import { useState, useEffect } from 'react';
import { Link } from 'react-router-dom';
import { BookOpen, CheckSquare, Trophy, Sparkles, X, HelpCircle } from 'lucide-react';
import { useApp } from '../store/AppContext';
import Card from '../components/ui/Card';
import Button from '../components/ui/Button';
import Tag from '../components/ui/Tag';
import * as db from '../lib/db';
import { storage } from '../lib/storage';
import { getAssignedTopic } from '../lib/learningService';
import { getYearProgress, getCurriculumCycle, getCurriculumWeek, getActiveVersion } from '../lib/curriculumService';

const Dashboard = () => {
  const { state } = useApp();
  const { currentUser, weekNumber } = state;

  const [dashData, setDashData] = useState({
    topic: null,
    learnDone: false,
    testResult: null,
    top3: [],
    myRank: 0,
    myPoints: 0,
    activity: [],
    yearProgress: null,
    hasCurriculum: false,
    theme: '',
  });

  useEffect(() => {
    if (!currentUser) return;

    const load = async () => {
      const [topic, learnDone, testResult, allUsers, leaderboard] = await Promise.all([
        getAssignedTopic(currentUser.id, weekNumber),
        db.getLearnDone(currentUser.id, weekNumber),
        db.getQuizResult(currentUser.id, weekNumber),
        db.getTeamMembers(),
        db.getLeaderboard(),
      ]);

      const nonAdminIds = allUsers.filter(u => u.role !== 'admin').map(u => u.id);
      const filtered = leaderboard.filter(u => nonAdminIds.includes(u.user_id));
      const top3 = filtered.slice(0, 3);
      const myRank = filtered.findIndex(u => u.user_id === currentUser.id) + 1;
      const myPoints = filtered.find(u => u.user_id === currentUser.id)?.points || 0;

      const activity = [];
      for (let w = weekNumber; w >= Math.max(1, weekNumber - 3); w--) {
        const [pastLearn, pastTest, pastTopic] = await Promise.all([
          db.getLearnDone(currentUser.id, w),
          db.getQuizResult(currentUser.id, w),
          getAssignedTopic(currentUser.id, w),
        ]);
        if (pastTest) activity.push({ type: 'test', week: w, topic: pastTopic?.label, score: pastTest.percentage, points: pastTest.points_earned });
        if (pastLearn) activity.push({ type: 'learn', week: w, topic: pastTopic?.label });
      }

      // Load curriculum progress
      let yearProgress = null;
      let curriculumExists = false;
      try {
        const activeVersion = await getActiveVersion();
        curriculumExists = !!activeVersion;
        if (curriculumExists) {
          yearProgress = await getYearProgress(currentUser.id, weekNumber);
        }
      } catch (e) {
        console.warn('[Dashboard] Could not load curriculum data:', e.message);
      }

      setDashData({
        topic,
        learnDone,
        testResult,
        top3,
        myRank,
        myPoints,
        activity,
        yearProgress,
        hasCurriculum: curriculumExists,
        theme: topic?.theme || '',
      });
    };

    load();
  }, [currentUser, weekNumber]);

  const { topic, learnDone, testResult, top3, myRank, myPoints, activity, yearProgress, hasCurriculum: curriculumActive, theme } = dashData;
  const currentCycle = getCurriculumCycle(weekNumber);
  const currWeek = getCurriculumWeek(weekNumber);

  const explainerKey = currentUser ? `dashboard:explainer-dismissed:${currentUser.id}` : null;
  const [explainerOpen, setExplainerOpen] = useState(false);
  useEffect(() => {
    if (!explainerKey) return;
    setExplainerOpen(storage.get(explainerKey, false) !== true);
  }, [explainerKey]);

  const closeExplainer = () => {
    setExplainerOpen(false);
    if (explainerKey) storage.set(explainerKey, true);
  };

  const toggleExplainer = () => {
    if (explainerOpen) {
      closeExplainer();
    } else {
      setExplainerOpen(true);
    }
  };

  const explainerSteps = [
    { icon: BookOpen, title: 'Learn', text: 'Each week the curriculum gives you a theme — a small set of related topics from the knowledge base. Work through the theme session at your own pace.' },
    { icon: CheckSquare, title: 'Theme Test', text: 'When your theme session is done, take the 5-question theme test to lock in what you learned and earn points. You can also take an on-demand Topic Test anytime to drill a single topic.' },
    { icon: Trophy, title: 'Climb', text: 'Points add up on the leaderboard. The curriculum runs in perpetual 26-week cycles, so there is always a next step.' },
    { icon: Sparkles, title: 'Ask R42', text: 'R42, your AI study buddy, is on every screen (bottom-right). Ask it anything about your topic or the platform.' },
  ];

  return (
    <div className="p-6 md:p-10 space-y-8 animate-in fade-in slide-in-from-bottom-4 duration-500">
      <header className="flex items-start justify-between gap-4">
        <div>
          <h1 className="text-3xl md:text-5xl mb-2">Welcome, {currentUser?.name}</h1>
          <p className="text-fg-muted text-lg">
            {curriculumActive
              ? `Cycle ${currentCycle} · Week ${currWeek} of 26`
              : `Here is your overview for week ${weekNumber}.`}
          </p>
        </div>
        <button
          type="button"
          onClick={toggleExplainer}
          aria-label={explainerOpen ? 'Hide platform explainer' : 'How Respellion works'}
          aria-expanded={explainerOpen}
          title="How Respellion works"
          className="flex-shrink-0 w-10 h-10 rounded-full border border-bg-warm bg-paper text-fg-muted hover:text-fg hover:border-teal transition-colors flex items-center justify-center"
        >
          <HelpCircle size={20} />
        </button>
      </header>

      {/* Platform explainer — toggled via header help icon, per-user dismissed state */}
      {explainerOpen && (
        <Card className="relative border border-bg-warm bg-paper">
          <button
            type="button"
            onClick={closeExplainer}
            aria-label="Dismiss"
            className="absolute top-4 right-4 text-fg-muted hover:text-fg transition-colors"
          >
            <X size={18} />
          </button>
          <div className="flex items-start gap-3 mb-5 pr-8">
            <div>
              <div className="flex items-center gap-2 mb-1">
                <h3 className="text-xl">How Respellion works</h3>
                <Tag variant="accent" className="text-xs">New here?</Tag>
              </div>
              <p className="text-fg-muted text-sm">
                A perpetual learning loop that keeps you current with the company knowledge base.
                Use the navigation at the top (Home, Learn, Theme Test, Topic Test, Leaderboard) to move around.
              </p>
            </div>
          </div>
          <div className="grid grid-cols-1 sm:grid-cols-2 lg:grid-cols-4 gap-4">
            {explainerSteps.map(({ icon: Icon, title, text }) => (
              <div key={title} className="flex flex-col gap-2">
                <div className="w-9 h-9 rounded-[var(--r-org)] bg-sage text-teal-900 flex items-center justify-center">
                  <Icon size={18} />
                </div>
                <h4 className="font-bold">{title}</h4>
                <p className="text-sm text-fg-muted">{text}</p>
              </div>
            ))}
          </div>
        </Card>
      )}

      {/* Cycle Progress Bar (only when curriculum exists) */}
      {curriculumActive && yearProgress && (
        <Card className="border border-bg-warm">
          <div className="flex flex-col md:flex-row md:items-center justify-between gap-4">
            <div className="flex items-center gap-4">
              <div className="relative w-14 h-14 flex-shrink-0">
                <svg viewBox="0 0 36 36" className="w-full h-full -rotate-90">
                  <circle cx="18" cy="18" r="15.5" fill="none" stroke="var(--color-bg-warm)" strokeWidth="3" />
                  <circle
                    cx="18" cy="18" r="15.5" fill="none"
                    stroke="var(--color-teal)" strokeWidth="3"
                    strokeDasharray={`${yearProgress.percentage} 100`}
                    strokeLinecap="round"
                    className="transition-all duration-700"
                  />
                </svg>
                <span className="absolute inset-0 flex items-center justify-center text-xs font-bold">
                  {yearProgress.percentage}%
                </span>
              </div>
              <div>
                <h3 className="font-bold text-lg">Cycle Progress</h3>
                <p className="text-sm text-fg-muted">{yearProgress.completed} of {yearProgress.total} weeks completed</p>
              </div>
            </div>
            <div className="flex items-center gap-3">
              <Tag variant="dark" className="text-xs">Cycle {currentCycle}</Tag>
              <span className="text-sm text-fg-muted">{26 - currWeek} weeks remaining</span>
            </div>
          </div>
          {/* Visual week progress bar */}
          <div className="mt-4 flex gap-[2px] h-2 rounded-full overflow-hidden">
            {Array.from({ length: 26 }, (_, i) => {
              const w = i + 1;
              const isCurrent = w === currWeek;
              const isPast = w < currWeek;
              return (
                <div
                  key={w}
                  className="flex-1 rounded-sm transition-all"
                  style={{
                    backgroundColor: isCurrent
                      ? 'var(--color-teal)'
                      : isPast
                        ? 'var(--color-teal)'
                        : 'var(--color-bg-warm)',
                    opacity: isPast ? 0.4 : 1,
                  }}
                  title={`Week ${w}`}
                />
              );
            })}
          </div>
        </Card>
      )}

      <div className="grid grid-cols-1 md:grid-cols-2 gap-6">
        <Card className="flex flex-col border border-bg-warm" hoverable>
          <div className="flex justify-between items-start mb-4">
            <div>
              <h3 className="text-xl">Learning</h3>
              <p className="text-fg-muted text-sm mt-1">
                {curriculumActive ? `Week ${currWeek} topic:` : 'Your topic this week:'}
              </p>
            </div>
            {learnDone ? <Tag variant="success">Completed</Tag> : <Tag variant="accent">To Do</Tag>}
          </div>
          <h2 className="text-2xl mt-2 mb-6">{topic ? topic.label : 'No topic assigned'}</h2>
          <Link to="/learn" className="mt-auto">
            <Button className="w-full" variant={learnDone ? 'outline' : 'primary'}>
              {learnDone ? 'Review Learning Material' : 'Start Learning Session'}
            </Button>
          </Link>
        </Card>

        <Card className="flex flex-col border border-bg-warm" hoverable>
          <div className="flex justify-between items-start mb-4">
            <div>
              <h3 className="text-xl">Theme Test</h3>
              <p className="text-fg-muted text-sm mt-1">This week's theme — 5 questions</p>
            </div>
            {testResult ? <Tag variant="success">Score: {testResult.percentage}%</Tag> : <Tag variant="default">To Do</Tag>}
          </div>
          <div className="flex-1 flex items-center justify-center py-6 text-fg-subtle">
            {!learnDone ? 'Complete your theme session first' : testResult ? 'Theme test completed for this week' : 'Ready to test your knowledge'}
          </div>
          {learnDone && !testResult ? (
            <Link to="/test" className="mt-auto">
              <Button className="w-full">Start Theme Test</Button>
            </Link>
          ) : (
            <Link to="/test" className="mt-auto">
              <Button variant="outline" className="w-full">{testResult ? 'View Results' : 'Start Theme Test'}</Button>
            </Link>
          )}
        </Card>
      </div>

      <div className="grid grid-cols-1 lg:grid-cols-3 gap-6">
        <div className="lg:col-span-2">
          <h3 className="text-2xl mb-4">Recent Activity</h3>
          <Card className="p-0 overflow-hidden border border-bg-warm">
            <div className="divide-y divide-bg-warm">
              {activity.length === 0 ? (
                <div className="p-8 text-center text-fg-muted">No recent activity.</div>
              ) : (
                activity.slice(0, 5).map((act, i) => (
                  <div key={i} className="p-4 flex items-center gap-4 hover:bg-bg-warm transition-colors">
                    <div className={`w-10 h-10 rounded-[var(--r-org)] flex items-center justify-center font-bold ${act.type === 'test' ? 'bg-accent-soft text-purple-700' : 'bg-sage text-teal-900'
                      }`}>
                      {act.type === 'test' ? 'T' : 'L'}
                    </div>
                    <div>
                      <p className="font-medium">{act.type === 'test' ? 'Test completed' : 'Learning session'}: {act.topic}</p>
                      <p className="text-sm text-fg-muted">
                        Week {act.week} {act.type === 'test' && `· Score: ${act.score}%`}
                      </p>
                    </div>
                    {act.points > 0 && <div className="ml-auto text-teal font-bold">+{act.points} pts</div>}
                  </div>
                ))
              )}
            </div>
          </Card>
        </div>

        <div>
          <h3 className="text-2xl mb-4">Mini Leaderboard</h3>
          <Card className="border border-bg-warm">
            <div className="space-y-4">
              {top3.length === 0 ? (
                <div className="text-center text-fg-muted py-4">No points yet</div>
              ) : (
                top3.map((u, i) => (
                  <div key={u.user_id} className="flex items-center justify-between">
                    <div className="flex items-center gap-3">
                      <span className={`font-mono font-bold ${i === 0 ? 'text-yellow-500' : 'text-teal'}`}>{i + 1}.</span>
                      <span className="font-medium">{u.name} {u.user_id === currentUser?.id && '(You)'}</span>
                    </div>
                    <Tag variant="dark">{u.points} pts</Tag>
                  </div>
                ))
              )}
              {myRank > 3 && (
                <div className="flex items-center justify-between pt-4 border-t border-bg-warm">
                  <div className="flex items-center gap-3">
                    <span className="font-mono font-bold text-fg-muted">{myRank}.</span>
                    <span className="font-medium text-teal">You</span>
                  </div>
                  <Tag variant="default">{myPoints} pts</Tag>
                </div>
              )}
            </div>
            <Link to="/leaderboard">
              <Button variant="ghost" className="w-full mt-4 text-sm">View full leaderboard</Button>
            </Link>
          </Card>
        </div>
      </div>
    </div>
  );
};

export default Dashboard;
