import { getUserById, getRoleGrants } from 'officerdb';
import type { UserRole } from 'officerdb';
import {
  PERMISSION_BY_KEY,
  CORE_PERMISSIONS,
  permissionForApiPath,
  permissionForWsProvider,
  isRequestAllowedAtLevel,
  isSelfServiceRoute,
  type PermissionLevel,
} from './registry';

// Resolving "may this account do this". Every deny path in the platform ends up here.
//
// Two rules run the whole file:
//
//   1. The owner bypasses everything. isSuperAdmin is the single question asked first, and a Super Admin
//      never consults the grants table — which is why the schema refuses to store a row for that role.
//   2. Everyone else gets core permissions plus whatever their ROLE has been granted, and nothing else.
//      An unrecognised permission, a missing row, a database error, a user who no longer exists: all deny.
//
// Fail-closed is not decoration here. This function is what stands between a Member and a shell, and the
// failure mode of a permissive default is not a bug report — it is someone else's session. Every catch in
// this file returns "no", and none of them log-and-continue.

export type EffectivePermissions = {
  isOwner: boolean;
  /** Permission key → level. Empty for an account with nothing granted; the owner's is never consulted. */
  grants: Map<string, PermissionLevel>;
};

// ── Grant cache ───────────────────────────────────────────────────────────────────────────────────
//
// Keyed on ROLE, not user, so it holds at most one entry per role and a new account needs no warm-up.
//
// super-admin.ts deliberately does NOT cache, and says why: a cache with no invalidation contract is a
// staleness bug waiting for whoever builds the role UI. This one has a contract — the only writer is the
// grants API in api/users, which calls invalidateRoleGrants on every mutation, in this same process. That
// is the entire set of writers; if a second one ever appears it has to call this too, which is why the
// cache and its invalidator live in the same file as the reader that depends on them.
const grantCache = new Map<UserRole, Map<string, PermissionLevel>>();

/** Called by every path that writes a grant. Clears one role, or all of them. */
export function invalidateRoleGrants(role?: UserRole): void {
  if (role) grantCache.delete(role);
  else grantCache.clear();
}

async function grantsForRole(role: UserRole): Promise<Map<string, PermissionLevel>> {
  const cached = grantCache.get(role);
  if (cached) return cached;
  const grants = (await getRoleGrants(role)) as Map<string, PermissionLevel>;
  grantCache.set(role, grants);
  return grants;
}

/**
 * What this account may reach, resolved from its role.
 *
 * Core permissions come in at `write` unconditionally: they are the caller's own profile, dock and bug
 * reports, and a read-only version of "change your own password" is not a coherent thing to offer.
 *
 * `execution` and `admin` permissions are dropped even if a row somehow grants them. The API refuses to
 * write such a row, but this is the layer that has to hold if one ever exists — a constraint the database
 * does not enforce is a constraint the reader must.
 */
export async function getEffectivePermissions(userId: number | undefined): Promise<EffectivePermissions> {
  const empty: EffectivePermissions = { isOwner: false, grants: new Map() };
  if (!userId) return empty;

  try {
    const user = await getUserById(userId);
    if (!user) return empty;
    if (user.role === 'Super Admin') return { isOwner: true, grants: new Map() };

    const grants = new Map<string, PermissionLevel>();
    for (const permission of CORE_PERMISSIONS) grants.set(permission.key, 'write');

    // Whether the kernel can enforce a boundary for this account. `confined` permissions are dropped
    // without it — see below.
    const hasOsAccount = !!user.osUser;

    for (const [key, level] of await grantsForRole(user.role)) {
      const permission = PERMISSION_BY_KEY.get(key);
      // Unknown key: a permission that was renamed or removed while a grant survived. Ignore it — the
      // alternative is honouring a name nothing defines.
      if (!permission) continue;

      // A confined permission touches the filesystem or runs a process, and is safe only because the
      // account has its own Linux user to be confined to. Without one there is no boundary, so the grant
      // resolves to nothing rather than to the owner's home — which is what it WOULD resolve to, since
      // `getOwnerHomeDir` ignores the email it is passed, always.
      //
      // Dropped here rather than refused per-router so that one rule covers the HTTP routes, the
      // websocket doors and the dock all at once. A member with `files` granted but no OS account sees no
      // Files icon, gets a 403 from /api/file-browser, and cannot open the terminal socket — from this.
      if (permission.kind === 'confined') {
        if (!hasOsAccount) continue;
        grants.set(key, level);
        continue;
      }

      if (permission.kind !== 'app') continue;
      grants.set(key, level);
    }

    return { isOwner: false, grants };
  } catch {
    // A transient database error must never grant anything. Deny, and let the next request retry.
    return empty;
  }
}

/**
 * May this account make this HTTP request?
 *
 * `path` is the full request path. Paths outside `/api` are not this function's business — the DAV sync
 * door authenticates with its own app password and never carries a platform account.
 */
export async function isApiRequestAllowed(
  userId: number | undefined,
  method: string,
  path: string,
): Promise<{ allowed: boolean; reason?: string }> {
  const { isOwner, grants } = await getEffectivePermissions(userId);
  if (isOwner) return { allowed: true };

  const permission = permissionForApiPath(path);
  // Totality guarantees every mounted, non-exempt prefix maps to a permission, so reaching this branch
  // means either an exempt prefix (which the caller checks before us) or a path nothing serves. Deny:
  // a 403 on a route that does not exist is not a leak, and a permissive default here would be.
  if (!permission) return { allowed: false, reason: 'no permission covers this path' };

  // Checked before kind, because a self-service route acts on the caller and is therefore not the thing
  // the permission around it restricts. Exact method and path only — see the field's comment.
  if (isSelfServiceRoute(permission, method, path)) return { allowed: true };

  if (permission.kind === 'execution') {
    return { allowed: false, reason: `${permission.label} runs as the server owner and cannot be shared` };
  }
  if (permission.kind === 'admin') {
    return { allowed: false, reason: `${permission.label} is restricted to the server owner` };
  }

  const level = grants.get(permission.key);
  if (!level) return { allowed: false, reason: `your role does not have access to ${permission.label}` };

  if (!isRequestAllowedAtLevel(permission, level, method, path)) {
    return { allowed: false, reason: `you have read-only access to ${permission.label}` };
  }
  return { allowed: true };
}

/**
 * May this account open this WebSocket provider?
 *
 * There is no method to reason about, so a socket needs the permission at any level.
 *
 * That rule was written for cliamp and cliamp-audio — the music app's playback transport, and the only
 * grantable sockets there have ever been. Both left on 2026-08-15 with `plugins/music/cliamp/`, so every
 * provider reaching here today belongs to an `execution` permission and is refused above, structurally,
 * rather than by being left off a list. The rule stays because the first plugin to own a socket needs it.
 */
export async function isWsProviderAllowed(userId: number | undefined, provider: string): Promise<boolean> {
  const { isOwner, grants } = await getEffectivePermissions(userId);
  if (isOwner) return true;

  const permission = permissionForWsProvider(provider);
  // `confined` is admissible here as well as `app`: getEffectivePermissions has already dropped confined
  // grants for an account with no Linux user, so reaching this line with one in `grants` means the boundary
  // exists. Anything still `execution` is refused structurally, by not being in the map at all.
  if (!permission || (permission.kind !== 'app' && permission.kind !== 'confined')) return false;
  return grants.has(permission.key);
}