NdsImageValidator.cs

namespace NdsForge;

internal static class NdsImageValidator
{
    public static NdsValidationResult Validate(NdsImage image, NdsValidationOptions options)
    {
        var diagnostics = new List<NdsDiagnostic>();
        ValidateChecksum(
            diagnostics, "NDS1001", "header", image.Header.HeaderCrc,
            image.Header.RawData.Span[..0x15E], new(0, 0x160));
        ValidateChecksum(
            diagnostics, "NDS1002", "Nintendo logo", image.Header.NintendoLogoCrc,
            image.Header.RawData.Span.Slice(0xC0, 156), new(0xC0, 156));
 
        ValidateRegion(diagnostics, image.Length, "NDS1101", "ARM9 program", image.Header.Arm9.Data);
        ValidateRegion(diagnostics, image.Length, "NDS1102", "ARM7 program", image.Header.Arm7.Data);
        ValidateRegion(diagnostics, image.Length, "NDS1103", "filename table", image.Header.FileNameTable);
        ValidateRegion(diagnostics, image.Length, "NDS1104", "file allocation table", image.Header.FileAllocationTable);
        ValidateRegion(diagnostics, image.Length, "NDS1105", "ARM9 overlay table", image.Header.Arm9OverlayTable);
        ValidateRegion(diagnostics, image.Length, "NDS1106", "ARM7 overlay table", image.Header.Arm7OverlayTable);
        if (image.Header.Arm9i is not null)
        {
            ValidateRegion(diagnostics, image.Length, "NDS1107", "ARM9i program", image.Header.Arm9i.Data);
        }
 
        if (image.Header.Arm7i is not null)
        {
            ValidateRegion(diagnostics, image.Length, "NDS1108", "ARM7i program", image.Header.Arm7i.Data);
        }
 
        ValidateOverlays(diagnostics, image.Arm9Overlays);
        ValidateOverlays(diagnostics, image.Arm7Overlays);
        if (image.Banner is not null)
        {
            diagnostics.AddRange(image.Banner.ValidateCrcs(image.Header.BannerOffset));
        }
 
        NdsSecureAreaValidator.Validate(image, diagnostics, options.SecureAreaKeyTable);
        NdsDsiIntegrityValidator.Validate(image, diagnostics, options);
 
        return new NdsValidationResult(diagnostics);
    }

    private static void ValidateChecksum(
        List<NdsDiagnostic> diagnostics,
        string code,
        string name,
        ushort stored,
        ReadOnlySpan<byte> data,
        NdsRegion region)
    {
        ushort calculated = NdsChecksums.ComputeCrc16(data);
        if (stored != calculated)
        {
            diagnostics.Add(new(
                code,
                NdsDiagnosticSeverity.Error,
                $"The stored {name} CRC is 0x{stored:X4}, but the calculated value is 0x{calculated:X4}.",
                region));
        }
    }

    private static void ValidateRegion(
        List<NdsDiagnostic> diagnostics,
        long imageLength,
        string code,
        string name,
        NdsRegion region)
    {
        if (region.Offset < 0 || region.Length < 0 || region.Offset > imageLength - region.Length)
        {
            diagnostics.Add(new(
                code,
                NdsDiagnosticSeverity.Error,
                $"The {name} region at 0x{region.Offset:X} with length 0x{region.Length:X} is outside the 0x{imageLength:X}-byte image.",
                region));
        }
    }

    private static void ValidateOverlays(List<NdsDiagnostic> diagnostics, IEnumerable<NdsOverlay> overlays)
    {
        foreach (NdsOverlay overlay in overlays)
        {
            if (overlay.Data is null)
            {
                diagnostics.Add(new(
                    "NDS1201",
                    NdsDiagnosticSeverity.Error,
                    $"{overlay.Processor} overlay {overlay.Id} references missing FAT file ID {overlay.FileId}."));
            }
 
            if (overlay.StaticInitializerEnd < overlay.StaticInitializerStart)
            {
                diagnostics.Add(new(
                    "NDS1202",
                    NdsDiagnosticSeverity.Error,
                    $"{overlay.Processor} overlay {overlay.Id} has a reversed static-initializer range."));
            }
        }
    }
}