import React, { useMemo, useState, useEffect, useCallback } from 'react';
import * as XLSX from 'xlsx';
import { ProductForecastData, FilterState, CombinedKPIs } from '../types';
import { DownloadIcon, FunnelIcon, TrendingIcon, ChartIcon } from './Icons';
import { StockBadge } from './StockBadge';
import { Top50Badge } from './Top50Badge';
import { VendorStockBadge } from './VendorStockBadge';
import { InColumnStockFilter } from './InColumnStockFilter';
import { PAN_EU_COUNTRIES } from '../services/dataProcessor';
import {
    BarChart, Bar, XAxis, YAxis, CartesianGrid, Tooltip, ResponsiveContainer,
    LineChart, Line, Legend, ComposedChart, Area
} from 'recharts';

interface ForecastViewProps {
    data: ProductForecastData[];
    filters: FilterState;
    top50Ranking: { eu: Map<string, number>; uk: Map<string, number> };
    stockMap: Map<string, number>;
    top50Mode: 'eu' | 'uk';
    vendorStockMap?: Map<string, { eu: number; uk: number }>;
    stockFilter: string[];
    onStockFilterChange: (newFilters: string[]) => void;
    vendorStockFilter: string[];
    onVendorStockFilterChange: (newFilters: string[]) => void;
}

const MONTH_ORDER = ['Jan', 'Feb', 'Mar', 'Apr', 'May', 'Jun', 'Jul', 'Aug', 'Sep', 'Oct', 'Nov', 'Dec'];

const ForecastRow: React.FC<{
    item: ProductForecastData;
    activeMonths: string[];
    top50Ranking?: { eu: Map<string, number>; uk: Map<string, number> };
    top50Mode: 'eu' | 'uk';
    stockMap?: Map<string, number>;
    vendorStockMap?: Map<string, { eu: number; uk: number }>;
}> = React.memo(({ item, activeMonths, top50Ranking, top50Mode, stockMap, vendorStockMap }) => {
    const asin = item.asin.trim().toUpperCase();
    const ranks: { rank: number; label: string; theme: 'amber' | 'blue' | 'indigo' }[] = [];

    if (top50Ranking) {
        if (top50Mode === 'eu') {
            const rankEU = top50Ranking.eu.get(asin);
            if (rankEU) ranks.push({ rank: rankEU, label: 'EU', theme: 'indigo' });
        } else {
            const rankUK = top50Ranking.uk.get(asin);
            if (rankUK) ranks.push({ rank: rankUK, label: 'UK', theme: 'blue' });
        }
    }

    const monthlySales = activeMonths.map(m => (item.monthlyData && item.monthlyData[m]?.units) || 0);
    const avgMonthly = monthlySales.length > 0 ? monthlySales.reduce((a, b) => a + b, 0) / activeMonths.length : 0;
    const peakMonthly = monthlySales.length > 0 ? Math.max(...monthlySales) : 0;

    return (
        <tr key={item.asin} className="hover:bg-indigo-500/5 transition-colors group">
            <td className="px-6 py-4">
                <div className="flex flex-col gap-1.5">
                    <div className="flex items-center gap-1.5 mb-1">
                        {ranks.map((r, i) => (
                            <Top50Badge key={i} rank={r.rank} label={r.label} theme={r.theme} />
                        ))}
                        <span className="text-xs font-black text-indigo-400 tracking-tighter uppercase">
                            {item.sku}
                        </span>
                        <div className="px-2 py-0.5 rounded bg-slate-800/80 border border-white/5 text-[10px] font-bold text-slate-400 uppercase tracking-wider">
                            {item.asin}
                        </div>
                    </div>
                    <span className="text-xs text-white/70 line-clamp-1 group-hover:line-clamp-none transition-all" title={item.title}>{item.title}</span>
                    <div className="flex items-center gap-2 mt-1">
                        <span className="px-2 py-0.5 rounded bg-indigo-500/10 text-[9px] font-black text-indigo-300 uppercase tracking-widest border border-indigo-500/20">{item.line}</span>
                        {stockMap && (
                            <StockBadge stock={stockMap.get(item.sku?.replace(/(DE|EN)$/i, ''))} />
                        )}
                        <VendorStockBadge asin={item.asin} vendorStockMap={vendorStockMap} mode={top50Mode} avgWeeklySales={item.avgWeeklySales} />
                    </div>
                </div>
            </td>
            <td className="px-6 py-4 text-center">
                <span className="text-sm font-black text-white">{(item.actualUnits || 0).toLocaleString('de-DE')}</span>
            </td>
            <td className="px-6 py-4 text-center">
                <span className="text-sm font-black text-emerald-400">{(item.forecastUnits || 0).toLocaleString('de-DE')}</span>
            </td>
            <td className="px-6 py-4 text-center">
                <div className="flex flex-col items-center">
                    <span className="text-sm font-black text-indigo-400">{(Math.round(avgMonthly) || 0).toLocaleString('de-DE')}</span>
                    <span className="text-[9px] text-slate-500 font-bold uppercase tracking-tighter">Peak: {(Math.round(peakMonthly) || 0).toLocaleString('de-DE')}</span>
                </div>
            </td>
            <td className="px-6 py-4">
                <div className="h-10 w-full min-w-[120px]">
                    <ResponsiveContainer width="100%" height="100%">
                        <BarChart data={activeMonths.map(m => ({ name: m, units: (item.monthlyData && item.monthlyData[m]?.units) || 0 }))}>
                            <Bar dataKey="units" fill="#6366f1" radius={[2, 2, 0, 0]} />
                        </BarChart>
                    </ResponsiveContainer>
                </div>
            </td>
            <td className="px-6 py-4 text-center">
                <div className="flex flex-col items-center">
                    <span className={`text-sm font-black ${item.accuracy >= 80 ? 'text-emerald-400' : item.accuracy >= 50 ? 'text-amber-400' : 'text-rose-400'}`}>
                        {item.accuracy}%
                    </span>
                    <div className="w-16 h-1.5 bg-slate-800 rounded-full mt-1 overflow-hidden border border-white/5">
                        <div
                            className={`h-full transition-all duration-1000 ${item.accuracy >= 80 ? 'bg-emerald-500' : item.accuracy >= 50 ? 'bg-amber-500' : 'bg-rose-500'}`}
                            style={{ width: `${item.accuracy}%` }}
                        />
                    </div>
                </div>
            </td>
        </tr>
    );
});

const ForecastView: React.FC<ForecastViewProps> = ({
    data,
    filters,
    top50Ranking,
    stockMap,
    vendorStockMap,
    stockFilter,
    onStockFilterChange,
    vendorStockFilter,
    onVendorStockFilterChange,
    top50Mode
}) => {
    const [searchTerm, setSearchTerm] = useState('');
    const [showOnlyTop50, setShowOnlyTop50] = useState(false);
    const [displayCount, setDisplayCount] = useState(50);

    const lastDataMonthIdx = useMemo(() => {
        for (let i = MONTH_ORDER.length - 1; i >= 0; i--) {
            if (data.some(p => p.monthlyData[MONTH_ORDER[i]]?.units > 0)) return i;
        }
        return 0;
    }, [data]);

    const activeMonths = useMemo(() => {
        if (filters.month && filters.month.length > 0) {
            return filters.month.map(m => m.split('-')[0]);
        }
        return MONTH_ORDER.slice(0, lastDataMonthIdx + 1);
    }, [filters.month, lastDataMonthIdx]);

    const baseFilteredData = useMemo(() => {
        let result = data;
        if (filters.line && filters.line.length > 0) result = result.filter(p => filters.line.includes(p.line));
        if (filters.asin && filters.asin.length > 0) result = result.filter(p => filters.asin.includes(p.asin));
        if (filters.sku && filters.sku.length > 0) result = result.filter(p => filters.sku.includes(p.sku));
        return result;
    }, [data, filters.line, filters.asin, filters.sku]);

    const globalSummary = useMemo(() => {
        return baseFilteredData.reduce((acc, curr) => ({
            actualUnits: acc.actualUnits + curr.actualUnits,
            forecastUnits: acc.forecastUnits + curr.forecastUnits,
        }), { actualUnits: 0, forecastUnits: 0 });
    }, [baseFilteredData]);

    const finalFilteredData = useMemo(() => {
        let result = baseFilteredData;
        if (showOnlyTop50 && top50Ranking) {
            const currentRankMap = top50Mode === 'eu' ? top50Ranking.eu : top50Ranking.uk;
            result = result.filter(p => currentRankMap.has(p.asin.toUpperCase()));
        }
        if (searchTerm) {
            const s = searchTerm.toLowerCase();
            result = result.filter(p => p.sku.toLowerCase().includes(s) || p.asin.toLowerCase().includes(s) || p.title.toLowerCase().includes(s));
        }
        return result;
    }, [baseFilteredData, searchTerm, showOnlyTop50, top50Ranking, top50Mode]);

    const handleExportExcel = useCallback(() => {
        const exportData = finalFilteredData.map(p => ({
            SKU: p.sku,
            ASIN: p.asin,
            Title: p.title,
            Line: p.line,
            'Actual Units (2025)': p.actualUnits,
            'Forecast Units (2025)': p.forecastUnits,
            'Accuracy (%)': p.accuracy
        }));
        const ws = XLSX.utils.json_to_sheet(exportData);
        const wb = XLSX.utils.book_new();
        XLSX.utils.book_append_sheet(wb, ws, 'Forecast');
        XLSX.writeFile(wb, `Forecast_Export_${new Date().toISOString().slice(0, 10)}.xlsx`);
    }, [finalFilteredData]);

    return (
        <div className="flex flex-col gap-6 animate-fade-in">
            <div className="grid grid-cols-1 md:grid-cols-2 lg:grid-cols-4 gap-4">
                <div className="bg-slate-900/50 backdrop-blur-xl border border-white/10 p-5 rounded-2xl shadow-xl">
                    <div className="flex items-center gap-3 mb-3">
                        <div className="p-2 bg-indigo-500/20 rounded-lg"><ChartIcon /></div>
                        <span className="text-[10px] font-black text-indigo-400 uppercase tracking-widest">Global Actuals</span>
                    </div>
                    <div className="text-3xl font-black text-white tabular-nums">{(globalSummary.actualUnits || 0).toLocaleString('de-DE')}</div>
                </div>
                <div className="bg-slate-900/50 backdrop-blur-xl border border-white/10 p-5 rounded-2xl shadow-xl">
                    <div className="flex items-center gap-3 mb-3">
                        <div className="p-2 bg-emerald-500/20 rounded-lg"><TrendingIcon /></div>
                        <span className="text-[10px] font-black text-emerald-400 uppercase tracking-widest">Global Forecast</span>
                    </div>
                    <div className="text-3xl font-black text-emerald-400 tabular-nums">{(globalSummary.forecastUnits || 0).toLocaleString('de-DE')}</div>
                </div>
            </div>

            <div className="bg-slate-900 border border-white/10 rounded-2xl overflow-hidden shadow-2xl flex-1 flex flex-col">
                <div className="p-6 border-b border-white/5 flex flex-col md:flex-row justify-between gap-4 bg-slate-800/20">
                    <h3 className="text-lg font-bold text-white uppercase tracking-tight">Product Performance Comparison</h3>
                    <div className="flex items-center gap-4">
                        {top50Ranking && (top50Ranking.eu.size > 0 || top50Ranking.uk.size > 0) && (
                            <div className="flex bg-slate-950/50 p-1 rounded-xl border border-white/10 shadow-sm">
                                <button
                                    onClick={() => setShowOnlyTop50(!showOnlyTop50)}
                                    className={`flex items-center gap-2 px-3 py-1.5 rounded-lg text-xs font-bold transition-all ${showOnlyTop50 ? 'bg-gradient-to-r from-amber-500 to-orange-500 text-white shadow-lg' : 'text-slate-400 hover:text-amber-400'}`}
                                >
                                    <span className="text-sm">🏆</span>
                                    Top 50 ({top50Mode.toUpperCase()})
                                </button>
                            </div>
                        )}
                        <input
                            type="text"
                            placeholder="Search..."
                            value={searchTerm}
                            onChange={(e) => setSearchTerm(e.target.value)}
                            className="bg-slate-950 border border-white/10 rounded-xl px-4 py-2 text-sm text-white focus:outline-none w-64"
                        />
                        <button onClick={handleExportExcel} className="p-2 bg-slate-800 hover:bg-slate-700 text-white rounded-xl border border-white/5 transition-all"><DownloadIcon /></button>
                    </div>
                </div>

                <div className="overflow-x-auto custom-scrollbar">
                    <table className="w-full text-left border-collapse">
                        <thead className="bg-slate-800/40">
                            <tr>
                                <th className="px-6 py-4 font-black text-slate-400 uppercase tracking-widest text-[10px] min-w-[300px]">
                                    <div className="flex items-center gap-2">
                                        <span>Product Details</span>
                                        <div className="flex items-center gap-1 scale-75 origin-left">
                                            <InColumnStockFilter
                                                currentFilters={stockFilter}
                                                onFilterChange={onStockFilterChange}
                                                title="Warehouse Stock"
                                            />
                                            <InColumnStockFilter
                                                currentFilters={vendorStockFilter}
                                                onFilterChange={onVendorStockFilterChange}
                                                title="Vendor Stock"
                                                options={[
                                                    'Out of Stock (0)',
                                                    'In Stock (>0)',
                                                    'In Stock (>20)',
                                                    'Low Stock (<10)',
                                                ]}
                                            />
                                        </div>
                                    </div>
                                </th>
                                <th className="px-6 py-4 font-black text-slate-400 uppercase tracking-widest text-[10px] text-center">Actuals</th>
                                <th className="px-6 py-4 font-black text-slate-400 uppercase tracking-widest text-[10px] text-center">Forecast</th>
                                <th className="px-6 py-4 font-black text-slate-400 uppercase tracking-widest text-[10px] text-center">Avg/Mo</th>
                                <th className="px-6 py-4 font-black text-slate-400 uppercase tracking-widest text-[10px]">Trend</th>
                                <th className="px-6 py-4 font-black text-slate-400 uppercase tracking-widest text-[10px] text-center">Accuracy</th>
                            </tr>
                        </thead>
                        <tbody className="divide-y divide-white/5">
                            {finalFilteredData.slice(0, displayCount).map(p => (
                                <ForecastRow
                                    key={p.asin}
                                    item={p}
                                    activeMonths={activeMonths}
                                    top50Ranking={top50Ranking}
                                    top50Mode={top50Mode}
                                    stockMap={stockMap}
                                    vendorStockMap={vendorStockMap}
                                />
                            ))}
                        </tbody>
                    </table>
                    {displayCount < finalFilteredData.length && (
                        <div className="p-6 text-center bg-slate-800/20">
                            <button onClick={() => setDisplayCount(prev => prev + 50)} className="px-6 py-2 bg-indigo-600 hover:bg-indigo-500 text-white rounded-xl text-xs font-black uppercase tracking-widest">Load More</button>
                        </div>
                    )}
                </div>
            </div>
        </div>
    );
};

export default ForecastView;