import { DynamicStructuredTool } from '@langchain/core/tools';
import { z } from 'zod';
import type { FastifyBaseLogger } from 'fastify';
import type { WebExploreSubagent } from '../../harness/subagents/web-explore/index.js';
import type { SubagentContext } from '../../harness/subagents/base-subagent.js';
import type { HarnessEvent } from '../../harness/harness-events.js';

export interface WebExploreAgentToolConfig {
  webExploreSubagent: WebExploreSubagent;
  context: SubagentContext;
  logger: FastifyBaseLogger;
}

/**
 * Creates a LangChain tool that delegates to the web-explore subagent.
 * The subagent decides whether to use web search or arXiv based on the instruction.
 */
export function createWebExploreAgentTool(config: WebExploreAgentToolConfig): DynamicStructuredTool & { streamFunc: (args: { instruction: string }, signal?: AbortSignal) => AsyncGenerator<HarnessEvent, string> } {
  const { webExploreSubagent, context, logger } = config;

  async function* streamFunc({ instruction }: { instruction: string }, signal?: AbortSignal): AsyncGenerator<HarnessEvent, string> {
    logger.info({ instruction: instruction.substring(0, 100) }, 'Streaming web-explore subagent');
    const gen = webExploreSubagent.streamEvents(context, instruction, signal);
    let step: IteratorResult<HarnessEvent, string>;
    while (!(step = await gen.next()).done) {
      yield step.value;
    }
    return step.value;
  }

  const tool = new DynamicStructuredTool({
    name: 'web_explore',
    description: `Search the EXTERNAL web or academic databases and return a summarized answer.

Use this tool ONLY for external, public information:
- Current events, news, or real-time information
- External documentation, tutorials, or how-to guides for third-party libraries/tools
- Academic papers, research findings, or scientific topics
- Any topic requiring external sources

NEVER use this tool for:
- Questions about the Dexorder platform itself (workspace tools, chartState, indicators, strategies)
- Internal API usage (workspace_patch, workspace_read, etc.) — consult the system prompt instead
- Anything that can be answered from the context already available

The subagent will search the web (or arXiv for academic queries), fetch relevant content, and return a markdown summary with cited sources.`,
    schema: z.object({
      instruction: z.string().describe(
        'What to search for and summarize. Be specific — include the topic, what aspects matter, ' +
        'and any context that helps narrow the search (e.g. "recent papers on momentum factor in equities" ' +
        'or "how to configure rate limiting in Fastify").'
      ),
    }),
    func: async ({ instruction }: { instruction: string }): Promise<string> => {
      logger.info({ instruction: instruction.substring(0, 100) }, 'Delegating to web-explore subagent');

      try {
        return await webExploreSubagent.execute(context, instruction);
      } catch (error) {
        logger.error({ error, errorMessage: (error as Error)?.message }, 'Web explore subagent failed');
        throw error;
      }
    },
  });

  return Object.assign(tool, { streamFunc });
}