"use client";

/**
 * 策略说明的获取钩子。
 *
 * 说明/公式由后端 `describe_strategy` 从 spec **真实推导**（不是前端拼字符串）：
 * 这样「页面显示的公式」与「引擎实际执行的规则」只有一个来源，
 * 不会出现文案与实现漂移（本平台最怕的问题）。
 *
 * 两个入口：
 * - `useStrategyDoc(params)`：未保存的参数也能实时预览（POST /strategies/describe），
 *   带去抖，避免每次按键都请求。
 * - `useStrategyDocById(id)`：已保存策略（GET /strategies/{id}/describe）。
 */
import { useEffect, useMemo, useRef, useState } from "react";

import { apiGet, apiPost } from "@/lib/api";
import type { StrategyDoc } from "@/lib/types";
import { paramsToSpec, type StrategyParams } from "@/components/StrategyParamsForm";

export interface DocState {
  doc: StrategyDoc | null;
  loading: boolean;
  error: string;
}

const EMPTY: DocState = { doc: null, loading: false, error: "" };

/** 未保存参数 → 说明（去抖 500ms） */
export function useStrategyDoc(params: StrategyParams | null, enabled = true): DocState {
  const [state, setState] = useState<DocState>(EMPTY);
  const timer = useRef<ReturnType<typeof setTimeout> | null>(null);
  // 只依赖会改变说明的字段，避免改「初始资金」也重新请求
  const key = useMemo(() => {
    if (!params) return "";
    return JSON.stringify({
      f: params.factors,
      a: params.priceAdjustment,
      n: params.topN,
      x: params.holdX,
      m: params.mMonths,
      y: params.yMonths,
      r: params.rebalance,
      fp: params.fillPolicy,
      c: params.conditions,
      s: params.excludeSt,
      l: params.minListingDays,
      cost: [params.commission, params.stamp, params.slippage, params.minCommission],
    });
  }, [params]);

  useEffect(() => {
    if (!params || !enabled || !key) {
      setState(EMPTY);
      return;
    }
    let alive = true;
    if (timer.current) clearTimeout(timer.current);
    setState((s) => ({ ...s, loading: true }));
    timer.current = setTimeout(() => {
      apiPost<StrategyDoc>("/strategies/describe", paramsToSpec(params))
        .then((doc) => alive && setState({ doc, loading: false, error: "" }))
        .catch((e: Error) => alive && setState({ doc: null, loading: false, error: e.message }));
    }, 500);
    return () => {
      alive = false;
      if (timer.current) clearTimeout(timer.current);
    };
    // key 已覆盖所有影响说明的字段
    // eslint-disable-next-line react-hooks/exhaustive-deps
  }, [key, enabled]);

  return state;
}

/** 已保存策略 → 说明 */
export function useStrategyDocById(id: string | null): DocState {
  const [state, setState] = useState<DocState>(EMPTY);
  useEffect(() => {
    if (!id) {
      setState(EMPTY);
      return;
    }
    let alive = true;
    setState({ doc: null, loading: true, error: "" });
    apiGet<StrategyDoc>(`/strategies/${encodeURIComponent(id)}/describe`)
      .then((doc) => alive && setState({ doc, loading: false, error: "" }))
      .catch((e: Error) => alive && setState({ doc: null, loading: false, error: e.message }));
    return () => {
      alive = false;
    };
  }, [id]);
  return state;
}