namespace Ludarium.Application;

/// <summary>
/// Selects the one unique read-only GameCube or Wii image a Dolphin session may launch.
/// </summary>
/// <remarks>
/// Dolphin serves two platforms from one mount, so a runtime path always names its platform
/// directory. Everything else — path safety, prefix rebasing, capability vocabulary — is shared with
/// every other native player.
/// </remarks>
public static class DolphinLaunchPolicy
{
    public static NativeRemotePlayer Player => NativeRemotePlayerRegistry.Dolphin;

    public static IReadOnlyList<string> SupportedPlatforms => Player.Platforms;

    /// <summary>A disc image below this size is a stub, a companion file or a partial download.</summary>
    private const long MinimumImageBytes = 1024 * 1024;

    public static NativeRemotePlayCapability EvaluateCapability(Guid gameId, string? platform, bool runtimeReady,
        IReadOnlyList<NativeLaunchCandidate> candidates, DateTimeOffset? checkedAt = null,
        bool vaultBacked = false)
    {
        var now = checkedAt ?? DateTimeOffset.UtcNow;
        if (!Player.Owns(platform))
            return Unavailable(NativeRemotePlayState.UnsupportedPlatform,
                "Only GameCube and Wii games can use the isolated Dolphin player.");
        if (!runtimeReady)
            return Unavailable(NativeRemotePlayState.RuntimeUnavailable,
                "The isolated Dolphin runtime or exact-title controller is not available.");
        if (candidates.Count == 0)
            return Unavailable(NativeRemotePlayState.MissingGame,
                "No linked Dolphin-compatible disc image was found for this game.");
        if (!candidates.Any(candidate => candidate.SourceReadOnly))
            return Unavailable(NativeRemotePlayState.SourceNotReadOnly,
                "The linked source is not mounted read-only, so playback is blocked.");
        if (SelectGame(candidates) is null)
            return Unavailable(NativeRemotePlayState.AmbiguousMapping,
                "Ludarium could not identify one unique read-only Dolphin-compatible image for this game.");
        return NativeRemotePlayPolicy.Available(Player, gameId,
            "The exact linked game is ready in the isolated Dolphin player.", now, platform, vaultBacked);

        NativeRemotePlayCapability Unavailable(NativeRemotePlayState state, string message) =>
            NativeRemotePlayPolicy.Unavailable(Player, gameId, state, message, now, platform);
    }

    public static NativeLaunchCandidate? SelectGame(IReadOnlyList<NativeLaunchCandidate> candidates)
    {
        var eligible = candidates.Where(candidate => candidate.SourceReadOnly &&
            candidate.Size > MinimumImageBytes && Player.AcceptsExtension(candidate.RelativePath) &&
            NativeRemotePlayPolicy.IsSafeRelativePath(candidate.RelativePath)).ToArray();
        return eligible.Length == 1 ? eligible[0] : null;
    }

    public static string ToRuntimePath(string platform, string relativePath, string catalogPrefix)
    {
        if (!Player.Owns(platform)) throw new InvalidOperationException("Unsupported Dolphin platform.");
        return NativeRemotePlayPolicy.ToRuntimePath(relativePath, catalogPrefix, Player.Extensions, platform);
    }
}