export type DomainNodeType = 'LOCAL_TERMINAL_NODE' | 'CLOUD_RESIDENT_NODE'

export type PublicDomainStatus = 'PUBLIC_PREVIEW' | 'RESTRICTED_PREVIEW' | 'UNAVAILABLE'

export interface PublicThemePreview {
  assetRef: string
  description: string
}

export interface PublicDomainVestibule {
  accessModes: DomainNodeType[]
  displayName: string
  domainId: string
  formalName: string
  publicStatus: PublicDomainStatus
  purpose: string
  responsibleParty: string
  themePreview: PublicThemePreview | null
}

export interface DomainManifestProvenance {
  digest: string
  repositoryId: string
  signature: string
  signerId: string
  sourceCommit: string
}

export interface DomainRuntimeDescriptor {
  backendVersion: string
  channelIds: string[]
  forbiddenDataScopes: string[]
  frontendVersion: string
  healthCheckRef: string
  moduleIds: string[]
  rollbackVersion: string
  routeRef: string
  themePackageRef: string
}

export interface VerifiedDomainManifest {
  public: PublicDomainVestibule
  provenance: DomainManifestProvenance
  runtime: DomainRuntimeDescriptor
  schema: 'gh-aios.domain-manifest/v1'
  verification: {
    manifestDigest: string
    state: 'verified'
    verifiedAt: number
  }
}

export interface DomainSessionCapability {
  capabilityId: string
  domainId: string
  expiresAt: number
  nodeId: string
  scopes: string[]
}

export interface DomainConnectionReceipt {
  connectionId: string
  domainId: string
  manifestDigest: string
  nodeId: string
  receiptId: string
  state: 'online'
}

export interface LighthouseState {
  stage: 'lighthouse'
}

export interface VestibuleState {
  domain: PublicDomainVestibule
  stage: 'vestibule'
}

export interface AccessState {
  manifest: VerifiedDomainManifest
  nodeType: DomainNodeType
  receipt: DomainConnectionReceipt | null
  session: DomainSessionCapability | null
  stage: 'access'
}

export interface RuntimeState {
  manifest: VerifiedDomainManifest
  mode: 'connected' | 'disconnected-readonly'
  nodeType: DomainNodeType
  receipt: DomainConnectionReceipt
  session: DomainSessionCapability
  stage: 'runtime'
}

export type DomainAccessState = LighthouseState | VestibuleState | AccessState | RuntimeState

export class DomainContractError extends Error {
  readonly code: string

  constructor(code: string) {
    super(code)
    this.code = code
    this.name = 'DomainContractError'
  }
}

const SHA256 = /^[a-f0-9]{64}$/
const SOURCE_COMMIT = /^[a-f0-9]{40,64}$/
const REQUIRED_ENTER_SCOPE = 'domain:enter'

function required(value: string, code: string): string {
  if (!value.trim()) throw new DomainContractError(code)
  return value
}

function publicDomain(domain: PublicDomainVestibule): PublicDomainVestibule {
  required(domain.domainId, 'domain_manifest_public_id_missing')
  required(domain.formalName, 'domain_manifest_formal_name_missing')
  required(domain.displayName, 'domain_manifest_display_name_missing')
  required(domain.purpose, 'domain_manifest_public_purpose_missing')
  required(domain.responsibleParty, 'domain_manifest_responsible_party_missing')
  if (!domain.accessModes.length) {
    throw new DomainContractError('domain_manifest_access_modes_missing')
  }
  if (domain.accessModes.some(mode => mode !== 'LOCAL_TERMINAL_NODE' && mode !== 'CLOUD_RESIDENT_NODE')) {
    throw new DomainContractError('domain_manifest_access_mode_invalid')
  }
  if (domain.themePreview) {
    required(domain.themePreview.assetRef, 'domain_manifest_theme_preview_ref_missing')
    required(domain.themePreview.description, 'domain_manifest_theme_preview_description_missing')
  }
  return {
    accessModes: [...domain.accessModes],
    displayName: domain.displayName,
    domainId: domain.domainId,
    formalName: domain.formalName,
    publicStatus: domain.publicStatus,
    purpose: domain.purpose,
    responsibleParty: domain.responsibleParty,
    themePreview: domain.themePreview ? { ...domain.themePreview } : null,
  }
}

export function assertVerifiedDomainManifest(
  manifest: VerifiedDomainManifest,
): VerifiedDomainManifest {
  if (manifest.schema !== 'gh-aios.domain-manifest/v1') {
    throw new DomainContractError('domain_manifest_schema_unsupported')
  }
  publicDomain(manifest.public)
  if (manifest.verification.state !== 'verified' || !Number.isFinite(manifest.verification.verifiedAt)) {
    throw new DomainContractError('domain_manifest_not_verified')
  }
  if (!SHA256.test(manifest.provenance.digest)
    || manifest.verification.manifestDigest !== manifest.provenance.digest) {
    throw new DomainContractError('domain_manifest_digest_invalid')
  }
  if (!SOURCE_COMMIT.test(manifest.provenance.sourceCommit)) {
    throw new DomainContractError('domain_manifest_source_commit_invalid')
  }
  required(manifest.provenance.repositoryId, 'domain_manifest_repository_missing')
  required(manifest.provenance.signerId, 'domain_manifest_signer_missing')
  required(manifest.provenance.signature, 'domain_manifest_signature_missing')
  required(manifest.runtime.routeRef, 'domain_manifest_route_missing')
  required(manifest.runtime.themePackageRef, 'domain_manifest_theme_package_missing')
  required(manifest.runtime.healthCheckRef, 'domain_manifest_health_check_missing')
  required(manifest.runtime.rollbackVersion, 'domain_manifest_rollback_version_missing')
  return manifest
}

export function projectPublicDomainVestibule(
  manifest: VerifiedDomainManifest,
): PublicDomainVestibule {
  return publicDomain(assertVerifiedDomainManifest(manifest).public)
}

export const INITIAL_DOMAIN_ACCESS_STATE: LighthouseState = { stage: 'lighthouse' }

export function selectPublicDomain(
  state: LighthouseState | VestibuleState,
  domain: PublicDomainVestibule,
): VestibuleState {
  void state
  return { domain: publicDomain(domain), stage: 'vestibule' }
}

export function beginDomainAccess(
  state: VestibuleState,
  manifest: VerifiedDomainManifest,
  nodeType: DomainNodeType,
): AccessState {
  const verified = assertVerifiedDomainManifest(manifest)
  if (verified.public.domainId !== state.domain.domainId) {
    throw new DomainContractError('domain_manifest_selected_domain_mismatch')
  }
  if (!verified.public.accessModes.includes(nodeType)) {
    throw new DomainContractError('domain_node_type_not_allowed')
  }
  return {
    manifest: verified,
    nodeType,
    receipt: null,
    session: null,
    stage: 'access',
  }
}

export function acceptDomainSession(
  state: AccessState,
  session: DomainSessionCapability,
  now: number,
): AccessState {
  if (session.domainId !== state.manifest.public.domainId) {
    throw new DomainContractError('domain_session_domain_mismatch')
  }
  if (session.expiresAt <= now) {
    throw new DomainContractError('domain_session_expired')
  }
  if (!session.scopes.includes(REQUIRED_ENTER_SCOPE)) {
    throw new DomainContractError('domain_session_enter_scope_missing')
  }
  required(session.capabilityId, 'domain_session_capability_id_missing')
  required(session.nodeId, 'domain_session_node_id_missing')
  return { ...state, session: { ...session, scopes: [...session.scopes] } }
}

export function acceptDomainConnectionReceipt(
  state: AccessState,
  receipt: DomainConnectionReceipt,
): AccessState {
  if (!state.session) {
    throw new DomainContractError('domain_connection_session_missing')
  }
  if (receipt.domainId !== state.manifest.public.domainId) {
    throw new DomainContractError('domain_connection_domain_mismatch')
  }
  if (receipt.nodeId !== state.session.nodeId) {
    throw new DomainContractError('domain_connection_node_mismatch')
  }
  if (receipt.manifestDigest !== state.manifest.provenance.digest) {
    throw new DomainContractError('domain_connection_manifest_mismatch')
  }
  required(receipt.connectionId, 'domain_connection_id_missing')
  required(receipt.receiptId, 'domain_connection_receipt_id_missing')
  return { ...state, receipt: { ...receipt } }
}

export function enterDomainRuntime(state: AccessState, now: number): RuntimeState {
  if (!state.session) throw new DomainContractError('domain_runtime_session_missing')
  if (!state.receipt) throw new DomainContractError('domain_runtime_connection_receipt_missing')
  if (state.session.expiresAt <= now) throw new DomainContractError('domain_session_expired')
  return {
    manifest: state.manifest,
    mode: 'connected',
    nodeType: state.nodeType,
    receipt: state.receipt,
    session: state.session,
    stage: 'runtime',
  }
}

export function disconnectDomainRuntime(state: RuntimeState): RuntimeState {
  return { ...state, mode: 'disconnected-readonly' }
}

export function returnToLighthouse(): LighthouseState {
  return INITIAL_DOMAIN_ACCESS_STATE
}