import {
  assertProductionDatabaseTransport,
  createDatabaseTransportPolicy,
  type DatabaseTransportPolicy,
  type DatabaseTransportPolicyInput,
} from "@ekklesia/core/database";
import {
  type CreateIdentityConfigOptions,
  createIdentityConfig,
  type IdentityConfig,
  type IdentityConfigInput,
} from "@ekklesia/core/identity";
import {
  createMailProviderConfig,
  type MailProviderConfig,
  type MailProviderConfigInput,
} from "@ekklesia/core/mail";
import {
  createStorageProviderConfig,
  type StorageProviderConfig,
  type StorageProviderConfigInput,
} from "@ekklesia/core/storage";
import {
  type ClientAddressConfig,
  type ClientAddressConfigInput,
  createClientAddressConfig,
} from "./client-address.js";

export type ApiConfigErrorCode =
  | "DATABASE_URL_INVALID"
  | "DATABASE_URL_MISSING"
  | "HOST_INVALID"
  | "PORT_INVALID";

/** Never carries the offending database URL, host, port, or any other caller-supplied value. */
export class ApiConfigError extends Error {
  readonly code: ApiConfigErrorCode;

  constructor(code: ApiConfigErrorCode) {
    super(apiConfigErrorMessages[code]);
    this.name = "ApiConfigError";
    this.code = code;
    this.stack = `${this.name}: ${this.message}`;
    Object.freeze(this);
  }
}

const apiConfigErrorMessages: Readonly<Record<ApiConfigErrorCode, string>> = Object.freeze({
  DATABASE_URL_INVALID:
    "The API database URL must be an absolute postgres:// or postgresql:// URL.",
  DATABASE_URL_MISSING: "The API database URL is required.",
  HOST_INVALID: "The API listen address must be a non-empty host.",
  PORT_INVALID:
    "The API listen port must be an integer between 0 and 65535 (0 requests an OS-assigned port).",
});

const defaultHost = "127.0.0.1";
const defaultPort = 3000;

export interface ApiRuntimeConfig {
  readonly clientAddress: ClientAddressConfig;
  readonly databaseUrl: string;
  /** The one validated PostgreSQL transport policy this runtime's single pool uses. */
  readonly databaseTransport: DatabaseTransportPolicy;
  readonly host: string;
  readonly identity: IdentityConfig;
  readonly port: number;
  /**
   * The validated host object-storage provider, or `undefined` when this installation has none
   * (ADR 0030).
   *
   * `undefined` is a complete, valid deployment: modules that declare no logical buckets are
   * unaffected, and a module that does declare one is reported blocked rather than crashing
   * anything. These values reach Core's provider and nowhere else — no module, module UI, browser
   * bundle, diagnostic, or API response ever sees the endpoint or the credentials.
   */
  readonly storage: StorageProviderConfig | undefined;
  /**
   * The validated host outbound-email provider, or `undefined` when this installation has none
   * (ADR 0037).
   *
   * `undefined` is a valid deployment: the platform starts, every existing feature works, and the
   * initial platform owner — created already verified by an operator command — can still sign in
   * (ADR 0038). What it cannot do is verify a new account or deliver a password reset; each attempt
   * reports a sanitized `MAIL_NOT_CONFIGURED` out of band rather than changing any HTTP response.
   * These values reach Core's provider and nowhere else — no module, browser bundle, diagnostic, or
   * API response ever sees the host or the password.
   */
  readonly mail: MailProviderConfig | undefined;
}

export interface ApiRuntimeConfigInput {
  /** Optional. Defaults to direct mode (trusts only the actual immediate socket peer) — no proxy
   * trust unless explicitly configured. See `./client-address.js`. */
  readonly clientAddress?: ClientAddressConfigInput | undefined;
  readonly databaseUrl?: unknown;
  /** Optional. Defaults to certificate-verified TLS in production and plaintext in development;
   * production can never select plaintext. See `@ekklesia/core/database`'s transport policy. */
  readonly databaseTransport?: DatabaseTransportPolicyInput;
  readonly host?: unknown;
  readonly identity: IdentityConfigInput;
  readonly port?: unknown;
  /** Optional. Omitted, or with no endpoint, means this installation has no object storage. */
  readonly storage?: StorageProviderConfigInput;
  /** Optional. Omitted, or with no host, means this installation sends no outbound email. */
  readonly mail?: MailProviderConfigInput;
}

export interface CreateApiRuntimeConfigOptions {
  readonly environment?: CreateIdentityConfigOptions["environment"];
}

function validateDatabaseUrl(databaseUrl: unknown): string {
  if (typeof databaseUrl !== "string" || databaseUrl.trim().length === 0) {
    throw new ApiConfigError("DATABASE_URL_MISSING");
  }
  let protocol: string;
  try {
    protocol = new URL(databaseUrl).protocol;
  } catch {
    throw new ApiConfigError("DATABASE_URL_INVALID");
  }
  if (protocol !== "postgres:" && protocol !== "postgresql:") {
    throw new ApiConfigError("DATABASE_URL_INVALID");
  }
  return databaseUrl;
}

function validateHost(host: unknown): string {
  if (host === undefined) {
    return defaultHost;
  }
  if (typeof host !== "string" || host.trim().length === 0) {
    throw new ApiConfigError("HOST_INVALID");
  }
  return host;
}

function validatePort(port: unknown): number {
  if (port === undefined) {
    return defaultPort;
  }
  const numericPort = typeof port === "string" ? Number(port) : port;
  if (
    typeof numericPort !== "number" ||
    !Number.isInteger(numericPort) ||
    numericPort < 0 ||
    numericPort > 65_535
  ) {
    throw new ApiConfigError("PORT_INVALID");
  }
  return numericPort;
}

/**
 * Validates explicit, typed API runtime configuration, delegating identity fields to Core's
 * existing `createIdentityConfig` rather than defining a competing identity configuration
 * contract. Performs no environment reads, network calls, or database access.
 */
export function createApiRuntimeConfig(
  input: ApiRuntimeConfigInput,
  options: CreateApiRuntimeConfigOptions = {},
): ApiRuntimeConfig {
  const databaseUrl = validateDatabaseUrl(input.databaseUrl);
  const host = validateHost(input.host);
  const port = validatePort(input.port);
  const identity = createIdentityConfig(
    input.identity,
    options.environment === undefined ? {} : { environment: options.environment },
  );
  const clientAddress = createClientAddressConfig(input.clientAddress);
  const environment = options.environment ?? "production";
  const databaseTransport = createDatabaseTransportPolicy(input.databaseTransport, {
    environment,
  });
  // Fails here — before `startApi` constructs a pool, Better Auth, the module runtime, or a
  // listener — if a production deployment would connect without certificate-verified TLS, or if
  // the URL carries TLS parameters that could override the policy.
  assertProductionDatabaseTransport(databaseUrl, databaseTransport, environment);

  // Validated in the same pass as every other runtime value, before `startApi` constructs a pool,
  // a provider client, or a listener — so a malformed endpoint or a half-supplied credential pair
  // fails startup with a sanitized code rather than surfacing later as a confusing storage error.
  const storage = createStorageProviderConfig(input.storage, { environment });

  // Validated in the same pass as everything else, so a malformed port, a half-supplied credential
  // pair, or a production deployment that asked for plaintext SMTP fails startup with a sanitized
  // code — rather than surfacing later as a confusing failure the first time something tries to
  // send a password-reset email.
  const mail = createMailProviderConfig(input.mail, { environment });

  return Object.freeze({
    clientAddress,
    databaseTransport,
    databaseUrl,
    host,
    identity,
    mail,
    port,
    storage,
  });
}

/**
 * The exact browser origins the API trusts: CORS on `/api/auth/*` and `/api/v1/*`, and every
 * mutation route's origin check (ADR 0045).
 *
 * The configured trusted origins plus the identity base URL's own origin, which is where the API
 * lives. Better Auth already trusts its base URL implicitly; this makes the API's own checks agree,
 * so a page the API itself serves (the display host, and the Dashboard in the same-origin topology)
 * passes without an operator listing the API's origin. Order is preserved and duplicates removed;
 * every entry is already a canonical origin.
 */
export function apiTrustedOrigins(
  identity: Pick<IdentityConfig, "baseUrl" | "trustedOrigins">,
): readonly string[] {
  return Object.freeze([...new Set([...identity.trustedOrigins, identity.baseUrl])]);
}