import type {
  DomainRuntimeHandoffCandidate,
  DomainRuntimeHandoffSource,
} from './domain-access-orchestrator.js';
import {
  assertVerifiedNodePossession,
  type NodePossessionChallenge,
  type NodePossessionResponse,
  type VerifiedNodePossession,
} from './node-possession-proof.js';
import type { VerifiedNodeRegistration } from './node-registration.js';
import { randomUUID } from 'node:crypto';
import {
  assertRegisteredDomainRuntimeHandoffEndpoint,
  resolveDomainRuntimeHandoffEndpoint,
  type DomainRuntimeHandoffEndpoint,
} from './domain-runtime-handoff-registry.js';
import {
  assertLoadedDomainRuntimeHandoffSnapshot,
  type DomainRuntimeHandoffSnapshotLoader,
} from './domain-runtime-handoff-snapshot.js';

const IDENTIFIER_PATTERN = /^[A-Z0-9][A-Z0-9._:-]{1,159}$/;
const REQUEST_SCHEMA = 'gh-aios.domain-runtime-handoff-request/v1' as const;
const RESPONSE_SCHEMA = 'gh-aios.domain-runtime-handoff-response/v1' as const;
const consumedPossessions = new WeakSet<object>();
const MAX_RESPONSE_BYTES = 256 * 1024;

export interface DomainRuntimeHandoffRequest {
  accountId: string;
  challenge: Readonly<NodePossessionChallenge>;
  domainId: string;
  endpointId: string;
  issuedAt: number;
  nodeId: string;
  nodeType: VerifiedNodeRegistration['nodeType'];
  registration: Readonly<VerifiedNodeRegistration>;
  requestId: string;
  response: Readonly<NodePossessionResponse>;
  schema: typeof REQUEST_SCHEMA;
}

export interface DomainRuntimeHandoffTransport {
  request(
    endpoint: Readonly<DomainRuntimeHandoffEndpoint>,
    input: Readonly<DomainRuntimeHandoffRequest>,
  ): Promise<unknown>;
}

function isRecord(value: unknown): value is Record<string, unknown> {
  return typeof value === 'object' && value !== null && !Array.isArray(value);
}

function hasExactKeys(value: Record<string, unknown>, expected: readonly string[]): boolean {
  const actual = Object.keys(value).sort();
  const keys = [...expected].sort();
  return actual.length === keys.length && actual.every((key, index) => key === keys[index]);
}

function parseResponse(
  input: unknown,
  request: DomainRuntimeHandoffRequest,
): Readonly<DomainRuntimeHandoffCandidate> | null {
  if (!isRecord(input)
    || !hasExactKeys(input, ['handoff', 'request_id', 'schema', 'signer_lookup', 'status'])
    || input.schema !== RESPONSE_SCHEMA
    || input.request_id !== request.requestId
    || (input.status !== 'ISSUED' && input.status !== 'NOT_AUTHORIZED')) {
    return null;
  }
  if (input.status === 'NOT_AUTHORIZED') {
    if (input.handoff !== null || input.signer_lookup !== null) return null;
    return null;
  }
  if (!isRecord(input.handoff)
    || !isRecord(input.signer_lookup)
    || !hasExactKeys(input.signer_lookup, ['repository_id', 'signer_id'])
    || typeof input.signer_lookup.repository_id !== 'string'
    || !IDENTIFIER_PATTERN.test(input.signer_lookup.repository_id)
    || typeof input.signer_lookup.signer_id !== 'string'
    || !IDENTIFIER_PATTERN.test(input.signer_lookup.signer_id)) return null;
  return Object.freeze({
    handoff: input.handoff,
    signerLookup: Object.freeze({
      repositoryId: input.signer_lookup.repository_id,
      signerId: input.signer_lookup.signer_id,
    }),
  });
}

export class StrictDomainRuntimeHandoffSource implements DomainRuntimeHandoffSource {
  constructor(
    private readonly endpoint: DomainRuntimeHandoffEndpoint,
    private readonly transport: DomainRuntimeHandoffTransport,
    private readonly clock: () => number = Date.now,
    private readonly requestId: () => string = () => `HANDOFF-REQ-${randomUUID().toUpperCase()}`,
  ) {}

  async read(possession: VerifiedNodePossession): Promise<Readonly<DomainRuntimeHandoffCandidate> | null> {
    try {
      const verified = assertVerifiedNodePossession(possession);
      if (consumedPossessions.has(verified)) return null;
      const endpoint = assertRegisteredDomainRuntimeHandoffEndpoint(this.endpoint);
      if (endpoint.status !== 'ACTIVE'
        || !endpoint.domainIds.includes(verified.registration.domainId)
        || !endpoint.nodeTypes.includes(verified.registration.nodeType)) return null;
      const issuedAt = this.clock();
      const requestId = this.requestId();
      if (!Number.isSafeInteger(issuedAt)
        || issuedAt < verified.verifiedAt
        || issuedAt >= verified.challenge.expiresAt
        || issuedAt >= verified.registration.expiresAt
        || !IDENTIFIER_PATTERN.test(requestId)) return null;
      const request = Object.freeze({
        accountId: verified.registration.accountId,
        challenge: verified.challenge,
        domainId: verified.registration.domainId,
        endpointId: endpoint.endpointId,
        issuedAt,
        nodeId: verified.registration.nodeId,
        nodeType: verified.registration.nodeType,
        registration: verified.registration,
        requestId,
        response: verified.response,
        schema: REQUEST_SCHEMA,
      });
      consumedPossessions.add(verified);
      return parseResponse(await this.transport.request(endpoint, request), request);
    } catch {
      return null;
    }
  }
}

export class AnchoredDomainRuntimeHandoffSource implements DomainRuntimeHandoffSource {
  constructor(
    private readonly snapshots: DomainRuntimeHandoffSnapshotLoader,
    private readonly transport: DomainRuntimeHandoffTransport,
    private readonly clock: () => number = Date.now,
    private readonly requestId: () => string = () => `HANDOFF-REQ-${randomUUID().toUpperCase()}`,
  ) {}

  async read(possession: VerifiedNodePossession): Promise<Readonly<DomainRuntimeHandoffCandidate> | null> {
    try {
      const verified = assertVerifiedNodePossession(possession);
      const snapshot = assertLoadedDomainRuntimeHandoffSnapshot(await this.snapshots.refresh());
      if (snapshot.receipt.status !== 'CURRENT' || !snapshot.registry) return null;
      const endpoint = resolveDomainRuntimeHandoffEndpoint(snapshot.registry, {
        domainId: verified.registration.domainId,
        nodeType: verified.registration.nodeType,
      });
      if (!endpoint) return null;
      return new StrictDomainRuntimeHandoffSource(
        endpoint,
        this.transport,
        this.clock,
        this.requestId,
      ).read(verified);
    } catch {
      return null;
    }
  }
}

export class HttpDomainRuntimeHandoffTransport implements DomainRuntimeHandoffTransport {
  constructor(private readonly fetcher: typeof fetch = fetch) {}

  async request(
    inputEndpoint: Readonly<DomainRuntimeHandoffEndpoint>,
    input: Readonly<DomainRuntimeHandoffRequest>,
  ): Promise<unknown> {
    const endpoint = assertRegisteredDomainRuntimeHandoffEndpoint(inputEndpoint);
    if (endpoint.status !== 'ACTIVE'
      || input.endpointId !== endpoint.endpointId
      || !endpoint.domainIds.includes(input.domainId)
      || !endpoint.nodeTypes.includes(input.nodeType)) {
      throw new Error('domain_runtime_handoff_endpoint_scope_invalid');
    }
    const response = await this.fetcher(endpoint.url, {
      body: JSON.stringify(input),
      cache: 'no-store',
      credentials: 'omit',
      headers: { Accept: 'application/json', 'Content-Type': 'application/json' },
      method: 'POST',
      redirect: 'manual',
      referrerPolicy: 'no-referrer',
      signal: AbortSignal.timeout(5000),
    });
    if (!response.ok || response.status < 200 || response.status >= 300
      || response.type === 'opaqueredirect') throw new Error('domain_runtime_handoff_http_rejected');
    const contentType = response.headers.get('content-type')?.split(';', 1)[0].trim().toLowerCase();
    if (contentType !== 'application/json') throw new Error('domain_runtime_handoff_content_type_invalid');
    const declaredLength = response.headers.get('content-length');
    if (declaredLength !== null
      && (!/^\d+$/.test(declaredLength) || Number(declaredLength) > MAX_RESPONSE_BYTES)) {
      throw new Error('domain_runtime_handoff_response_too_large');
    }
    const bytes = new Uint8Array(await response.arrayBuffer());
    if (bytes.byteLength > MAX_RESPONSE_BYTES) throw new Error('domain_runtime_handoff_response_too_large');
    let text: string;
    try { text = new TextDecoder('utf-8', { fatal: true }).decode(bytes); }
    catch { throw new Error('domain_runtime_handoff_response_encoding_invalid'); }
    try { return JSON.parse(text); }
    catch { throw new Error('domain_runtime_handoff_response_json_invalid'); }
  }
}