using System.Runtime.InteropServices;
using WhiteMagic;
using WhiteMagic.Discovery;
using WhiteMagicTest;

namespace WhiteMagicTest.Discovery;

/// <summary>
/// Tests for <see cref="PatternScanner"/>.
/// </summary>
public class PatternScannerTests
{
    private static InProcessReader CreateReader()
    {
        return new InProcessReader();
    }

    [Fact]
    public void Find_exact_pattern_returns_correct_address()
    {
        using var reader = CreateReader();

        // Create a buffer with known bytes
        byte[] buffer = new byte[256];
        buffer[10] = 0xDE;
        buffer[11] = 0xAD;
        buffer[12] = 0xBE;
        buffer[13] = 0xEF;

        GCHandle pin = GCHandle.Alloc(buffer, GCHandleType.Pinned);
        try
        {
            IntPtr addr = pin.AddrOfPinnedObject();
            IntPtr end = addr + buffer.Length;

            // Search for the exact pattern
            byte[] pattern = { 0xDE, 0xAD, 0xBE, 0xEF };
            IntPtr found = PatternScanner.Find(reader, pattern, null, addr, end);

            Assert.Equal(addr + 10, found);
        }
        finally
        {
            pin.Free();
        }
    }

    [Fact]
    public void Find_with_wildcard_mask_ignores_wildcard_bytes()
    {
        using var reader = CreateReader();

        // Create a buffer with known bytes
        byte[] buffer = new byte[256];
        buffer[20] = 0x12;
        buffer[21] = 0x34;  // This byte is wildcard
        buffer[22] = 0x56;
        buffer[23] = 0x78;

        GCHandle pin = GCHandle.Alloc(buffer, GCHandleType.Pinned);
        try
        {
            IntPtr addr = pin.AddrOfPinnedObject();
            IntPtr end = addr + buffer.Length;

            // Search with wildcard mask (x = match, ? = wildcard)
            byte[] pattern = { 0x12, 0x00, 0x56, 0x78 };
            string mask = "x?xx";  // Second byte is wildcard
            IntPtr found = PatternScanner.Find(reader, pattern, mask, addr, end);

            Assert.Equal(addr + 20, found);
        }
        finally
        {
            pin.Free();
        }
    }

    [Fact]
    public void Find_pattern_not_found_returns_zero()
    {
        using var reader = CreateReader();

        // Create a buffer without the target pattern
        byte[] buffer = new byte[256];
        for (int i = 0; i < buffer.Length; i++)
            buffer[i] = 0xAA;

        GCHandle pin = GCHandle.Alloc(buffer, GCHandleType.Pinned);
        try
        {
            IntPtr addr = pin.AddrOfPinnedObject();
            IntPtr end = addr + buffer.Length;

            // Search for pattern that doesn't exist
            byte[] pattern = { 0xDE, 0xAD, 0xBE, 0xEF };
            IntPtr found = PatternScanner.Find(reader, pattern, null, addr, end);

            Assert.Equal(IntPtr.Zero, found);
        }
        finally
        {
            pin.Free();
        }
    }

    [Fact]
    public void Find_empty_pattern_throws()
    {
        using var reader = CreateReader();

        byte[] pattern = Array.Empty<byte>();
        var ex = Assert.Throws<ArgumentException>(() =>
            PatternScanner.Find(reader, pattern, null, IntPtr.Zero, (IntPtr)1000));

        Assert.Contains("Pattern cannot be empty", ex.Message);
    }

    [Fact]
    public void Find_mask_length_mismatch_throws()
    {
        using var reader = CreateReader();

        byte[] pattern = { 0xDE, 0xAD, 0xBE, 0xEF };
        string mask = "xxx";  // Wrong length

        var ex = Assert.Throws<ArgumentException>(() =>
            PatternScanner.Find(reader, pattern, mask, IntPtr.Zero, (IntPtr)1000));

        Assert.Contains("Mask length", ex.Message);
    }

    [Fact]
    public void Find_invalid_mask_char_throws()
    {
        using var reader = CreateReader();

        byte[] pattern = { 0xDE, 0xAD, 0xBE, 0xEF };
        string mask = "axxx";  // 'a' is invalid

        var ex = Assert.Throws<ArgumentException>(() =>
            PatternScanner.Find(reader, pattern, mask, IntPtr.Zero, (IntPtr)1000));
    }

    [Fact]
    public void Find_null_mask_treats_all_as_exact()
    {
        using var reader = CreateReader();

        byte[] buffer = new byte[256];
        buffer[50] = 0xAB;
        buffer[51] = 0xCD;

        GCHandle pin = GCHandle.Alloc(buffer, GCHandleType.Pinned);
        try
        {
            IntPtr addr = pin.AddrOfPinnedObject();
            IntPtr end = addr + buffer.Length;

            // Null mask should behave like "xx" (exact match)
            byte[] pattern = { 0xAB, 0xCD };
            IntPtr found = PatternScanner.Find(reader, pattern, null, addr, end);

            Assert.Equal(addr + 50, found);
        }
        finally
        {
            pin.Free();
        }
    }

    [Fact]
    public void FindInModule_scans_current_process_module()
    {
        using var reader = CreateReader();

        // Get the current process's main module
        var currentProcess = System.Diagnostics.Process.GetCurrentProcess();
        var mainModule = currentProcess.MainModule;
        Assert.NotNull(mainModule);

        // MZ header is always at the start of the main module
        byte[] pattern = { 0x4D, 0x5A };
        IntPtr found = PatternScanner.FindInModule(reader, pattern, null, mainModule);

        Assert.Equal(mainModule.BaseAddress, found);
    }
}