using System;
using System.Collections.ObjectModel;
using System.IO;
using System.Linq;
using System.Text;
using CommunityToolkit.Mvvm.ComponentModel;
using CommunityToolkit.Mvvm.Input;
using Lagerprogramm.Models;
using Lagerprogramm.Services;

namespace Lagerprogramm.ViewModels;

public partial class DeductionsViewModel : ObservableObject
{
    private readonly JsonDataService _dataService;
    private readonly AppData _appData;

    public AppData AppData => _appData;

    [ObservableProperty]
    private ObservableCollection<Deduction> _deductions = new();

    [ObservableProperty]
    private ObservableCollection<TransactionLine> _lines = new();

    [ObservableProperty]
    private DateTime _date = DateTime.Now;

    [ObservableProperty]
    private string _comment = string.Empty;

    [ObservableProperty]
    private string _customer = string.Empty;

    [ObservableProperty]
    private bool _generateDeliveryNote;

    public ObservableCollection<string> PartNumbers { get; } = new();

    public DeductionsViewModel(JsonDataService dataService, AppData appData)
    {
        _dataService = dataService;
        _appData = appData;
        RefreshPartNumbers();
        foreach (var d in appData.Deductions.OrderByDescending(d => d.Date))
            Deductions.Add(d);
        Lines.Add(new TransactionLine());
    }

    [RelayCommand]
    private void AddLine() => Lines.Add(new TransactionLine());

    [RelayCommand]
    private void RemoveLine(TransactionLine? line)
    {
        if (line is null) return;
        Lines.Remove(line);
    }

    [RelayCommand]
    private void SearchPart(TransactionLine? line)
    {
    }

    [RelayCommand]
    private void SearchDeduction()
    {
    }

    [RelayCommand]
    private void Save()
    {
        if (Lines.Count == 0) return;
        if (Lines.Any(l => string.IsNullOrWhiteSpace(l.PartInternalNumber) || l.Quantity <= 0))
            return;

        foreach (var line in Lines)
        {
            var part = _appData.Parts.FirstOrDefault(p => p.InternalPartNumber == line.PartInternalNumber);
            if (part is null || part.StockQuantity < line.Quantity)
                return;
        }

        var deduction = new Deduction
        {
            Date = Date,
            Comment = Comment.Trim(),
            Customer = Customer.Trim(),
            GenerateDeliveryNote = GenerateDeliveryNote,
            Lines = Lines.Select(l => new TransactionLine
            {
                PartInternalNumber = l.PartInternalNumber.Trim(),
                Quantity = l.Quantity
            }).ToList()
        };
        _appData.Deductions.Add(deduction);
        Deductions.Insert(0, deduction);

        foreach (var line in deduction.Lines)
        {
            var part = _appData.Parts.FirstOrDefault(p => p.InternalPartNumber == line.PartInternalNumber);
            if (part is not null)
                part.StockQuantity -= line.Quantity;
        }

        _dataService.Save(_appData);

        if (GenerateDeliveryNote)
            WriteDeliveryNote(deduction);

        Comment = string.Empty;
        Customer = string.Empty;
        GenerateDeliveryNote = false;
        Date = DateTime.Now;
        Lines.Clear();
        Lines.Add(new TransactionLine());
        RefreshPartNumbers();
    }

    [RelayCommand]
    private void DeleteDeduction(Deduction? deduction)
    {
        if (deduction is null) return;
        foreach (var line in deduction.Lines)
        {
            var part = _appData.Parts.FirstOrDefault(p => p.InternalPartNumber == line.PartInternalNumber);
            if (part is not null)
                part.StockQuantity += line.Quantity;
        }
        _appData.Deductions.Remove(deduction);
        Deductions.Remove(deduction);
        _dataService.Save(_appData);
        RefreshPartNumbers();
    }

    private void RefreshPartNumbers()
    {
        PartNumbers.Clear();
        foreach (var p in _appData.Parts.OrderBy(p => p.InternalPartNumber))
            PartNumbers.Add(p.InternalPartNumber);
    }

    private void WriteDeliveryNote(Deduction deduction)
    {
        var path = string.IsNullOrWhiteSpace(_appData.Settings.StoragePath)
            ? Environment.GetFolderPath(Environment.SpecialFolder.UserProfile)
            : _appData.Settings.StoragePath;
        if (!Directory.Exists(path))
            Directory.CreateDirectory(path);

        var fileName = Path.Combine(path, $"DeliveryNote_{deduction.Id:N}_{deduction.Date:yyyyMMdd}.txt");
        var sb = new StringBuilder();
        sb.AppendLine("Delivery Note");
        sb.AppendLine($"Company: {_appData.Settings.CompanyName}");
        sb.AppendLine($"Date: {deduction.Date:yyyy-MM-dd}");
        sb.AppendLine($"Customer: {deduction.Customer}");
        sb.AppendLine();
        foreach (var line in deduction.Lines)
        {
            var part = _appData.Parts.FirstOrDefault(p => p.InternalPartNumber == line.PartInternalNumber);
            sb.AppendLine($"Part: {line.PartInternalNumber}  Qty: {line.Quantity}");
            if (part is not null)
            {
                sb.AppendLine($"  Description: {part.Description}");
                sb.AppendLine($"  MSRP: {part.Msrp:C}");
                sb.AppendLine($"  Line Total: {part.Msrp * line.Quantity:C}");
            }
            sb.AppendLine();
        }
        var grandTotal = deduction.Lines
            .Sum(l => (_appData.Parts.FirstOrDefault(p => p.InternalPartNumber == l.PartInternalNumber)?.Msrp ?? 0) * l.Quantity);
        sb.AppendLine($"Grand Total: {grandTotal:C}");
        sb.AppendLine();
        sb.AppendLine($"Comment: {deduction.Comment}");

        File.WriteAllText(fileName, sb.ToString());
    }
}