using System;
using System.Collections.ObjectModel;
using System.Linq;
using System.Windows.Input;

namespace XLAB2
{
    internal sealed class CreateDocumentWindowViewModel : ObservableObject
    {
        private DateTime? _acceptedOn;
        private string _documentSequenceNumber;
        private GroupOption _selectedAccountingBook;
        private GroupOption _selectedDocumentType;
        private string _validationMessage;

        public CreateDocumentWindowViewModel(DocumentEditorResult seed, DocumentNumberDirectory directory)
        {
            if (directory == null)
            {
                throw new ArgumentNullException("directory");
            }

            AccountingBooks = new ObservableCollection<GroupOption>(directory.AccountingBooks ?? Array.Empty<GroupOption>());
            DocumentTypes = new ObservableCollection<GroupOption>(directory.DocumentTypes ?? Array.Empty<GroupOption>());

            _acceptedOn = seed != null ? seed.AcceptedOn : DateTime.Today;
            _documentSequenceNumber = seed == null ? string.Empty : seed.DocumentSequenceNumber ?? string.Empty;
            _selectedAccountingBook = ResolveSelectedOption(AccountingBooks, seed == null ? null : seed.AccountingBookKey);
            _selectedDocumentType = ResolveSelectedOption(DocumentTypes, seed == null ? null : seed.DocumentTypeKey);

            ConfirmCommand = new RelayCommand(Confirm);
            CancelCommand = new RelayCommand(Cancel);
        }

        public event EventHandler<bool?> CloseRequested;

        public DateTime? AcceptedOn
        {
            get { return _acceptedOn; }
            set
            {
                if (SetProperty(ref _acceptedOn, value))
                {
                    ClearValidationMessage();
                }
            }
        }

        public ObservableCollection<GroupOption> AccountingBooks { get; private set; }

        public ICommand CancelCommand { get; private set; }

        public ICommand ConfirmCommand { get; private set; }

        public string DocumentNumber
        {
            get
            {
                return DocumentNumberFormatter.Build(
                    SelectedDocumentType == null ? null : SelectedDocumentType.Title,
                    SelectedAccountingBook == null ? null : SelectedAccountingBook.Title,
                    DocumentSequenceNumber);
            }
        }

        public string DocumentSequenceNumber
        {
            get { return _documentSequenceNumber; }
            set
            {
                if (SetProperty(ref _documentSequenceNumber, value))
                {
                    ClearValidationMessage();
                    OnPropertyChanged("DocumentNumber");
                }
            }
        }

        public ObservableCollection<GroupOption> DocumentTypes { get; private set; }

        public GroupOption SelectedAccountingBook
        {
            get { return _selectedAccountingBook; }
            set
            {
                if (SetProperty(ref _selectedAccountingBook, value))
                {
                    ClearValidationMessage();
                    OnPropertyChanged("DocumentNumber");
                }
            }
        }

        public GroupOption SelectedDocumentType
        {
            get { return _selectedDocumentType; }
            set
            {
                if (SetProperty(ref _selectedDocumentType, value))
                {
                    ClearValidationMessage();
                    OnPropertyChanged("DocumentNumber");
                }
            }
        }

        public string ValidationMessage
        {
            get { return _validationMessage; }
            private set { SetProperty(ref _validationMessage, value); }
        }

        public DocumentEditorResult ToResult()
        {
            return new DocumentEditorResult
            {
                AccountingBookKey = SelectedAccountingBook == null ? string.Empty : SelectedAccountingBook.Key,
                AccountingBookTitle = SelectedAccountingBook == null ? string.Empty : SelectedAccountingBook.Title,
                DocumentNumber = DocumentNumber,
                DocumentSequenceNumber = DocumentSequenceNumber == null ? string.Empty : DocumentSequenceNumber.Trim(),
                DocumentTypeKey = SelectedDocumentType == null ? string.Empty : SelectedDocumentType.Key,
                DocumentTypeTitle = SelectedDocumentType == null ? string.Empty : SelectedDocumentType.Title,
                AcceptedOn = AcceptedOn.HasValue ? AcceptedOn.Value : DateTime.Today,
                IssuedOn = null
            };
        }

        private void Cancel(object parameter)
        {
            RaiseCloseRequested(false);
        }

        private void ClearValidationMessage()
        {
            if (!string.IsNullOrEmpty(ValidationMessage))
            {
                ValidationMessage = string.Empty;
            }
        }

        private void Confirm(object parameter)
        {
            if (SelectedDocumentType == null)
            {
                ValidationMessage = "Выберите тип документа.";
                return;
            }

            if (SelectedAccountingBook == null)
            {
                ValidationMessage = "Выберите книгу учета.";
                return;
            }

            if (string.IsNullOrWhiteSpace(DocumentSequenceNumber))
            {
                ValidationMessage = "Введите номер документа.";
                return;
            }

            if (!AcceptedOn.HasValue)
            {
                ValidationMessage = "Укажите дату приемки.";
                return;
            }

            if (DocumentNumber.Length > DocumentNumberFormatter.MaxLength)
            {
                ValidationMessage = string.Format(
                    "Итоговый номер документа не должен превышать {0} символов.",
                    DocumentNumberFormatter.MaxLength);
                return;
            }

            ValidationMessage = string.Empty;
            RaiseCloseRequested(true);
        }

        private static GroupOption ResolveSelectedOption(ObservableCollection<GroupOption> items, string preferredKey)
        {
            if (items == null || items.Count == 0)
            {
                return null;
            }

            if (!string.IsNullOrWhiteSpace(preferredKey))
            {
                var matchingItem = items.FirstOrDefault(delegate(GroupOption item)
                {
                    return item != null
                           && string.Equals(item.Key, preferredKey.Trim(), StringComparison.OrdinalIgnoreCase);
                });

                if (matchingItem != null)
                {
                    return matchingItem;
                }
            }

            return items[0];
        }

        private void RaiseCloseRequested(bool? dialogResult)
        {
            var handler = CloseRequested;
            if (handler != null)
            {
                handler(this, dialogResult);
            }
        }
    }
}