// <copyright file="MediaAttachmentRepository.cs" company="PlaceholderCompany">
// Copyright (c) PlaceholderCompany. All rights reserved.
// </copyright>

namespace Jellyfin.Server.Implementations.Item;

using System;
using System.Collections.Generic;
using System.Collections.Immutable;
using System.Linq;
using System.Threading;
using System.Threading.Tasks;
using Jellyfin.Database.Implementations;
using Jellyfin.Database.Implementations.Entities;
using MediaBrowser.Controller.Persistence;
using MediaBrowser.Model.Entities;
using Microsoft.EntityFrameworkCore;

/// <summary>
/// Manager for handling Media Attachments.
/// </summary>
/// <param name="dbProvider">Efcore Factory.</param>
public class MediaAttachmentRepository(IDbContextFactory<JellyfinDbContext> dbProvider) : IMediaAttachmentRepository
{
    /// <inheritdoc />
    public async Task SaveMediaAttachmentsAsync(
        Guid id,
        IReadOnlyList<MediaAttachment> attachments,
        CancellationToken cancellationToken = default)
    {
        await using var context = dbProvider.CreateDbContext();

        // Use the execution strategy to handle transactional consistency and retries
        // This is required for PostgreSQL NpgsqlRetryingExecutionStrategy
        var executionStrategy = context.Database.CreateExecutionStrategy();
        await executionStrategy.ExecuteAsync(async () =>
        {
            // Users may replace a media with a version that includes attachments to one without them.
            // So when saving attachments is triggered by a library scan, we always unconditionally
            // clear the old ones, and then add the new ones if given.
            await context.AttachmentStreamInfos
                .Where(e => e.ItemId.Equals(id))
                .ExecuteDeleteAsync(cancellationToken)
                .ConfigureAwait(false);

            if (attachments.Any())
            {
                await context.AttachmentStreamInfos
                    .AddRangeAsync(attachments.Select(e => Map(e, id)), cancellationToken)
                    .ConfigureAwait(false);
            }

            await context.SaveChangesAsync(cancellationToken).ConfigureAwait(false);
        }).ConfigureAwait(false);
    }

    /// <inheritdoc />
    public async Task<IReadOnlyList<MediaAttachment>> GetMediaAttachmentsAsync(
        MediaAttachmentQuery filter,
        CancellationToken cancellationToken = default)
    {
        await using var context = dbProvider.CreateDbContext();
        var query = context.AttachmentStreamInfos
            .AsNoTracking()
            .Where(e => e.ItemId.Equals(filter.ItemId));

        if (filter.Index.HasValue)
        {
            query = query.Where(e => e.Index == filter.Index);
        }

        var attachments = await query
            .ToArrayAsync(cancellationToken)
            .ConfigureAwait(false);

        return attachments.Select(Map).ToArray();
    }

    private MediaAttachment Map(AttachmentStreamInfo attachment)
    {
        return new MediaAttachment()
        {
            Codec = attachment.Codec,
            CodecTag = attachment.CodecTag,
            Comment = attachment.Comment,
            FileName = attachment.Filename,
            Index = attachment.Index,
            MimeType = attachment.MimeType,
        };
    }

    private AttachmentStreamInfo Map(MediaAttachment attachment, Guid id)
    {
        return new AttachmentStreamInfo()
        {
            Codec = attachment.Codec,
            CodecTag = attachment.CodecTag,
            Comment = attachment.Comment,
            Filename = attachment.FileName,
            Index = attachment.Index,
            MimeType = attachment.MimeType,
            ItemId = id,
            Item = null!
        };
    }
}
