export const FIFTH_DOMAIN_DISCOVERY_URL = 'https://guanghulab.com/.well-known/guanghu.json'

export interface FifthDomainDiscovery {
  access: 'public-read-only'
  canonicalRepository: string
  name: string
  nodeMap: string
  repositoryMap: string
  resolveApi: string
  schema: 'guanghu.ai-discovery/v1'
  searchApi: string
}

type Fetcher = (input: RequestInfo | URL, init?: RequestInit) => Promise<Pick<Response, 'ok' | 'json'>>

function requiredString(document: Record<string, unknown>, key: string): string {
  const value = document[key]
  if (typeof value !== 'string' || !value.trim()) throw new Error(`Fifth Domain discovery is missing ${key}.`)
  return value
}

function requiredHttpsUrl(document: Record<string, unknown>, key: string): string {
  const value = requiredString(document, key)
  if (!value.startsWith('https://guanghulab.com/')) throw new Error(`Fifth Domain discovery ${key} is not a trusted HTTPS route.`)
  return value
}

export function parseFifthDomainDiscovery(value: unknown): FifthDomainDiscovery {
  if (!value || typeof value !== 'object' || Array.isArray(value)) throw new Error('Fifth Domain discovery is not an object.')
  const document = value as Record<string, unknown>
  if (document.schema !== 'guanghu.ai-discovery/v1') throw new Error('Fifth Domain discovery schema is unsupported.')
  if (document.access !== 'public-read-only') throw new Error('Fifth Domain connection must remain public-read-only.')

  return {
    access: 'public-read-only',
    canonicalRepository: requiredHttpsUrl(document, 'canonical_repository'),
    name: requiredString(document, 'name'),
    nodeMap: requiredHttpsUrl(document, 'server_node_map'),
    repositoryMap: requiredHttpsUrl(document, 'repository_map'),
    resolveApi: requiredHttpsUrl(document, 'resolve_api'),
    schema: 'guanghu.ai-discovery/v1',
    searchApi: requiredHttpsUrl(document, 'search_api'),
  }
}

export async function fetchFifthDomainDiscovery(
  fetcher: Fetcher = fetch,
  signal?: AbortSignal,
): Promise<FifthDomainDiscovery> {
  const response = await fetcher(FIFTH_DOMAIN_DISCOVERY_URL, {
    cache: 'no-store',
    credentials: 'omit',
    signal,
  })
  if (!response.ok) throw new Error('Fifth Domain public route did not respond successfully.')
  return parseFifthDomainDiscovery(await response.json())
}