import OpenAI from "openai";
import type { ChatCompletionMessageParam } from "openai/resources/chat/completions";

const PLANNER_SYSTEM_PROMPT = `You are a tool-use planner. Given a user message and available tools, decide:
1. Does this request need any tools? (simple questions like "what is 2+2" do not)
2. If yes, which specific tools are needed?
3. What is the execution plan?

Respond in this exact JSON format:
{"needs_tools": boolean, "tools_needed": ["tool_name", ...], "plan": "brief description"}

Only include tools that are actually necessary. Do not over-plan.`;

export interface PlanResult {
  needsTools: boolean;
  toolsNeeded: string[];
  plan: string;
}

export async function planToolUsage(
  client: OpenAI,
  model: string,
  userMessage: string,
  availableTools: string[]
): Promise<PlanResult> {
  try {
    const response = await client.chat.completions.create({
      model,
      messages: [
        { role: "system", content: PLANNER_SYSTEM_PROMPT },
        {
          role: "user",
          content: `Available tools: ${availableTools.join(", ")}\n\nUser message: ${userMessage}`,
        },
      ],
      max_tokens: 200,
      temperature: 0,
    });

    const content = response.choices[0]?.message?.content?.trim() ?? "";
    const jsonMatch = content.match(/\{[\s\S]*\}/);
    if (!jsonMatch) {
      return { needsTools: true, toolsNeeded: [], plan: "proceed with all tools" };
    }

    const parsed = JSON.parse(jsonMatch[0]);
    return {
      needsTools: parsed.needs_tools ?? true,
      toolsNeeded: parsed.tools_needed ?? [],
      plan: parsed.plan ?? "",
    };
  } catch {
    return { needsTools: true, toolsNeeded: [], plan: "" };
  }
}