import { type Api, createModels, createProvider, type Model, type MutableModels } from "@earendil-works/pi-ai";
import { anthropicMessagesApi } from "@earendil-works/pi-ai/api/anthropic-messages.lazy";
import { openAICompletionsApi } from "@earendil-works/pi-ai/api/openai-completions.lazy";
import type { CompactionPolicy } from "@earendil-works/pi-durable";
import type { ResolvedAgentSettings } from "../settings.ts";

/** Pi 侧需要的模型装配结果(仅在 src/pi/* 内部流转) */
export interface ResolvedPiModel {
  models: MutableModels;
  model: Model<Api>;
  /** 夹到模型支持范围后的思考档位;缺省用设置值 */
  thinkingLevel?: ResolvedAgentSettings["thinkingLevel"];
}

export type PiModelResolver = (settings: ResolvedAgentSettings) => ResolvedPiModel | Promise<ResolvedPiModel>;

const ANTHROPIC_DEFAULT_BASE = "https://api.anthropic.com";
const PROVIDER_ID = { anthropic: "umt-anthropic", "openai-compatible": "umt-openai-compatible" } as const;

/**
 * 设置 → pi-ai createProvider。apiKey 只在请求时经 auth.resolve 交给 SDK,不读环境变量。
 * Anthropic baseUrl 不带 /v1;OpenAI 兼容 baseUrl 带 /v1(与 spike 抓包结论一致)。
 */
export function resolveModelFromSettings(settings: ResolvedAgentSettings): ResolvedPiModel {
  if (settings.provider !== "anthropic" && settings.provider !== "openai-compatible")
    throw new Error(`provider ${settings.provider} 需要按模型服务装配(PiAgentRuntimeOptions.upstream)`);
  if (!settings.apiKey) throw new Error("未配置模型服务密钥");
  const providerId = PROVIDER_ID[settings.provider];
  const common = {
    id: settings.model,
    name: settings.model,
    provider: providerId,
    reasoning: settings.thinkingLevel !== "off",
    input: ["text"] as ("text" | "image")[],
    cost: { input: 0, output: 0, cacheRead: 0, cacheWrite: 0 },
    contextWindow: settings.contextBudgetTokens,
    maxTokens: Math.min(settings.maxOutputTokens, Math.floor(settings.contextBudgetTokens / 2)),
  };
  const apiKey = settings.apiKey;
  const auth = { apiKey: { name: "umt-secret", resolve: async () => ({ auth: { apiKey } }) } };
  const models = createModels();
  let model: Model<Api>;
  if (settings.provider === "anthropic") {
    const m: Model<"anthropic-messages"> = {
      ...common,
      api: "anthropic-messages",
      baseUrl: (settings.baseUrl ?? ANTHROPIC_DEFAULT_BASE).replace(/\/+$/, "").replace(/\/v1$/, ""),
    };
    models.setProvider(createProvider({ id: providerId, auth, models: [m], api: anthropicMessagesApi() }));
    model = m;
  } else {
    if (!settings.baseUrl) throw new Error("openai-compatible 模型服务必须配置 baseUrl(带 /v1)");
    const m: Model<"openai-completions"> = {
      ...common,
      api: "openai-completions",
      baseUrl: settings.baseUrl.replace(/\/+$/, ""),
      compat: { supportsDeveloperRole: false },
    };
    models.setProvider(createProvider({ id: providerId, auth, models: [m], api: openAICompletionsApi() }));
    model = m;
  }
  return { models, model };
}

/**
 * 压缩设置:threshold 模式下占用达到 threshold 比例时阻塞压缩;manual 只允许手动 compact()。
 * backgroundTokens=0:不做 pi-durable 的后台提前压缩,行为与 pi-agent-core 0.99 的阈值压缩一致。
 */
export function compactionFromSettings(settings: ResolvedAgentSettings, contextWindow: number): CompactionPolicy {
  const reserveTokens = Math.max(256, Math.round(contextWindow * (1 - settings.compaction.threshold)));
  return {
    enabled: settings.compaction.mode === "threshold",
    reserveTokens,
    keepRecentTokens: Math.max(256, Math.round(contextWindow * 0.25)),
    backgroundTokens: 0,
  };
}