using System.Collections.Immutable;
using System.Diagnostics.CodeAnalysis;
using System.Text.Json;
using SideScrollerGame.Sim.Math;
using SideScrollerGame.Sim.Runtime;

namespace SideScrollerGame.Sim.Serialization;

[ExcludeFromCodeCoverage]
internal static class SimulationStateSerializer
{
    [ExcludeFromCodeCoverage]
    private sealed record SimulationStateDocument
    {
        public int Version { get; init; }

        public int Tick { get; init; }

        public int Seed { get; init; }

        public ulong RandomState { get; init; }

        public ulong LastRandomValue { get; init; }

        public ImmutableArray<PlayerStateDocument> Players { get; init; }

        public ImmutableArray<string> ActivatedTriggerIds { get; init; }
    }

    [ExcludeFromCodeCoverage]
    private sealed record PlayerStateDocument
    {
        public int PlayerId { get; init; }

        public int PositionX { get; init; }

        public int PositionY { get; init; }

        public sbyte MoveAxisX { get; init; }

        public sbyte MoveAxisY { get; init; }

        public short AimAxisX { get; init; }

        public short AimAxisY { get; init; }

        public int SelectedWeaponSlot { get; init; }

        public int ButtonMask { get; init; }

        public int Health { get; init; }
    }

    public static byte[] Serialize(SimulationState state)
    {
        List<PlayerStateDocument> players = new(state.Players.Length);
        foreach (var player in state.Players)
        {
            players.Add(new()
            {
                PlayerId = player.PlayerId.Value,
                PositionX = player.Position.m_X.m_Value,
                PositionY = player.Position.m_Y.m_Value,
                MoveAxisX = player.MoveAxisX,
                MoveAxisY = player.MoveAxisY,
                AimAxisX = player.AimAxisX,
                AimAxisY = player.AimAxisY,
                SelectedWeaponSlot = player.SelectedWeaponSlot,
                ButtonMask = player.ButtonMask,
                Health = player.Health
            });
        }

        return JsonSerializer.SerializeToUtf8Bytes(new SimulationStateDocument
        {
            Version = SimulationDefaults.StateFormatVersion,
            Tick = state.Tick,
            Seed = state.Seed,
            RandomState = state.RandomState,
            LastRandomValue = state.LastRandomValue,
            Players = players.ToImmutableArray(),
            ActivatedTriggerIds = state.ActivatedTriggerIds.Order(StringComparer.Ordinal).ToImmutableArray()
        });
    }

    public static SimulationState Deserialize(byte[] data)
    {
        var document = JsonSerializer.Deserialize<SimulationStateDocument>(data) ?? throw new InvalidOperationException("Simulation state payload was empty.");
        if (document.Version != SimulationDefaults.StateFormatVersion)
            throw new NotSupportedException($"Unsupported simulation state version {document.Version}.");

        var players = ImmutableArray.CreateBuilder<PlayerState>(document.Players.Length);
        foreach (var player in document.Players)
            players.Add(new(new(player.PlayerId), new(new() { m_Value = player.PositionX }, new FixPoint16 { m_Value = player.PositionY }), player.MoveAxisX, player.MoveAxisY, player.AimAxisX, player.AimAxisY, player.SelectedWeaponSlot, player.ButtonMask, player.Health));

        return new(document.Tick, document.Seed, document.RandomState, document.LastRandomValue, players.MoveToImmutable(), document.ActivatedTriggerIds.ToImmutableHashSet(StringComparer.Ordinal));
    }
}