// Licensed to the .NET Foundation under one or more agreements.
// The .NET Foundation licenses this file to you under the MIT license.

using System.Diagnostics;
using System.Dynamic.Utils;

namespace System.Linq.Expressions.Interpreter
{
    internal abstract class DivInstruction : Instruction
    {
        private static Instruction? s_Int16, s_Int32, s_Int64, s_UInt16, s_UInt32, s_UInt64, s_Single, s_Double;

        public override int ConsumedStack => 2;
        public override int ProducedStack => 1;
        public override string InstructionName => "Div";

        private DivInstruction() { }

        private sealed class DivInt16 : DivInstruction
        {
            public override int Run(InterpretedFrame frame)
            {
                int index = frame.StackIndex;
                object?[] stack = frame.Data;
                object? left = stack[index - 2];
                if (left != null)
                {
                    object? right = stack[index - 1];
                    stack[index - 2] = right == null ? null : (object)unchecked((short)((short)left / (short)right));
                }

                frame.StackIndex = index - 1;
                return 1;
            }
        }

        private sealed class DivInt32 : DivInstruction
        {
            public override int Run(InterpretedFrame frame)
            {
                int index = frame.StackIndex;
                object?[] stack = frame.Data;
                object? left = stack[index - 2];
                if (left != null)
                {
                    object? right = stack[index - 1];
                    stack[index - 2] = right == null ? null : ScriptingRuntimeHelpers.Int32ToObject((int)left / (int)right);
                }

                frame.StackIndex = index - 1;
                return 1;
            }
        }

        private sealed class DivInt64 : DivInstruction
        {
            public override int Run(InterpretedFrame frame)
            {
                int index = frame.StackIndex;
                object?[] stack = frame.Data;
                object? left = stack[index - 2];
                if (left != null)
                {
                    object? right = stack[index - 1];
                    stack[index - 2] = right == null ? null : (object)((long)left / (long)right);
                }

                frame.StackIndex = index - 1;
                return 1;
            }
        }

        private sealed class DivUInt16 : DivInstruction
        {
            public override int Run(InterpretedFrame frame)
            {
                int index = frame.StackIndex;
                object?[] stack = frame.Data;
                object? left = stack[index - 2];
                if (left != null)
                {
                    object? right = stack[index - 1];
                    stack[index - 2] = right == null ? null : (object)unchecked((ushort)((ushort)left / (ushort)right));
                }

                frame.StackIndex = index - 1;
                return 1;
            }
        }

        private sealed class DivUInt32 : DivInstruction
        {
            public override int Run(InterpretedFrame frame)
            {
                int index = frame.StackIndex;
                object?[] stack = frame.Data;
                object? left = stack[index - 2];
                if (left != null)
                {
                    object? right = stack[index - 1];
                    stack[index - 2] = right == null ? null : (object)((uint)left / (uint)right);
                }

                frame.StackIndex = index - 1;
                return 1;
            }
        }

        private sealed class DivUInt64 : DivInstruction
        {
            public override int Run(InterpretedFrame frame)
            {
                int index = frame.StackIndex;
                object?[] stack = frame.Data;
                object? left = stack[index - 2];
                if (left != null)
                {
                    object? right = stack[index - 1];
                    stack[index - 2] = right == null ? null : (object)((ulong)left / (ulong)right);
                }

                frame.StackIndex = index - 1;
                return 1;
            }
        }

        private sealed class DivSingle : DivInstruction
        {
            public override int Run(InterpretedFrame frame)
            {
                int index = frame.StackIndex;
                object?[] stack = frame.Data;
                object? left = stack[index - 2];
                if (left != null)
                {
                    object? right = stack[index - 1];
                    stack[index - 2] = right == null ? null : (object)((float)left / (float)right);
                }

                frame.StackIndex = index - 1;
                return 1;
            }
        }

        private sealed class DivDouble : DivInstruction
        {
            public override int Run(InterpretedFrame frame)
            {
                int index = frame.StackIndex;
                object?[] stack = frame.Data;
                object? left = stack[index - 2];
                if (left != null)
                {
                    object? right = stack[index - 1];
                    stack[index - 2] = right == null ? null : (object)((double)left / (double)right);
                }

                frame.StackIndex = index - 1;
                return 1;
            }
        }

        public static Instruction Create(Type type)
        {
            Debug.Assert(!type.IsEnum);
            return type.GetNonNullableType().GetTypeCode() switch
            {
                TypeCode.Int16 => s_Int16 ??= new DivInt16(),
                TypeCode.Int32 => s_Int32 ??= new DivInt32(),
                TypeCode.Int64 => s_Int64 ??= new DivInt64(),
                TypeCode.UInt16 => s_UInt16 ??= new DivUInt16(),
                TypeCode.UInt32 => s_UInt32 ??= new DivUInt32(),
                TypeCode.UInt64 => s_UInt64 ??= new DivUInt64(),
                TypeCode.Single => s_Single ??= new DivSingle(),
                TypeCode.Double => s_Double ??= new DivDouble(),
                _ => throw ContractUtils.Unreachable,
            };
        }
    }
}