using QuestPDF.Fluent;
using QuestPDF.Helpers;
using QuestPDF.Infrastructure;
using System;
using System.Collections.Generic;
using System.Linq;
using timetracker.Shared;

namespace timetracker.Server.Services
{
    public class PdfGeneratorService
    {
        public PdfGeneratorService()
        {
            // Configure QuestPDF community license
            QuestPDF.Settings.License = LicenseType.Community;
        }

        public byte[] GenerateTimesheetPdf(
            User user, 
            Tenant? tenant, 
            AppSettings settings, 
            int year, 
            int month, 
            List<WorkDay> workDays, 
            List<VacationDay> vacationDays, 
            List<PublicHoliday> holidays)
        {
            var document = Document.Create(container =>
            {
                container.Page(page =>
                {
                    page.Size(PageSizes.A4);
                    page.Margin(2, Unit.Centimetre);
                    page.PageColor(Colors.White);
                    page.DefaultTextStyle(x => x.FontSize(10).FontFamily(Fonts.Arial));

                    page.Header().Element(c => ComposeHeader(c, user, tenant, year, month));
                    page.Content().Element(c => ComposeContent(c, user, settings, year, month, workDays, vacationDays, holidays));
                    page.Footer().Element(ComposeFooter);
                });
            });

            return document.GeneratePdf();
        }

        private void ComposeHeader(IContainer container, User user, Tenant? tenant, int year, int month)
        {
            var monthName = new DateTime(year, month, 1).ToString("MMMM yyyy", new System.Globalization.CultureInfo("de-DE"));
            var companyName = tenant?.Name ?? "Hauptdomain";

            container.Row(row =>
            {
                row.RelativeItem().Column(column =>
                {
                    column.Item().Text($"Stundenzettel - {monthName}").FontSize(20).SemiBold().FontColor(Colors.Blue.Darken2);
                    column.Item().Text($"Mitarbeiter: {user.Username}").FontSize(14).SemiBold();
                    column.Item().PaddingTop(2).Text($"Firma: {companyName}").FontSize(11).FontColor(Colors.Grey.Darken2);
                });
            });
        }

        private void ComposeContent(IContainer container, User user, AppSettings settings, int year, int month, List<WorkDay> workDays, List<VacationDay> vacationDays, List<PublicHoliday> holidays)
        {
            TimeSpan totalNet = TimeSpan.Zero;
            TimeSpan totalTarget = TimeSpan.Zero;
            TimeSpan totalOvertime = TimeSpan.Zero;

            container.PaddingVertical(1, Unit.Centimetre).Column(column =>
            {
                column.Item().Element(c => ComposeTable(c, settings, year, month, workDays, vacationDays, holidays, out totalNet, out totalTarget, out totalOvertime));
                
                column.Item().PaddingTop(25).Element(c => ComposeSummary(c, totalNet, totalTarget, totalOvertime));

                column.Item().PaddingTop(50).Element(ComposeSignatures);
            });
        }

        private void ComposeTable(IContainer container, AppSettings settings, int year, int month, List<WorkDay> workDays, List<VacationDay> vacationDays, List<PublicHoliday> holidays, out TimeSpan totalNetOut, out TimeSpan totalTargetOut, out TimeSpan totalOvertimeOut)
        {
            var holidayMap = holidays.ToDictionary(h => h.Date, h => h.Name);
            var vacationSet = vacationDays.Select(v => v.Date).ToHashSet();
            var daysInMonth = DateTime.DaysInMonth(year, month);
            
            var totalNet = TimeSpan.Zero;
            var totalTarget = TimeSpan.Zero;
            var totalOvertime = TimeSpan.Zero;

            container.Table(table =>
            {
                table.ColumnsDefinition(columns =>
                {
                    columns.ConstantColumn(70);  // Datum
                    columns.ConstantColumn(50);  // Start
                    columns.ConstantColumn(50);  // Ende
                    columns.ConstantColumn(60);  // Pause
                    columns.ConstantColumn(60);  // Netto
                    columns.ConstantColumn(60);  // Gleitzeit
                    columns.RelativeColumn();    // Info
                });

                table.Header(header =>
                {
                    header.Cell().Element(CellStyle).Text("Datum");
                    header.Cell().Element(CellStyle).AlignRight().Text("Start");
                    header.Cell().Element(CellStyle).AlignRight().Text("Ende");
                    header.Cell().Element(CellStyle).AlignRight().Text("Pause");
                    header.Cell().Element(CellStyle).AlignRight().Text("Netto");
                    header.Cell().Element(CellStyle).AlignRight().Text("Gleitzeit");
                    header.Cell().Element(CellStyle).Text("Info/Status");

                    static IContainer CellStyle(IContainer container)
                    {
                        return container.DefaultTextStyle(x => x.SemiBold()).PaddingVertical(5).BorderBottom(1).BorderColor(Colors.Black);
                    }
                });

                for (int day = 1; day <= daysInMonth; day++)
                {
                    var date = new DateOnly(year, month, day);
                    var wd = workDays.FirstOrDefault(w => w.Date == date);
                    var isWorkDay = settings.IsWorkDay(date.DayOfWeek);
                    var isVacation = vacationSet.Contains(date);
                    var holidayName = holidayMap.GetValueOrDefault(date);

                    TimeSpan? net = null;
                    TimeSpan breakSum = TimeSpan.Zero;

                    if (wd?.StartTime != null && wd.EndTime != null)
                    {
                        var gross = wd.EndTime.Value.ToTimeSpan() - wd.StartTime.Value.ToTimeSpan();
                        breakSum = wd.Breaks
                            .Where(b => b.StartTime.HasValue && b.EndTime.HasValue && b.EndTime > b.StartTime)
                            .Aggregate(TimeSpan.Zero, (s, b) =>
                                s + (b.EndTime!.Value.ToTimeSpan() - b.StartTime!.Value.ToTimeSpan()));
                        var minMinutes = gross.TotalHours >= 9.0 ? 45 : 30;
                        var minBreak = TimeSpan.FromMinutes(Math.Max(minMinutes, settings.MinimumBreakMinutes));
                        var finalBreak = breakSum > minBreak ? breakSum : minBreak;
                        net = gross - finalBreak;
                        if (net < TimeSpan.Zero) net = null;
                    }

                    var target = isWorkDay ? TimeSpan.FromHours(settings.DailyTargetHours) : TimeSpan.Zero;
                    var overtime = net.HasValue ? net.Value - target : TimeSpan.Zero;

                    if (net.HasValue) totalNet += net.Value;
                    if (isWorkDay) totalTarget += target;
                    if (isWorkDay && net.HasValue) totalOvertime += overtime;

                    string status = "";
                    if (!string.IsNullOrEmpty(holidayName)) status = holidayName;
                    else if (isVacation) status = "Urlaub";
                    else if (!isWorkDay) status = "Wochenende";

                    var bgColor = Colors.White;
                    if (!isWorkDay || !string.IsNullOrEmpty(holidayName)) bgColor = Colors.Grey.Lighten4;
                    if (isVacation) bgColor = Colors.Orange.Lighten4;

                    table.Cell().Element(c => CellStyle(c, bgColor)).Text(date.ToString("dd.MM.yyyy"));
                    table.Cell().Element(c => CellStyle(c, bgColor)).AlignRight().Text(wd?.StartTime?.ToString(@"HH\:mm") ?? "-");
                    table.Cell().Element(c => CellStyle(c, bgColor)).AlignRight().Text(wd?.EndTime?.ToString(@"HH\:mm") ?? "-");
                    table.Cell().Element(c => CellStyle(c, bgColor)).AlignRight().Text(net.HasValue ? FormatTs(breakSum) : "-");
                    table.Cell().Element(c => CellStyle(c, bgColor)).AlignRight().Text(net.HasValue ? FormatTs(net.Value) : "-");
                    
                    var overtimeColor = overtime < TimeSpan.Zero ? Colors.Red.Darken2 : Colors.Green.Darken2;
                    table.Cell().Element(c => CellStyle(c, bgColor)).AlignRight().Text(net.HasValue ? FormatTs(overtime, true) : "-").FontColor(net.HasValue && overtime != TimeSpan.Zero ? overtimeColor : Colors.Black);
                    
                    table.Cell().Element(c => CellStyle(c, bgColor)).Text(status).FontColor(Colors.Grey.Darken2);

                    static IContainer CellStyle(IContainer container, string bgColor)
                    {
                        return container.BorderBottom(1).BorderColor(Colors.Grey.Lighten3).Background(bgColor).PaddingVertical(3).PaddingHorizontal(2);
                    }
                }
            });

            totalNetOut = totalNet;
            totalTargetOut = totalTarget;
            totalOvertimeOut = totalOvertime;
        }

        private void ComposeSummary(IContainer container, TimeSpan totalNet, TimeSpan totalTarget, TimeSpan totalOvertime)
        {
            container.Background(Colors.Grey.Lighten4).Padding(10).Row(row =>
            {
                row.RelativeItem().Column(column =>
                {
                    column.Item().Text("Zusammenfassung").SemiBold();
                    column.Item().Text($"Soll-Stunden: {FormatTs(totalTarget)}");
                    column.Item().Text($"Ist-Stunden: {FormatTs(totalNet)}");
                    
                    var overtimeColor = totalOvertime < TimeSpan.Zero ? Colors.Red.Darken2 : Colors.Green.Darken2;
                    column.Item().Text($"Saldo: {FormatTs(totalOvertime, true)}").SemiBold().FontColor(totalOvertime != TimeSpan.Zero ? overtimeColor : Colors.Black);
                });
            });
        }

        private void ComposeSignatures(IContainer container)
        {
            container.Row(row =>
            {
                row.RelativeItem().Column(column =>
                {
                    column.Item().LineHorizontal(1);
                    column.Item().PaddingTop(5).Text("Datum, Unterschrift Mitarbeiter").FontSize(10);
                });
                row.ConstantItem(50); // space
                row.RelativeItem().Column(column =>
                {
                    column.Item().LineHorizontal(1);
                    column.Item().PaddingTop(5).Text("Datum, Unterschrift Arbeitgeber").FontSize(10);
                });
            });
        }

        private void ComposeFooter(IContainer container)
        {
            container.AlignCenter().Text(x =>
            {
                x.Span("Seite ");
                x.CurrentPageNumber();
                x.Span(" von ");
                x.TotalPages();
            });
        }

        private static string FormatTs(TimeSpan ts, bool sign = false)
        {
            var neg = ts < TimeSpan.Zero;
            var abs = neg ? ts.Negate() : ts;
            var h = (int)abs.TotalHours;
            var m = abs.Minutes;
            if (!sign) return $"{h}:{m:D2} h";
            return neg ? $"-{h}:{m:D2} h" : $"+{h}:{m:D2} h";
        }
    }
}