using System.Collections.Immutable;
using SideScrollerGame.Sim.Definitions;
using SideScrollerGame.Sim.Serialization;

namespace SideScrollerGame.Sim.Replay;

public static class ReplayPlayer
{
    public static ImmutableArray<int> Play(ReplayRecord replay, GameDefinition gameDefinition, SimulationConfig config)
    {
        if (replay.ContentHash != GameDefinitionHasher.Compute(gameDefinition))
            throw new InvalidOperationException("Replay content hash does not match the supplied game definition.");

        if (replay.TicksPerSecond != config.TicksPerSecond)
            throw new InvalidOperationException("Replay tick rate does not match the supplied simulation config.");

        var hashes = ImmutableArray.CreateBuilder<int>(replay.Ticks.Length);
        Simulation simulation = new(gameDefinition, config, replay.Seed);
        foreach (var recordedTick in replay.Ticks)
        {
            var result = simulation.Step(recordedTick.ActionBatch);
            if (result.StateHash != recordedTick.ExpectedStateHash)
                throw new InvalidOperationException($"Replay diverged at tick {recordedTick.ActionBatch.Tick}.");

            hashes.Add(result.StateHash);
        }

        return hashes.MoveToImmutable();
    }
}