"use client";

import Link from "next/link";
import { useParams } from "next/navigation";
import { useEffect, useState } from "react";
import ProgressBar from "@/components/ProgressBar";
import { getCourseBySlug } from "@/lib/data/courseCatalog";
import { getCourseProgressPercent, progressUpdatedEventName } from "@/lib/progress/localProgress";
import { teacherCoursesUpdatedEventName } from "@/lib/data/teacherCourses";
import { supabaseBrowser } from "@/lib/supabase/browser";
import type { Course } from "@/types/course";

export default function CourseDetailPage() {
  const params = useParams<{ slug: string }>();
  const slug = params.slug;
  const [course, setCourse] = useState<Course | undefined>(() => getCourseBySlug(slug));
  const [hasResolvedCourse, setHasResolvedCourse] = useState(false);

  const [userId, setUserId] = useState("guest");
  const [isAuthed, setIsAuthed] = useState(false);
  const [progress, setProgress] = useState(0);

  useEffect(() => {
    const loadCourse = () => {
      setCourse(getCourseBySlug(slug));
      setHasResolvedCourse(true);
    };
    loadCourse();
    window.addEventListener(teacherCoursesUpdatedEventName, loadCourse);
    return () => window.removeEventListener(teacherCoursesUpdatedEventName, loadCourse);
  }, [slug]);

  useEffect(() => {
    const client = supabaseBrowser();
    if (!client) return;

    client.auth.getUser().then(({ data }) => {
      const nextId = data.user?.id ?? "guest";
      setUserId(nextId);
      setIsAuthed(Boolean(data.user));
    });

    const { data } = client.auth.onAuthStateChange((_event, session) => {
      setUserId(session?.user?.id ?? "guest");
      setIsAuthed(Boolean(session?.user));
    });

    return () => data.subscription.unsubscribe();
  }, []);

  useEffect(() => {
    if (!course) return;
    const load = () => setProgress(getCourseProgressPercent(userId, course.slug, course.lessons.length));
    load();
    window.addEventListener(progressUpdatedEventName, load);
    return () => window.removeEventListener(progressUpdatedEventName, load);
  }, [course, userId]);

  if (!course && !hasResolvedCourse) {
    return (
      <div className="rounded-xl border border-slate-200 bg-white p-6 shadow-sm">
        <p className="text-slate-600">Loading course...</p>
      </div>
    );
  }

  if (!course) {
    return (
      <div className="rounded-xl border border-slate-200 bg-white p-6 shadow-sm">
        <h1 className="text-2xl font-bold text-slate-900">Course not found</h1>
        <p className="mt-2 text-slate-600">The requested course slug does not exist in mock data.</p>
        <Link className="mt-4 inline-flex rounded-md bg-ink px-4 py-2 text-sm font-semibold text-white" href="/courses">
          Back to courses
        </Link>
      </div>
    );
  }

  const redirect = `/courses/${course.slug}/learn`;
  const loginUrl = `/auth/login?redirectTo=${encodeURIComponent(redirect)}`;

  return (
    <div className="grid gap-7 lg:grid-cols-[1.9fr_0.9fr]">
      <section className="pt-1">
        <Link className="inline-flex items-center gap-2 text-lg text-slate-600 hover:text-brand md:text-2xl" href="/courses">
          <span className="text-xl">{"<-"}</span>
          Back to Courses
        </Link>

        <div className="mt-6 flex items-center gap-3 text-base text-slate-600 md:text-lg">
          <span className="rounded-full bg-accent px-4 py-1 text-base font-semibold text-white">{course.level}</span>
          <span>Contract Law</span>
        </div>

        <h1 className="acve-heading mt-5 text-4xl leading-tight md:text-7xl">{course.title}</h1>
        <p className="mt-5 max-w-5xl text-xl leading-relaxed text-slate-600 md:text-4xl">{course.summary}</p>

        <div className="mt-7 flex flex-wrap items-center gap-5 text-lg text-slate-600 md:text-3xl">
          <span className="font-semibold text-slate-800">Rating {course.rating.toFixed(1)}</span>
          <span>{course.students.toLocaleString()} students</span>
          <span>{course.weeks} weeks</span>
          <span>{course.lessonsCount} lessons</span>
        </div>
      </section>

      <aside className="acve-panel space-y-5 p-7">
        <h2 className="text-2xl text-slate-700 md:text-4xl">Your Progress</h2>
        <div className="flex items-end justify-between">
          <p className="text-4xl font-semibold text-brand md:text-6xl">{progress}%</p>
          <p className="text-lg text-slate-600 md:text-3xl">
            {Math.round((progress / 100) * course.lessonsCount)}/{course.lessonsCount} lessons
          </p>
        </div>
        <ProgressBar value={progress} />
        <div className="border-t border-slate-200 pt-5 text-lg text-slate-700 md:text-3xl">
          <p className="mb-1 text-base text-slate-500 md:text-2xl">Instructor</p>
          <p className="mb-4 font-semibold text-slate-800">{course.instructor}</p>
          <p className="mb-1 text-base text-slate-500 md:text-2xl">Duration</p>
          <p className="mb-4 font-semibold text-slate-800">{course.weeks} weeks</p>
          <p className="mb-1 text-base text-slate-500 md:text-2xl">Level</p>
          <p className="font-semibold text-slate-800">{course.level}</p>
        </div>
        {isAuthed ? (
          <Link className="acve-button-primary mt-2 inline-flex w-full justify-center px-4 py-3 text-xl font-semibold md:text-2xl hover:brightness-105" href={redirect}>
            Start Course
          </Link>
        ) : (
          <Link className="acve-button-primary mt-2 inline-flex w-full justify-center px-4 py-3 text-xl font-semibold md:text-2xl hover:brightness-105" href={loginUrl}>
            Login to start
          </Link>
        )}
      </aside>
    </div>
  );
}