import { useEffect, useMemo, useState } from "react";
import { useNavigate } from "react-router-dom";
import { House, ChevronLeft, ChevronRight, Layers } from "lucide-react";
import AppBreadcrumb from "@/components/generic/Breadcrumb/AppBreadcrumb";
import { Input } from "@/components/ui/input";
import {
    Select, SelectContent, SelectItem, SelectTrigger, SelectValue,
} from "@/components/ui/select";
import { Button } from "@/components/ui/button";
import { useLibrary } from "@/contexts/ClientLibraryContext";
import { useClientTiers } from "@/contexts/ClientTiersProvider";
import LessonUpsellModal from "../components/LessonUpsellModal";
import { LessonCard, LessonCardSkeleton } from "../components/LessonCard";
import { PageMeta } from "@/contexts/MetadataContext";

const ITEMS_PER_PAGE = 10;

// ─── Pagination ───────────────────────────────────────────────────────────────

const Pagination = ({ currentPage, totalPages, totalItems, itemsPerPage, onPageChange }) => {
    const start = (currentPage - 1) * itemsPerPage + 1;
    const end = Math.min(currentPage * itemsPerPage, totalItems);

    const getPages = () => {
        const pages = [];
        if (totalPages <= 5) {
            for (let i = 1; i <= totalPages; i++) pages.push(i);
        } else {
            pages.push(1);
            if (currentPage > 3) pages.push("...");
            for (let i = Math.max(2, currentPage - 1); i <= Math.min(totalPages - 1, currentPage + 1); i++) pages.push(i);
            if (currentPage < totalPages - 2) pages.push("...");
            pages.push(totalPages);
        }
        return pages;
    };

    return (
        <div className="flex items-center justify-between w-full pt-4 border-t">
            <div className="text-sm text-muted-foreground">
                Showing <span className="font-medium text-foreground">{start}–{end}</span> of{" "}
                <span className="font-medium text-foreground">{totalItems}</span> lessons
            </div>
            <div className="flex items-center gap-1">
                <Button onClick={() => onPageChange(currentPage - 1)} disabled={currentPage === 1} variant="ghost" size="sm">
                    <ChevronLeft />
                </Button>
                {getPages().map((page, i) =>
                    page === "..." ? (
                        <span key={`ellipsis-${i}`} className="w-7 h-7 flex items-center justify-center text-xs text-muted-foreground">···</span>
                    ) : (
                        <Button key={page} size="sm" variant={currentPage === page ? "default" : "outline"} onClick={() => onPageChange(page)}>
                            {page}
                        </Button>
                    )
                )}
                <Button onClick={() => onPageChange(currentPage + 1)} disabled={currentPage === totalPages} variant="ghost" size="sm">
                    <ChevronRight />
                </Button>
            </div>
        </div>
    );
};

// ─── Main Page ────────────────────────────────────────────────────────────────

const LessonsList = () => {
    const navigate = useNavigate();
    const { lessons, lessonsLoading, getLessons } = useLibrary();
    const { tierMap, getTierCategories } = useClientTiers();

    const [currentPage, setCurrentPage] = useState(1);
    const [search, setSearch] = useState("");
    const [lockFilter, setLockFilter] = useState("All");
    const [modalOpen, setModalOpen] = useState(false);
    const [selectedLesson, setSelectedLesson] = useState(null);

    useEffect(() => {
        getLessons();
        getTierCategories();
        // eslint-disable-next-line react-hooks/exhaustive-deps
    }, []);

    const filtered = useMemo(() =>
        lessons
            .filter((l) => {
                const matchSearch = l.title.toLowerCase().includes(search.toLowerCase()) ||
                    (l.description ?? "").toLowerCase().includes(search.toLowerCase());
                const matchLock = lockFilter === "All"
                    || (lockFilter === "Unlocked" && !l.is_locked)
                    || (lockFilter === "Locked" && l.is_locked);
                return matchSearch && matchLock;
            })
            .sort((a, b) => a.title.localeCompare(b.title)),
        [lessons, search, lockFilter]
    );

    const totalPages = Math.max(1, Math.ceil(filtered.length / ITEMS_PER_PAGE));
    const paginated = filtered.slice((currentPage - 1) * ITEMS_PER_PAGE, currentPage * ITEMS_PER_PAGE);

    const handleViewDetails = (lesson) => {
        if (lesson.is_locked) {
            setSelectedLesson(lesson);
            setModalOpen(true);
        } else {
            navigate(`/lessons/${lesson.uuid}`);
        }
    };

    const items = [
        { label: "Home", icon: <House className="size-4" />, to: `/dashboard` },
        { label: "Lessons" },
    ];

    return (
        <div>
            <PageMeta title="Lessons - STARR" description="Browse standalone lessons you can start right away." />
            <div className="py-24 bg-accent/70 min-h-screen">
                <div className="flex flex-col gap-4 justify-between lg:container lg:mx-auto pt-2">
                    <AppBreadcrumb items={items} />

                    {/* Search & Filters */}
                    <div className="fixed top-[67px] left-0 right-0 z-10 bg-card border-b lg:static lg:bg-transparent lg:border-none py-3 xs:px-4 md:px-6 lg:px-0">
                        <div className="flex items-center xs:flex-col lg:flex-row gap-4">
                            <Input
                                placeholder="Search lessons..."
                                className="w-full bg-card lg:max-w-64 text-sm"
                                value={search}
                                onChange={(e) => { setSearch(e.target.value); setCurrentPage(1); }}
                            />
                            <Select value={lockFilter} onValueChange={(v) => { setLockFilter(v); setCurrentPage(1); }}>
                                <SelectTrigger className="w-full lg:w-48 bg-card">
                                    <SelectValue placeholder="Access" />
                                </SelectTrigger>
                                <SelectContent>
                                    <SelectItem value="All">All Lessons</SelectItem>
                                    <SelectItem value="Unlocked">Unlocked</SelectItem>
                                    <SelectItem value="Locked">Locked</SelectItem>
                                </SelectContent>
                            </Select>
                            <Select value="lessons" onValueChange={(v) => {
                                if (v === "courses") navigate("/course");
                                if (v === "units") navigate("/units");
                            }}>
                                <SelectTrigger className="w-full lg:w-48 bg-card">
                                    <SelectValue placeholder="Browse" />
                                </SelectTrigger>
                                <SelectContent>
                                    <SelectItem value="courses">Courses</SelectItem>
                                    <SelectItem value="units">Units</SelectItem>
                                    <SelectItem value="lessons">Lessons</SelectItem>
                                </SelectContent>
                            </Select>
                        </div>
                    </div>

                    {/* Lesson Grid */}
                    {lessonsLoading ? (
                        <div className="xs:pt-12 lg:pt-0 grid grid-cols-1 sm:grid-cols-2 lg:grid-cols-3 xl:grid-cols-4 gap-4">
                            {Array.from({ length: 8 }).map((_, i) => <LessonCardSkeleton key={i} />)}
                        </div>
                    ) : paginated.length === 0 ? (
                        <div className="flex flex-col items-center justify-center py-20">
                            <Layers className="size-40 text-primary" />
                            <p className="text-md">No lessons found</p>
                        </div>
                    ) : (
                        <div className="xs:pt-12 lg:pt-0 grid grid-cols-1 sm:grid-cols-2 lg:grid-cols-3 xl:grid-cols-4 gap-4 mb-4 xs:px-4 lg:px-0">
                            {paginated.map((lesson) => (
                                <LessonCard
                                    key={lesson.lesson_id}
                                    lesson={lesson}
                                    onViewDetails={handleViewDetails}
                                />
                            ))}
                        </div>
                    )}

                    {!lessonsLoading && filtered.length > ITEMS_PER_PAGE && (
                        <Pagination
                            currentPage={currentPage}
                            totalPages={totalPages}
                            totalItems={filtered.length}
                            itemsPerPage={ITEMS_PER_PAGE}
                            onPageChange={setCurrentPage}
                        />
                    )}
                </div>
            </div>

            <LessonUpsellModal
                open={modalOpen}
                onOpenChange={setModalOpen}
                lesson={selectedLesson}
                tierMap={tierMap}
            />
        </div>
    );
};

export default LessonsList;