"use client";

import { useEffect, useId, useRef, useState } from "react";
import { Check, ChevronDown } from "lucide-react";
import type { Board } from "@/lib/api";

type BoardPickerProps = {
  boards: Board[];
  value: number;
  onChange: (id: number) => void;
  disabled?: boolean;
  loading?: boolean;
  /** 提交校验失败后再为 true，用于红色错误态 */
  invalid?: boolean;
  id?: string;
};

function boardColorIndex(b: Board, fallbackIndex: number) {
  return Math.max(0, b.color_index ?? fallbackIndex) % 8;
}

export default function BoardPicker({
  boards,
  value,
  onChange,
  disabled,
  loading,
  invalid = false,
  id,
}: BoardPickerProps) {
  const listId = useId();
  const rootRef = useRef<HTMLDivElement>(null);
  const [open, setOpen] = useState(false);
  const [activeIndex, setActiveIndex] = useState(0);

  const selectedIdx = boards.findIndex((b) => b.id === value);
  const selected = selectedIdx >= 0 ? boards[selectedIdx] : null;

  useEffect(() => {
    if (!open) return;
    setActiveIndex(selectedIdx >= 0 ? selectedIdx : 0);
  }, [open, selectedIdx]);

  useEffect(() => {
    if (!open) return;
    const onDoc = (e: MouseEvent) => {
      if (!rootRef.current?.contains(e.target as Node)) setOpen(false);
    };
    const onKey = (e: KeyboardEvent) => {
      if (e.key === "Escape") {
        e.preventDefault();
        setOpen(false);
      }
    };
    document.addEventListener("mousedown", onDoc);
    document.addEventListener("keydown", onKey);
    return () => {
      document.removeEventListener("mousedown", onDoc);
      document.removeEventListener("keydown", onKey);
    };
  }, [open]);

  const pick = (id: number) => {
    onChange(id);
    setOpen(false);
  };

  const onTriggerKeyDown = (e: React.KeyboardEvent) => {
    if (disabled || loading) return;
    if (e.key === "ArrowDown" || e.key === "Enter" || e.key === " ") {
      e.preventDefault();
      setOpen(true);
    }
  };

  const onMenuKeyDown = (e: React.KeyboardEvent) => {
    if (!boards.length) return;
    if (e.key === "ArrowDown") {
      e.preventDefault();
      setActiveIndex((i) => (i + 1) % boards.length);
    } else if (e.key === "ArrowUp") {
      e.preventDefault();
      setActiveIndex((i) => (i - 1 + boards.length) % boards.length);
    } else if (e.key === "Enter" || e.key === " ") {
      e.preventDefault();
      const b = boards[activeIndex];
      if (b) pick(b.id);
    } else if (e.key === "Home") {
      e.preventDefault();
      setActiveIndex(0);
    } else if (e.key === "End") {
      e.preventDefault();
      setActiveIndex(boards.length - 1);
    }
  };

  const empty = !loading && !selected;
  const showError = empty && invalid;
  const label = loading
    ? "加载板块…"
    : selected
      ? selected.name
      : boards.length === 0
        ? "暂无可用板块"
        : "请选择板块";

  const colorIdx = selected
    ? boardColorIndex(selected, selectedIdx)
    : 0;

  return (
    <div className="j13-board-picker" ref={rootRef}>
      <button
        id={id}
        type="button"
        className={`j13-board-trigger${showError ? " is-invalid" : ""}`}
        disabled={disabled || loading || boards.length === 0}
        aria-haspopup="listbox"
        aria-expanded={open}
        aria-controls={listId}
        aria-invalid={showError || undefined}
        onClick={() => setOpen((v) => !v)}
        onKeyDown={onTriggerKeyDown}
      >
        <span
          className={`j13-board-trigger-ico${selected ? ` av-${colorIdx}` : " is-placeholder"}`}
          aria-hidden
        >
          {(selected?.name || "板").slice(0, 1)}
        </span>
        <span className="j13-board-trigger-copy">
          <span className="j13-board-trigger-name">{label}</span>
          {showError ? (
            <span className="j13-board-trigger-hint">请选择板块后再发布</span>
          ) : empty ? (
            <span className="j13-board-trigger-hint">发布前必须选择</span>
          ) : loading ? (
            <span className="j13-board-trigger-hint">正在加载</span>
          ) : null}
        </span>
        <ChevronDown
          size={16}
          className="shrink-0 opacity-60"
          style={{
            color: "var(--ink-3)",
            transform: open ? "rotate(180deg)" : undefined,
            transition: "transform 0.15s ease",
          }}
        />
      </button>

      {open && (
        <ul
          id={listId}
          role="listbox"
          aria-label="选择板块"
          className="j13-board-menu"
          tabIndex={-1}
          onKeyDown={onMenuKeyDown}
        >
          {boards.map((b, i) => {
            const selectedHere = b.id === value;
            const c = boardColorIndex(b, i);
            return (
              <li key={b.id} role="presentation">
                <button
                  type="button"
                  role="option"
                  aria-selected={selectedHere}
                  className={`j13-board-option${
                    selectedHere ? " is-selected" : ""
                  }${i === activeIndex ? " is-active" : ""}`}
                  onMouseEnter={() => setActiveIndex(i)}
                  onClick={() => pick(b.id)}
                >
                  <span className={`j13-board-trigger-ico av-${c}`} aria-hidden>
                    {b.name.slice(0, 1)}
                  </span>
                  <span className="flex-1 min-w-0 truncate">{b.name}</span>
                  {selectedHere && <Check size={15} className="shrink-0" />}
                </button>
              </li>
            );
          })}
        </ul>
      )}
    </div>
  );
}

/** 编辑态只读板块徽章（与触发器同高） */
export function BoardBadge({
  name,
  colorIndex = 0,
}: {
  name: string;
  colorIndex?: number;
}) {
  const c = Math.max(0, colorIndex) % 8;
  return (
    <div className="j13-board-badge">
      <span className={`j13-board-trigger-ico av-${c}`} aria-hidden>
        {name.slice(0, 1)}
      </span>
      <span className="truncate">{name}</span>
    </div>
  );
}