import type { LLMProvider } from "@maia/core";
import { buildChatBody, parseSse } from "./openai";
import { authHeaders, joinUrl, type MaiaSettings } from "./settings";

export * from "./settings";
export { buildChatBody, parseSse } from "./openai";

async function errorText(response: Response): Promise<string> {
  try {
    return (await response.text()).slice(0, 500);
  } catch {
    return "";
  }
}

/**
 * Provider unique : toutes les requêtes des agents partent au format OpenAI vers le endpoint OpenAI de LiteLLM
 * (LiteLLM_URL + OpenAI_EndPoint), quel que soit le modèle choisi.
 */
export function createLiteLLMProvider(model: string, settings: MaiaSettings): LLMProvider {
  const url = joinUrl(settings.LiteLLM_URL, settings.OpenAI_EndPoint);
  return {
    id: "litellm",
    model,
    capabilities: { tools: true },
    async *chat(req, signal) {
      let response: Response;
      try {
        response = await fetch(url, {
          method: "POST",
          headers: { "Content-Type": "application/json", Accept: "text/event-stream", ...authHeaders(settings) },
          body: JSON.stringify(buildChatBody(model, req)),
          signal,
        });
      } catch (err) {
        if (signal?.aborted) throw err;
        throw new Error(`LiteLLM injoignable (${url}) : ${(err as Error).message}`);
      }
      if (!response.ok) {
        throw new Error(`Échec de l'appel au modèle ${model} (HTTP ${response.status} ${response.statusText}). ${await errorText(response)}`);
      }
      if (!response.body) throw new Error("Réponse LiteLLM sans contenu.");
      yield* parseSse(response.body as unknown as AsyncIterable<Uint8Array>);
    },
  };
}

export interface ModelChoice {
  value: string; // "litellm:<modèle>"
  label: string;
  hint?: string;
}

/** Modèles disponibles sur le serveur LiteLLM (LiteLLM_URL + LiteLLM_Models). */
export async function listLiteLLMModels(settings: MaiaSettings, signal?: AbortSignal): Promise<ModelChoice[]> {
  const url = joinUrl(settings.LiteLLM_URL, settings.LiteLLM_Models);
  let response: Response;
  try {
    response = await fetch(url, { headers: { Accept: "application/json", ...authHeaders(settings) }, signal });
  } catch (err) {
    throw new Error(`LiteLLM injoignable (${url}) : ${(err as Error).message}`);
  }
  if (!response.ok) {
    throw new Error(`Liste des modèles refusée (HTTP ${response.status} ${response.statusText}) : ${url}. ${await errorText(response)}`);
  }
  const json = (await response.json()) as { data?: { id?: string; model_name?: string }[] };
  const names = new Set<string>();
  for (const m of json.data ?? []) {
    const name = m.id ?? m.model_name;
    if (name) names.add(name);
  }
  return [...names].sort().map((name) => ({ value: `litellm:${name}`, label: name, hint: "LiteLLM" }));
}