game-ideas/src/GameIdeas/Server/GameIdeas.WebAPI/Services/Games/GameReadService.cs

using AutoMapper;
using GameIdeas.Shared.Constants;
using GameIdeas.Shared.Dto;
using GameIdeas.Shared.Exceptions;
using GameIdeas.Shared.Model;
using GameIdeas.WebAPI.Context;
using Microsoft.EntityFrameworkCore;
using System.Linq.Expressions;

namespace GameIdeas.WebAPI.Services.Games;

public class GameReadService(GameIdeasContext context, IMapper mapper) : IGameReadService
{
    public async Task<IEnumerable<GameDto>> GetGames(GameFilterDto filter)
    {
        var query = context.Games
            .Include(g => g.GamePlatforms).ThenInclude(gp => gp.Platform)
            .Include(g => g.GameProperties)
            .Include(g => g.GameTags).ThenInclude(gt => gt.Tag)
            .Include(g => g.GamePublishers)
            .Include(g => g.GameDevelopers)
            .AsQueryable();

        ApplyFilter(ref query, filter);

        ApplyOrder(ref query, filter);

        var games = await query.Skip((filter.CurrentPage - 1) * GlobalConstants.NUMBER_PER_PAGE)
            .Take(GlobalConstants.NUMBER_PER_PAGE)
            .ToListAsync();

        if (!string.IsNullOrWhiteSpace(filter.Title))
        {
            games = ApplySearchGameFilter(games, filter).ToList();
        }

        return mapper.Map<IEnumerable<GameDto>>(games);
    }

    public async Task<GameDetailDto> GetGameById(int gameId)
    {
        var game = await context.Games
            .Include(g => g.CreationUser)
            .Include(g => g.ModificationUser)
            .Include(g => g.GamePlatforms).ThenInclude(p => p.Platform)
            .Include(g => g.GameProperties).ThenInclude(p => p.Property)
            .Include(g => g.GameTags).ThenInclude(p => p.Tag)
            .Include(g => g.GamePublishers).ThenInclude(p => p.Publisher)
            .Include(g => g.GameDevelopers).ThenInclude(p => p.Developer)
            .FirstOrDefaultAsync(g => g.Id == gameId);

        return game == null
            ? throw new NotFoundException($"[{typeof(Game).FullName}] with ID {gameId} has not been found in context")
            : mapper.Map<GameDetailDto>(game);
    }

    private static void ApplyOrder(ref IQueryable<Game> query, GameFilterDto filter)
    {
        if (filter.SortType != null && filter.SortPropertyName != null)
        {
            var param = Expression.Parameter(typeof(Game), "x");
            Expression propertyAccess = Expression.PropertyOrField(param, filter.SortPropertyName);
            var converted = Expression.Convert(propertyAccess, typeof(object));
            var lambda = Expression.Lambda<Func<Game, object>>(converted, param);
            
            if (filter.SortType == Shared.Enum.SortType.Ascending)
            {
                query = Queryable.OrderBy(query, lambda);
            }
            else
            {
                query = Queryable.OrderByDescending(query, lambda);
            }
        }
    }

    private static void ApplyFilter(ref IQueryable<Game> query, GameFilterDto filter)
    {
        if (filter.PlatformIds != null)
        {
            query = query.Where(game => filter.PlatformIds.All(plat =>
                game.GamePlatforms.Any(gp => gp.PlatformId == plat)));
        }
    }

    private static IEnumerable<Game> ApplySearchGameFilter(IEnumerable<Game> query, GameFilterDto filter)
    {
        var keywords = filter.Title?
                        .Split([' '], StringSplitOptions.RemoveEmptyEntries)
                        .Select(k => k.Trim())
                        .ToArray() ?? [];

        query = query
            .Where(game => keywords.All(
                kw => game.Title.Contains(kw, StringComparison.OrdinalIgnoreCase)
            ))
            .OrderBy(game => keywords.Min(kw =>
                game.Title.IndexOf(kw, StringComparison.OrdinalIgnoreCase)
            ))
            .ThenBy(game => game.Title.Length);

        return query;
    }
}