From 6ecab3d995f0b59a9b890dfde6fbaaf16e7fa0c2 Mon Sep 17 00:00:00 2001
From: adelikat <adelikat@tasvideos.org>
Date: Sat, 29 Feb 2020 14:11:06 -0600
Subject: [PATCH] convert more decoders

---
 .../cheats/GbGameSharkDecoder.cs              | 44 +++++++++++--------
 BizHawk.Client.EmuHawk/tools/GameShark.cs     | 24 +++++-----
 2 files changed, 37 insertions(+), 31 deletions(-)

diff --git a/BizHawk.Client.Common/cheats/GbGameSharkDecoder.cs b/BizHawk.Client.Common/cheats/GbGameSharkDecoder.cs
index 73fd993310..5d37ee2d65 100644
--- a/BizHawk.Client.Common/cheats/GbGameSharkDecoder.cs
+++ b/BizHawk.Client.Common/cheats/GbGameSharkDecoder.cs
@@ -1,29 +1,36 @@
-using System.Globalization;
+using System;
+using System.Globalization;
 
 namespace BizHawk.Client.Common.cheats
 {
-	// TODO: validate string and throw
-	public class GbGameSharkDecoder
+	public static class GbGameSharkDecoder
 	{
-		private readonly string _code;
-
-		public GbGameSharkDecoder(string code)
-		{
-			_code = code;
-			Decode();
-		}
-
-		public int Address { get; private set; }
-		public int Value { get; private set; }
-
 		// Sample Input for GB/GBC:
 		// 010FF6C1
 		// Becomes:
 		// Address C1F6
 		// Value 0F
-		public void Decode()
+		public static IDecodeResult Decode(string code)
 		{
-			string code = _code.Remove(0, 2);
+			if (code == null)
+			{
+				throw new ArgumentNullException(nameof(code));
+			}
+
+			if (code.Length != 8 || code.Contains("-"))
+			{
+				return new InvalidCheatCode("GameShark codes must be 8 characters with no dashes.");
+			}
+
+			var test = code.Substring(0, 2);
+			if (test != "00" && test != "01")
+			{
+				return new InvalidCheatCode("All GameShark Codes for GameBoy need to start with 00 or 01");
+			}
+
+			var result = new DecodeResult { Size = WatchSize.Byte };
+
+			code = code.Remove(0, 2);
 
 			var valueStr = code.Remove(2, 4);
 			code = code.Remove(0, 2);
@@ -31,8 +38,9 @@ namespace BizHawk.Client.Common.cheats
 			var addrStr = code.Remove(0, 2);
 			addrStr = addrStr + code.Remove(2, 2);
 
-			Value = int.Parse(valueStr, NumberStyles.HexNumber);
-			Address = int.Parse(addrStr, NumberStyles.HexNumber);
+			result.Value = int.Parse(valueStr, NumberStyles.HexNumber);
+			result.Address = int.Parse(addrStr, NumberStyles.HexNumber);
+			return result;
 		}
 	}
 }
diff --git a/BizHawk.Client.EmuHawk/tools/GameShark.cs b/BizHawk.Client.EmuHawk/tools/GameShark.cs
index 0b94dc43c5..187ffdc25c 100644
--- a/BizHawk.Client.EmuHawk/tools/GameShark.cs
+++ b/BizHawk.Client.EmuHawk/tools/GameShark.cs
@@ -121,23 +121,21 @@ namespace BizHawk.Client.EmuHawk
 			}
 
 			// Game Shark codes
-			if (code.Length == 8 && code.Contains("-") == false)
+			if (code.Length == 8 && !code.Contains("-"))
 			{
-				var test = code.Remove(2, 6);
-				switch (test)
+				var result = GbGameSharkDecoder.Decode(code);
+				if (result.IsValid)
 				{
-					case "00":
-					case "01":
-						break;
-					default:
-						MessageBox.Show("All GameShark Codes for GameBoy need to start with 00 or 01", "Input Error", MessageBoxButtons.OK, MessageBoxIcon.Error);
-						return;
+					var description = Description(code);
+					Global.CheatList.Add(result.ToCheat(MemoryDomains.SystemBus, description));
+				}
+				else
+				{
+					InputError(result.Error);
 				}
-
-				var decoder = new GbGameSharkDecoder(code);
-				var watch = Watch.GenerateWatch(MemoryDomains["System Bus"], decoder.Address, WatchSize.Word, Common.DisplayType.Hex, false, txtDescription.Text);
-				Global.CheatList.Add(new Cheat(watch, decoder.Value));
 			}
+
+			InputError($"Unknown code type: {code}");
 		}
 
 		private void GBA(string cheat)