/**
 * 设计系统 UI 基元（纯展示，无副作用）：页头 / 卡片 / 指标卡 / 徽标 /
 * 按钮 / 表单字段 / 提示条 / 空态 / 骨架 / 进度 / 回测结果区块。
 */
import { useId } from "react";
import type { ButtonHTMLAttributes, InputHTMLAttributes, ReactNode } from "react";
import type { BacktestSummary } from "@/lib/types";
import { Icon, type IconName } from "@/components/icons";

export function cx(...parts: Array<string | false | null | undefined>): string {
  return parts.filter(Boolean).join(" ");
}

/* ---------- 页头 ---------- */

export function PageHeader({
  title,
  sub,
  actions,
}: {
  title: string;
  sub?: ReactNode;
  actions?: ReactNode;
}) {
  return (
    <header className="page-head">
      <div>
        <h1 className="page-title">{title}</h1>
        {sub ? <p className="page-sub">{sub}</p> : null}
      </div>
      {actions ? <div className="page-actions">{actions}</div> : null}
    </header>
  );
}

/* ---------- 卡片 ---------- */

export function Card({
  title,
  sub,
  icon,
  tools,
  children,
  flush = false,
  className,
}: {
  title?: ReactNode;
  sub?: ReactNode;
  icon?: IconName;
  tools?: ReactNode;
  children: ReactNode;
  flush?: boolean;
  className?: string;
}) {
  const hasHead = title != null || tools != null;
  return (
    <section className={cx("card", className)}>
      {hasHead ? (
        <div className="card__head">
          <div className="card__title">
            {icon ? <Icon name={icon} size={17} /> : null}
            <span>
              {title}
              {sub ? <span className="card__sub">　{sub}</span> : null}
            </span>
          </div>
          {tools ? <div className="card__tools">{tools}</div> : null}
        </div>
      ) : null}
      <div className={flush ? "card__body--flush" : "card__body"}>{children}</div>
    </section>
  );
}

/* ---------- 指标卡 ---------- */

export function Metric({
  label,
  icon,
  value,
  sub,
  tone = "plain",
  small = false,
}: {
  label: ReactNode;
  icon?: IconName;
  value: ReactNode;
  sub?: ReactNode;
  tone?: "plain" | "pos" | "neg" | "warn" | "accent";
  small?: boolean;
}) {
  return (
    <div className="metric">
      <div className="metric__label">
        {icon ? <Icon name={icon} size={14} /> : null}
        {label}
      </div>
      <div
        className={cx(
          "metric__value",
          small && "metric__value--sm",
          tone !== "plain" && `tone-${tone}`,
        )}
      >
        {value}
      </div>
      {sub ? <div className="metric__sub">{sub}</div> : null}
    </div>
  );
}

/* ---------- 徽标 ---------- */

export function Pill({
  tone = "default",
  children,
  icon,
}: {
  tone?: "default" | "accent" | "pos" | "neg" | "warn" | "violet";
  children: ReactNode;
  icon?: IconName;
}) {
  return (
    <span className={cx("pill", tone !== "default" && `pill--${tone}`)}>
      {icon ? <Icon name={icon} size={12} /> : null}
      {children}
    </span>
  );
}

/* ---------- 按钮 ---------- */

interface BtnProps extends ButtonHTMLAttributes<HTMLButtonElement> {
  variant?: "primary" | "ghost" | "danger";
  size?: "sm" | "md";
  icon?: IconName;
  loading?: boolean;
  children?: ReactNode;
}

export function Btn({
  variant = "ghost",
  size = "md",
  icon,
  loading = false,
  children,
  className,
  ...rest
}: BtnProps) {
  return (
    <button
      className={cx(
        "btn",
        variant === "primary" && "btn--primary",
        variant === "danger" && "btn--danger",
        size === "sm" && "btn--sm",
        className,
      )}
      disabled={rest.disabled || loading}
      {...rest}
    >
      {loading ? <Icon name="spinner" size={14} className="spin" /> : icon ? <Icon name={icon} size={15} /> : null}
      {children}
    </button>
  );
}

/* ---------- 表单 ---------- */

export function Field({
  label,
  hint,
  htmlFor,
  children,
  className,
}: {
  label: ReactNode;
  hint?: ReactNode;
  htmlFor?: string;
  children: ReactNode;
  className?: string;
}) {
  return (
    <div className={cx("field", className)}>
      <label className="field__label" htmlFor={htmlFor}>
        {label}
      </label>
      {children}
      {hint ? <span className="field__hint">{hint}</span> : null}
    </div>
  );
}

interface TextInputProps extends InputHTMLAttributes<HTMLInputElement> {
  mono?: boolean;
}

/** 统一样式的 input（含原生控件），mono 用于代码/数值输入。 */
export function TextInput({ className, mono, ...rest }: TextInputProps) {
  return <input className={cx("input", mono && "mono", className)} {...rest} />;
}

export function SearchBox({
  value,
  onChange,
  onClear,
  placeholder,
  label,
}: {
  value: string;
  onChange: (v: string) => void;
  onClear?: () => void;
  placeholder?: string;
  label?: string;
}) {
  const inputId = useId();
  return (
    <div className="searchbox" role="search">
      <label className="sr-only" htmlFor={inputId}>
        {label ?? "搜索"}
      </label>
      <Icon name="search" size={16} />
      <TextInput
        id={inputId}
        type="search"
        className="input"
        placeholder={placeholder}
        value={value}
        onChange={(e) => onChange(e.target.value)}
      />
      {value && onClear ? (
        <button type="button" className="icon-btn clear" aria-label="清空搜索" onClick={onClear}>
          <Icon name="x" size={13} />
        </button>
      ) : null}
    </div>
  );
}

/* ---------- 提示条 / 空态 / 加载 ---------- */

export function Banner({
  tone = "info",
  children,
  icon,
}: {
  tone?: "error" | "warn" | "info" | "muted";
  children: ReactNode;
  icon?: IconName;
}) {
  const ic: IconName =
    icon ?? (tone === "error" || tone === "warn" ? "alert" : tone === "muted" ? "info" : "info");
  return (
    <div className={cx("banner", `banner--${tone}`)} role={tone === "error" ? "alert" : undefined}>
      <Icon name={ic} size={16} />
      <div>{children}</div>
    </div>
  );
}

export function Empty({
  icon = "archive",
  title,
  hint,
  children,
}: {
  icon?: IconName;
  title: ReactNode;
  hint?: ReactNode;
  children?: ReactNode;
}) {
  return (
    <div className="empty">
      <Icon name={icon} size={30} />
      <strong>{title}</strong>
      {hint ? <p className="hint" style={{ maxWidth: 460, margin: "4px auto 0" }}>{hint}</p> : null}
      {children ? <div style={{ marginTop: 14 }}>{children}</div> : null}
    </div>
  );
}

export function SkeletonLines({ n = 3, height = 14 }: { n?: number; height?: number }) {
  return (
    <div className="stack" aria-hidden="true">
      {Array.from({ length: n }).map((_, i) => (
        <div
          key={i}
          className="skeleton"
          style={{ height, width: i === n - 1 ? "62%" : "100%" }}
        />
      ))}
    </div>
  );
}

export function Loading({ label = "加载中…" }: { label?: string }) {
  return (
    <div className="row" style={{ color: "var(--text-2)", padding: "10px 0" }} role="status">
      <Icon name="spinner" size={16} className="spin" />
      <span className="hint">{label}</span>
    </div>
  );
}

export function Progress({
  value,
  label,
}: {
  /** 0-100 */
  value: number;
  label?: ReactNode;
}) {
  return (
    <div>
      {label ? (
        <div className="hint" style={{ marginBottom: 2 }}>
          {label}
        </div>
      ) : null}
      <div
        className="progress"
        role="progressbar"
        aria-valuenow={Math.round(value)}
        aria-valuemin={0}
        aria-valuemax={100}
      >
        <div className="progress__bar" style={{ width: `${Math.max(0, Math.min(100, value))}%` }} />
      </div>
    </div>
  );
}

/* ---------- 数值 ---------- */

export function Signed({
  value,
  suffix = "",
  digits = 2,
  arrow = true,
}: {
  value: number;
  suffix?: string;
  digits?: number;
  arrow?: boolean;
}) {
  const cls = value > 0 ? "tone-pos" : value < 0 ? "tone-neg" : "";
  return (
    <span className={cx("num delta", cls)}>
      {arrow ? (value > 0 ? <Icon name="arrowUp" size={12} /> : value < 0 ? <Icon name="arrowDown" size={12} /> : null) : null}
      {value > 0 ? "+" : ""}
      {value.toFixed(digits)}
      {suffix}
    </span>
  );
}

/* ---------- 回测 / 因子结果共用区块 ---------- */

export function BacktestMetrics({ s }: { s: BacktestSummary }) {
  return (
    <div className="metric-grid">
      <Metric label="期末净值" value={s.final_equity.toLocaleString()} sub={`起始 ${s.initial_capital.toLocaleString()}`} />
      <Metric label="区间收益" tone={s.total_return_pct >= 0 ? "pos" : "neg"} value={<Signed value={s.total_return_pct} suffix="%" />} sub={`${s.start} ~ ${s.end}`} />
      <Metric label="年化收益" tone={s.annual_return_pct >= 0 ? "pos" : "neg"} value={<Signed value={s.annual_return_pct} suffix="%" />} />
      <Metric
        label="Sharpe"
        tone={s.sharpe >= 1 ? "pos" : s.sharpe < 0 ? "neg" : "plain"}
        value={s.sharpe.toFixed(2)}
        sub={`波动 ${s.volatility_pct.toFixed(2)}%`}
      />
      <Metric label="最大回撤" tone="neg" value={<span className="num">{s.max_drawdown_pct.toFixed(2)}%</span>} />
      <Metric label="胜率 / 换手" value={`${s.win_rate_pct.toFixed(1)}%`} sub={`交易 ${s.total_trades} 笔 · 平均换手 ${s.avg_turnover_pct.toFixed(0)}%`} />
    </div>
  );
}

/* ---------- 月度收益（热力着色） ---------- */

export function MonthlyReturnsTable({
  rows,
}: {
  rows: { year: number; month: number; return_pct: number }[];
}) {
  const byYear = new Map<number, Map<number, number>>();
  for (const r of rows) {
    if (!byYear.has(r.year)) byYear.set(r.year, new Map());
    byYear.get(r.year)!.set(r.month, r.return_pct);
  }
  const months = Array.from({ length: 12 }, (_, i) => i + 1);
  const years = [...byYear.keys()].sort();
  if (years.length === 0) return <Empty title="无月度收益数据" />;
  return (
    <div className="table-wrap">
      <table className="tbl">
        <thead>
          <tr>
            <th>年份</th>
            {months.map((m) => (
              <th key={m} style={{ textAlign: "right", minWidth: 62 }}>
                {m}月
              </th>
            ))}
          </tr>
        </thead>
        <tbody>
          {years.map((y) => {
            const row = byYear.get(y)!;
            return (
              <tr key={y}>
                <td className="cell-strong">{y}</td>
                {months.map((m) => {
                  const v = row.get(m);
                  if (v == null)
                    return (
                      <td key={m} style={{ textAlign: "right" }}>
                        <span className="cell-heat flat">—</span>
                      </td>
                    );
                  const cls = v > 0 ? "pos" : v < 0 ? "neg" : "flat";
                  return (
                    <td key={m} style={{ textAlign: "right" }}>
                      <span className={`cell-heat ${cls}`}>
                        {v > 0 ? "+" : ""}
                        {v.toFixed(2)}%
                      </span>
                    </td>
                  );
                })}
              </tr>
            );
          })}
        </tbody>
      </table>
    </div>
  );
}

export function UnimplementedNote({ items }: { items: string[] }) {
  if (!items || items.length === 0) return null;
  return (
    <Card title="未建模约束（如实标注）" icon="info">
      <ul className="hint" style={{ margin: 0, paddingLeft: 18 }}>
        {items.map((u, i) => (
          <li key={i}>{u}</li>
        ))}
      </ul>
    </Card>
  );
}