// The access file, <configDir>/access.json (federation design section 3.5,
// FED R1, #414). It names the extra users who may sign in to this instance
// and the grants that let them reach a business's threads. The validator is
// pure: providers, peers, businesses and the owner's sign-in subjects come in
// as arguments. Any failed rule refuses the whole file, which leaves every
// user with no grant (fail closed).

import { join } from "node:path";
import { refuse } from "./errors.mjs";
import { configDir } from "./organization-config.mjs";
import { isPlainObject, requireObject, rejectUnknownKeys, requireId, requirePositiveInt, readJsonFile, deepFreeze } from "./util.mjs";
// FED R3 r5 (row 274): LEVELS, the all marker and covers() live in the vocabulary, which the session
// sandbox mounts, because the broker checks a user's grant with covers(). This file re-exports them.
import { LEVELS, GRANT_ALL as ALL, covers } from "./vocabulary.mjs";

export { LEVELS, covers };

// Ids a user may never take: the bus's own principals.
const RESERVED_USERS = Object.freeze(["human", "tester"]);
const LOCAL_HOME = "local";
const UUID = /^[0-9a-f]{8}-[0-9a-f]{4}-[0-9a-f]{4}-[0-9a-f]{4}-[0-9a-f]{12}$/;
const ISO_TIME = /^\d{4}-\d{2}-\d{2}T\d{2}:\d{2}:\d{2}(\.\d{1,3})?Z$/;
const SUB_MAX = 255;

export function accessFilePath(dir = configDir()) {
  return join(dir, "access.json");
}

function requireArray(value, where) {
  if (!Array.isArray(value)) refuse(`${where} must be an array`);
  return value;
}

function requireText(value, where) {
  if (typeof value !== "string" || value.length === 0 || value.length > SUB_MAX || value.includes("\0")) {
    refuse(`${where} must be a non-empty string of at most ${SUB_MAX} characters`);
  }
  return value;
}

function subjectKey(provider, sub) {
  return JSON.stringify([provider, sub]);
}

function checkContext(context) {
  const where = "access context";
  requireObject(context, where);
  rejectUnknownKeys(context, ["providers", "peers", "businesses", "ssoSubjects"], where);
  const providers = new Set(requireArray(context.providers, `${where}.providers`).map((p, i) => requireText(p, `${where}.providers[${i}]`)));
  const peers = new Set(requireArray(context.peers, `${where}.peers`).map((p, i) => requireId(p, `${where}.peers[${i}]`)));
  if (peers.has(LOCAL_HOME)) refuse(`${where}.peers must not name ${JSON.stringify(LOCAL_HOME)}`);
  requireObject(context.businesses, `${where}.businesses`);
  const businesses = new Map();
  for (const [id, business] of Object.entries(context.businesses)) {
    const at = `${where}.businesses.${id}`;
    requireId(id, `${where}.businesses key`);
    requireObject(business, at);
    requireId(business.human, `${at}.human`);
    const instances = requireArray(business.instances, `${at}.instances`).map((x, i) => requireId(x, `${at}.instances[${i}]`));
    businesses.set(id, { human: business.human, instances: new Set(instances) });
  }
  const owners = new Set();
  requireArray(context.ssoSubjects, `${where}.ssoSubjects`).forEach((s, i) => {
    const at = `${where}.ssoSubjects[${i}]`;
    requireObject(s, at);
    owners.add(subjectKey(requireText(s.provider, `${at}.provider`), requireText(s.sub, `${at}.sub`)));
  });
  return { providers, peers, businesses, owners };
}

function checkUser(user, at, ctx, humans, seenSubjects) {
  requireObject(user, at);
  rejectUnknownKeys(user, ["id", "home", "subjects"], at);
  requireId(user.id, `${at}.id`);
  if (RESERVED_USERS.includes(user.id)) refuse(`${at}.id must not be ${JSON.stringify(user.id)}, a bus principal`);
  if (humans.has(user.id)) refuse(`${at}.id must not be a business's human (${JSON.stringify(user.id)})`);
  if (user.home !== LOCAL_HOME && !ctx.peers.has(user.home)) {
    refuse(`${at}.home must be a configured peer or ${JSON.stringify(LOCAL_HOME)}`);
  }
  const subjects = requireArray(user.subjects, `${at}.subjects`);
  if (subjects.length === 0) refuse(`${at}.subjects must not be empty`);
  subjects.forEach((s, i) => {
    const sat = `${at}.subjects[${i}]`;
    requireObject(s, sat);
    rejectUnknownKeys(s, ["provider", "sub"], sat);
    if (typeof s.provider !== "string" || !ctx.providers.has(s.provider)) {
      refuse(`${sat}.provider must be a configured provider`);
    }
    requireText(s.sub, `${sat}.sub`);
    const key = subjectKey(s.provider, s.sub);
    if (ctx.owners.has(key)) refuse(`${sat} is an owner sign-in subject (console.sso.subjects)`);
    if (seenSubjects.has(key)) refuse(`${sat} appears more than once in the file`);
    seenSubjects.add(key);
  });
}

// Either ["*"] alone or a non-empty list of distinct entries, each checked.
function checkScope(value, where, check) {
  const list = requireArray(value, where);
  if (list.length === 0) refuse(`${where} must not be empty`);
  if (list.includes(ALL)) {
    if (list.length !== 1) refuse(`${where} must be ["*"] alone or list entries without "*"`);
    return;
  }
  const seen = new Set();
  list.forEach((entry, i) => {
    check(entry, `${where}[${i}]`);
    if (seen.has(entry)) refuse(`duplicate entry in ${where}: ${JSON.stringify(entry)}`);
    seen.add(entry);
  });
}

function checkExpires(value, where) {
  if (typeof value !== "string" || !ISO_TIME.test(value) || Number.isNaN(Date.parse(value))) {
    refuse(`${where} must be an ISO time such as 2026-12-31T00:00:00Z`);
  }
  const iso = new Date(value).toISOString();
  if (iso.slice(0, 19) !== value.slice(0, 19)) refuse(`${where} is not a real time`);
}

function checkGrant(grant, at, ctx, users, seenGrants) {
  requireObject(grant, at);
  rejectUnknownKeys(grant, ["id", "user", "business", "projects", "instances", "level", "expires"], at);
  requireId(grant.id, `${at}.id`);
  if (seenGrants.has(grant.id)) refuse(`${at}.id is a duplicate grant id: ${grant.id}`);
  seenGrants.add(grant.id);
  if (typeof grant.user !== "string" || !users.has(grant.user)) refuse(`${at}.user must name a user in this file`);
  if (typeof grant.business !== "string" || !ctx.businesses.has(grant.business)) {
    refuse(`${at}.business must name a declared business`);
  }
  const business = ctx.businesses.get(grant.business);
  checkScope(grant.projects, `${at}.projects`, (p, where) => {
    if (typeof p !== "string" || !UUID.test(p)) refuse(`${where} must be "*" or a bus project id, a lowercase UUID`);
  });
  checkScope(grant.instances, `${at}.instances`, (x, where) => {
    if (typeof x !== "string" || !business.instances.has(x)) refuse(`${where} must be "*" or a declared instance of the grant's business`);
  });
  if (!LEVELS.includes(grant.level)) refuse(`${at}.level must be one of ${LEVELS.join(", ")}`);
  if (grant.expires !== undefined) checkExpires(grant.expires, `${at}.expires`);
}

// Check a parsed access document against the instance's context. Returns the
// document frozen. Every refusal is a BusinessError naming the key path. An
// expired grant is not refused: covers() treats it as absent.
export function checkAccess(document, context) {
  const ctx = checkContext(context);
  const humans = new Set([...ctx.businesses.values()].map((b) => b.human));
  if (!isPlainObject(document)) refuse("access file must be a JSON object");
  rejectUnknownKeys(document, ["accessVersion", "revision", "users", "grants"], "access file");
  if (document.accessVersion !== 1) refuse(`accessVersion must be 1`);
  requirePositiveInt(document.revision, "revision");
  const users = new Set();
  const seenSubjects = new Set();
  requireArray(document.users, "users").forEach((user, i) => {
    checkUser(user, `users[${i}]`, ctx, humans, seenSubjects);
    if (users.has(user.id)) refuse(`users[${i}].id is a duplicate user id: ${user.id}`);
    users.add(user.id);
  });
  const seenGrants = new Set();
  requireArray(document.grants, "grants").forEach((grant, i) => checkGrant(grant, `grants[${i}]`, ctx, users, seenGrants));
  return deepFreeze(structuredClone(document));
}

// Read and check the access file. One descriptor, opened without following a
// link, serves the stat checks and the read (readJsonFile). The file holds
// authority, so it must belong to this uid and not be writable by group or
// other, as the business file is.
export function loadAccess(file, context, { uid = process.getuid() } = {}) {
  const document = readJsonFile(file, "access file", (stat) => {
    if (stat.uid !== uid) refuse(`access file must belong to uid ${uid}`);
    if ((stat.mode & 0o022) !== 0) refuse(`access file must not be writable by group or other (mode ${(stat.mode & 0o777).toString(8)})`);
  });
  return checkAccess(document, context);
}