/**
 * Browser-side LLM client. Speaks to a backend proxy that brokers to the
 * configured provider (Anthropic, OpenAI, etc.) using the same request
 * shape as pi-ai's normalized completions. When the proxy is unreachable
 * or unconfigured the client returns { configured: false } and the caller
 * is expected to fall back to a deterministic path.
 */

import { api } from "./api";

export interface LlmMessage {
  role: "system" | "user" | "assistant";
  content: string;
}

export interface LlmRequest {
  messages: LlmMessage[];
  max_tokens?: number;
}

export interface LlmReply {
  ok: true;
  content: string;
  provider?: string;
}

export interface LlmUnconfigured {
  ok: false;
  configured: false;
  reason: string;
}

export interface LlmError {
  ok: false;
  configured: true;
  error: string;
}

export type LlmResponse = LlmReply | LlmUnconfigured | LlmError;

export const llmClient = {
  async chat(req: LlmRequest, signal?: AbortSignal): Promise<LlmResponse> {
    try {
      const res = await fetch(`${api.config.baseUrl}/internal/canvas-llm/chat`, {
        method: "POST",
        headers: {
          "Content-Type": "application/json",
          Authorization: `Bearer ${sessionStorage.getItem("fm.mc.token.v1")}`,
        },
        body: JSON.stringify({ messages: req.messages, max_tokens: req.max_tokens ?? 512 }),
        signal,
      });
      if (res.status === 404) return { ok: false, configured: false, reason: "LLM proxy not wired" };
      if (res.status === 503) return { ok: false, configured: false, reason: "LLM provider not configured" };
      if (!res.ok) return { ok: false, configured: true, error: `Provider error ${res.status}` };
      const body = await res.json();
      if (typeof body?.content !== "string") return { ok: false, configured: true, error: "Provider returned unparseable body" };
      return { ok: true, content: body.content, provider: body.provider };
    } catch (e) {
      return { ok: false, configured: false, reason: `LLM proxy unreachable: ${(e as Error).message}` };
    }
  },
};