import React, { useRef, useState, useEffect } from "react";
import { ArrowDown, Check, BookOpen, TrendingUp } from "lucide-react";
import LinearTransformationWidget from "../../../components/lessons/LinearTransformationWidget";
import Quiz from "../../../components/lessons/Quiz";
import { LINEAR_TRANSFORMATIONS_QUIZ_DATA } from "../../../utils/constants";

interface LessonProps {
  onFinish?: () => void;
}

const LinearTransformationsLesson: React.FC<LessonProps> = ({ onFinish }) => {
  const [activeSection, setActiveSection] = useState(0);
  const sectionsRef = useRef<(HTMLElement | null)[]>([]);

  const scrollToSection = (index: number) => {
    setActiveSection(index);
    sectionsRef.current[index]?.scrollIntoView({
      behavior: "smooth",
      block: "start",
    });
  };

  useEffect(() => {
    const observer = new IntersectionObserver(
      (entries) => {
        entries.forEach((entry) => {
          if (entry.isIntersecting) {
            const index = sectionsRef.current.indexOf(
              entry.target as HTMLElement,
            );
            if (index !== -1) setActiveSection(index);
          }
        });
      },
      { rootMargin: "-20% 0px -60% 0px" },
    );
    sectionsRef.current.forEach((section) => {
      if (section) observer.observe(section);
    });
    return () => observer.disconnect();
  }, []);

  const SectionMarker = ({
    index,
    title,
    icon: Icon,
  }: {
    index: number;
    title: string;
    icon: any;
  }) => {
    const isActive = activeSection === index;
    const isPast = activeSection > index;
    return (
      <button
        onClick={() => scrollToSection(index)}
        className={`flex items-center gap-3 p-3 w-full rounded-lg transition-all ${isActive ? "bg-white shadow-md border border-blue-100" : "hover:bg-slate-100"}`}
      >
        <div
          className={`w-8 h-8 rounded-full flex items-center justify-center shrink-0 ${isActive ? "bg-blue-600 text-white" : isPast ? "bg-blue-400 text-white" : "bg-slate-200 text-slate-500"}`}
        >
          {isPast ? (
            <Check className="w-4 h-4" />
          ) : (
            <Icon className="w-4 h-4" />
          )}
        </div>
        <div className="text-left">
          <p
            className={`text-sm font-bold ${isActive ? "text-blue-900" : "text-slate-600"}`}
          >
            {title}
          </p>
        </div>
      </button>
    );
  };

  return (
    <div className="flex flex-col lg:flex-row min-h-screen">
      <aside className="w-full lg:w-64 lg:fixed lg:top-20 lg:bottom-0 lg:overflow-y-auto p-4 border-r border-slate-200 bg-slate-50 z-0 hidden lg:block">
        <nav className="space-y-2">
          <SectionMarker
            index={0}
            title="Shift, Reflect & Scale"
            icon={TrendingUp}
          />
          <SectionMarker index={1} title="Practice" icon={BookOpen} />
        </nav>
      </aside>

      <div className="flex-1 lg:ml-64 p-6 md:p-12 max-w-4xl mx-auto">
        {/* Section 1 */}
        <section
          ref={(el) => {
            sectionsRef.current[0] = el;
          }}
          className="min-h-screen flex flex-col justify-center mb-24 pt-20 lg:pt-0"
        >
          <h2 className="text-4xl font-extrabold text-slate-900 mb-6">
            Function Transformations
          </h2>
          <div className="prose prose-slate text-lg text-slate-600 mb-8">
            <p>
              Given a base function f(x), transformations let you shift, flip,
              and scale it predictably. These rules apply to <em>any</em>{" "}
              function type — linear, quadratic, absolute value, or otherwise.
              The SAT tests these with graphs, tables, and algebraic forms, so
              you must recognize them quickly.
            </p>
          </div>

          {/* Transformation Table */}
          <div className="bg-blue-50 border border-blue-200 rounded-2xl p-6 mb-8 space-y-5">
            <h3 className="text-lg font-bold text-blue-900">
              All Six Transformations
            </h3>
            <div className="overflow-x-auto rounded-xl border border-blue-200">
              <table className="w-full text-sm border-collapse">
                <thead>
                  <tr className="bg-blue-900 text-white">
                    <th className="p-3 text-left">Transformation</th>
                    <th className="p-3 text-left">Notation</th>
                    <th className="p-3 text-left">Effect on Graph</th>
                    <th className="p-3 text-left">Effect on Points</th>
                  </tr>
                </thead>
                <tbody className="divide-y divide-blue-100">
                  <tr className="bg-white">
                    <td className="p-3 font-bold">Shift Up k units</td>
                    <td className="p-3 font-mono text-blue-700">f(x) + k</td>
                    <td className="p-3 text-slate-600">
                      Entire graph moves up by k
                    </td>
                    <td className="p-3 text-slate-600">(x, y) → (x, y + k)</td>
                  </tr>
                  <tr className="bg-slate-50">
                    <td className="p-3 font-bold">Shift Down k units</td>
                    <td className="p-3 font-mono text-blue-700">f(x) − k</td>
                    <td className="p-3 text-slate-600">
                      Entire graph moves down by k
                    </td>
                    <td className="p-3 text-slate-600">(x, y) → (x, y − k)</td>
                  </tr>
                  <tr className="bg-red-50">
                    <td className="p-3 font-bold text-red-900">
                      Shift Right h units
                    </td>
                    <td className="p-3 font-mono text-red-700">f(x − h)</td>
                    <td className="p-3 text-red-800">Graph moves RIGHT by h</td>
                    <td className="p-3 text-red-700">(x, y) → (x + h, y)</td>
                  </tr>
                  <tr className="bg-red-50">
                    <td className="p-3 font-bold text-red-900">
                      Shift Left h units
                    </td>
                    <td className="p-3 font-mono text-red-700">f(x + h)</td>
                    <td className="p-3 text-red-800">Graph moves LEFT by h</td>
                    <td className="p-3 text-red-700">(x, y) → (x − h, y)</td>
                  </tr>
                  <tr className="bg-white">
                    <td className="p-3 font-bold">Reflect over x-axis</td>
                    <td className="p-3 font-mono text-blue-700">−f(x)</td>
                    <td className="p-3 text-slate-600">
                      Graph flips vertically
                    </td>
                    <td className="p-3 text-slate-600">(x, y) → (x, −y)</td>
                  </tr>
                  <tr className="bg-slate-50">
                    <td className="p-3 font-bold">Reflect over y-axis</td>
                    <td className="p-3 font-mono text-blue-700">f(−x)</td>
                    <td className="p-3 text-slate-600">
                      Graph flips horizontally
                    </td>
                    <td className="p-3 text-slate-600">(x, y) → (−x, y)</td>
                  </tr>
                </tbody>
              </table>
            </div>

            {/* The #1 Trap */}
            <div className="bg-red-100 border border-red-300 rounded-xl p-5">
              <p className="font-bold text-red-900 text-base mb-2">
                ⚠ The #1 Trap — Horizontal Shifts Are BACKWARDS
              </p>
              <p className="text-slate-700 text-sm mb-2">
                f(x − 3) shifts the graph <strong>right 3</strong> (NOT left).
                f(x + 2) shifts the graph <strong>left 2</strong> (NOT right).
              </p>
              <p className="text-slate-600 text-sm">
                Why? Because to get the same y-value, x must be 3 larger. The
                shift in the graph is always <em>opposite</em> to the sign
                inside.
              </p>
              <div className="font-mono text-sm mt-2 bg-white rounded p-2 text-slate-700">
                <p>f(x) = x² has vertex at (0, 0)</p>
                <p>g(x) = (x − 3)² → vertex at (3, 0) → shifted RIGHT 3 ✓</p>
                <p>h(x) = (x + 2)² → vertex at (−2, 0) → shifted LEFT 2 ✓</p>
              </div>
            </div>

            {/* Combined Transformations */}
            <div className="bg-white rounded-xl p-5 border border-blue-100">
              <p className="font-bold text-blue-800 mb-3">
                Combined Transformations — Apply in Order
              </p>
              <p className="text-slate-600 text-sm mb-3">
                When multiple transformations are applied, you can read them
                directly from the equation. Apply in this order: horizontal
                shift → vertical stretch/compress → reflection → vertical shift.
              </p>
              <div className="space-y-3">
                <div className="bg-blue-50 rounded-lg p-4 text-sm">
                  <p className="font-semibold text-blue-800 mb-2">
                    Example: g(x) = −f(x − 2) + 3
                  </p>
                  <div className="space-y-1 text-slate-700">
                    <div className="flex gap-2">
                      <span className="font-bold text-red-600">
                        → shift right 2:
                      </span>
                      <span>f(x − 2) moves graph right 2</span>
                    </div>
                    <div className="flex gap-2">
                      <span className="font-bold text-purple-600">
                        → reflect over x-axis:
                      </span>
                      <span>−f(...) flips graph vertically</span>
                    </div>
                    <div className="flex gap-2">
                      <span className="font-bold text-blue-600">
                        → shift up 3:
                      </span>
                      <span>+ 3 moves graph up 3</span>
                    </div>
                    <p className="font-mono text-blue-700 font-bold mt-1">
                      If f has point (4, 1), then g has point (4 + 2, −1 + 3) =
                      (6, 2)
                    </p>
                  </div>
                </div>

                <div className="bg-blue-50 rounded-lg p-4 text-sm">
                  <p className="font-semibold text-blue-800 mb-2">
                    Example: h(x) = 2f(x + 1) − 4
                  </p>
                  <div className="space-y-1 text-slate-700">
                    <div className="flex gap-2">
                      <span className="font-bold text-red-600">
                        → shift left 1:
                      </span>
                      <span>f(x + 1) moves graph left 1</span>
                    </div>
                    <div className="flex gap-2">
                      <span className="font-bold text-green-600">
                        → stretch vertically by 2:
                      </span>
                      <span>all y-values multiply by 2</span>
                    </div>
                    <div className="flex gap-2">
                      <span className="font-bold text-blue-600">
                        → shift down 4:
                      </span>
                      <span>− 4 moves graph down 4</span>
                    </div>
                  </div>
                </div>
              </div>
            </div>

            {/* SAT Question Type */}
            <div className="bg-sky-50 border border-sky-200 rounded-xl p-4 text-sm">
              <p className="font-bold text-sky-900 mb-1">
                SAT Question Type: Table of Values
              </p>
              <p className="text-slate-700">
                The SAT may give you a table of values for f(x) and ask for
                values of g(x) = f(x − 2) + 1. Strategy: for each value in the
                g(x) table, work backwards. To find g(3), you need f(3 − 2) + 1
                = f(1) + 1. Look up f(1) in the original table, then add 1.
              </p>
            </div>
          </div>

          <LinearTransformationWidget />

          <button
            onClick={() => scrollToSection(1)}
            className="mt-12 group flex items-center text-blue-600 font-bold hover:text-blue-800 transition-colors"
          >
            Next: Practice Quiz{" "}
            <ArrowDown className="ml-2 w-5 h-5 group-hover:translate-y-1 transition-transform" />
          </button>
        </section>

        {/* Section 2: Quiz */}
        <section
          ref={(el) => {
            sectionsRef.current[1] = el;
          }}
          className="min-h-screen flex flex-col justify-center"
        >
          <h2 className="text-4xl font-extrabold text-slate-900 mb-8">
            Practice Time
          </h2>
          {LINEAR_TRANSFORMATIONS_QUIZ_DATA.map((quiz, idx) => (
            <div key={quiz.id} className="mb-12">
              <Quiz data={quiz} />
            </div>
          ))}
          <div className="p-8 bg-blue-900 rounded-2xl text-white text-center mt-12">
            <h3 className="text-2xl font-bold mb-4">Topic Mastered!</h3>
            <button
              onClick={onFinish}
              className="px-6 py-3 bg-white text-blue-900 font-bold rounded-full hover:bg-blue-50 transition-colors"
            >
              Finish Lesson ✓
            </button>
          </div>
        </section>
      </div>
    </div>
  );
};

export default LinearTransformationsLesson;