using Microsoft.EntityFrameworkCore;
using MealPlanner.Data;
using MealPlanner.Models;

namespace MealPlanner.Services;

public class ShoppingListService(AppDbContext db)
{
    public async Task<List<ShoppingItem>> GetShoppingListAsync(Guid mealPlanId, string userId)
    {
        var plan = await db.MealPlans
            .Include(p => p.Entries)
                .ThenInclude(e => e.Recipe)
                    .ThenInclude(r => r.Ingredients)
            .FirstOrDefaultAsync(p => p.Id == mealPlanId);

        if (plan is null) return [];
        if (plan.UserId != userId) throw new UnauthorizedAccessException();

        var settings = await db.UserSettings.FindAsync(userId);
        int householdSize = settings?.HouseholdSize ?? 2;

        var checkedItems = await db.CheckedShoppingItems
            .Where(c => c.MealPlanId == mealPlanId && c.UserId == userId)
            .ToDictionaryAsync(c => c.ItemName.ToLowerInvariant(), c => c.IsChecked);

        // Aggregate ingredients
        var aggregated = new Dictionary<string, ShoppingItem>(StringComparer.OrdinalIgnoreCase);

        foreach (var entry in plan.Entries)
        {
            foreach (var ing in entry.Recipe.Ingredients)
            {
                var key = ing.Name.Trim().ToLowerInvariant();

                if (!aggregated.TryGetValue(key, out var item))
                {
                    item = new ShoppingItem
                    {
                        Name = ing.Name.Trim(),
                        Unit = ing.Unit,
                        Category = ing.Category,
                        TotalAmount = null,
                        IsChecked = checkedItems.TryGetValue(key, out var chk) && chk,
                    };
                    aggregated[key] = item;
                }

                if (ing.Amount.HasValue)
                {
                    item.TotalAmount = (item.TotalAmount ?? 0) + ing.Amount.Value * householdSize;
                }
            }
        }

        return [.. aggregated.Values.OrderBy(i => i.Category).ThenBy(i => i.Name)];
    }

    public async Task<CheckedShoppingItem> ToggleCheckAsync(Guid mealPlanId, string itemName, string userId)
    {
        var plan = await db.MealPlans.FindAsync(mealPlanId);
        if (plan is null) throw new KeyNotFoundException("Meal plan not found");
        if (plan.UserId != userId) throw new UnauthorizedAccessException();

        var key = itemName.ToLowerInvariant();

        var existing = await db.CheckedShoppingItems
            .FirstOrDefaultAsync(c => c.MealPlanId == mealPlanId && c.UserId == userId
                && c.ItemName.ToLower() == key);

        if (existing is null)
        {
            existing = new CheckedShoppingItem
            {
                Id = Guid.NewGuid(),
                MealPlanId = mealPlanId,
                ItemName = itemName,
                UserId = userId,
                IsChecked = true,
            };
            db.CheckedShoppingItems.Add(existing);
        }
        else
        {
            existing.IsChecked = !existing.IsChecked;
        }

        await db.SaveChangesAsync();
        return existing;
    }
}