/**
 * Document RAG retrieval pipeline.
 *
 * Simpler than Graph RAG — embeds the query, finds similar document chunks,
 * and synthesizes an answer from the chunk content.
 *
 * Python reference: trustgraph-flow/trustgraph/retrieval/document_rag/
 */

import type {
  FlowRequestor,
  TextCompletionRequest,
  TextCompletionResponse,
  EmbeddingsRequest,
  EmbeddingsResponse,
  DocumentEmbeddingsRequest,
  DocumentEmbeddingsResponse,
  PromptRequest,
  PromptResponse,
} from "@trustgraph/base";

export interface DocumentRagClients {
  llm: FlowRequestor<TextCompletionRequest, TextCompletionResponse>;
  embeddings: FlowRequestor<EmbeddingsRequest, EmbeddingsResponse>;
  docEmbeddings: FlowRequestor<DocumentEmbeddingsRequest, DocumentEmbeddingsResponse>;
  prompt: FlowRequestor<PromptRequest, PromptResponse>;
}

export type ChunkCallback = (text: string, endOfStream: boolean) => Promise<void>;

export class DocumentRag {
  private readonly clients: DocumentRagClients;

  constructor(clients: DocumentRagClients) {
    this.clients = clients;
  }

  async query(
    queryText: string,
    options?: {
      collection?: string;
      streaming?: boolean;
      chunkCallback?: ChunkCallback;
    },
  ): Promise<string> {
    const collection = options?.collection ?? "default";

    // Step 1: Embed the query
    const embResp = await this.clients.embeddings.request({ text: [queryText] });
    const vectors = (embResp as EmbeddingsResponse).vectors;

    // Step 2: Find similar document chunks
    const docResp = await this.clients.docEmbeddings.request({
      vectors,
      limit: 10,
      collection,
      user: "default",
    });
    const chunks = (docResp as DocumentEmbeddingsResponse).chunks ?? [];
    console.log(`[DocumentRag] Found ${chunks.length} matching chunks`);

    // Step 3: Build context from chunks
    const context = chunks
      .flatMap((c) =>
        c.content !== undefined && c.content.length > 0 ? [c.content] : [],
      )
      .join("\n\n---\n\n");

    // Step 4: Synthesize answer
    const promptResp = await this.clients.prompt.request({
      name: "document-rag-synthesize",
      variables: { query: queryText, context },
    });

    const resp = await this.clients.llm.request({
      system: (promptResp as PromptResponse).system,
      prompt: (promptResp as PromptResponse).prompt,
    });

    return (resp as TextCompletionResponse).response;
  }
}