import React, { useState, useMemo } from 'react';
import { CurrentView, ResearchPaper } from '../types';
import { SECTION_IDS, RESEARCH_ALL_CONTENT } from '../constants';
import Button from './Button';
import { ArrowUturnLeftIcon } from './icons';
import ResearchCard from './ResearchCard';
import FilterSortBar, { ViewMode, SortOptionKey, SortOption } from './FilterSortBar';

interface ResearchAllSectionProps {
  researchPapers: ResearchPaper[]; 
  setCurrentView: (view: CurrentView) => void;
  setSelectedItemId: (id: string | null) => void;
}

const sortOptions: SortOption[] = [
  { key: 'newest', label: 'Сначала новые' },
  { key: 'oldest', label: 'Сначала старые' },
  { key: 'alphabetical', label: 'По алфавиту (А-Я)' },
];

const ResearchAllSection: React.FC<ResearchAllSectionProps> = ({ researchPapers, setCurrentView, setSelectedItemId }) => {
  const [viewMode, setViewMode] = useState<ViewMode>('grid');
  const [selectedCategories, setSelectedCategories] = useState<string[]>([]);
  const [selectedSort, setSelectedSort] = useState<SortOptionKey>('newest');


  const handleBackClick = () => {
    setCurrentView('main');
    setSelectedItemId(null);
    setTimeout(() => {
      document.getElementById(SECTION_IDS.latestResearch)?.scrollIntoView({ behavior: 'smooth' });
    }, 0);
  };
  
  const availableCategories = useMemo(() => {
    if (!researchPapers) return [];
    return Array.from(new Set(researchPapers.map(p => p.category))).sort();
  }, [researchPapers]);

  const handleCategoryChange = (category: string) => {
    setSelectedCategories(prev =>
      prev.includes(category)
        ? prev.filter(c => c !== category)
        : [...prev, category]
    );
  };

  const filteredAndSortedPapers = useMemo(() => {
    if (!researchPapers) return [];
    
    const filtered = selectedCategories.length > 0
      ? researchPapers.filter(p => selectedCategories.includes(p.category))
      : researchPapers;

    return [...filtered].sort((a, b) => {
      switch (selectedSort) {
        case 'newest':
          return new Date(b.publishedAt || 0).getTime() - new Date(a.publishedAt || 0).getTime();
        case 'oldest':
          return new Date(a.publishedAt || 0).getTime() - new Date(b.publishedAt || 0).getTime();
        case 'alphabetical':
          return a.title.localeCompare(b.title);
        default:
          return 0;
      }
    });
  }, [researchPapers, selectedCategories, selectedSort]);


  if (!researchPapers) { 
    return (
      <section 
        id={SECTION_IDS.researchAllPage}
        className="py-16 md:py-24 bg-white min-h-screen flex justify-center items-center"
      >
        <p className="text-slate-600 font-inter">Загрузка исследований...</p>
      </section>
    );
  }
  
  const layoutClasses = viewMode === 'grid'
    ? "grid grid-cols-1 sm:grid-cols-2 lg:grid-cols-3 gap-6 md:gap-8"
    : "flex flex-col gap-4";

  return (
    <section 
      id={SECTION_IDS.researchAllPage}
      className="py-16 md:py-24 bg-white min-h-screen"
    >
      <div className="container mx-auto px-4 sm:px-6 lg:px-8">
        <header className="mb-8 md:mb-8">
          <div className="flex flex-col sm:flex-row sm:items-center sm:justify-between">
            <h1 className="font-quicksand text-4xl sm:text-5xl md:text-6xl font-bold text-slate-900 mb-4 sm:mb-0">
              {RESEARCH_ALL_CONTENT.title}
            </h1>
            <Button
              variant="outline"
              size="md"
              onClick={handleBackClick}
              leftIcon={<ArrowUturnLeftIcon />}
              className="self-start sm:self-center"
            >
              {RESEARCH_ALL_CONTENT.backButtonTextPrefix} {RESEARCH_ALL_CONTENT.backButtonTextSuffix}
            </Button>
          </div>
           <p className="mt-4 text-lg md:text-xl text-slate-700 max-w-3xl">
            {RESEARCH_ALL_CONTENT.subtitle}
          </p>
        </header>

        <FilterSortBar
          viewMode={viewMode}
          onViewChange={setViewMode}
          availableCategories={availableCategories}
          selectedCategories={selectedCategories}
          onCategoryChange={handleCategoryChange}
          onClearCategories={() => setSelectedCategories([])}
          sortOptions={sortOptions}
          selectedSort={selectedSort}
          onSortChange={setSelectedSort}
        />
        
        {filteredAndSortedPapers.length > 0 ? (
          <div className={layoutClasses}>
            {filteredAndSortedPapers.map(paper => (
              <ResearchCard 
                key={paper.id} 
                paper={paper} 
                setCurrentView={setCurrentView}
                setSelectedItemId={setSelectedItemId}
                viewMode={viewMode}
              />
            ))}
          </div>
        ) : (
          <div className="text-center py-10">
            <h2 className="text-2xl font-quicksand font-semibold text-slate-700 mb-3">{RESEARCH_ALL_CONTENT.emptyStateTitle}</h2>
            <p className="text-slate-600 font-inter">
              {RESEARCH_ALL_CONTENT.emptyStateMessage}
            </p>
          </div>
        )}
      </div>
    </section>
  );
};

export default ResearchAllSection;