using LctMonolith.Models.Database;
using Microsoft.EntityFrameworkCore;
using Serilog;
using System.Text.Json;
using LctMonolith.Database.UnitOfWork;
using LctMonolith.Services.Contracts;

namespace LctMonolith.Services;

/// <summary>
/// Store purchase operations and inventory management.
/// </summary>
public class StoreService : IStoreService
{
    private readonly IUnitOfWork _uow;

    public StoreService(IUnitOfWork uow)
    {
        _uow = uow;
    }

    public async Task<IEnumerable<StoreItem>> GetActiveItemsAsync(CancellationToken ct = default)
    {
        return await _uow.StoreItems.Query(i => i.IsActive).ToListAsync(ct);
    }

    public async Task<UserInventoryItem> PurchaseAsync(Guid userId, Guid itemId, int quantity, CancellationToken ct = default)
    {
        if (quantity <= 0) throw new ArgumentOutOfRangeException(nameof(quantity));
        var user = await _uow.Users.Query(u => u.Id == userId).FirstOrDefaultAsync(ct) ?? throw new KeyNotFoundException("User not found");
        var item = await _uow.StoreItems.Query(i => i.Id == itemId && i.IsActive).FirstOrDefaultAsync(ct) ?? throw new KeyNotFoundException("Item not found or inactive");
        var totalPrice = item.Price * quantity;
        if (user.Mana < totalPrice) throw new InvalidOperationException("Insufficient mana");
        if (item.Stock.HasValue && item.Stock.Value < quantity) throw new InvalidOperationException("Insufficient stock");

        user.Mana -= totalPrice;
        if (item.Stock.HasValue) item.Stock -= quantity;

        var inv = await _uow.UserInventoryItems.FindAsync(userId, itemId);
        if (inv == null)
        {
            inv = new UserInventoryItem
            {
                UserId = userId,
                StoreItemId = itemId,
                Quantity = quantity,
                AcquiredAt = DateTime.UtcNow
            };
            await _uow.UserInventoryItems.AddAsync(inv, ct);
        }
        else
        {
            inv.Quantity += quantity;
        }

        await _uow.Transactions.AddAsync(new Transaction
        {
            UserId = userId,
            StoreItemId = itemId,
            Type = TransactionType.Purchase,
            ManaAmount = -totalPrice
        }, ct);

        await _uow.EventLogs.AddAsync(new EventLog
        {
            Type = EventType.ItemPurchased,
            UserId = userId,
            Data = JsonSerializer.Serialize(new { itemId, quantity, totalPrice })
        }, ct);

        await _uow.SaveChangesAsync(ct);
        Log.Information("User {User} purchased {Qty} of {Item}", userId, quantity, itemId);
        return inv;
    }
}