import type {
  BuiltInHostProtocol,
  Host,
  HostProtocol,
  PluginConfigurationValue,
  PluginConnectionConfig,
} from './models';
import { isEncryptedCredentialPlaceholder } from './credentials';

const CONTRIBUTION_ID = /^[a-z0-9](?:[a-z0-9-]*[a-z0-9])?(?:\.[a-z0-9](?:[a-z0-9-]*[a-z0-9])?)+\.[A-Za-z][A-Za-z0-9_-]*(?:\.[A-Za-z][A-Za-z0-9_-])*$/u;
const MAX_CONTRIBUTION_ID_LENGTH = 192;
const PLUGIN_PROTOCOL_PREFIX = 'plugin:';
const MAX_CONFIGURATION_BYTES = 128 * 1024;
const MAX_CONFIGURATION_DEPTH = 32;
const MAX_CONFIGURATION_ENTRIES = 4096;
const BUILT_IN_HOST_PROTOCOLS = new Set<BuiltInHostProtocol>([
  'ssh',
  'telnet',
  'mosh',
  'et',
  'local',
  'serial',
]);

export const pluginProtocolForProvider = (providerId: string): HostProtocol => `plugin:${providerId}`;

export const isPluginHostProtocol = (protocol?: string): protocol is `plugin:${string}` => (
  typeof protocol === 'string'
  && protocol.startsWith(PLUGIN_PROTOCOL_PREFIX)
  && protocol.length <= PLUGIN_PROTOCOL_PREFIX.length + MAX_CONTRIBUTION_ID_LENGTH
  && CONTRIBUTION_ID.test(protocol.slice(PLUGIN_PROTOCOL_PREFIX.length))
);

export const isBuiltInHostProtocol = (protocol?: string): protocol is BuiltInHostProtocol => (
  typeof protocol === 'string' && BUILT_IN_HOST_PROTOCOLS.has(protocol as BuiltInHostProtocol)
);

export const isPluginCredentialCatalogEntryAvailable = (
  id: string,
  value: string | undefined,
  catalogIds: ReadonlySet<string>,
): value is string => (
  catalogIds.has(id)
  && typeof value === 'string'
  && value.length > 0
  && !isEncryptedCredentialPlaceholder(value)
  && new TextEncoder().encode(value).byteLength <= 64 * 1024
);

export const isSafePluginAuthenticationUrl = (value: string): boolean => {
  try {
    const url = new URL(value);
    if (url.username || url.password) return false;
    if (url.protocol === 'https:') return true;
    if (url.protocol !== 'http:') return false;
    const hostname = url.hostname.toLowerCase();
    return hostname === 'localhost'
      || hostname === '[::1]'
      || /^127(?:\.\d{1,3}){3}$/u.test(hostname);
  } catch {
    return false;
  }
};

function validateConfiguration(value: unknown, depth: number, budget: { entries: number }): value is PluginConfigurationValue {
  if (depth > MAX_CONFIGURATION_DEPTH || ++budget.entries > MAX_CONFIGURATION_ENTRIES) return false;
  if (value === null || typeof value === 'string' || typeof value === 'boolean') return true;
  if (typeof value === 'number') return Number.isFinite(value);
  if (Array.isArray(value)) return value.every((item) => validateConfiguration(item, depth + 1, budget));
  if (!value || typeof value !== 'object' || Object.getPrototypeOf(value) !== Object.prototype) return false;
  return Object.entries(value).every(([key, item]) => (
    key.length > 0
    && key.length <= 256
    && key !== '__proto__'
    && key !== 'prototype'
    && key !== 'constructor'
    && validateConfiguration(item, depth + 1, budget)
  ));
}

export function sanitizePluginConnection(
  value: unknown,
  protocol?: string,
): PluginConnectionConfig | undefined {
  if (!value || typeof value !== 'object' || Array.isArray(value)) return undefined;
  const candidate = value as Partial<PluginConnectionConfig>;
  if (typeof candidate.providerId !== 'string' || !CONTRIBUTION_ID.test(candidate.providerId)
    || candidate.providerId.length > MAX_CONTRIBUTION_ID_LENGTH
    || protocol !== pluginProtocolForProvider(candidate.providerId)
    || !validateConfiguration(candidate.configuration, 0, { entries: 0 })) {
    return undefined;
  }
  const serialized = JSON.stringify(candidate.configuration);
  if (new TextEncoder().encode(serialized).byteLength > MAX_CONFIGURATION_BYTES) return undefined;
  const authenticationProviderId = typeof candidate.authenticationProviderId === 'string'
    && CONTRIBUTION_ID.test(candidate.authenticationProviderId)
    && candidate.authenticationProviderId.length <= 192
    ? candidate.authenticationProviderId
    : undefined;
  const credentialId = typeof candidate.credentialId === 'string'
    && candidate.credentialId.length >= 16
    && candidate.credentialId.length <= 256
    && !candidate.credentialId.includes('\0')
    ? candidate.credentialId
    : undefined;
  return {
    providerId: candidate.providerId,
    configuration: structuredClone(candidate.configuration),
    ...(authenticationProviderId ? { authenticationProviderId } : {}),
    ...(credentialId ? { credentialId } : {}),
  };
}

/**
 * Plugin Providers own their connection and authentication configuration.
 * Remove hidden first-party protocol state so switching an existing host to a
 * plugin cannot retain credentials or transport behavior that the plugin UI
 * cannot display or manage.
 */
export function stripBuiltInConnectionFieldsForPluginHost(host: Host): Host {
  if (!isPluginHostProtocol(host.protocol)) return host;
  const {
    port: _port,
    identityId: _identityId,
    identityFileId: _identityFileId,
    identityFilePaths: _identityFilePaths,
    password: _password,
    savePassword: _savePassword,
    authMethod: _authMethod,
    authPolicyVersion: _authPolicyVersion,
    requiresMfa: _requiresMfa,
    useSshAgent: _useSshAgent,
    identityAgent: _identityAgent,
    identitiesOnly: _identitiesOnly,
    addKeysToAgent: _addKeysToAgent,
    useKeychain: _useKeychain,
    agentForwarding: _agentForwarding,
    x11Forwarding: _x11Forwarding,
    proxy: _proxy,
    proxyProfileId: _proxyProfileId,
    proxyConfig: _proxyConfig,
    hostChain: _hostChain,
    moshEnabled: _moshEnabled,
    moshServerPath: _moshServerPath,
    etEnabled: _etEnabled,
    etPort: _etPort,
    protocols: _protocols,
    telnetPort: _telnetPort,
    telnetEnabled: _telnetEnabled,
    telnetIdentityId: _telnetIdentityId,
    telnetUsername: _telnetUsername,
    telnetPassword: _telnetPassword,
    serialConfig: _serialConfig,
    sftpSudo: _sftpSudo,
    legacyAlgorithms: _legacyAlgorithms,
    skipEcdsaHostKey: _skipEcdsaHostKey,
    algorithms: _algorithms,
    keepaliveInterval: _keepaliveInterval,
    keepaliveCountMax: _keepaliveCountMax,
    keepaliveOverride: _keepaliveOverride,
    sshTcpConnectTimeoutSeconds: _sshTcpConnectTimeoutSeconds,
    sshAuthReadyTimeoutSeconds: _sshAuthReadyTimeoutSeconds,
    ...pluginHost
  } = host;
  return pluginHost;
}