// ============================================================
// SessionSidebar — 会话历史侧边栏（Overlay 抽屉式）
// 职责：展示会话列表、搜索、新建/切换/删除/重命名会话
// 设计：overlay 覆盖在主界面之上，不挤压主界面空间
// ============================================================

import { useMemo, useState } from "react";
import { useI18n } from "../../lib/i18n";
import type { SessionSummary } from "../../types";

interface SessionSidebarProps {
  sessions: SessionSummary[];
  activeSessionId: string | null;
  open: boolean;
  onClose: () => void;
  onNewSession: () => void;
  onSelectSession: (id: string) => void;
  onDeleteSession: (id: string) => void;
  onRenameSession: (id: string, title: string) => void;
}

/** 格式化相对时间 */
function formatRelativeTime(ts: number): string {
  const now = Date.now();
  const diff = now - ts;
  const min = 60 * 1000;
  const hour = 60 * min;
  const day = 24 * hour;

  if (diff < min) return "刚刚";
  if (diff < hour) return `${Math.floor(diff / min)}分钟前`;
  if (diff < day) return `${Math.floor(diff / hour)}小时前`;
  if (diff < 2 * day) return "昨天";
  if (diff < 7 * day) return `${Math.floor(diff / day)}天前`;
  const d = new Date(ts);
  return `${d.getMonth() + 1}/${d.getDate()}`;
}

/** 判断两个时间戳是否为同一天 */
function isSameDay(ts: number, ref: Date): boolean {
  const d = new Date(ts);
  return d.getFullYear() === ref.getFullYear() &&
    d.getMonth() === ref.getMonth() &&
    d.getDate() === ref.getDate();
}

type TimeGroup = "today" | "yesterday" | "earlier";

function getTimeGroup(ts: number, today: Date, yesterday: Date): TimeGroup {
  if (isSameDay(ts, today)) return "today";
  if (isSameDay(ts, yesterday)) return "yesterday";
  return "earlier";
}

export function SessionSidebar({
  sessions,
  activeSessionId,
  open,
  onClose,
  onNewSession,
  onSelectSession,
  onDeleteSession,
  onRenameSession,
}: SessionSidebarProps) {
  const { t } = useI18n();
  const [editingId, setEditingId] = useState<string | null>(null);
  const [editTitle, setEditTitle] = useState("");
  const [searchQuery, setSearchQuery] = useState("");

  const handleStartRename = (id: string, currentTitle: string) => {
    setEditingId(id);
    setEditTitle(currentTitle);
  };

  const handleConfirmRename = () => {
    if (editingId && editTitle.trim()) {
      onRenameSession(editingId, editTitle.trim());
    }
    setEditingId(null);
    setEditTitle("");
  };

  const handleCancelRename = () => {
    setEditingId(null);
    setEditTitle("");
  };

  const handleSelect = (id: string) => {
    onSelectSession(id);
    // 选择后自动收起侧边栏
    onClose();
  };

  // 过滤 + 分组
  const grouped = useMemo(() => {
    const today = new Date();
    const yesterday = new Date(today);
    yesterday.setDate(yesterday.getDate() - 1);

    const filtered = searchQuery.trim()
      ? sessions.filter((s) =>
          s.title.toLowerCase().includes(searchQuery.toLowerCase()) ||
          s.preview.toLowerCase().includes(searchQuery.toLowerCase())
        )
      : sessions;

    const groups: Record<TimeGroup, SessionSummary[]> = {
      today: [],
      yesterday: [],
      earlier: [],
    };

    for (const session of filtered) {
      const group = getTimeGroup(session.lastActiveAt, today, yesterday);
      groups[group].push(session);
    }

    return groups;
  }, [sessions, searchQuery]);

  const groupLabels: Record<TimeGroup, string> = {
    today: t("sidebar.today"),
    yesterday: t("sidebar.yesterday"),
    earlier: t("sidebar.earlier"),
  };

  return (
    <>
      <div
        className={`sidebar-backdrop ${open ? 'sidebar-backdrop--visible' : ''}`}
        onClick={onClose}
      />
      <div className={`sidebar ${open ? 'sidebar--open' : 'sidebar--collapsed'}`}>
        {/* 头部：新建 + 收起 */}
        <div className="sidebar__header">
          <button className="sidebar__new-btn" onClick={onNewSession}>
            ✚ {t("sidebar.new")}
          </button>
          <button className="sidebar__toggle" onClick={onClose} title={t("sidebar.collapse")}>
            ✕
          </button>
        </div>

        {/* 搜索栏 */}
        <div className="sidebar__search">
          <input
            className="sidebar__search-input"
            type="text"
            placeholder={t("sidebar.search")}
            value={searchQuery}
            onChange={(e) => setSearchQuery(e.target.value)}
          />
        </div>

        {/* 会话列表（按时间分组） */}
        <div className="sidebar__list">
          {sessions.length === 0 ? (
            <div className="sidebar__empty">{t("sidebar.empty")}</div>
          ) : (
            (["today", "yesterday", "earlier"] as TimeGroup[]).map((groupKey) => {
              const items = grouped[groupKey];
              if (items.length === 0) return null;
              return (
                <div key={groupKey}>
                  <div className="sidebar__group">{groupLabels[groupKey]}</div>
                  {items.map((session) => (
                    <div
                      key={session.id}
                      className={`sidebar__item ${session.id === activeSessionId ? "sidebar__item--active" : ""}`}
                      onClick={() => handleSelect(session.id)}
                    >
                      {editingId === session.id ? (
                        <div className="sidebar__edit" onClick={(e) => e.stopPropagation()}>
                          <input
                            className="sidebar__edit-input"
                            value={editTitle}
                            onChange={(e) => setEditTitle(e.target.value)}
                            onKeyDown={(e) => {
                              if (e.key === "Enter") handleConfirmRename();
                              if (e.key === "Escape") handleCancelRename();
                            }}
                            autoFocus
                          />
                          <button className="sidebar__edit-btn" onClick={handleConfirmRename}>✓</button>
                          <button className="sidebar__edit-btn" onClick={handleCancelRename}>✕</button>
                        </div>
                      ) : (
                        <>
                          {/* 视频标记图标 */}
                          {session.messageCount > 5 && (
                            <span className="sidebar__item-icon" title={t("sidebar.video")}><svg width="12" height="12" viewBox="0 0 24 24" fill="none" stroke="currentColor" strokeWidth="2" strokeLinecap="round" strokeLinejoin="round"><polygon points="23 7 16 12 23 17 23 7"/><rect x="1" y="5" width="15" height="14" rx="2" ry="2"/></svg></span>
                          )}
                          <div className="sidebar__item-content">
                            <div className="sidebar__item-title">{session.title}</div>
                            <div className="sidebar__item-meta">
                              {session.messageCount > 0 && (
                                <span>{session.messageCount}{t("sidebar.messages")}</span>
                              )}
                              <span>{formatRelativeTime(session.lastActiveAt)}</span>
                            </div>
                          </div>
                          <div className="sidebar__item-actions">
                            <button
                              className="sidebar__action-btn"
                              onClick={(e) => {
                                e.stopPropagation();
                                handleStartRename(session.id, session.title);
                              }}
                              title={t("sidebar.rename")}
                            >
                              <svg width="14" height="14" viewBox="0 0 24 24" fill="none" stroke="currentColor" strokeWidth="2" strokeLinecap="round" strokeLinejoin="round"><path d="M11 4H4a2 2 0 0 0-2 2v14a2 2 0 0 0 2 2h14a2 2 0 0 0 2-2v-7"/><path d="M18.5 2.5a2.121 2.121 0 0 1 3 3L12 15l-4 1 1-4 9.5-9.5z"/></svg>
                            </button>
                            <button
                              className="sidebar__action-btn sidebar__action-btn--danger"
                              onClick={(e) => {
                                e.stopPropagation();
                                onDeleteSession(session.id);
                              }}
                              title={t("sidebar.delete")}
                            >
                              <svg width="14" height="14" viewBox="0 0 24 24" fill="none" stroke="currentColor" strokeWidth="2" strokeLinecap="round" strokeLinejoin="round"><polyline points="3 6 5 6 21 6"/><path d="M19 6v14a2 2 0 0 1-2 2H7a2 2 0 0 1-2-2V6m3 0V4a2 2 0 0 1 2-2h4a2 2 0 0 1 2 2v2"/></svg>
                            </button>
                          </div>
                        </>
                      )}
                    </div>
                  ))}
                </div>
              );
            })
          )}
        </div>
      </div>
    </>
  );
}