deepdrft/DeepDrftData/Repositories/TrackRepository.cs

using Data.Data.Repositories;
using Data.Errors;
using DeepDrftData.Data;
using DeepDrftModels.DTOs;
using DeepDrftModels.Entities;
using Microsoft.EntityFrameworkCore;
using Microsoft.Extensions.Logging;
using Models.Common;

namespace DeepDrftData.Repositories;

public class TrackRepository : Repository<DeepDrftContext, TrackEntity>
{
    public TrackRepository(
        DeepDrftContext context,
        ILogger<Repository<DeepDrftContext, TrackEntity>> logger,
        IDbExceptionClassifier? classifier = null)
        : base(context, logger, classifier: classifier)
    {
    }

    // Lookup by vault entry key. The base Repository<> only exposes id-based queries, so this
    // uses Query (soft-delete filtered) rather than the raw DbSet.
    public async Task<TrackEntity?> GetByEntryKeyAsync(string entryKey)
        => await Query.FirstOrDefaultAsync(t => t.EntryKey == entryKey);

    // Picks one track uniformly at random. Two round-trips (count, then a single offset row)
    // rather than ORDER BY random() so the database never sorts the whole table — the catalogue
    // is small today but this keeps the cost flat as it grows. Returns null when empty so the
    // service surfaces a valid empty-library state, not an error. Uses Query (soft-delete
    // filtered) so deleted tracks are never candidates.
    public async Task<TrackEntity?> GetRandomAsync(CancellationToken cancellationToken = default)
    {
        var count = await Query.CountAsync(cancellationToken);
        if (count == 0)
            return null;

        var index = Random.Shared.Next(count);
        return await Query
            .OrderBy(t => t.Id)
            .Skip(index)
            .Take(1)
            .FirstOrDefaultAsync(cancellationToken);
    }

    // Paged query with optional filter predicates. Built off Query (soft-delete filtered) rather than the
    // base GetPagedAsync(paging) overload, which takes no where-clause. The OrderBy expression and
    // direction ride in on the PagingParameters the manager already built, so sort + filter +
    // pagination compose. Filter predicates apply before sort and Skip/Take so TotalCount reflects
    // the filtered set.
    public async Task<PagedResult<TrackEntity>> GetPagedFilteredAsync(
        PagingParameters<TrackEntity> paging,
        TrackFilter? filter,
        CancellationToken ct = default)
    {
        IQueryable<TrackEntity> query = Query;

        if (filter is not null)
        {
            if (!string.IsNullOrWhiteSpace(filter.SearchText))
            {
                // Postgres case-insensitive LIKE. The '%' wraps make it a contains-match; ILike is
                // EF-translatable where ToLower().Contains() is not. Album is nullable — ILike on a
                // null column yields false, which is the desired "no match" behaviour.
                var pattern = $"%{filter.SearchText}%";
                query = query.Where(t =>
                    EF.Functions.ILike(t.TrackName, pattern)
                    || EF.Functions.ILike(t.Artist, pattern)
                    || (t.Album != null && EF.Functions.ILike(t.Album, pattern)));
            }

            if (!string.IsNullOrWhiteSpace(filter.Album))
                query = query.Where(t => t.Album == filter.Album);

            if (!string.IsNullOrWhiteSpace(filter.Genre))
                query = query.Where(t => t.Genre == filter.Genre);
        }

        var totalCount = await query.CountAsync(ct);

        if (paging.OrderBy is not null)
        {
            query = paging.IsDescending
                ? query.OrderByDescending(paging.OrderBy)
                : query.OrderBy(paging.OrderBy);
        }

        var items = await query
            .Skip(paging.Skip)
            .Take(paging.PageSize)
            .ToListAsync(ct);

        return new PagedResult<TrackEntity>
        {
            Items = items,
            TotalCount = totalCount,
            Page = paging.Page,
            PageSize = paging.PageSize,
        };
    }

    // Distinct albums (non-null) with track counts and a representative cover key. The cover is the
    // first non-null ImagePath in the group; GroupBy + projection keeps it a single round-trip.
    public async Task<List<AlbumSummaryDto>> GetDistinctAlbumsAsync(CancellationToken ct = default)
        => await Query
            .Where(t => t.Album != null)
            .GroupBy(t => t.Album!)
            .Select(g => new AlbumSummaryDto
            {
                Album = g.Key,
                TrackCount = g.Count(),
                CoverImageKey = g
                    .Where(t => t.ImagePath != null)
                    .OrderBy(t => t.Id)
                    .Select(t => t.ImagePath)
                    .FirstOrDefault(),
            })
            .OrderBy(a => a.Album)
            .ToListAsync(ct);

    // Distinct genres (non-null) with track counts.
    public async Task<List<GenreSummaryDto>> GetDistinctGenresAsync(CancellationToken ct = default)
        => await Query
            .Where(t => t.Genre != null)
            .GroupBy(t => t.Genre!)
            .Select(g => new GenreSummaryDto
            {
                Genre = g.Key,
                TrackCount = g.Count(),
            })
            .OrderBy(g => g.Genre)
            .ToListAsync(ct);

    protected override void UpdateEntity(TrackEntity target, TrackEntity source)
    {
        base.UpdateEntity(target, source); // copies CreatedAt, UpdatedAt, IsDeleted
        target.EntryKey = source.EntryKey;
        target.TrackName = source.TrackName;
        target.Artist = source.Artist;
        target.Album = source.Album;
        target.Genre = source.Genre;
        target.ReleaseDate = source.ReleaseDate;
        target.ImagePath = source.ImagePath;
        target.CreatedByUserId = source.CreatedByUserId;
    }
}