinkSync(bundle, alias);
  return alias;
}