import { useEffect, useMemo, useRef, useState } from 'react';
import * as api from '../api/client';
import type { SessionCandidate } from '../types';

/**
 * 三段式地址输入：name -> @path -> .session
 * 每段都向 /contacts/suggest 询问候选，未命中时也允许自由输入。
 * 值本身始终是完整字符串 name@path.session。
 *
 * session 段的候选带标题与来源标记：一个工作区下可能有十几条会话，
 * 光看 brisk-harbor / witty-planet 这类随机短名分不出哪条在谈什么。
 */
export default function AddressInput({
  value,
  onChange,
  placeholder,
  allowMultiple = false,
  autoFocus = false
}: {
  value: string;
  onChange: (v: string) => void;
  placeholder?: string;
  /** 抄送场景：允许逗号分隔多个地址，补全只作用于最后一段 */
  allowMultiple?: boolean;
  autoFocus?: boolean;
}) {
  const [open, setOpen] = useState(false);
  const [items, setItems] = useState<string[]>([]);
  // session 段的富候选，与 items 同序。其他段为空数组。
  const [meta, setMeta] = useState<SessionCandidate[]>([]);
  const [kind, setKind] = useState<'name' | 'path' | 'session'>('name');
  const [active, setActive] = useState(0);
  const [menuLayout, setMenuLayout] = useState({ flip: false, maxHeight: 288 });
  const boxRef = useRef<HTMLDivElement>(null);

  // 当前正在编辑的那一段（多地址时取最后一段）
  const { head, editing } = useMemo(() => {
    if (!allowMultiple) return { head: '', editing: value };
    const idx = Math.max(value.lastIndexOf(','), value.lastIndexOf(';'));
    if (idx < 0) return { head: '', editing: value };
    return { head: value.slice(0, idx + 1), editing: value.slice(idx + 1).trimStart() };
  }, [value, allowMultiple]);

  // 把编辑段拆成 name / path / session 三部分
  const parts = useMemo(() => parseParts(editing), [editing]);

  useEffect(() => {
    let cancelled = false;
    const run = async () => {
      try {
        // 决定问哪一层：还没写 @ -> 问 name；写了 @ 没写 . -> 问 path；写了 . -> 问 session
        const res = parts.hasDot
          ? await api.suggestAddress(parts.name, parts.path)
          : parts.hasAt
          ? await api.suggestAddress(parts.name)
          : await api.suggestAddress();
        if (cancelled) return;

        const frag = parts.hasDot ? parts.session : parts.hasAt ? parts.path : parts.name;
        const lower = frag.toLowerCase();
        const all = res.suggestions || [];
        const cands = res.candidates || [];

        // 过滤时保持 suggestions 与 candidates 同序：candidates 是按下标对应的，
        // 分别过滤两个数组会让标题错位到别的别名上。
        const keep: number[] = [];
        all.forEach((s, i) => {
          const c = cands[i];
          // 标题也参与匹配：想找「缓存选型」那条会话时，人记得的是标题而不是随机短名
          const hay = c?.title ? `${s} ${c.title}`.toLowerCase() : s.toLowerCase();
          if (hay.includes(lower)) keep.push(i);
        });

        setKind(res.kind);
        setItems(keep.map(i => all[i]));
        setMeta(cands.length ? keep.map(i => cands[i]).filter(Boolean) : []);
        setActive(0);
      } catch {
        if (!cancelled) {
          setItems([]);
          setMeta([]);
        }
      }
    };
    const t = setTimeout(run, 120);
    return () => {
      cancelled = true;
      clearTimeout(t);
    };
  }, [parts.name, parts.path, parts.session, parts.hasAt, parts.hasDot]);

  useEffect(() => {
    const onDocClick = (e: MouseEvent) => {
      if (boxRef.current && !boxRef.current.contains(e.target as Node)) setOpen(false);
    };
    document.addEventListener('mousedown', onDocClick);
    return () => document.removeEventListener('mousedown', onDocClick);
  }, []);

  // 补全菜单根据 Visual Viewport 剩余空间向上翻转；软键盘出现后也实时重算。
  useEffect(() => {
    if (!open || items.length === 0) return;
    const update = () => {
      const box = boxRef.current;
      if (!box) return;
      const rect = box.getBoundingClientRect();
      const viewport = window.visualViewport;
      const top = viewport?.offsetTop ?? 0;
      const bottom = top + (viewport?.height ?? window.innerHeight);
      const above = Math.max(0, rect.top - top - 8);
      const below = Math.max(0, bottom - rect.bottom - 8);
      const flip = below < Math.min(240, above) && above > below;
      setMenuLayout({ flip, maxHeight: Math.max(96, Math.min(288, flip ? above : below)) });
    };
    update();
    window.addEventListener('resize', update, { passive: true });
    window.addEventListener('scroll', update, { passive: true, capture: true });
    window.visualViewport?.addEventListener('resize', update, { passive: true });
    window.visualViewport?.addEventListener('scroll', update, { passive: true });
    return () => {
      window.removeEventListener('resize', update);
      window.removeEventListener('scroll', update, { capture: true });
      window.visualViewport?.removeEventListener('resize', update);
      window.visualViewport?.removeEventListener('scroll', update);
    };
  }, [open, items.length]);

  /** 选中一个候选后拼回完整地址 */
  const apply = (choice: string) => {
    let next: string;
    if (kind === 'name') {
      next = `${choice}@`;
    } else if (kind === 'path') {
      next = `${parts.name}@${choice}.`;
    } else {
      next = `${parts.name}@${parts.path}.${choice}`;
    }
    onChange(allowMultiple ? `${head}${head ? ' ' : ''}${next}` : next);
    // name/path 选完仍停留在补全态，继续下一段
    setOpen(kind !== 'session');
  };

  const onKeyDown = (e: React.KeyboardEvent<HTMLInputElement>) => {
    if (!open || items.length === 0) return;
    if (e.key === 'ArrowDown') {
      e.preventDefault();
      setActive(i => (i + 1) % items.length);
    } else if (e.key === 'ArrowUp') {
      e.preventDefault();
      setActive(i => (i - 1 + items.length) % items.length);
    } else if (e.key === 'Enter' || e.key === 'Tab') {
      e.preventDefault();
      apply(items[active]);
    } else if (e.key === 'Escape') {
      setOpen(false);
    }
  };

  const hint =
    kind === 'name'
      ? 'Agent 名'
      : kind === 'path'
      ? '工作区路径'
      : '会话别名（new 为新建）';

  return (
    <div ref={boxRef} className="relative">
      <input
        value={value}
        autoFocus={autoFocus}
        onChange={e => {
          onChange(e.target.value);
          setOpen(true);
        }}
        onFocus={() => setOpen(true)}
        onKeyDown={onKeyDown}
        placeholder={placeholder}
        spellCheck={false}
        className="w-full text-sm font-mono border border-gray-300 rounded-md px-2.5 py-1.5 focus:outline-none focus:ring-2 focus:ring-blue-100 focus:border-blue-400"
      />

      {open && items.length > 0 && (
        <div
          className={`absolute z-20 w-full overflow-y-auto bg-white border border-gray-200 rounded-md shadow-lg ${
            menuLayout.flip ? 'bottom-full mb-1' : 'top-full mt-1'
          }`}
          style={{ maxHeight: menuLayout.maxHeight }}
        >
          <div className="px-2.5 py-1 text-[10px] text-gray-400 border-b border-gray-100">
            {hint}
          </div>
          {items.map((s, i) => {
            const c = meta[i];
            return (
              <button
                key={s}
                onMouseDown={e => {
                  e.preventDefault();
                  apply(s);
                }}
                onMouseEnter={() => setActive(i)}
                className={`w-full text-left px-2.5 py-1.5 ${
                  i === active ? 'bg-blue-50' : 'hover:bg-gray-50'
                }`}
              >
                <div className="flex items-center gap-1.5">
                  <span
                    className={`text-sm font-mono truncate ${
                      i === active ? 'text-blue-700' : 'text-gray-700'
                    }`}
                  >
                    {s}
                  </span>
                  <div className="flex-1" />
                  {/* 平台侧会话本侧还没有邮件线索：标出来，让人知道这一封是「接入」
                      一条已经在跑的会话，而不是继续一条已有的邮件往来 */}
                  {c?.source === 'platform' && (
                    <span
                      className="shrink-0 px-1 py-0.5 rounded bg-blue-100 text-blue-700 text-[9px]"
                      title="平台侧已有的会话，本站还没有对应的邮件往来"
                    >
                      平台
                    </span>
                  )}
                  {c?.source === 'new' && (
                    <span className="shrink-0 text-[10px] text-gray-400 font-sans">新建会话</span>
                  )}
                  {(c?.unread ?? 0) > 0 && (
                    <span className="shrink-0 px-1 py-0.5 rounded bg-red-600 text-white text-[9px]">
                      {c!.unread}
                    </span>
                  )}
                </div>
                {c?.title && c.source !== 'new' && (
                  <p className="text-[10px] text-gray-400 truncate mt-0.5">{c.title}</p>
                )}
              </button>
            );
          })}
        </div>
      )}
    </div>
  );
}

/** 把 name@path.session 拆段；path 内允许 . 与 /，按最后一个 . 切 */
function parseParts(s: string) {
  const at = s.indexOf('@');
  if (at < 0) {
    return { name: s, path: '', session: '', hasAt: false, hasDot: false };
  }
  const name = s.slice(0, at);
  const rest = s.slice(at + 1);
  const dot = rest.lastIndexOf('.');
  if (dot < 0) {
    return { name, path: rest, session: '', hasAt: true, hasDot: false };
  }
  return {
    name,
    path: rest.slice(0, dot),
    session: rest.slice(dot + 1),
    hasAt: true,
    hasDot: true
  };
}