import React, { useState, useEffect } from 'react';
import { Link } from 'react-router-dom';
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 { getAssignedTopic } from '../lib/learningService';

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: [],
  });

  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 });
      }

      setDashData({ topic, learnDone, testResult, top3, myRank, myPoints, activity });
    };

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

  const { topic, learnDone, testResult, top3, myRank, myPoints, activity } = dashData;

  return (
    <div className="p-6 md:p-10 space-y-8 animate-in fade-in slide-in-from-bottom-4 duration-500">
      <header>
        <h1 className="text-3xl md:text-5xl mb-2">Welcome, {currentUser?.name}</h1>
        <p className="text-fg-muted text-lg">Here is your overview for week {weekNumber}.</p>
      </header>

      <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">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">Testing</h3>
              <p className="text-fg-muted text-sm mt-1">Weekly test — 10 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 learning session first' : testResult ? 'Test completed for this week' : 'Ready to test your knowledge'}
          </div>
          {learnDone && !testResult ? (
            <Link to="/test" className="mt-auto">
              <Button className="w-full">Start Test</Button>
            </Link>
          ) : (
            <Link to="/test" className="mt-auto">
              <Button variant="outline" className="w-full">{testResult ? 'View Results' : 'Start 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;