import { useCallback, useEffect, useState } from 'react';
import { BookOpen, Download, Loader2, Plus, Sparkles } from 'lucide-react';
import { useLocation, useNavigate } from 'react-router-dom';
import {
  downloadLearningCourse,
  fetchMyLearningCourses,
  LEARNING_LIBRARY_CHANGED_EVENT,
  listInstalledLearningCourses,
} from '@/lib/learning';
import { cn } from '@/lib/utils';
import type { InstalledLearningCourse, LearningCourse } from '../../../shared/learning';

type LearningSidebarProps = {
  sidebarCollapsed: boolean;
};

export function LearningSidebar({ sidebarCollapsed }: LearningSidebarProps) {
  const navigate = useNavigate();
  const location = useLocation();
  const [installed, setInstalled] = useState<Record<string, InstalledLearningCourse>>({});
  const [ownedCourses, setOwnedCourses] = useState<LearningCourse[]>([]);
  const [loading, setLoading] = useState(true);
  const [downloading, setDownloading] = useState<string | null>(null);
  const [error, setError] = useState<string | null>(null);

  const loadCourses = useCallback(async () => {
    setLoading(true);
    setError(null);
    try {
      const [localCourses, personalCourses] = await Promise.all([
        listInstalledLearningCourses(),
        fetchMyLearningCourses().catch(() => []),
      ]);
      setInstalled(Object.fromEntries(localCourses.map((record) => [record.course.id, record])));
      setOwnedCourses(personalCourses);
    } catch (cause) {
      setError(cause instanceof Error ? cause.message : '个人课程暂时无法读取');
    } finally {
      setLoading(false);
    }
  }, []);

  useEffect(() => {
    void loadCourses();
    const refresh = () => void loadCourses();
    window.addEventListener(LEARNING_LIBRARY_CHANGED_EVENT, refresh);
    return () => window.removeEventListener(LEARNING_LIBRARY_CHANGED_EVENT, refresh);
  }, [loadCourses]);

  const personalCourses = (() => {
    const courses = new Map<string, LearningCourse>();
    for (const record of Object.values(installed)) courses.set(record.course.id, record.course);
    for (const course of ownedCourses) courses.set(course.id, course);
    return [...courses.values()];
  })();

  const openCourse = useCallback(async (course: LearningCourse) => {
    if (installed[course.id]) {
      navigate(`/learning/course/${encodeURIComponent(course.id)}`);
      return;
    }
    setDownloading(course.id);
    setError(null);
    try {
      const record = await downloadLearningCourse(course.id);
      setInstalled((current) => ({ ...current, [course.id]: record }));
      navigate(`/learning/course/${encodeURIComponent(course.id)}`);
    } catch (cause) {
      setError(cause instanceof Error ? cause.message : '课程下载失败');
    } finally {
      setDownloading(null);
    }
  }, [installed, navigate]);

  const catalogActive = location.pathname === '/learning';

  return (
    <div data-testid="sidebar-learning-navigation" className="px-1 py-1">
      <button
        type="button"
        aria-label="课程广场"
        aria-current={catalogActive ? 'page' : undefined}
        onClick={() => navigate('/learning')}
        className={cn(
          'motion-press flex min-h-9 w-full items-center gap-2 rounded-lg px-2 py-1.5 text-left text-sm font-semibold transition-colors active:scale-[0.985]',
          catalogActive ? 'bg-brand-soft text-foreground' : 'text-foreground hover:bg-surface-subtle',
          sidebarCollapsed && 'justify-center px-0',
        )}
      >
        <BookOpen className="h-4 w-4 shrink-0 text-brand" />
        {!sidebarCollapsed ? <span>课程广场</span> : null}
      </button>

      <button
        type="button"
        aria-label="生成课程"
        onClick={() => navigate('/learning?generate=1')}
        className={cn(
          'motion-press mt-1 flex min-h-9 w-full items-center gap-2 rounded-lg px-2 py-1.5 text-left text-sm font-medium text-foreground transition-colors hover:bg-surface-subtle active:scale-[0.985]',
          sidebarCollapsed && 'justify-center px-0',
        )}
      >
        <Plus className="h-4 w-4 shrink-0 text-brand" />
        {!sidebarCollapsed ? <span>生成课程</span> : null}
      </button>

      {!sidebarCollapsed ? (
        <div className="mt-4">
          <div className="flex min-h-8 items-center gap-2 px-2 text-xs font-semibold text-muted-foreground">
            <Sparkles className="h-4 w-4 shrink-0" />
            <span className="min-w-0 flex-1 truncate">我的课程</span>
            {!loading ? <span className="tabular-nums">{personalCourses.length}</span> : null}
          </div>

          {loading ? (
            <div role="status" className="flex items-center px-2 py-3 text-xs font-medium text-muted-foreground">
              <Loader2 className="mr-2 h-3.5 w-3.5 animate-spin" />正在读取课程
            </div>
          ) : error ? (
            <button
              type="button"
              className="w-full rounded-lg px-2 py-3 text-left text-xs font-medium leading-5 text-destructive hover:bg-destructive/5"
              onClick={() => void loadCourses()}
            >
              {error}，点击重试
            </button>
          ) : personalCourses.length === 0 ? (
            <p className="px-2 py-3 text-xs font-medium leading-5 text-muted-foreground">
              下载或生成课程后，会显示在这里。
            </p>
          ) : (
            <div className="mt-1 space-y-1">
              {personalCourses.map((course) => {
                const isInstalled = Boolean(installed[course.id]);
                const isActive = location.pathname === `/learning/course/${encodeURIComponent(course.id)}`;
                const courseMeta = course.origin === 'user_single'
                  ? isInstalled ? '我生成的，已下载' : '我生成的，待下载'
                  : '已下载到本机';

                return (
                  <button
                    type="button"
                    key={course.id}
                    aria-label={`${isInstalled ? '打开' : '下载'}课程 ${course.title}`}
                    aria-current={isActive ? 'page' : undefined}
                    disabled={downloading === course.id}
                    onClick={() => void openCourse(course)}
                    className={cn(
                      'motion-press group/course flex w-full items-center gap-2 rounded-xl px-2.5 py-2 text-left transition-[background-color,color,transform] active:scale-[0.985]',
                      isActive ? 'bg-brand-selected text-foreground ring-1 ring-brand/20' : 'hover:bg-surface-tertiary',
                    )}
                  >
                    <span className="min-w-0 flex-1">
                      <span className="block truncate text-sm font-semibold text-foreground">{course.title}</span>
                      <span className="mt-0.5 block truncate text-[11px] font-medium text-muted-foreground">{courseMeta}</span>
                    </span>
                    {downloading === course.id ? (
                      <Loader2 className="h-3.5 w-3.5 shrink-0 animate-spin text-brand" />
                    ) : isInstalled ? (
                      <BookOpen className="h-3.5 w-3.5 shrink-0 text-muted-foreground" />
                    ) : (
                      <Download className="h-3.5 w-3.5 shrink-0 text-muted-foreground" />
                    )}
                  </button>
                );
              })}
            </div>
          )}
        </div>
      ) : null}
    </div>
  );
}