import { getGoogleVertexRequestConfig } from './google-vertex-model-catalog-config';
import {
  GoogleInteractionsLanguageModel,
  GoogleLanguageModel,
  GoogleSpeechModel,
  type GoogleInteractionsAgentName,
  type GoogleInteractionsModelId,
  type GoogleInteractionsModelInput,
} from '@ai-sdk/google/internal';
import {
  InvalidArgumentError,
  LoadAPIKeyError,
  type Experimental_VideoModelV4,
  type ImageModelV4,
  type LanguageModelV4,
  type ProviderV4,
  type SpeechModelV4,
  type TranscriptionModelV4,
} from '@ai-sdk/provider';
import {
  generateId,
  isValidHostnamePart,
  loadOptionalSetting,
  loadSetting,
  normalizeHeaders,
  resolve,
  withoutTrailingSlash,
  withUserAgentSuffix,
  type FetchFunction,
  type Resolvable,
  type WebSocketConstructor,
} from '@ai-sdk/provider-utils';
import { VERSION } from './version';
import type { GoogleVertexConfig } from './google-vertex-config';
import { GoogleVertexEmbeddingModel } from './google-vertex-embedding-model';
import type { GoogleVertexEmbeddingModelId } from './google-vertex-embedding-model-options';
import { GoogleVertexImageModel } from './google-vertex-image-model';
import type { GoogleVertexImageModelId } from './google-vertex-image-settings';
import type { GoogleVertexModelId } from './google-vertex-options';
import { GoogleVertexCloudTTSSpeechModel } from './google-vertex-cloud-tts-speech-model';
import { googleVertexTools } from './google-vertex-tools';
import { GoogleVertexTranscriptionModel } from './google-vertex-transcription-model';
import type { GoogleVertexTranscriptionModelId } from './google-vertex-transcription-model-options';
import { GoogleVertexGeminiTranscriptionModel } from './gemini-transcription/google-vertex-gemini-transcription-model';
import { GoogleVertexVideoModel } from './google-vertex-video-model';
import type { GoogleVertexVideoModelId } from './google-vertex-video-settings';
import type { GoogleVertexSpeechModelId } from './google-vertex-speech-model-options';

const EXPRESS_MODE_BASE_URL =
  'https://aiplatform.googleapis.com/v1/publishers/google';

// Tuned models are served from a deployed endpoint and addressed by their
// `endpoints/{id}` resource, which replaces `publishers/google/models/{id}`.
// https://cloud.google.com/vertex-ai/generative-ai/docs/deploy/overview
function isEndpointModelId(modelId: string): boolean {
  return getGoogleVertexRequestConfig(modelId).language?.endpoint === true;
}

// set `x-goog-api-key` header to API key for express mode
function createExpressModeFetch(
  apiKey: Resolvable<string>,
  customFetch?: FetchFunction,
): FetchFunction {
  return async (url, init) => {
    const resolvedApiKey = await resolve(apiKey);
    if (
      typeof apiKey !== 'string' &&
      (typeof resolvedApiKey !== 'string' || !resolvedApiKey.trim())
    ) {
      throw new LoadAPIKeyError({
        message: 'Google Vertex API key must be a non-empty string.',
      });
    }

    const modifiedInit: RequestInit = {
      ...init,
      headers: {
        ...(init?.headers ? normalizeHeaders(init.headers) : {}),
        'x-goog-api-key': resolvedApiKey,
      },
    };
    return (customFetch ?? fetch)(url.toString(), modifiedInit);
  };
}

export interface GoogleVertexProvider extends ProviderV4 {
  /**
   * Creates a model for text generation.
   */
  (modelId: GoogleVertexModelId): LanguageModelV4;

  languageModel: (modelId: GoogleVertexModelId) => LanguageModelV4;

  /**
   * Creates a language model targeting the Gemini Interactions API
   * (`.../locations/{region}/interactions`) on Vertex, reusing the Vertex
   * OAuth credentials. Pass a model id (e.g. `gemini-omni-flash-preview`) or an
   * `{ agent }` / `{ managedAgent }` reference.
   */
  interactions(
    modelIdOrAgent:
      | GoogleInteractionsModelId
      | { agent: GoogleInteractionsAgentName }
      | { managedAgent: string },
  ): LanguageModelV4;

  /**
   * Creates a model for image generation.
   */
  image(modelId: GoogleVertexImageModelId): ImageModelV4;

  /**
   * Creates a model for image generation.
   */
  imageModel(modelId: GoogleVertexImageModelId): ImageModelV4;

  tools: typeof googleVertexTools;

  /**
   * @deprecated Use `embeddingModel` instead.
   */
  textEmbeddingModel(
    modelId: GoogleVertexEmbeddingModelId,
  ): GoogleVertexEmbeddingModel;

  /**
   * Creates a model for video generation.
   */
  video(modelId: GoogleVertexVideoModelId): Experimental_VideoModelV4;

  /**
   * Creates a model for video generation.
   */
  videoModel(modelId: GoogleVertexVideoModelId): Experimental_VideoModelV4;

  /**
   * Creates a model for speech generation (text-to-speech).
   */
  speech(modelId: GoogleVertexSpeechModelId): SpeechModelV4;

  /**
   * Creates a model for speech generation (text-to-speech).
   */
  speechModel(modelId: GoogleVertexSpeechModelId): SpeechModelV4;

  /**
   * Creates a model for transcription (speech-to-text).
   */
  transcription(
    modelId: GoogleVertexTranscriptionModelId,
  ): TranscriptionModelV4;

  /**
   * Creates a model for transcription (speech-to-text).
   */
  transcriptionModel(
    modelId: GoogleVertexTranscriptionModelId,
  ): TranscriptionModelV4;
}

export interface GoogleVertexProviderSettings {
  /**
   * Optional. The API key for the Google Cloud project. If provided, the
   * provider will use express mode with API key authentication. Defaults to
   * the value of the `GOOGLE_VERTEX_API_KEY` environment variable.
   * A callback is resolved before each request and must return a non-empty key.
   */
  apiKey?: Resolvable<string>;

  /**
   * Your Google Vertex location. Defaults to the environment variable `GOOGLE_VERTEX_LOCATION`.
   */
  location?: string;

  /**
   * Your Google Vertex project. Defaults to the environment variable `GOOGLE_VERTEX_PROJECT`.
   */
  project?: string;

  /**
   * Headers to use for requests. Can be:
   * - A headers object
   * - A Promise that resolves to a headers object
   * - A function that returns a headers object
   * - A function that returns a Promise of a headers object
   */
  headers?: Resolvable<Record<string, string | undefined>>;

  /**
   * Custom fetch implementation. You can use it as a middleware to intercept requests,
   * or to provide a custom fetch implementation for e.g. testing.
   */
  fetch?: FetchFunction;

  // for testing
  generateId?: () => string;

  /**
   * Base URL for the Google Vertex API calls.
   */
  baseURL?: string;

  /**
   * Custom WebSocket implementation for streaming transcription. Useful for
   * runtimes that need a WebSocket constructor with header support (e.g. the
   * `ws` package in Node.js, which Vertex's OAuth Bearer header requires).
   */
  webSocket?: WebSocketConstructor;

  /**
   * Settings for downloading remote files in tool results before sending them
   * to Vertex as inline data.
   */
  toolResultDownloads?: {
    /**
     * Maximum size in bytes for each downloaded file. Defaults to 7 MiB.
     */
    maxBytes?: number;
  };
}

/**
 * Create a Google Vertex AI provider instance.
 */
export function createGoogleVertex(
  options: GoogleVertexProviderSettings = {},
): GoogleVertexProvider {
  const apiKey =
    typeof options.apiKey === 'string' || options.apiKey == null
      ? loadOptionalSetting({
          settingValue: options.apiKey,
          environmentVariableName: 'GOOGLE_VERTEX_API_KEY',
        })
      : options.apiKey;

  const loadGoogleVertexProject = () =>
    loadSetting({
      settingValue: options.project,
      settingName: 'project',
      environmentVariableName: 'GOOGLE_VERTEX_PROJECT',
      description: 'Google Vertex project',
    });

  const loadGoogleVertexLocation = () => {
    const location = loadSetting({
      settingValue: options.location,
      settingName: 'location',
      environmentVariableName: 'GOOGLE_VERTEX_LOCATION',
      description: 'Google Vertex location',
    });
    if (!isValidHostnamePart(location)) {
      throw new InvalidArgumentError({
        argument: 'location',
        message:
          'Invalid Google Vertex location. Expected a single DNS label (letters, digits, and hyphens). Use `baseURL` for custom endpoints.',
      });
    }
    return location;
  };

  // Tuned models are addressed via their deployed endpoint
  // `.../locations/{region}/endpoints/{id}` instead of the base-model
  // `.../publishers/google/models/{id}` path, so they omit the
  // `/publishers/google` suffix from the base URL.
  const loadBaseURL = ({ endpoint = false }: { endpoint?: boolean } = {}) => {
    if (apiKey) {
      return withoutTrailingSlash(options.baseURL) ?? EXPRESS_MODE_BASE_URL;
    }

    const baseURL = withoutTrailingSlash(options.baseURL);
    if (baseURL != null) {
      return baseURL;
    }

    const region = loadGoogleVertexLocation();
    const project = loadGoogleVertexProject();

    const getHost = () => {
      if (region === 'global') {
        return 'aiplatform.googleapis.com';
      } else if (region === 'eu' || region === 'us') {
        return `aiplatform.${region}.rep.googleapis.com`;
      } else {
        return `${region}-aiplatform.googleapis.com`;
      }
    };

    return `https://${getHost()}/v1beta1/projects/${project}/locations/${region}${
      endpoint ? '' : '/publishers/google'
    }`;
  };

  const createConfig = (
    name: string,
    { endpoint = false }: { endpoint?: boolean } = {},
  ): GoogleVertexConfig => {
    const getHeaders = async () => {
      const originalHeaders = await resolve(options.headers ?? {});
      return withUserAgentSuffix(
        originalHeaders,
        `ai-sdk-google-vertex/${VERSION}`,
      );
    };

    return {
      provider: `google.vertex.${name}`,
      headers: getHeaders,
      fetch: apiKey
        ? createExpressModeFetch(apiKey, options.fetch)
        : options.fetch,
      baseURL: loadBaseURL({ endpoint }),
    };
  };

  const createChatModel = (modelId: GoogleVertexModelId) => {
    const endpoint = isEndpointModelId(modelId);

    if (endpoint && apiKey) {
      throw new Error(
        'Google Vertex tuned models do not support Express Mode API keys. Use standard Google Cloud credentials instead.',
      );
    }

    return new GoogleLanguageModel(modelId, {
      ...createConfig('chat', { endpoint }),
      generateId: options.generateId ?? generateId,
      supportedUrls: () => ({
        '*': [
          // HTTP URLs:
          /^https?:\/\/.*$/,
          // Google Cloud Storage URLs:
          /^gs:\/\/.*$/,
        ],
      }),
      downloadToolResultFiles: {
        maxBytes: options.toolResultDownloads?.maxBytes ?? 7 * 1024 * 1024,
        supportsGoogleCloudStorageUrls: true,
        fetch: options.fetch,
      },
    });
  };

  const createInteractionsModel = (
    modelIdOrAgent:
      | GoogleInteractionsModelId
      | { agent: GoogleInteractionsAgentName }
      | { managedAgent: string },
  ) => {
    if (apiKey) {
      throw new Error(
        'Google Vertex Interactions models do not support Express Mode API keys. Use standard Google Cloud credentials instead.',
      );
    }

    return new GoogleInteractionsLanguageModel(
      modelIdOrAgent as GoogleInteractionsModelInput,
      {
        // The Interactions API is a location-scoped resource
        // (`.../locations/{region}/interactions`), so it uses the
        // endpoint-style base URL without the `/publishers/google` suffix that
        // the base-model paths carry.
        ...createConfig('interactions', { endpoint: true }),
        generateId: options.generateId ?? generateId,
      },
    );
  };

  const createEmbeddingModel = (modelId: GoogleVertexEmbeddingModelId) =>
    new GoogleVertexEmbeddingModel(modelId, createConfig('embedding'));

  const createImageModel = (modelId: GoogleVertexImageModelId) =>
    new GoogleVertexImageModel(modelId, {
      ...createConfig('image'),
      generateId: options.generateId ?? generateId,
    });

  const createVideoModel = (modelId: GoogleVertexVideoModelId) =>
    new GoogleVertexVideoModel(modelId, {
      ...createConfig('video'),
      generateId: options.generateId ?? generateId,
    });

  const createSpeechModel = (modelId: GoogleVertexSpeechModelId) => {
    if (getGoogleVertexRequestConfig(modelId).speech?.api === 'cloud-tts') {
      if (apiKey) {
        throw new Error(
          'Google Vertex Chirp speech models do not support Express Mode API keys. Use standard Google Cloud credentials instead.',
        );
      }

      const config = createConfig('speech');
      return new GoogleVertexCloudTTSSpeechModel(modelId, {
        provider: config.provider,
        headers: config.headers,
        fetch: config.fetch,
      });
    }

    return new GoogleSpeechModel(modelId, createConfig('speech'));
  };

  // Cloud Speech-to-Text reuses the Vertex auth headers from createConfig, but
  // targets the Speech-to-Text API.
  const createTranscriptionModel = (
    modelId: GoogleVertexTranscriptionModelId,
  ) => {
    if (apiKey) {
      throw new Error(
        'Google Vertex transcription models do not support Express Mode API keys. Use standard Google Cloud credentials instead.',
      );
    }

    const config = createConfig('transcription');

    // Gemini transcription models (`gemini-3.5-transcribe[-live]`) use the
    // Vertex generateContent / Live API surfaces; everything else routes to
    // Cloud Speech-to-Text (Chirp, telephony).
    if (getGoogleVertexRequestConfig(modelId).transcription?.api === 'gemini') {
      return new GoogleVertexGeminiTranscriptionModel(modelId, {
        provider: config.provider,
        baseURL: loadBaseURL(),
        headers: config.headers,
        fetch: config.fetch,
        webSocket: options.webSocket,
        project: loadGoogleVertexProject(),
        location: loadGoogleVertexLocation(),
      });
    }

    return new GoogleVertexTranscriptionModel(modelId, {
      provider: config.provider,
      headers: config.headers,
      fetch: config.fetch,
      project: loadGoogleVertexProject(),
      location: loadGoogleVertexLocation(),
    });
  };

  const provider = function (modelId: GoogleVertexModelId) {
    if (new.target) {
      throw new Error(
        'The Google Vertex AI model function cannot be called with the new keyword.',
      );
    }

    return createChatModel(modelId);
  };

  provider.specificationVersion = 'v4' as const;
  provider.languageModel = createChatModel;
  provider.interactions = createInteractionsModel;
  provider.embeddingModel = createEmbeddingModel;
  provider.textEmbeddingModel = createEmbeddingModel;
  provider.image = createImageModel;
  provider.imageModel = createImageModel;
  provider.video = createVideoModel;
  provider.videoModel = createVideoModel;
  provider.speech = createSpeechModel;
  provider.speechModel = createSpeechModel;
  provider.transcription = createTranscriptionModel;
  provider.transcriptionModel = createTranscriptionModel;
  provider.tools = googleVertexTools;

  return provider;
}