/**
 * Embeddings handler.
 */

import * as http from 'node:http';
import type {
  IApiError,
  IEmbeddingData,
  IEmbeddingsRequest,
  IEmbeddingsResponse,
} from '../../interfaces/api.ts';
import { ClusterCoordinator } from '../../cluster/coordinator.ts';
import { ContainerManager } from '../../containers/container-manager.ts';
import { logger } from '../../logger.ts';
import { ModelRegistry } from '../../models/registry.ts';

export class EmbeddingsHandler {
  private containerManager: ContainerManager;
  private modelRegistry: ModelRegistry;
  private clusterCoordinator: ClusterCoordinator;

  constructor(
    containerManager: ContainerManager,
    modelRegistry: ModelRegistry,
    clusterCoordinator: ClusterCoordinator,
  ) {
    this.containerManager = containerManager;
    this.modelRegistry = modelRegistry;
    this.clusterCoordinator = clusterCoordinator;
  }

  public async handleEmbeddings(
    req: http.IncomingMessage,
    res: http.ServerResponse,
    body: IEmbeddingsRequest,
  ): Promise<void> {
    const canonicalModel = await this.resolveCanonicalModel(body.model);
    const requestBody: IEmbeddingsRequest = {
      ...body,
      model: canonicalModel,
    };

    logger.dim(`Embeddings request for model: ${canonicalModel}`);

    try {
      const container = await this.containerManager.findContainerForModel(canonicalModel);
      if (container) {
        const response = await this.generateEmbeddings(container, requestBody);
        res.writeHead(200, { 'Content-Type': 'application/json' });
        res.end(JSON.stringify(response));
        return;
      }

      const ensured = await this.clusterCoordinator.ensureModelViaControlPlane(canonicalModel);
      if (!ensured) {
        this.sendError(
          res,
          404,
          `Embedding model "${canonicalModel}" not found`,
          'model_not_found',
        );
        return;
      }

      if (ensured.location.nodeName === this.clusterCoordinator.getLocalNodeName()) {
        const localContainer = await this.containerManager.findContainerForModel(canonicalModel);
        if (!localContainer) {
          this.sendError(
            res,
            503,
            `Embedding model "${canonicalModel}" is not ready`,
            'server_error',
          );
          return;
        }

        const response = await this.generateEmbeddings(localContainer, requestBody);
        res.writeHead(200, { 'Content-Type': 'application/json' });
        res.end(JSON.stringify(response));
        return;
      }

      const response = await fetch(`${ensured.location.endpoint}/v1/embeddings`, {
        method: 'POST',
        headers: this.buildForwardHeaders(req),
        body: JSON.stringify(requestBody),
      });

      const text = await response.text();
      res.writeHead(response.status, {
        'Content-Type': response.headers.get('content-type') || 'application/json',
      });
      res.end(text);
    } catch (error) {
      const message = error instanceof Error ? error.message : String(error);
      logger.error(`Embeddings error: ${message}`);
      this.sendError(res, 500, `Embeddings generation failed: ${message}`, 'server_error');
    }
  }

  private async resolveCanonicalModel(modelName: string): Promise<string> {
    const model = await this.modelRegistry.getModel(modelName);
    return model?.id || modelName;
  }

  private async generateEmbeddings(
    container: import('../../containers/base-container.ts').BaseContainer,
    request: IEmbeddingsRequest,
  ): Promise<IEmbeddingsResponse> {
    const inputs = Array.isArray(request.input) ? request.input : [request.input];
    const embeddings: IEmbeddingData[] = [];
    let totalTokens = 0;

    for (let i = 0; i < inputs.length; i++) {
      const input = inputs[i];
      const embedding = await this.getEmbeddingFromContainer(container, request.model, input);

      embeddings.push({
        object: 'embedding',
        embedding: embedding.vector,
        index: i,
      });

      totalTokens += embedding.tokenCount;
    }

    return {
      object: 'list',
      data: embeddings,
      model: request.model,
      usage: {
        prompt_tokens: totalTokens,
        total_tokens: totalTokens,
      },
    };
  }

  private async getEmbeddingFromContainer(
    container: import('../../containers/base-container.ts').BaseContainer,
    model: string,
    input: string,
  ): Promise<{ vector: number[]; tokenCount: number }> {
    const endpoint = container.getEndpoint();
    const containerType = container.type;

    if (containerType === 'vllm') {
      return this.getVllmEmbedding(endpoint, model, input);
    }

    if (containerType === 'tgi') {
      return this.getTgiEmbedding(endpoint, model, input);
    }

    throw new Error(`Container type ${containerType} does not support embeddings`);
  }

  private async getVllmEmbedding(
    endpoint: string,
    model: string,
    input: string,
  ): Promise<{ vector: number[]; tokenCount: number }> {
    const response = await fetch(`${endpoint}/v1/embeddings`, {
      method: 'POST',
      headers: { 'Content-Type': 'application/json' },
      body: JSON.stringify({ model, input }),
    });

    if (!response.ok) {
      throw new Error(`vLLM embedding error: ${await response.text()}`);
    }

    const result = await response.json() as IEmbeddingsResponse;
    return {
      vector: result.data[0].embedding,
      tokenCount: result.usage.total_tokens,
    };
  }

  private async getTgiEmbedding(
    endpoint: string,
    _model: string,
    input: string,
  ): Promise<{ vector: number[]; tokenCount: number }> {
    const response = await fetch(`${endpoint}/embed`, {
      method: 'POST',
      headers: { 'Content-Type': 'application/json' },
      body: JSON.stringify({ inputs: input }),
    });

    if (!response.ok) {
      throw new Error(`TGI embedding error: ${await response.text()}`);
    }

    const result = await response.json() as number[][];
    return {
      vector: result[0],
      tokenCount: Math.ceil(input.length / 4),
    };
  }

  private buildForwardHeaders(req: http.IncomingMessage): Record<string, string> {
    const headers: Record<string, string> = {
      'Content-Type': 'application/json',
    };

    if (typeof req.headers.authorization === 'string') {
      headers.Authorization = req.headers.authorization;
    }

    if (typeof req.headers['x-request-id'] === 'string') {
      headers['X-Request-Id'] = req.headers['x-request-id'];
    }

    return headers;
  }

  private sendError(
    res: http.ServerResponse,
    statusCode: number,
    message: string,
    type: string,
    param?: string,
  ): void {
    const error: IApiError = {
      error: {
        message,
        type,
        param,
      },
    };

    res.writeHead(statusCode, { 'Content-Type': 'application/json' });
    res.end(JSON.stringify(error));
  }
}