GerbilManager/GerbilManagerWebAPI/Endpoints/LitterEndpoints.cs

using GerbilManagerWebAPI.Common;
using GerbilManagerWebAPI.Dtos;
using GerbilManagerWebAPI.Models;
using Gridify;
using Microsoft.AspNetCore.Http.HttpResults;
using Microsoft.EntityFrameworkCore;

namespace GerbilManagerWebAPI.Endpoints
{
    public static class LitterEndpoints
    {
        public static IEndpointRouteBuilder MapLitterEndpoints(this IEndpointRouteBuilder app)
        {
            var group = app.MapGroup("/litters").WithTags("Litters");

            // GET /litters  (Gridify: date range + orderBy=date supported on the DateOnly column)
            group.MapGet("/", async ([AsParameters] GridifyParams query, ApplicationContext db) =>
                TypedResults.Ok(await db.Litters.AsNoTracking().ToPagedResultAsync(query, ToDto)));

            group.MapGet("/{id:guid}", async Task<Results<Ok<LitterDto>, NotFound>> (Guid id, ApplicationContext db) =>
            {
                var l = await db.Litters.AsNoTracking().FirstOrDefaultAsync(x => x.Id == id);
                return l is null ? TypedResults.NotFound() : TypedResults.Ok(ToDto(l));
            });

            group.MapPost("/", async Task<Results<Created<LitterDto>, BadRequest<ParentGenderError>, BadRequest<string>>> (LitterInput input, ApplicationContext db) =>
            {
                var err = await ValidateParents(db, input.FatherId, input.MotherId);
                if (err is not null) return TypedResults.BadRequest(err);
                var mortalityErr = ValidateMortality(input.DeathsWithin8Weeks, input.TotalBorn);
                if (mortalityErr is not null) return TypedResults.BadRequest(mortalityErr);

                var l = new Litter { Id = Guid.NewGuid(), Name = input.Name, Date = input.Date };
                Apply(l, input);
                db.Litters.Add(l);
                await db.SaveChangesAsync();
                return TypedResults.Created($"/litters/{l.Id}", ToDto(l));
            });

            group.MapPut("/{id:guid}", async Task<Results<NoContent, NotFound, BadRequest<ParentGenderError>, BadRequest<string>>> (Guid id, LitterInput input, ApplicationContext db) =>
            {
                var l = await db.Litters.FirstOrDefaultAsync(x => x.Id == id);
                if (l is null) return TypedResults.NotFound();
                var err = await ValidateParents(db, input.FatherId, input.MotherId);
                if (err is not null) return TypedResults.BadRequest(err);
                var mortalityErr = ValidateMortality(input.DeathsWithin8Weeks, input.TotalBorn);
                if (mortalityErr is not null) return TypedResults.BadRequest(mortalityErr);
                l.Name = input.Name;
                l.Date = input.Date;
                Apply(l, input);
                await db.SaveChangesAsync();
                return TypedResults.NoContent();
            });

            group.MapDelete("/{id:guid}", async Task<Results<NoContent, NotFound>> (Guid id, ApplicationContext db) =>
            {
                var l = await db.Litters.FirstOrDefaultAsync(x => x.Id == id);
                if (l is null) return TypedResults.NotFound();
                db.Litters.Remove(l);
                await db.SaveChangesAsync();
                return TypedResults.NoContent();
            });

            return app;
        }

        // father must not be female; mother must not be male (unknown is allowed).
        private static async Task<ParentGenderError?> ValidateParents(ApplicationContext db, Guid? fatherId, Guid? motherId)
        {
            var father = fatherId is Guid f ? await db.Gerbils.AsNoTracking().FirstOrDefaultAsync(x => x.Id == f) : null;
            var mother = motherId is Guid m ? await db.Gerbils.AsNoTracking().FirstOrDefaultAsync(x => x.Id == m) : null;
            if (father?.Gender == Gender.female || mother?.Gender == Gender.male)
            {
                return new ParentGenderError("InvalidParentGender",
                    father?.Gender ?? Gender.unknown, mother?.Gender ?? Gender.unknown);
            }
            return null;
        }

        private static void Apply(Litter l, LitterInput i)
        {
            l.TotalBorn = i.TotalBorn;
            l.DeathsWithin8Weeks = i.DeathsWithin8Weeks;
            l.FatherId = i.FatherId;
            l.MotherId = i.MotherId;
            l.ExpectedGoHomeDate = i.ExpectedGoHomeDate;
            l.Notes = i.Notes;
        }

        private static string? ValidateMortality(int? deaths, int? totalBorn)
        {
            if (deaths is null) return null;
            if (deaths < 0) return "DeathsWithin8Weeks darf nicht negativ sein.";
            if (totalBorn is not null && deaths > totalBorn)
                return "DeathsWithin8Weeks darf nicht größer als TotalBorn sein.";
            return null;
        }

        private static LitterDto ToDto(Litter l) => new(
            l.Id, l.Name, l.Date, l.TotalBorn, l.DeathsWithin8Weeks,
            l.FatherId, l.MotherId, l.ExpectedGoHomeDate, l.Notes, l.Provenance);
    }

    /// <summary>400 body for a father×mother gender mismatch; frontend localises by Code.</summary>
    public record ParentGenderError(string Code, Gender FatherGender, Gender MotherGender);
}