using Microsoft.AspNetCore.Mvc;
using Microsoft.AspNetCore.Mvc.RazorPages;
using Microsoft.EntityFrameworkCore;
using MoneyMap.Data;
using MoneyMap.Models;
using MoneyMap.Services;

namespace MoneyMap.Pages
{
    public class EditTransactionModel : PageModel
    {
        private readonly MoneyMapContext _db;
        private readonly IReceiptManager _receiptManager;
        private readonly IReceiptParser _receiptParser;
        private readonly IReferenceDataService _referenceDataService;
        private readonly IMerchantService _merchantService;

        public EditTransactionModel(MoneyMapContext db, IReceiptManager receiptManager, IReceiptParser receiptParser, IReferenceDataService referenceDataService, IMerchantService merchantService)
        {
            _db = db;
            _receiptManager = receiptManager;
            _receiptParser = receiptParser;
            _referenceDataService = referenceDataService;
            _merchantService = merchantService;
        }

        [BindProperty]
        public TransactionEditModel Transaction { get; set; } = new();

        [BindProperty]
        public IFormFile? ReceiptFile { get; set; }

        [BindProperty]
        public bool UseCustomCategory { get; set; }

        [BindProperty]
        public bool UseCustomMerchant { get; set; }

        public List<string> AvailableCategories { get; set; } = new();
        public List<Merchant> AvailableMerchants { get; set; } = new();
        public List<ReceiptWithItems> Receipts { get; set; } = new();

        [TempData]
        public string? SuccessMessage { get; set; }

        [TempData]
        public string? ErrorMessage { get; set; }

        public async Task<IActionResult> OnGetAsync(long id)
        {
            var transaction = await _db.Transactions
                .Include(t => t.Card)
                    .ThenInclude(c => c!.Account)
                .Include(t => t.Account)
                .Include(t => t.TransferToAccount)
                .Include(t => t.Merchant)
                .Include(t => t.Receipts)
                    .ThenInclude(r => r.LineItems)
                .FirstOrDefaultAsync(t => t.Id == id);

            if (transaction == null)
                return NotFound();

            Transaction = new TransactionEditModel
            {
                Id = transaction.Id,
                Date = transaction.Date,
                Name = transaction.Name,
                Memo = transaction.Memo,
                Amount = transaction.Amount,
                Category = transaction.Category ?? "",
                MerchantId = transaction.MerchantId,
                Notes = transaction.Notes ?? "",
                CardLabel = transaction.PaymentMethodLabel,
                AccountLabel = transaction.Card?.Account?.DisplayLabel ?? transaction.Account?.DisplayLabel ?? "None"
            };

            Receipts = transaction.Receipts?.Select(r => new ReceiptWithItems
            {
                Receipt = r,
                LineItems = r.LineItems?.OrderBy(li => li.LineNumber).ToList() ?? new List<ReceiptLineItem>()
            }).ToList() ?? new List<ReceiptWithItems>();

            await LoadAvailableCategoriesAsync();
            await LoadAvailableMerchantsAsync();

            // Check if current category exists in list
            UseCustomCategory = !string.IsNullOrWhiteSpace(Transaction.Category)
                && !AvailableCategories.Contains(Transaction.Category);

            // Check if current merchant exists in list
            UseCustomMerchant = Transaction.MerchantId.HasValue
                && !AvailableMerchants.Any(m => m.Id == Transaction.MerchantId.Value);

            return Page();
        }

        public async Task<IActionResult> OnPostAsync()
        {
            // Remove Category from model state validation if it's empty (category is optional)
            if (string.IsNullOrWhiteSpace(Transaction.Category))
            {
                ModelState.Remove("Transaction.Category");
            }

            // Remove Notes from model state validation if it's empty
            if (string.IsNullOrWhiteSpace(Transaction.Notes))
            {
                ModelState.Remove("Transaction.Notes");
            }

            // Remove MerchantName from validation (it's only used when creating new merchant)
            ModelState.Remove("Transaction.MerchantName");

            if (!ModelState.IsValid)
            {
                await LoadDataAsync();
                return Page();
            }

            var transaction = await _db.Transactions.FindAsync(Transaction.Id);
            if (transaction == null)
                return NotFound();

            // Update category and notes
            transaction.Category = string.IsNullOrWhiteSpace(Transaction.Category)
                ? ""
                : Transaction.Category.Trim();

            transaction.Notes = string.IsNullOrWhiteSpace(Transaction.Notes)
                ? ""
                : Transaction.Notes.Trim();

            // Update merchant
            if (!string.IsNullOrWhiteSpace(Transaction.MerchantName))
            {
                // Create or get merchant if custom name was entered
                var merchantId = await _merchantService.GetOrCreateIdAsync(Transaction.MerchantName);
                transaction.MerchantId = merchantId;
            }
            else if (Transaction.MerchantId.HasValue && Transaction.MerchantId.Value > 0)
            {
                // Existing merchant was selected
                transaction.MerchantId = Transaction.MerchantId.Value;
            }
            else
            {
                // No merchant selected
                transaction.MerchantId = null;
            }

            await _db.SaveChangesAsync();

            SuccessMessage = "Transaction updated successfully!";
            return RedirectToPage(new { id = Transaction.Id });
        }

        public async Task<IActionResult> OnPostUploadReceiptAsync()
        {
            if (ReceiptFile == null)
            {
                ErrorMessage = "Please select a file to upload.";
                await LoadDataAsync();
                return Page();
            }

            var result = await _receiptManager.UploadReceiptAsync(Transaction.Id, ReceiptFile);

            if (result.IsSuccess)
            {
                SuccessMessage = "Receipt uploaded successfully!";
            }
            else
            {
                ErrorMessage = result.ErrorMessage;
            }

            return RedirectToPage(new { id = Transaction.Id });
        }

        public async Task<IActionResult> OnPostUnmapReceiptAsync(long receiptId)
        {
            var receipt = await _db.Receipts.FindAsync(receiptId);
            if (receipt != null)
            {
                receipt.TransactionId = null;
                await _db.SaveChangesAsync();
                SuccessMessage = "Receipt unmapped successfully! You can now find it on the Receipts page.";
            }
            else
            {
                ErrorMessage = "Receipt not found.";
            }

            return RedirectToPage(new { id = Transaction.Id });
        }

        public async Task<IActionResult> OnPostDeleteReceiptAsync(long receiptId)
        {
            var success = await _receiptManager.DeleteReceiptAsync(receiptId);

            if (success)
            {
                SuccessMessage = "Receipt deleted permanently!";
            }
            else
            {
                ErrorMessage = "Failed to delete receipt.";
            }

            return RedirectToPage(new { id = Transaction.Id });
        }

        public async Task<IActionResult> OnPostParseReceiptAsync(long receiptId)
        {
            var result = await _receiptParser.ParseReceiptAsync(receiptId);

            if (result.IsSuccess)
            {
                SuccessMessage = result.Message;
            }
            else
            {
                ErrorMessage = result.Message;
            }

            return RedirectToPage(new { id = Transaction.Id });
        }

        private async Task LoadDataAsync()
        {
            await LoadAvailableCategoriesAsync();
            await LoadAvailableMerchantsAsync();

            var transaction = await _db.Transactions
                .Include(t => t.Receipts)
                    .ThenInclude(r => r.LineItems)
                .FirstOrDefaultAsync(t => t.Id == Transaction.Id);

            if (transaction != null)
            {
                Receipts = transaction.Receipts?.Select(r => new ReceiptWithItems
                {
                    Receipt = r,
                    LineItems = r.LineItems?.OrderBy(li => li.LineNumber).ToList() ?? new List<ReceiptLineItem>()
                }).ToList() ?? new List<ReceiptWithItems>();
            }
        }

        private async Task LoadAvailableCategoriesAsync()
        {
            AvailableCategories = await _referenceDataService.GetAvailableCategoriesAsync();
        }

        private async Task LoadAvailableMerchantsAsync()
        {
            AvailableMerchants = await _referenceDataService.GetAvailableMerchantsAsync();
        }

        public class TransactionEditModel
        {
            public long Id { get; set; }
            public DateTime Date { get; set; }
            public string Name { get; set; } = "";
            public string Memo { get; set; } = "";
            public decimal Amount { get; set; }
            public string Category { get; set; } = "";
            public int? MerchantId { get; set; }
            public string? MerchantName { get; set; } = "";
            public string? Notes { get; set; } = "";
            public string CardLabel { get; set; } = "";
            public string AccountLabel { get; set; } = "";
        }

        public class ReceiptWithItems
        {
            public Receipt Receipt { get; set; } = null!;
            public List<ReceiptLineItem> LineItems { get; set; } = new();
        }
    }
}