import { Type } from "typebox";

import { ChunkingManager, getChunkSize } from "../shared/chunking";
import { serializeResponseWithMeta, type SerializedToolResult } from "../shared/serialize";

export interface GetNextChunkDeps {
  chunkingManager: ChunkingManager;
}

export function createGetNextChunkTool(deps: GetNextChunkDeps) {
  return {
    name: "get_next_chunk",
    label: "Get Next Chunk",
    description:
      "Get next chunk of large response using continuation token from previous chunked response.",
    promptSnippet: "Fetch the next chunk of a previously chunked rtfd response by continuation token",
    parameters: Type.Object({
      continuation_token: Type.String({
        description: "Token from the continuation_token field in a chunked response",
      }),
    }),
    async execute(
      _toolCallId: string,
      params: { continuation_token: string },
    ): Promise<SerializedToolResult> {
      const chunkSize = getChunkSize();

      if (chunkSize === 0) {
        return serializeResponseWithMeta({
          error: "Chunking is disabled (RTFD_CHUNK_TOKENS=0)",
        });
      }

      const result = deps.chunkingManager.getNextChunk(params.continuation_token, chunkSize);

      if (result === null) {
        return serializeResponseWithMeta({
          error: "Invalid or expired continuation token. Tokens expire after 10 minutes.",
        });
      }

      const chunkData: Record<string, unknown> = { ...result };

      if (chunkData.has_more) {
        chunkData.hint = `Call get_next_chunk('${chunkData.continuation_token}') for more content`;
      }

      return serializeResponseWithMeta(chunkData);
    },
  };
}