using System.Diagnostics.CodeAnalysis;
using Recyclarr.Common.Extensions;

namespace Recyclarr.TrashLib.Config.Parsing.PostProcessing.ConfigMerging;

[SuppressMessage("ReSharper", "WithExpressionModifiesAllMembers")]
public abstract class ServiceConfigMerger<T> where T : ServiceConfigYaml
{
    protected static TVal? Combine<TVal>(TVal? a, TVal? b, Func<TVal, TVal, TVal?> combine)
    {
        if (b is null)
        {
            return a;
        }

        if (a is null)
        {
            return b;
        }

        return combine(a, b);
    }

    public virtual T Merge(T a, T b)
    {
        return a with
        {
            CustomFormats = Combine(a.CustomFormats, b.CustomFormats, MergeCustomFormats),
            QualityProfiles = MergeQualityProfiles(a.QualityProfiles, b.QualityProfiles),
            QualityDefinition = Combine(a.QualityDefinition, b.QualityDefinition,
                (a1, b1) => a1 with
                {
                    Type = b1.Type ?? a1.Type,
                    PreferredRatio = b1.PreferredRatio ?? a1.PreferredRatio
                }),

            DeleteOldCustomFormats =
            b.DeleteOldCustomFormats ?? a.DeleteOldCustomFormats,

            ReplaceExistingCustomFormats =
            b.ReplaceExistingCustomFormats ?? a.ReplaceExistingCustomFormats
        };
    }

    private sealed record FlattenedCfs(string? ProfileName, int? Score, IReadOnlyCollection<string> TrashIds);

    private static IReadOnlyCollection<CustomFormatConfigYaml> MergeCustomFormats(
        IReadOnlyCollection<CustomFormatConfigYaml> a,
        IReadOnlyCollection<CustomFormatConfigYaml> b)
    {
        var flattenedA = FlattenCfs(a);
        var flattenedB = FlattenCfs(b);

        return flattenedA
            // This builds a list of TrashIds in side B that are assigned to matching profiles in A
            .Select(x => (A: x, B: flattenedB
                .Where(y => y.ProfileName.EqualsIgnoreCase(x.ProfileName)) // Ignore score
                .SelectMany(y => y.TrashIds)
                .Distinct(StringComparer.InvariantCultureIgnoreCase)
                .ToList()))
            // Add everything on side A that isn't on side B
            .Select(x => new CustomFormatConfigYaml
            {
                TrashIds = x.A.TrashIds
                    .Except(x.B, StringComparer.InvariantCultureIgnoreCase)
                    .ToList(),
                QualityProfiles = x.A.ProfileName is not null
                    ? new[] {new QualityScoreConfigYaml {Name = x.A.ProfileName, Score = x.A.Score}}
                    : null
            })
            .Concat(b)
            .ToList();

        static List<FlattenedCfs> FlattenCfs(IEnumerable<CustomFormatConfigYaml> cfs)
        {
            return cfs
                .Where(x => x.TrashIds is not null)
                .SelectMany(x => x is {QualityProfiles.Count: > 0}
                    ? x.QualityProfiles.Select(y => new FlattenedCfs(y.Name, y.Score, x.TrashIds!))
                    : new[] {new FlattenedCfs(null, null, x.TrashIds!)})
                .GroupBy(x => (Name: x.ProfileName, x.Score))
                .Select(x => new FlattenedCfs(x.Key.Name, x.Key.Score, x.SelectMany(y => y.TrashIds).ToList()))
                .ToList();
        }
    }

    private static IReadOnlyCollection<QualityProfileConfigYaml>? MergeQualityProfiles(
        IReadOnlyCollection<QualityProfileConfigYaml>? a,
        IReadOnlyCollection<QualityProfileConfigYaml>? b)
    {
        return Combine(a, b, (a1, b1) =>
        {
            return a1
                .FullOuterJoin(b1, JoinType.Hash,
                    x => x.Name,
                    x => x.Name,
                    l => l,
                    r => r,
                    MergeQualityProfile,
                    StringComparer.InvariantCultureIgnoreCase)
                .ToList();
        });
    }

    private static QualityProfileConfigYaml MergeQualityProfile(QualityProfileConfigYaml a, QualityProfileConfigYaml b)
    {
        return a with
        {
            Upgrade = Combine(a.Upgrade, b.Upgrade, (a1, b1) => a1 with
            {
                Allowed = b1.Allowed ?? a1.Allowed,
                UntilQuality = b1.UntilQuality ?? a1.UntilQuality,
                UntilScore = b1.UntilScore ?? a1.UntilScore
            }),
            MinFormatScore = b.MinFormatScore ?? a.MinFormatScore,
            QualitySort = b.QualitySort ?? a.QualitySort,
            ScoreSet = b.ScoreSet ?? a.ScoreSet,
            ResetUnmatchedScores = Combine(a.ResetUnmatchedScores, b.ResetUnmatchedScores, (a1, b1) => a1 with
            {
                Enabled = b1.Enabled ?? a1.Enabled,
                Except = Combine(a1.Except, b1.Except, (a2, b2) => Combine(a2, b2, (a3, b3) => a3
                    .Concat(b3)
                    .Distinct(StringComparer.InvariantCultureIgnoreCase)
                    .ToList()))
            }),
            Qualities = b.Qualities ?? a.Qualities
        };
    }
}