Kavita/API/Extensions/QueryableExtensions.cs

using System.Linq;
using System.Threading.Tasks;
using API.Data.Misc;
using API.Entities;
using API.Entities.Enums;
using Microsoft.EntityFrameworkCore;

namespace API.Extensions;

public static class QueryableExtensions
{
    public static IQueryable<Series> RestrictAgainstAgeRestriction(this IQueryable<Series> queryable, AgeRestriction restriction)
    {
        if (restriction.AgeRating == AgeRating.NotApplicable) return queryable;
        var q = queryable.Where(s => s.Metadata.AgeRating <= restriction.AgeRating);
        if (!restriction.IncludeUnknowns)
        {
            return q.Where(s => s.Metadata.AgeRating != AgeRating.Unknown);
        }

        return q;
    }

    public static IQueryable<CollectionTag> RestrictAgainstAgeRestriction(this IQueryable<CollectionTag> queryable, AgeRestriction restriction)
    {
        if (restriction.AgeRating == AgeRating.NotApplicable) return queryable;

        if (restriction.IncludeUnknowns)
        {
            return queryable.Where(c => c.SeriesMetadatas.All(sm =>
                sm.AgeRating <= restriction.AgeRating));
        }

        return queryable.Where(c => c.SeriesMetadatas.All(sm =>
            sm.AgeRating <= restriction.AgeRating && sm.AgeRating > AgeRating.Unknown));
    }

    public static IQueryable<Genre> RestrictAgainstAgeRestriction(this IQueryable<Genre> queryable, AgeRestriction restriction)
    {
        if (restriction.AgeRating == AgeRating.NotApplicable) return queryable;

        if (restriction.IncludeUnknowns)
        {
            return queryable.Where(c => c.SeriesMetadatas.All(sm =>
                sm.AgeRating <= restriction.AgeRating));
        }

        return queryable.Where(c => c.SeriesMetadatas.All(sm =>
            sm.AgeRating <= restriction.AgeRating && sm.AgeRating > AgeRating.Unknown));
    }

    public static IQueryable<Tag> RestrictAgainstAgeRestriction(this IQueryable<Tag> queryable, AgeRestriction restriction)
    {
        if (restriction.AgeRating == AgeRating.NotApplicable) return queryable;

        if (restriction.IncludeUnknowns)
        {
            return queryable.Where(c => c.SeriesMetadatas.All(sm =>
                sm.AgeRating <= restriction.AgeRating));
        }

        return queryable.Where(c => c.SeriesMetadatas.All(sm =>
            sm.AgeRating <= restriction.AgeRating && sm.AgeRating > AgeRating.Unknown));
    }

    public static IQueryable<Person> RestrictAgainstAgeRestriction(this IQueryable<Person> queryable, AgeRestriction restriction)
    {
        if (restriction.AgeRating == AgeRating.NotApplicable) return queryable;

        if (restriction.IncludeUnknowns)
        {
            return queryable.Where(c => c.SeriesMetadatas.All(sm =>
                sm.AgeRating <= restriction.AgeRating));
        }

        return queryable.Where(c => c.SeriesMetadatas.All(sm =>
            sm.AgeRating <= restriction.AgeRating && sm.AgeRating > AgeRating.Unknown));
    }

    public static IQueryable<ReadingList> RestrictAgainstAgeRestriction(this IQueryable<ReadingList> queryable, AgeRestriction restriction)
    {
        if (restriction.AgeRating == AgeRating.NotApplicable) return queryable;
        var q = queryable.Where(rl => rl.AgeRating <= restriction.AgeRating);

        if (!restriction.IncludeUnknowns)
        {
            return q.Where(rl => rl.AgeRating != AgeRating.Unknown);
        }

        return q;
    }

    public static Task<AgeRestriction> GetUserAgeRestriction(this DbSet<AppUser> queryable, int userId)
    {
        if (userId < 1)
        {
            return Task.FromResult(new AgeRestriction()
            {
                AgeRating = AgeRating.NotApplicable,
                IncludeUnknowns = true
            });
        }
        return queryable
            .AsNoTracking()
            .Where(u => u.Id == userId)
            .Select(u =>
                new AgeRestriction(){
                    AgeRating = u.AgeRestriction,
                    IncludeUnknowns = u.AgeRestrictionIncludeUnknowns
                })
            .SingleAsync();
    }

    /// <summary>
    /// Only applies the Take if it's greater than 0
    /// </summary>
    /// <param name="queryable"></param>
    /// <param name="takeAmt"></param>
    /// <typeparam name="T"></typeparam>
    /// <returns></returns>
    public static IQueryable<T> TakeIfGreaterThan0<T>(this IQueryable<T> queryable, int takeAmt)
    {
        if (takeAmt > 0)
        {
            return queryable.Take(takeAmt);
        }

        return queryable;
    }
}