import { apiError, type ApiErrorCode } from '@/lib/server/api-response';
import type {
  PersistClassroomOwnership,
  PersistedClassroomData,
} from '@/lib/server/classroom-storage';
import {
  evaluateResourceAuthorization,
  resolveIdentityEnforcementMode,
  type IdentityEnforcementMode,
} from '@/lib/server/authz/identity-enforcement';
import {
  resolveRequestPrincipal,
  type PrincipalResolution,
  type RequestPrincipalResolver,
} from '@/lib/server/authz/principal';
import { resourceOwnerBindingFromPrincipal } from '@/lib/server/authz/owner-binding';
import type { ResourceAuthorizationAction } from '@/lib/server/authz/resource-ownership';

export const CLASSROOM_MANAGE_ANY_CAPABILITY = 'classroom:manage:any';
export const CLASSROOM_CREATE_ANY_CAPABILITY = 'classroom:create:any';

export interface ClassroomAccessDeps {
  readonly mode?: IdentityEnforcementMode;
  readonly resolvePrincipal?: RequestPrincipalResolver;
}

export interface ClassroomAccessDenial {
  readonly allowed: false;
  readonly status: number;
  readonly code: ApiErrorCode;
  readonly message: string;
}

export interface ClassroomAccessAllowed {
  readonly allowed: true;
}

export type ClassroomAccessResult = ClassroomAccessAllowed | ClassroomAccessDenial;
export type ClassroomCreationAccessResult =
  | (ClassroomAccessAllowed & { readonly ownership: PersistClassroomOwnership })
  | ClassroomAccessDenial;

function classroomOwnership(classroom: PersistedClassroomData) {
  const hasOwner = Object.prototype.hasOwnProperty.call(classroom, 'ownerPrincipalId');
  const hasGuest = Object.prototype.hasOwnProperty.call(classroom, 'guestPrincipalId');
  if (hasOwner && hasGuest) return { state: 'unknown' as const };
  if (hasOwner) {
    return { state: 'owned' as const, ownerPrincipalId: classroom.ownerPrincipalId ?? '' };
  }
  if (hasGuest) {
    return { state: 'guest-owned' as const, guestPrincipalId: classroom.guestPrincipalId ?? '' };
  }
  return { state: 'legacy-unowned' as const };
}

async function resolvePrincipalSafely(
  request: Request,
  resolver?: RequestPrincipalResolver,
): Promise<PrincipalResolution> {
  try {
    return await (resolver ?? resolveRequestPrincipal)(request);
  } catch {
    return { state: 'unavailable', reason: 'resolver_failed' };
  }
}

function denialFor(principal: PrincipalResolution, indeterminate = false): ClassroomAccessDenial {
  if (principal.state === 'unavailable') {
    return {
      allowed: false,
      status: 503,
      code: 'IDENTITY_UNAVAILABLE',
      message: 'Identity verification is unavailable.',
    };
  }
  if (principal.state === 'anonymous') {
    return {
      allowed: false,
      status: 401,
      code: 'AUTHENTICATION_REQUIRED',
      message: 'Authentication is required.',
    };
  }
  if (indeterminate) {
    return {
      allowed: false,
      status: 409,
      code: 'OWNERSHIP_MIGRATION_REQUIRED',
      message: 'This classroom must be assigned to an account before it can be used.',
    };
  }
  return {
    allowed: false,
    status: 403,
    code: 'FORBIDDEN',
    message: 'You do not have access to this classroom.',
  };
}

/** Resolve the server-side owner binding for a newly persisted classroom. */
export async function authorizeClassroomCreation(
  request: Request,
  deps: ClassroomAccessDeps = {},
): Promise<ClassroomCreationAccessResult> {
  const principal = await resolvePrincipalSafely(request, deps.resolvePrincipal);
  const ownership = resourceOwnerBindingFromPrincipal(principal);
  const mode = deps.mode ?? resolveIdentityEnforcementMode();
  if (mode === 'shadow') return { allowed: true, ownership };
  if (principal.state !== 'authenticated') return denialFor(principal);
  if (ownership.ownerPrincipalId || ownership.guestPrincipalId) {
    return { allowed: true, ownership };
  }
  if (principal.principal.capabilities.includes(CLASSROOM_CREATE_ANY_CAPABILITY)) {
    return { allowed: true, ownership: {} };
  }
  return denialFor(principal);
}

/** Enforce access to an existing raw classroom when identity is required. */
export async function authorizeClassroomRequest(
  request: Request,
  classroom: PersistedClassroomData,
  action: ResourceAuthorizationAction,
  deps: ClassroomAccessDeps = {},
): Promise<ClassroomAccessResult> {
  if ((deps.mode ?? resolveIdentityEnforcementMode()) === 'shadow') {
    return { allowed: true };
  }
  const evaluation = await evaluateResourceAuthorization(
    {
      request,
      ownership: classroomOwnership(classroom),
      action,
      overrideCapability: CLASSROOM_MANAGE_ANY_CAPABILITY,
    },
    deps.resolvePrincipal ? { resolvePrincipal: deps.resolvePrincipal } : {},
  );
  return evaluation.decision.effect === 'allow'
    ? { allowed: true }
    : denialFor(evaluation.principal, evaluation.decision.effect === 'indeterminate');
}

export function classroomAccessError(result: ClassroomAccessDenial) {
  return apiError(result.code, result.status, result.message);
}