using System.Reflection.Metadata;
using Roslyn.Utilities;

namespace Microsoft.CodeAnalysis.CodeGen;

internal static class ILOpCodeExtensions
{
	public static int Size(this ILOpCode opcode)
	{
		if ((int)opcode <= 255)
		{
			return 1;
		}
		return 2;
	}

	public static ILOpCode GetLeaveOpcode(this ILOpCode opcode)
	{
		return opcode switch
		{
			ILOpCode.Br => ILOpCode.Leave, 
			ILOpCode.Br_s => ILOpCode.Leave_s, 
			_ => throw ExceptionUtilities.UnexpectedValue(opcode), 
		};
	}

	public static bool HasVariableStackBehavior(this ILOpCode opcode)
	{
		if (opcode - 40 <= ILOpCode.Ldarg_0 || opcode == ILOpCode.Callvirt || opcode == ILOpCode.Newobj)
		{
			return true;
		}
		return false;
	}

	public static bool IsControlTransfer(this ILOpCode opcode)
	{
		if (opcode.IsBranch())
		{
			return true;
		}
		switch (opcode)
		{
		case ILOpCode.Jmp:
		case ILOpCode.Ret:
		case ILOpCode.Switch:
		case ILOpCode.Throw:
		case ILOpCode.Endfinally:
		case ILOpCode.Endfilter:
		case ILOpCode.Rethrow:
			return true;
		default:
			return false;
		}
	}

	public static bool IsConditionalBranch(this ILOpCode opcode)
	{
		if (opcode - 44 <= ILOpCode.Stloc_1 || opcode - 57 <= ILOpCode.Stloc_1)
		{
			return true;
		}
		return false;
	}

	public static bool IsRelationalBranch(this ILOpCode opcode)
	{
		if (opcode - 46 <= ILOpCode.Ldloc_3 || opcode - 59 <= ILOpCode.Ldloc_3)
		{
			return true;
		}
		return false;
	}

	public static bool CanFallThrough(this ILOpCode opcode)
	{
		switch (opcode)
		{
		case ILOpCode.Jmp:
		case ILOpCode.Ret:
		case ILOpCode.Br_s:
		case ILOpCode.Br:
		case ILOpCode.Throw:
		case ILOpCode.Endfinally:
		case ILOpCode.Leave:
		case ILOpCode.Leave_s:
		case ILOpCode.Rethrow:
			return false;
		default:
			return true;
		}
	}

	public static int NetStackBehavior(this ILOpCode opcode)
	{
		return opcode.StackPushCount() - opcode.StackPopCount();
	}

	public static int StackPopCount(this ILOpCode opcode)
	{
		switch (opcode)
		{
		case ILOpCode.Nop:
		case ILOpCode.Break:
		case ILOpCode.Ldarg_0:
		case ILOpCode.Ldarg_1:
		case ILOpCode.Ldarg_2:
		case ILOpCode.Ldarg_3:
		case ILOpCode.Ldloc_0:
		case ILOpCode.Ldloc_1:
		case ILOpCode.Ldloc_2:
		case ILOpCode.Ldloc_3:
			return 0;
		case ILOpCode.Stloc_0:
		case ILOpCode.Stloc_1:
		case ILOpCode.Stloc_2:
		case ILOpCode.Stloc_3:
			return 1;
		case ILOpCode.Ldarg_s:
		case ILOpCode.Ldarga_s:
			return 0;
		case ILOpCode.Starg_s:
			return 1;
		case ILOpCode.Ldloc_s:
		case ILOpCode.Ldloca_s:
			return 0;
		case ILOpCode.Stloc_s:
			return 1;
		case ILOpCode.Ldnull:
		case ILOpCode.Ldc_i4_m1:
		case ILOpCode.Ldc_i4_0:
		case ILOpCode.Ldc_i4_1:
		case ILOpCode.Ldc_i4_2:
		case ILOpCode.Ldc_i4_3:
		case ILOpCode.Ldc_i4_4:
		case ILOpCode.Ldc_i4_5:
		case ILOpCode.Ldc_i4_6:
		case ILOpCode.Ldc_i4_7:
		case ILOpCode.Ldc_i4_8:
		case ILOpCode.Ldc_i4_s:
		case ILOpCode.Ldc_i4:
		case ILOpCode.Ldc_i8:
		case ILOpCode.Ldc_r4:
		case ILOpCode.Ldc_r8:
			return 0;
		case ILOpCode.Dup:
		case ILOpCode.Pop:
			return 1;
		case ILOpCode.Jmp:
			return 0;
		case ILOpCode.Call:
		case ILOpCode.Calli:
		case ILOpCode.Ret:
			return -1;
		case ILOpCode.Br_s:
			return 0;
		case ILOpCode.Brfalse_s:
		case ILOpCode.Brtrue_s:
			return 1;
		case ILOpCode.Beq_s:
		case ILOpCode.Bge_s:
		case ILOpCode.Bgt_s:
		case ILOpCode.Ble_s:
		case ILOpCode.Blt_s:
		case ILOpCode.Bne_un_s:
		case ILOpCode.Bge_un_s:
		case ILOpCode.Bgt_un_s:
		case ILOpCode.Ble_un_s:
		case ILOpCode.Blt_un_s:
			return 2;
		case ILOpCode.Br:
			return 0;
		case ILOpCode.Brfalse:
		case ILOpCode.Brtrue:
			return 1;
		case ILOpCode.Beq:
		case ILOpCode.Bge:
		case ILOpCode.Bgt:
		case ILOpCode.Ble:
		case ILOpCode.Blt:
		case ILOpCode.Bne_un:
		case ILOpCode.Bge_un:
		case ILOpCode.Bgt_un:
		case ILOpCode.Ble_un:
		case ILOpCode.Blt_un:
			return 2;
		case ILOpCode.Switch:
		case ILOpCode.Ldind_i1:
		case ILOpCode.Ldind_u1:
		case ILOpCode.Ldind_i2:
		case ILOpCode.Ldind_u2:
		case ILOpCode.Ldind_i4:
		case ILOpCode.Ldind_u4:
		case ILOpCode.Ldind_i8:
		case ILOpCode.Ldind_i:
		case ILOpCode.Ldind_r4:
		case ILOpCode.Ldind_r8:
		case ILOpCode.Ldind_ref:
			return 1;
		case ILOpCode.Stind_ref:
		case ILOpCode.Stind_i1:
		case ILOpCode.Stind_i2:
		case ILOpCode.Stind_i4:
		case ILOpCode.Stind_i8:
		case ILOpCode.Stind_r4:
		case ILOpCode.Stind_r8:
		case ILOpCode.Add:
		case ILOpCode.Sub:
		case ILOpCode.Mul:
		case ILOpCode.Div:
		case ILOpCode.Div_un:
		case ILOpCode.Rem:
		case ILOpCode.Rem_un:
		case ILOpCode.And:
		case ILOpCode.Or:
		case ILOpCode.Xor:
		case ILOpCode.Shl:
		case ILOpCode.Shr:
		case ILOpCode.Shr_un:
			return 2;
		case ILOpCode.Neg:
		case ILOpCode.Not:
		case ILOpCode.Conv_i1:
		case ILOpCode.Conv_i2:
		case ILOpCode.Conv_i4:
		case ILOpCode.Conv_i8:
		case ILOpCode.Conv_r4:
		case ILOpCode.Conv_r8:
		case ILOpCode.Conv_u4:
		case ILOpCode.Conv_u8:
			return 1;
		case ILOpCode.Callvirt:
			return -1;
		case ILOpCode.Cpobj:
			return 2;
		case ILOpCode.Ldobj:
			return 1;
		case ILOpCode.Ldstr:
			return 0;
		case ILOpCode.Newobj:
			return -1;
		case ILOpCode.Castclass:
		case ILOpCode.Isinst:
		case ILOpCode.Conv_r_un:
		case ILOpCode.Unbox:
		case ILOpCode.Throw:
		case ILOpCode.Ldfld:
		case ILOpCode.Ldflda:
			return 1;
		case ILOpCode.Stfld:
			return 2;
		case ILOpCode.Ldsfld:
		case ILOpCode.Ldsflda:
			return 0;
		case ILOpCode.Stsfld:
			return 1;
		case ILOpCode.Stobj:
			return 2;
		case ILOpCode.Conv_ovf_i1_un:
		case ILOpCode.Conv_ovf_i2_un:
		case ILOpCode.Conv_ovf_i4_un:
		case ILOpCode.Conv_ovf_i8_un:
		case ILOpCode.Conv_ovf_u1_un:
		case ILOpCode.Conv_ovf_u2_un:
		case ILOpCode.Conv_ovf_u4_un:
		case ILOpCode.Conv_ovf_u8_un:
		case ILOpCode.Conv_ovf_i_un:
		case ILOpCode.Conv_ovf_u_un:
		case ILOpCode.Box:
		case ILOpCode.Newarr:
		case ILOpCode.Ldlen:
			return 1;
		case ILOpCode.Ldelema:
		case ILOpCode.Ldelem_i1:
		case ILOpCode.Ldelem_u1:
		case ILOpCode.Ldelem_i2:
		case ILOpCode.Ldelem_u2:
		case ILOpCode.Ldelem_i4:
		case ILOpCode.Ldelem_u4:
		case ILOpCode.Ldelem_i8:
		case ILOpCode.Ldelem_i:
		case ILOpCode.Ldelem_r4:
		case ILOpCode.Ldelem_r8:
		case ILOpCode.Ldelem_ref:
			return 2;
		case ILOpCode.Stelem_i:
		case ILOpCode.Stelem_i1:
		case ILOpCode.Stelem_i2:
		case ILOpCode.Stelem_i4:
		case ILOpCode.Stelem_i8:
		case ILOpCode.Stelem_r4:
		case ILOpCode.Stelem_r8:
		case ILOpCode.Stelem_ref:
			return 3;
		case ILOpCode.Ldelem:
			return 2;
		case ILOpCode.Stelem:
			return 3;
		case ILOpCode.Unbox_any:
		case ILOpCode.Conv_ovf_i1:
		case ILOpCode.Conv_ovf_u1:
		case ILOpCode.Conv_ovf_i2:
		case ILOpCode.Conv_ovf_u2:
		case ILOpCode.Conv_ovf_i4:
		case ILOpCode.Conv_ovf_u4:
		case ILOpCode.Conv_ovf_i8:
		case ILOpCode.Conv_ovf_u8:
		case ILOpCode.Refanyval:
		case ILOpCode.Ckfinite:
		case ILOpCode.Mkrefany:
			return 1;
		case ILOpCode.Ldtoken:
			return 0;
		case ILOpCode.Conv_u2:
		case ILOpCode.Conv_u1:
		case ILOpCode.Conv_i:
		case ILOpCode.Conv_ovf_i:
		case ILOpCode.Conv_ovf_u:
			return 1;
		case ILOpCode.Add_ovf:
		case ILOpCode.Add_ovf_un:
		case ILOpCode.Mul_ovf:
		case ILOpCode.Mul_ovf_un:
		case ILOpCode.Sub_ovf:
		case ILOpCode.Sub_ovf_un:
			return 2;
		case ILOpCode.Endfinally:
		case ILOpCode.Leave:
		case ILOpCode.Leave_s:
			return 0;
		case ILOpCode.Stind_i:
			return 2;
		case ILOpCode.Conv_u:
			return 1;
		case ILOpCode.Arglist:
			return 0;
		case ILOpCode.Ceq:
		case ILOpCode.Cgt:
		case ILOpCode.Cgt_un:
		case ILOpCode.Clt:
		case ILOpCode.Clt_un:
			return 2;
		case ILOpCode.Ldftn:
			return 0;
		case ILOpCode.Ldvirtftn:
			return 1;
		case ILOpCode.Ldarg:
		case ILOpCode.Ldarga:
			return 0;
		case ILOpCode.Starg:
			return 1;
		case ILOpCode.Ldloc:
		case ILOpCode.Ldloca:
			return 0;
		case ILOpCode.Stloc:
		case ILOpCode.Localloc:
		case ILOpCode.Endfilter:
			return 1;
		case ILOpCode.Unaligned:
		case ILOpCode.Volatile:
		case ILOpCode.Tail:
			return 0;
		case ILOpCode.Initobj:
			return 1;
		case ILOpCode.Constrained:
			return 0;
		case ILOpCode.Cpblk:
		case ILOpCode.Initblk:
			return 3;
		case ILOpCode.Rethrow:
		case ILOpCode.Sizeof:
			return 0;
		case ILOpCode.Refanytype:
			return 1;
		case ILOpCode.Readonly:
			return 0;
		default:
			throw ExceptionUtilities.UnexpectedValue(opcode);
		}
	}

	public static int StackPushCount(this ILOpCode opcode)
	{
		switch (opcode)
		{
		case ILOpCode.Nop:
		case ILOpCode.Break:
			return 0;
		case ILOpCode.Ldarg_0:
		case ILOpCode.Ldarg_1:
		case ILOpCode.Ldarg_2:
		case ILOpCode.Ldarg_3:
		case ILOpCode.Ldloc_0:
		case ILOpCode.Ldloc_1:
		case ILOpCode.Ldloc_2:
		case ILOpCode.Ldloc_3:
			return 1;
		case ILOpCode.Stloc_0:
		case ILOpCode.Stloc_1:
		case ILOpCode.Stloc_2:
		case ILOpCode.Stloc_3:
			return 0;
		case ILOpCode.Ldarg_s:
		case ILOpCode.Ldarga_s:
			return 1;
		case ILOpCode.Starg_s:
			return 0;
		case ILOpCode.Ldloc_s:
		case ILOpCode.Ldloca_s:
			return 1;
		case ILOpCode.Stloc_s:
			return 0;
		case ILOpCode.Ldnull:
		case ILOpCode.Ldc_i4_m1:
		case ILOpCode.Ldc_i4_0:
		case ILOpCode.Ldc_i4_1:
		case ILOpCode.Ldc_i4_2:
		case ILOpCode.Ldc_i4_3:
		case ILOpCode.Ldc_i4_4:
		case ILOpCode.Ldc_i4_5:
		case ILOpCode.Ldc_i4_6:
		case ILOpCode.Ldc_i4_7:
		case ILOpCode.Ldc_i4_8:
		case ILOpCode.Ldc_i4_s:
		case ILOpCode.Ldc_i4:
		case ILOpCode.Ldc_i8:
		case ILOpCode.Ldc_r4:
		case ILOpCode.Ldc_r8:
			return 1;
		case ILOpCode.Dup:
			return 2;
		case ILOpCode.Pop:
		case ILOpCode.Jmp:
			return 0;
		case ILOpCode.Call:
		case ILOpCode.Calli:
			return -1;
		case ILOpCode.Ret:
		case ILOpCode.Br_s:
		case ILOpCode.Brfalse_s:
		case ILOpCode.Brtrue_s:
		case ILOpCode.Beq_s:
		case ILOpCode.Bge_s:
		case ILOpCode.Bgt_s:
		case ILOpCode.Ble_s:
		case ILOpCode.Blt_s:
		case ILOpCode.Bne_un_s:
		case ILOpCode.Bge_un_s:
		case ILOpCode.Bgt_un_s:
		case ILOpCode.Ble_un_s:
		case ILOpCode.Blt_un_s:
		case ILOpCode.Br:
		case ILOpCode.Brfalse:
		case ILOpCode.Brtrue:
		case ILOpCode.Beq:
		case ILOpCode.Bge:
		case ILOpCode.Bgt:
		case ILOpCode.Ble:
		case ILOpCode.Blt:
		case ILOpCode.Bne_un:
		case ILOpCode.Bge_un:
		case ILOpCode.Bgt_un:
		case ILOpCode.Ble_un:
		case ILOpCode.Blt_un:
		case ILOpCode.Switch:
			return 0;
		case ILOpCode.Ldind_i1:
		case ILOpCode.Ldind_u1:
		case ILOpCode.Ldind_i2:
		case ILOpCode.Ldind_u2:
		case ILOpCode.Ldind_i4:
		case ILOpCode.Ldind_u4:
		case ILOpCode.Ldind_i8:
		case ILOpCode.Ldind_i:
		case ILOpCode.Ldind_r4:
		case ILOpCode.Ldind_r8:
		case ILOpCode.Ldind_ref:
			return 1;
		case ILOpCode.Stind_ref:
		case ILOpCode.Stind_i1:
		case ILOpCode.Stind_i2:
		case ILOpCode.Stind_i4:
		case ILOpCode.Stind_i8:
		case ILOpCode.Stind_r4:
		case ILOpCode.Stind_r8:
			return 0;
		case ILOpCode.Add:
		case ILOpCode.Sub:
		case ILOpCode.Mul:
		case ILOpCode.Div:
		case ILOpCode.Div_un:
		case ILOpCode.Rem:
		case ILOpCode.Rem_un:
		case ILOpCode.And:
		case ILOpCode.Or:
		case ILOpCode.Xor:
		case ILOpCode.Shl:
		case ILOpCode.Shr:
		case ILOpCode.Shr_un:
		case ILOpCode.Neg:
		case ILOpCode.Not:
		case ILOpCode.Conv_i1:
		case ILOpCode.Conv_i2:
		case ILOpCode.Conv_i4:
		case ILOpCode.Conv_i8:
		case ILOpCode.Conv_r4:
		case ILOpCode.Conv_r8:
		case ILOpCode.Conv_u4:
		case ILOpCode.Conv_u8:
			return 1;
		case ILOpCode.Callvirt:
			return -1;
		case ILOpCode.Cpobj:
			return 0;
		case ILOpCode.Ldobj:
		case ILOpCode.Ldstr:
		case ILOpCode.Newobj:
		case ILOpCode.Castclass:
		case ILOpCode.Isinst:
		case ILOpCode.Conv_r_un:
		case ILOpCode.Unbox:
			return 1;
		case ILOpCode.Throw:
			return 0;
		case ILOpCode.Ldfld:
		case ILOpCode.Ldflda:
			return 1;
		case ILOpCode.Stfld:
			return 0;
		case ILOpCode.Ldsfld:
		case ILOpCode.Ldsflda:
			return 1;
		case ILOpCode.Stsfld:
		case ILOpCode.Stobj:
			return 0;
		case ILOpCode.Conv_ovf_i1_un:
		case ILOpCode.Conv_ovf_i2_un:
		case ILOpCode.Conv_ovf_i4_un:
		case ILOpCode.Conv_ovf_i8_un:
		case ILOpCode.Conv_ovf_u1_un:
		case ILOpCode.Conv_ovf_u2_un:
		case ILOpCode.Conv_ovf_u4_un:
		case ILOpCode.Conv_ovf_u8_un:
		case ILOpCode.Conv_ovf_i_un:
		case ILOpCode.Conv_ovf_u_un:
		case ILOpCode.Box:
		case ILOpCode.Newarr:
		case ILOpCode.Ldlen:
		case ILOpCode.Ldelema:
		case ILOpCode.Ldelem_i1:
		case ILOpCode.Ldelem_u1:
		case ILOpCode.Ldelem_i2:
		case ILOpCode.Ldelem_u2:
		case ILOpCode.Ldelem_i4:
		case ILOpCode.Ldelem_u4:
		case ILOpCode.Ldelem_i8:
		case ILOpCode.Ldelem_i:
		case ILOpCode.Ldelem_r4:
		case ILOpCode.Ldelem_r8:
		case ILOpCode.Ldelem_ref:
			return 1;
		case ILOpCode.Stelem_i:
		case ILOpCode.Stelem_i1:
		case ILOpCode.Stelem_i2:
		case ILOpCode.Stelem_i4:
		case ILOpCode.Stelem_i8:
		case ILOpCode.Stelem_r4:
		case ILOpCode.Stelem_r8:
		case ILOpCode.Stelem_ref:
			return 0;
		case ILOpCode.Ldelem:
			return 1;
		case ILOpCode.Stelem:
			return 0;
		case ILOpCode.Unbox_any:
		case ILOpCode.Conv_ovf_i1:
		case ILOpCode.Conv_ovf_u1:
		case ILOpCode.Conv_ovf_i2:
		case ILOpCode.Conv_ovf_u2:
		case ILOpCode.Conv_ovf_i4:
		case ILOpCode.Conv_ovf_u4:
		case ILOpCode.Conv_ovf_i8:
		case ILOpCode.Conv_ovf_u8:
		case ILOpCode.Refanyval:
		case ILOpCode.Ckfinite:
		case ILOpCode.Mkrefany:
		case ILOpCode.Ldtoken:
		case ILOpCode.Conv_u2:
		case ILOpCode.Conv_u1:
		case ILOpCode.Conv_i:
		case ILOpCode.Conv_ovf_i:
		case ILOpCode.Conv_ovf_u:
		case ILOpCode.Add_ovf:
		case ILOpCode.Add_ovf_un:
		case ILOpCode.Mul_ovf:
		case ILOpCode.Mul_ovf_un:
		case ILOpCode.Sub_ovf:
		case ILOpCode.Sub_ovf_un:
			return 1;
		case ILOpCode.Endfinally:
		case ILOpCode.Leave:
		case ILOpCode.Leave_s:
		case ILOpCode.Stind_i:
			return 0;
		case ILOpCode.Conv_u:
		case ILOpCode.Arglist:
		case ILOpCode.Ceq:
		case ILOpCode.Cgt:
		case ILOpCode.Cgt_un:
		case ILOpCode.Clt:
		case ILOpCode.Clt_un:
		case ILOpCode.Ldftn:
		case ILOpCode.Ldvirtftn:
		case ILOpCode.Ldarg:
		case ILOpCode.Ldarga:
			return 1;
		case ILOpCode.Starg:
			return 0;
		case ILOpCode.Ldloc:
		case ILOpCode.Ldloca:
			return 1;
		case ILOpCode.Stloc:
			return 0;
		case ILOpCode.Localloc:
			return 1;
		case ILOpCode.Endfilter:
		case ILOpCode.Unaligned:
		case ILOpCode.Volatile:
		case ILOpCode.Tail:
		case ILOpCode.Initobj:
		case ILOpCode.Constrained:
		case ILOpCode.Cpblk:
		case ILOpCode.Initblk:
		case ILOpCode.Rethrow:
			return 0;
		case ILOpCode.Sizeof:
		case ILOpCode.Refanytype:
			return 1;
		case ILOpCode.Readonly:
			return 0;
		default:
			throw ExceptionUtilities.UnexpectedValue(opcode);
		}
	}
}