import {
  EMBED_API_KEY,
  EMBED_BASE_URL,
  EMBED_MODEL,
} from "@mcpedia/config";

export interface EmbeddingProvider {
  /** Embed a batch of texts into vectors of fixed dimension. */
  embed(texts: string[]): Promise<number[][]>;
  readonly model: string;
  readonly dimensions: number;
}

/** Pinned embedding dimension for the configured OpenRouter model. */
export const EMBED_DIM = 2048;

/**
 * OpenRouter embeddings provider (we route through 9router's OpenAI-compatible
 * /v1 endpoint). `encoding_format: "float"` is REQUIRED — the Nvidia-backed
 * model rejects base64.
 */
export class OpenRouterEmbeddingProvider implements EmbeddingProvider {
  readonly model: string;
  private readonly baseUrl: string;
  private readonly apiKey: string;

  constructor(opts?: {
    baseUrl?: string;
    apiKey?: string;
    model?: string;
  }) {
    this.baseUrl = (opts?.baseUrl ?? EMBED_BASE_URL).replace(/\/$/, "");
    this.apiKey = opts?.apiKey ?? EMBED_API_KEY;
    this.model = opts?.model ?? EMBED_MODEL;
    // NOTE: we do NOT validate baseUrl/apiKey/model here. Throwing in the
    // constructor breaks `next build` (SSG data collection imports the search
    // package before any .env is present) and any runtime-injected env. The
    // provider is constructed lazily at first query, so an unset config
    // surfaces as a clear error from embed() at request time, not a build crash.
  }

  get dimensions(): number {
    return EMBED_DIM;
  }

  async embed(texts: string[]): Promise<number[][]> {
    if (texts.length === 0) return [];
    if (!this.baseUrl || !this.apiKey || !this.model) {
      throw new Error(
        "OpenRouterEmbeddingProvider: missing EMBED_BASE_URL / EMBED_API_KEY / EMBED_MODEL at request time",
      );
    }
    const res = await fetch(`${this.baseUrl}/embeddings`, {
      method: "POST",
      headers: {
        "Content-Type": "application/json",
        Authorization: `Bearer ${this.apiKey}`,
      },
      body: JSON.stringify({
        model: this.model,
        input: texts,
        encoding_format: "float",
      }),
    });
    if (!res.ok) {
      const body = await res.text().catch(() => "");
      throw new Error(
        `embedding request failed (${res.status}): ${body.slice(0, 300)}`,
      );
    }
    const json = (await res.json()) as {
      data?: { embedding: number[] }[];
    };
    const data = json.data;
    if (!data || data.length !== texts.length) {
      throw new Error(
        `embedding response mismatch: expected ${texts.length}, got ${data?.length ?? 0}`,
      );
    }
    return data.map((d) => d.embedding);
  }
}

/** Default singleton provider. */
export function createEmbeddingProvider(): EmbeddingProvider {
  return new OpenRouterEmbeddingProvider();
}