import React, { useRef, useState, useEffect } from "react";
import { ArrowDown, Check, BookOpen, AlertTriangle, Zap } from "lucide-react";
import { PracticeFromDataset } from "../../../components/lessons/LessonShell";
import {
  BOUNDARIES_EASY,
  BOUNDARIES_MEDIUM,
} from "../../../data/rw/boundaries";
import ClauseBreakdownWidget, {
  type ClauseExample,
} from "../../../components/lessons/ClauseBreakdownWidget";
import DecisionTreeWidget, {
  type TreeScenario,
  type TreeNode,
} from "../../../components/lessons/DecisionTreeWidget";

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

// ── Clause Breakdown data ──────────────────────────────────────────────────
const CLAUSE_EXAMPLES: ClauseExample[] = [
  {
    title: "Rule 1 — FANBOYS Comma",
    segments: [
      {
        text: "The study was carefully designed",
        type: "ic",
        label: "Independent Clause",
      },
      { text: ",", type: "punct" },
      { text: " but", type: "conjunction", label: "FANBOYS Conjunction" },
      {
        text: " the results were inconclusive",
        type: "ic",
        label: "Independent Clause",
      },
      { text: ".", type: "punct" },
    ],
  },
  {
    title: "Rule 2 — Introductory Element",
    segments: [
      {
        text: "After reviewing the data",
        type: "modifier",
        label: "Introductory Phrase",
      },
      { text: ",", type: "punct" },
      {
        text: " the researchers revised their hypothesis",
        type: "ic",
        label: "Main Clause",
      },
      { text: ".", type: "punct" },
    ],
  },
  {
    title: "Rule 3 — Nonessential Phrase",
    segments: [
      { text: "The experiment", type: "subject", label: "Subject" },
      { text: ",", type: "punct" },
      {
        text: " conducted in 2021",
        type: "modifier",
        label: "Nonessential Phrase",
      },
      { text: ",", type: "punct" },
      { text: " yielded unexpected results", type: "verb", label: "Predicate" },
      { text: ".", type: "punct" },
    ],
  },
];

// ── Decision Tree data ─────────────────────────────────────────────────────
const NO_FANBOYS_SUBTREE: TreeNode = {
  id: "no-fanboys",
  question:
    "Can BOTH sides stand alone as complete sentences (independent clauses)?",
  hint: "Check each side for its own subject + verb. A phrase or fragment cannot stand alone.",
  yesLabel: "Yes — both sides are complete sentences",
  noLabel: "No — one side is a phrase/fragment",
  yes: {
    id: "comma-splice",
    result:
      "⚠ Comma Splice! A comma alone cannot join two independent clauses. Fix: add a FANBOYS conjunction after the comma, or replace the comma with a semicolon.",
    resultType: "warning",
    ruleRef: "Fix: [IC]; [IC]  or  [IC], [FANBOYS] [IC]",
  },
  no: {
    id: "no-fanboys-no-two-ic",
    question:
      "Is there an introductory element (phrase or clause) at the START of the sentence?",
    hint: 'Introductory elements include: participial phrases ("Running quickly"), prepositional phrases ("After the meeting"), or adverb clauses ("Because she studied").',
    yesLabel: "Yes — opens with an introductory phrase/clause",
    noLabel: "No — sentence starts with the subject",
    yes: {
      id: "intro-element",
      result:
        "✓ Use a comma AFTER the introductory element to separate it from the main clause.",
      resultType: "correct",
      ruleRef: "[Introductory element], [Main clause]",
    },
    no: {
      id: "no-intro",
      question:
        "Is there a nonessential phrase in the MIDDLE that can be removed without changing the core meaning?",
      hint: "Removal test: delete the phrase — does the sentence still make complete sense? If yes, it's nonessential.",
      yesLabel: "Yes — removable nonessential phrase",
      noLabel: "No — no removable phrase",
      yes: {
        id: "nonessential",
        result:
          "✓ Use a comma on EACH SIDE of the nonessential phrase (two commas total).",
        resultType: "correct",
        ruleRef: "[Subject], [nonessential phrase], [predicate]",
      },
      no: {
        id: "no-comma",
        result:
          "✓ No comma needed here. Commas are only used for FANBOYS, introductory elements, nonessential info, or lists.",
        resultType: "info",
        ruleRef: "No comma — essential or uninterrupted structure",
      },
    },
  },
};

const COMMA_TREE: TreeNode = {
  id: "root",
  question:
    "Is there a FANBOYS conjunction (for, and, nor, but, or, yet, so) in this sentence?",
  hint: "Scan for these 7 words: For · And · Nor · But · Or · Yet · So",
  yesLabel: "Yes — there's a FANBOYS word",
  noLabel: "No FANBOYS conjunction",
  yes: {
    id: "has-fanboys",
    question:
      "Can BOTH sides of the conjunction stand alone as complete sentences?",
    hint: "Cover each side with your hand. Can it stand alone with its own subject and verb?",
    yesLabel: "Yes — both sides are complete sentences",
    noLabel: "No — one side is a phrase or fragment",
    yes: {
      id: "fanboys-both-ic",
      result: "✓ Use a comma BEFORE the FANBOYS conjunction.",
      resultType: "correct",
      ruleRef: "[Independent Clause], [FANBOYS] [Independent Clause]",
    },
    no: {
      id: "fanboys-not-both-ic",
      result:
        "✗ No comma needed before the conjunction. It is not joining two independent clauses.",
      resultType: "warning",
      ruleRef: "[IC] [FANBOYS] [phrase] — no comma",
    },
  },
  no: NO_FANBOYS_SUBTREE,
};

const TREE_SCENARIOS: TreeScenario[] = [
  {
    label: "Sentence 1",
    sentence:
      "The study was carefully designed, the results were inconclusive.",
    tree: COMMA_TREE,
  },
  {
    label: "Sentence 2",
    sentence:
      "After reviewing the data the researchers revised their hypothesis.",
    tree: COMMA_TREE,
  },
  {
    label: "Sentence 3",
    sentence: "The experiment conducted in 2021 yielded unexpected results.",
    tree: COMMA_TREE,
  },
];

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

  useEffect(() => {
    const observers: IntersectionObserver[] = [];
    sectionsRef.current.forEach((el, idx) => {
      if (!el) return;
      const obs = new IntersectionObserver(
        ([entry]) => {
          if (entry.isIntersecting) setActiveSection(idx);
        },
        { threshold: 0.3 },
      );
      obs.observe(el);
      observers.push(obs);
    });
    return () => observers.forEach((o) => o.disconnect());
  }, []);

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

  const SectionMarker = ({
    index,
    title,
    icon: Icon,
  }: {
    index: number;
    title: string;
    icon: React.ElementType;
  }) => {
    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 text-left transition-all ${isActive ? "bg-purple-50" : "hover:bg-slate-50"}`}
      >
        <div
          className={`w-8 h-8 rounded-full flex items-center justify-center shrink-0
          ${isActive ? "bg-purple-600 text-white" : isPast ? "bg-purple-400 text-white" : "bg-slate-200 text-slate-500"}`}
        >
          {isPast ? (
            <Check className="w-4 h-4" />
          ) : (
            <Icon className="w-4 h-4" />
          )}
        </div>
        <p
          className={`text-sm font-bold ${isActive ? "text-purple-900" : "text-slate-600"}`}
        >
          {title}
        </p>
      </button>
    );
  };

  return (
    <div className="flex flex-col lg:flex-row min-h-screen">
      <aside className="w-full lg:w-64 lg:fixed lg:top-14 lg:bottom-0 lg:overflow-y-auto p-4 border-r border-slate-200 bg-slate-50 lg:bg-transparent z-0 hidden lg:block">
        <nav className="space-y-2 pt-6">
          <SectionMarker index={0} title="Clause Anatomy" icon={BookOpen} />
          <SectionMarker
            index={1}
            title="Decision Tree Lab"
            icon={AlertTriangle}
          />
          <SectionMarker index={2} title="Practice Questions" icon={Zap} />
        </nav>
      </aside>

      <div className="flex-1 lg:ml-64 p-6 md:p-12 max-w-4xl mx-auto">
        {/* Section 0 — Concept + Clause Breakdown */}
        <section
          ref={(el) => {
            sectionsRef.current[0] = el;
          }}
          className="min-h-screen flex flex-col justify-center mb-24 pt-20 lg:pt-0"
        >
          <div className="inline-flex items-center gap-2 bg-purple-100 text-purple-700 px-3 py-1 rounded-full text-xs font-bold uppercase tracking-wider mb-4 w-fit">
            Standard English Conventions
          </div>
          <h2 className="text-4xl font-extrabold text-slate-900 mb-2">
            Punctuation: Commas
          </h2>
          <p className="text-lg text-slate-500 mb-8">
            See how sentences are built — then learn exactly where commas go.
          </p>

          {/* Rule summary */}
          <div className="grid grid-cols-1 sm:grid-cols-2 gap-4 mb-8">
            {[
              {
                num: 1,
                rule: "FANBOYS",
                desc: "Comma before for/and/nor/but/or/yet/so when joining two complete sentences.",
              },
              {
                num: 2,
                rule: "Introductory Element",
                desc: "Comma after any word, phrase, or clause that opens the sentence.",
              },
              {
                num: 3,
                rule: "Nonessential Phrase",
                desc: "Two commas around any removable mid-sentence insertion.",
              },
              {
                num: 4,
                rule: "Lists of 3+",
                desc: "Commas between items in a series; SAT prefers the Oxford comma.",
              },
            ].map((r) => (
              <div
                key={r.num}
                className="bg-purple-50 border border-purple-200 rounded-xl p-4"
              >
                <div className="flex items-center gap-2 mb-1">
                  <span className="w-6 h-6 rounded-full bg-purple-600 text-white flex items-center justify-center text-xs font-bold shrink-0">
                    {r.num}
                  </span>
                  <span className="font-bold text-purple-900 text-sm">
                    {r.rule}
                  </span>
                </div>
                <p className="text-xs text-slate-600 ml-8">{r.desc}</p>
              </div>
            ))}
          </div>

          {/* Clause Breakdown */}
          <h3 className="text-xl font-bold text-slate-800 mb-3">
            Sentence Anatomy
          </h3>
          <p className="text-sm text-slate-500 mb-4">
            Hover over any colored span to see its label. Use the tabs to switch
            between examples.
          </p>
          <ClauseBreakdownWidget
            examples={CLAUSE_EXAMPLES}
            accentColor="purple"
          />

          <div className="mt-6 bg-purple-900 text-white rounded-2xl p-5">
            <p className="font-bold mb-1">Golden Rule</p>
            <p className="text-sm text-purple-100">
              A comma alone can <em>never</em> join two independent clauses —
              that's a comma splice. Every comma needs a job: FANBOYS, intro
              element, nonessential info, or list.
            </p>
          </div>

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

        {/* Section 1 — Decision Tree */}
        <section
          ref={(el) => {
            sectionsRef.current[1] = el;
          }}
          className="min-h-screen flex flex-col justify-center mb-24"
        >
          <h2 className="text-4xl font-extrabold text-slate-900 mb-2">
            Decision Tree Lab
          </h2>
          <p className="text-lg text-slate-500 mb-8">
            Work through the grammar logic one question at a time. Click your
            answer at each step.
          </p>

          {/* Trap callouts */}
          <div className="space-y-3 mb-8">
            {[
              {
                label: "Comma Splice",
                desc: "Two full sentences joined by a comma alone. The most tested comma error.",
              },
              {
                label: "Missing Second Comma",
                desc: "Nonessential phrases need a comma on EACH side — never just one.",
              },
              {
                label: "Subject–Verb Comma",
                desc: "Never put a single comma between a subject and its verb.",
              },
            ].map((t) => (
              <div
                key={t.label}
                className="flex gap-3 bg-red-50 border border-red-200 rounded-xl px-4 py-3"
              >
                <AlertTriangle className="w-4 h-4 text-red-500 shrink-0 mt-0.5" />
                <div>
                  <p className="text-sm font-bold text-red-800">{t.label}</p>
                  <p className="text-xs text-slate-600 mt-0.5">{t.desc}</p>
                </div>
              </div>
            ))}
          </div>

          <DecisionTreeWidget scenarios={TREE_SCENARIOS} accentColor="purple" />

          <button
            onClick={() => scrollToSection(2)}
            className="mt-12 group flex items-center text-purple-600 font-bold hover:text-purple-800 transition-colors"
          >
            Next: Practice Questions{" "}
            <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[2] = el;
          }}
          className="min-h-screen flex flex-col justify-center mb-24"
        >
          <h2 className="text-4xl font-extrabold text-slate-900 mb-6">
            Practice Questions
          </h2>
          {BOUNDARIES_EASY.slice(0, 2).map((q) => (
            <PracticeFromDataset key={q.id} question={q} color="purple" />
          ))}
          {BOUNDARIES_MEDIUM.slice(0, 1).map((q) => (
            <PracticeFromDataset key={q.id} question={q} color="purple" />
          ))}
          <div className="mt-8 text-center">
            <button
              onClick={onFinish}
              className="px-6 py-3 bg-purple-900 text-white font-bold rounded-full hover:bg-purple-700 transition-colors"
            >
              Finish Lesson ✓
            </button>
          </div>
        </section>
      </div>
    </div>
  );
};

export default EBRWCommasLesson;
