using System;
using System.Collections.Generic;
using System.Reflection.Emit;
using HarmonyLib;

namespace Aki.Reflection.CodeWrapper
{
    /// <summary>
    /// Helper class to generate IL code for transpilers
    /// </summary>
    public class CodeGenerator
    {
        public static List<CodeInstruction> GenerateInstructions(List<Code> codes)
        {
            var list = new List<CodeInstruction>();

            foreach (Code code in codes)
            {
                list.Add(ParseCode(code));
            }

            return list;
        }

        private static CodeInstruction ParseCode(Code code)
        {
            if (!code.HasOperand)
            {
                return new CodeInstruction(code.OpCode) { labels = GetLabelList(code) };
            }

            if (code.OpCode == OpCodes.Ldfld || code.OpCode == OpCodes.Stfld)
            {
                return new CodeInstruction(code.OpCode, AccessTools.Field(code.CallerType, code.OperandTarget as string)) { labels = GetLabelList(code) };
            }

            if (code.OpCode == OpCodes.Call || code.OpCode == OpCodes.Callvirt)
            {
                return new CodeInstruction(code.OpCode, AccessTools.Method(code.CallerType, code.OperandTarget as string, code.Parameters)) { labels = GetLabelList(code) };
            }

            if (code.OpCode == OpCodes.Box)
            {
                return new CodeInstruction(code.OpCode, code.CallerType) { labels = GetLabelList(code) };
            }

            if (code.OpCode == OpCodes.Br || code.OpCode == OpCodes.Brfalse || code.OpCode == OpCodes.Brtrue || code.OpCode == OpCodes.Brtrue_S
                || code.OpCode == OpCodes.Brfalse_S || code.OpCode == OpCodes.Br_S)
            {
                return new CodeInstruction(code.OpCode, code.OperandTarget) { labels = GetLabelList(code) };
            }

            throw new ArgumentException($"Code with OpCode {nameof(code.OpCode)} is not supported.");
        }

        private static List<Label> GetLabelList(Code code)
        {
            if (code.GetLabel() == null)
            {
                return new List<Label>();
            }

            return new List<Label>() { (Label)code.GetLabel() };
        }
    }
}