import { useCallback, useEffect, useMemo, useState } from 'react';
import { Search, Cpu, Zap, BookOpen, CheckCircle2, Circle, Trophy, Loader2, Layers } from 'lucide-react';
import { motion, AnimatePresence } from 'motion/react';
import { cn } from '@/lib/utils';
import { fetchCTopics, type CChapterTopic } from '@/lib/cProgrammingClient';
import CContentPage from './CContentPage';

const STORAGE_KEY = 'ryp_c_completed';

function loadCompleted(): Record<string, boolean> {
  try { return JSON.parse(localStorage.getItem(STORAGE_KEY) || '{}'); } catch { return {}; }
}

const LEVEL_COLORS: Record<string, string> = {
  Core: 'border-blue-500/20 bg-blue-500/20 text-blue-400',
  Beginner: 'border-emerald-500/20 bg-emerald-500/20 text-emerald-400',
  Intermediate: 'border-cyan-500/20 bg-cyan-500/20 text-cyan-400',
  Advanced: 'border-purple-500/20 bg-purple-500/20 text-purple-400',
};

interface CLearningPathProps {
  onBack: () => void;
}

export default function CLearningPath({ onBack }: CLearningPathProps) {
  const [topics, setTopics] = useState<CChapterTopic[]>([]);
  const [loading, setLoading] = useState(true);
  const [selectedTopic, setSelectedTopic] = useState<CChapterTopic | null>(null);
  const [searchQuery, setSearchQuery] = useState('');
  const [completed, setCompleted] = useState<Record<string, boolean>>(loadCompleted);

  useEffect(() => {
    fetchCTopics()
      .then(data => {
        setTopics(data);
        setLoading(false);
      })
      .catch(err => {
        console.error('Failed to fetch C topics:', err);
        setLoading(false);
      });
  }, []);

  const toggleTopic = useCallback((id: string) => {
    setCompleted(prev => {
      const next = { ...prev, [id]: !prev[id] };
      localStorage.setItem(STORAGE_KEY, JSON.stringify(next));
      return next;
    });
  }, []);

  const totalDone = topics.filter(t => completed[t.id]).length;
  const totalAll = topics.length;
  const totalSections = useMemo(() => topics.reduce((sum, topic) => sum + topic.section_count, 0), [topics]);
  const totalContent = useMemo(() => topics.reduce((sum, topic) => sum + topic.content_count, 0), [topics]);
  const pct = totalAll > 0 ? Math.round((totalDone / totalAll) * 100) : 0;

  const filteredTopics = topics.filter(topic => {
    const query = searchQuery.toLowerCase();
    return (
      topic.chapter_name.toLowerCase().includes(query) ||
      topic.subtitle?.toLowerCase().includes(query) ||
      topic.sections.some(section =>
        section.section.toLowerCase().includes(query) ||
        section.section_title.toLowerCase().includes(query)
      )
    );
  });

  return (
    <div className="mx-auto max-w-5xl space-y-8 pb-12">
      <AnimatePresence mode="wait">
        {selectedTopic ? (
          <CContentPage
            key="content"
            chapterNo={selectedTopic.chapter_no}
            onBack={() => setSelectedTopic(null)}
          />
        ) : (
          <motion.div
            key="list"
            initial={{ opacity: 0, y: 18 }}
            animate={{ opacity: 1, y: 0 }}
            exit={{ opacity: 0, y: -18 }}
            className="space-y-8"
          >
            <div className="flex flex-col gap-4 md:flex-row md:items-start md:justify-between">
              <div>
                <div className="flex items-center gap-2 text-xs font-black uppercase tracking-[0.28em] text-blue-300/80">
                  <Cpu size={16} /> Coding Language
                </div>
                <h2 className="mt-3 text-4xl font-black tracking-tight text-white">C Programming</h2>
                <p className="mt-2 max-w-2xl text-sm leading-6 text-slate-400">
                  Study C from the fundamentals of syntax and memory to files, preprocessors, linked lists, and common pitfalls.
                </p>
                <button
                  onClick={onBack}
                  className="mt-4 text-xs font-bold text-blue-400 underline underline-offset-4 hover:text-blue-300"
                >
                  Back to Coding Languages
                </button>
              </div>
              <div className="relative mt-1 shrink-0">
                <Search className="absolute left-4 top-1/2 -translate-y-1/2 text-zinc-500" size={16} />
                <input
                  type="text"
                  placeholder="Search chapters or topics..."
                  value={searchQuery}
                  onChange={e => setSearchQuery(e.target.value)}
                  className="h-11 w-72 rounded-2xl border border-zinc-800 bg-zinc-950/60 pl-10 pr-4 text-sm text-white outline-none transition-all placeholder-zinc-600 focus:border-blue-500/50 focus:ring-1 focus:ring-blue-500/30"
                />
              </div>
            </div>

            <div className="relative overflow-hidden rounded-[2rem] border border-blue-500/20 bg-[#07111f]/95 p-8 shadow-[0_24px_80px_-60px_rgba(59,130,246,0.5)] backdrop-blur-xl">
              <div className="absolute inset-0 bg-[radial-gradient(circle_at_top_right,rgba(59,130,246,0.16),transparent_55%)]" />
              <div className="absolute inset-0 bg-[radial-gradient(circle_at_bottom_left,rgba(14,165,233,0.08),transparent_50%)]" />
              <div className="relative z-10 flex flex-col gap-6 md:flex-row md:items-center md:justify-between">
                <div className="flex items-center gap-5">
                  <div className="flex h-16 w-16 shrink-0 items-center justify-center rounded-2xl border border-blue-500/20 bg-blue-500/10 text-blue-400 shadow-inner">
                    <BookOpen size={28} />
                  </div>
                  <div>
                    <div className="inline-flex items-center gap-2 rounded-full border border-blue-400/20 bg-blue-400/10 px-3 py-1">
                      <Zap size={12} className="text-blue-300" />
                      <span className="text-[10px] font-black uppercase tracking-widest text-blue-300">Track Progress</span>
                    </div>
                    <div className="mt-2 flex items-end gap-2">
                      <span className="text-4xl font-black text-white">{totalDone}</span>
                      <span className="mb-1 text-lg font-bold text-zinc-500">/ {totalAll} chapters</span>
                    </div>
                    <div className="mt-2 flex flex-wrap gap-2 text-xs font-semibold text-zinc-500">
                      <span>{totalSections} database topics</span>
                      <span className="text-zinc-700">|</span>
                      <span>{totalContent} with stored details</span>
                    </div>
                  </div>
                </div>
                <div className="mt-6 flex w-full flex-col items-start gap-3 md:mt-0 md:w-auto md:min-w-[200px] md:items-end">
                  <div className="flex w-full justify-between text-xs font-bold text-zinc-400 md:w-auto">
                    <span>Completion</span>
                    <span className={pct === 100 ? 'text-blue-400' : 'text-cyan-400'}>{pct}%</span>
                  </div>
                  <div className="h-3 w-full overflow-hidden rounded-full bg-zinc-800/80">
                    <motion.div
                      className={cn('h-full rounded-full', pct === 100
                        ? 'bg-gradient-to-r from-blue-500 to-blue-400'
                        : 'bg-gradient-to-r from-blue-500 to-cyan-500'
                      )}
                      initial={{ width: 0 }}
                      animate={{ width: `${pct}%` }}
                      transition={{ duration: 0.8, ease: 'easeOut' }}
                    />
                  </div>
                  {pct === 100 && (
                    <div className="flex w-fit items-center gap-1.5 rounded-full border border-blue-500/30 bg-blue-500/10 px-4 py-1.5 text-xs font-black text-blue-400">
                      <Trophy size={12} /> C Mastered!
                    </div>
                  )}
                </div>
              </div>
            </div> 

            {loading ? (
              <div className="flex h-40 items-center justify-center">
                <Loader2 className="h-8 w-8 animate-spin text-blue-500" />
              </div>
            ) : (
              <section>
                <div className="mb-4 flex items-center justify-between">
                  <div className="flex items-center gap-3">
                    <div className="h-5 w-1.5 rounded-full bg-gradient-to-b from-blue-400 to-cyan-600" />
                    <h3 className="text-lg font-black tracking-tight text-white">Course Chapters</h3>
                    <span className="rounded-full border border-zinc-700 bg-zinc-900 px-3 py-0.5 text-[10px] font-black uppercase tracking-widest text-zinc-400">
                      {filteredTopics.length} chapters
                    </span>
                  </div>
                </div>

                <div className="overflow-hidden rounded-[20px] border border-zinc-800/80 bg-zinc-950/50 shadow-xl backdrop-blur-sm">
                  <div className="border-b border-zinc-800/60 bg-zinc-900/60 px-5 py-2.5 text-[9px] font-black uppercase tracking-[0.28em] text-zinc-600">
                    <div className="grid grid-cols-[28px_28px_1fr_auto] items-center gap-4">
                      <span>Done</span><span>#</span><span>Chapter</span><span className="text-right">Action</span>
                    </div>
                  </div>
                  {filteredTopics.map((topic, idx) => {
                    const done = !!completed[topic.id];
                    return (
                      <motion.div
                        key={topic.id}
                        initial={{ opacity: 0, y: 6 }}
                        animate={{ opacity: 1, y: 0 }}
                        transition={{ delay: idx * 0.025 }}
                        className={cn(
                          'group flex items-center gap-4 border-b border-zinc-800/40 px-5 py-4 transition-colors last:border-b-0',
                          idx % 2 === 0 ? 'bg-zinc-950/30' : 'bg-zinc-900/20',
                          done ? 'bg-blue-500/[0.03]' : 'cursor-pointer hover:bg-zinc-800/50',
                        )}
                        onClick={(e) => {
                          if ((e.target as HTMLElement).closest('button.checkbox-btn')) return;
                          setSelectedTopic(topic);
                        }}
                      >
                        <button type="button" onClick={() => toggleTopic(topic.id)} className="checkbox-btn shrink-0 transition-transform hover:scale-110">
                          {done
                            ? <CheckCircle2 size={18} className="text-blue-400" />
                            : <Circle size={18} className="text-zinc-600 group-hover:text-zinc-400" />}
                        </button>
                        <div className={cn('flex h-6 w-6 shrink-0 items-center justify-center rounded-full text-[10px] font-black',
                          done ? 'bg-blue-500/20 text-blue-400' : 'bg-zinc-800 text-zinc-500')}>
                          {topic.chapter_no}
                        </div>
                        <div className="min-w-0 flex-1">
                          <div className={cn('flex items-center gap-2 text-sm font-semibold transition-colors',
                            done ? 'text-blue-400 line-through decoration-blue-500/40' : 'text-zinc-200 group-hover:text-white')}>
                            <span className="truncate">{topic.chapter_name}</span>
                            <span className={cn('rounded-full border px-2 py-0.5 text-[10px] font-medium no-underline', LEVEL_COLORS[topic.level] ?? LEVEL_COLORS.Core)}>
                              {topic.level}
                            </span>
                          </div>
                          <div className="mt-1 flex flex-wrap items-center gap-2">
                            <span className="inline-flex items-center gap-1 text-xs text-zinc-500">
                              <Layers size={12} />
                              {topic.section_count} topics
                            </span>
                            {topic.sections.slice(0, 3).map(section => (
                              <span key={section.id || section.section} className="max-w-[160px] truncate rounded-lg border border-zinc-800 bg-zinc-900/70 px-2 py-0.5 text-[10px] font-medium text-zinc-500">
                                {section.section} {section.section_title}
                              </span>
                            ))}
                            {topic.sections.length > 3 && (
                              <span className="text-[10px] font-bold text-zinc-600">+{topic.sections.length - 3} more</span>
                            )}
                          </div>
                        </div>
                        <button
                          className="shrink-0 flex items-center gap-1.5 rounded-xl border border-blue-500/20 bg-blue-500/10 px-3 py-1.5 text-xs font-bold text-blue-400 shadow-[0_0_15px_rgba(59,130,246,0.15)] transition-all hover:bg-blue-500/20 hover:text-blue-300 group-hover:shadow-[0_0_20px_rgba(59,130,246,0.3)]"
                          onClick={(e) => {
                            e.stopPropagation();
                            setSelectedTopic(topic);
                          }}
                        >
                          <BookOpen size={12} /> Study
                        </button>
                      </motion.div>
                    );
                  })}
                  {filteredTopics.length === 0 && !loading && (
                    <div className="p-8 text-center text-sm text-zinc-500">
                      No chapters found.
                    </div>
                  )}
                </div>
              </section>
            )}
          </motion.div>
        )}
      </AnimatePresence>
    </div>
  );
}