using System.Diagnostics;
using System.Diagnostics.CodeAnalysis;
using System.Globalization;
using System.Text;
using NubLang.Syntax.Binding.Node;
using NubLang.Syntax.Tokenization;

namespace NubLang.Generation.QBE;

public static class QBEGenerator
{
    private static BoundSyntaxTree _syntaxTree = null!;
    private static BoundDefinitionTable _definitionTable = null!;

    private static QBEWriter _writer = null!;
    private static List<CStringLiteral> _cStringLiterals = [];
    private static List<StringLiteral> _stringLiterals = [];
    private static Stack<string> _breakLabels = [];
    private static Stack<string> _continueLabels = [];
    private static Queue<(BoundAnonymousFunc Func, string Name)> _anonymousFunctions = [];
    private static Dictionary<BoundTraitFuncImpl, string> _implFunctions = [];
    private static Stack<Variable> _variables = [];
    private static Stack<int> _variableScopes = [];
    private static int _tmpIndex;
    private static int _labelIndex;
    private static int _anonymousFuncIndex;
    private static int _cStringLiteralIndex;
    private static int _stringLiteralIndex;
    private static int _implFuncNameIndex;
    private static bool _codeIsReachable = true;

    public static string Emit(BoundSyntaxTree syntaxTree, BoundDefinitionTable definitionTable, string file)
    {
        _syntaxTree = syntaxTree;
        _definitionTable = definitionTable;

        _writer = new QBEWriter(file);

        _cStringLiterals = [];
        _stringLiterals = [];
        _breakLabels = [];
        _continueLabels = [];
        _anonymousFunctions = [];
        _implFunctions = [];
        _variables = [];
        _variableScopes = [];
        _tmpIndex = 0;
        _labelIndex = 0;
        _anonymousFuncIndex = 0;
        _cStringLiteralIndex = 0;
        _stringLiteralIndex = 0;
        _implFuncNameIndex = 0;
        _codeIsReachable = true;

        foreach (var structDef in _definitionTable.GetStructs())
        {
            EmitStructDefinition(structDef);
            _writer.NewLine();
        }

        foreach (var trait in _definitionTable.GetTraits())
        {
            EmitTraitVTable(trait);
            _writer.NewLine();
        }

        foreach (var funcDef in _syntaxTree.Definitions.OfType<BoundLocalFunc>())
        {
            EmitFuncDefinition(funcDef, LocalFuncName(funcDef), funcDef.Parameters, funcDef.ReturnType, funcDef.Body, funcDef.Exported);
            _writer.NewLine();
        }

        while (_anonymousFunctions.TryDequeue(out var anon))
        {
            EmitFuncDefinition(anon.Func, anon.Name, anon.Func.Parameters, anon.Func.ReturnType, anon.Func.Body, false);
            _writer.NewLine();
        }

        foreach (var (impl, name) in _implFunctions)
        {
            EmitFuncDefinition(impl, name, impl.Parameters, impl.ReturnType, impl.Body, false);
            _writer.NewLine();
        }

        foreach (var cStringLiteral in _cStringLiterals)
        {
            _writer.WriteLine($"data {cStringLiteral.Name} = {{ b \"{cStringLiteral.Value}\", b 0 }}");
        }

        foreach (var stringLiteral in _stringLiterals)
        {
            var bytes = Encoding.UTF8.GetBytes(stringLiteral.Value).Select(b => $"b {b}");
            _writer.WriteLine($"data {stringLiteral.Name} = {{ l {stringLiteral.Value.Length}, {string.Join(", ", bytes)} }}");
        }

        return _writer.ToString();
    }

    private static string TmpName()
    {
        return $"%t{++_tmpIndex}";
    }

    private static string LabelName()
    {
        return $"@l{++_labelIndex}";
    }

    private static string CStringName()
    {
        return $"$cstring{++_cStringLiteralIndex}";
    }

    private static string StringName()
    {
        return $"$string{++_stringLiteralIndex}";
    }

    private static string LocalFuncName(BoundLocalFunc funcDef)
    {
        return funcDef.Exported ? $"${funcDef.Name}" : $"${funcDef.Namespace}_{funcDef.Name}";
    }

    private static string ExternFuncName(BoundExternFunc funcDef)
    {
        return $"${funcDef.CallName}";
    }

    private static string ImplFuncName()
    {
        return $"$impl{++_implFuncNameIndex}";
    }

    private static string CustomTypeName(NubCustomType customType)
    {
        return CustomTypeName(customType.Namespace, customType.Name);
    }

    private static string CustomTypeName(string @namespace, string name)
    {
        return $":{@namespace}_{name}";
    }

    private static void EmitStore(NubType type, string value, string destination)
    {
        string store;

        if (type.IsSimpleType(out var simpleType, out _))
        {
            store = simpleType.StorageSize switch
            {
                StorageSize.I8 or StorageSize.U8 => "storeb",
                StorageSize.I16 or StorageSize.U16 => "storeh",
                StorageSize.I32 or StorageSize.U32 => "storew",
                StorageSize.I64 or StorageSize.U64 => "storel",
                StorageSize.F32 => "stores",
                StorageSize.F64 => "stored",
                _ => throw new ArgumentOutOfRangeException(nameof(simpleType.StorageSize))
            };
        }
        else
        {
            store = "storel";
        }

        _writer.Indented($"{store} {value}, {destination}");
    }

    private static Val EmitLoad(NubType type, string from)
    {
        string load;

        if (type.IsSimpleType(out var simpleType, out _))
        {
            load = simpleType.StorageSize switch
            {
                StorageSize.I64 or StorageSize.U64 => "loadl",
                StorageSize.I32 or StorageSize.U32 => "loadw",
                StorageSize.I16 => "loadsh",
                StorageSize.I8 => "loadsb",
                StorageSize.U16 => "loaduh",
                StorageSize.U8 => "loadub",
                StorageSize.F64 => "loadd",
                StorageSize.F32 => "loads",
                _ => throw new ArgumentOutOfRangeException(nameof(simpleType.StorageSize))
            };
        }
        else
        {
            load = "loadl";
        }

        var into = TmpName();

        _writer.Indented($"{into} {QBEAssign(type)} {load} {from}");

        return new Val(into, type, ValKind.Direct);
    }

    private static void EmitMemcpy(string source, string destination, string length)
    {
        _writer.Indented($"call $nub_memcpy(l {source}, l {destination}, l {length})");
    }

    private static string EmitArraySizeInBytes(NubArrayType type, string array)
    {
        var size = TmpName();
        _writer.Indented($"{size} =l loadl {array}");
        _writer.Indented($"{size} =l mul {size}, {type.ElementType.Size(_definitionTable)}");
        _writer.Indented($"{size} =l add {size}, 8");
        return size;
    }

    private static string EmitCStringSizeInBytes(string cstring)
    {
        var size = TmpName();
        _writer.Indented($"{size} =l call $nub_cstring_length(l {cstring})");
        _writer.Indented($"{size} =l add {size}, 1");
        return size;
    }

    private static string EmitStringSizeInBytes(string nubstring)
    {
        var size = TmpName();
        _writer.Indented($"{size} =l loadl {nubstring}");
        _writer.Indented($"{size} =l add {size}, 8");
        return size;
    }

    private static bool EmitTryMoveInto(BoundExpression source, string destinationPointer)
    {
        switch (source)
        {
            case BoundArrayInitializer arrayInitializer:
            {
                _writer.WriteDebugLocation(arrayInitializer);
                EmitStore(source.Type, EmitUnwrap(EmitArrayInitializer(arrayInitializer)), destinationPointer);
                return true;
            }
            case BoundStructInitializer structInitializer:
            {
                _writer.WriteDebugLocation(structInitializer);
                EmitStructInitializer(structInitializer, destinationPointer);
                return true;
            }
            case BoundLiteral { Kind: LiteralKind.String } literal:
            {
                _writer.WriteDebugLocation(literal);
                EmitStore(source.Type, EmitUnwrap(EmitLiteral(literal)), destinationPointer);
                return true;
            }
        }

        return false;
    }

    private static void EmitCopyIntoOrInitialize(BoundExpression source, string destinationPointer)
    {
        // If the source is a value which is not used yet such as an array/struct initializer or literal, we can skip copying
        if (EmitTryMoveInto(source, destinationPointer))
        {
            return;
        }

        var value = EmitUnwrap(EmitExpression(source));

        if (source.Type.IsSimpleType(out var simpleType, out var complexType))
        {
            EmitStore(simpleType, value, destinationPointer);
        }
        else
        {
            if (complexType is NubCustomType customType)
            {
                EmitMemcpy(value, destinationPointer, customType.Size(_definitionTable).ToString());
            }
            else
            {
                var size = complexType switch
                {
                    NubArrayType arrayType => EmitArraySizeInBytes(arrayType, value),
                    NubCStringType => EmitCStringSizeInBytes(value),
                    NubStringType => EmitStringSizeInBytes(value),
                    _ => throw new ArgumentOutOfRangeException(nameof(source.Type))
                };

                var buffer = TmpName();
                _writer.Indented($"{buffer} =l alloc8 {size}");
                EmitMemcpy(value, buffer, size);
                EmitStore(complexType, buffer, destinationPointer);
            }
        }
    }

    private static bool EmitTryCreateWithoutCopy(BoundExpression source, [NotNullWhen(true)] out string? destination)
    {
        switch (source)
        {
            case BoundArrayInitializer:
            case BoundStructInitializer:
            case BoundLiteral { Kind: LiteralKind.String }:
            {
                destination = EmitUnwrap(EmitExpression(source));
                return true;
            }
        }

        destination = null;
        return false;
    }

    private static string EmitCreateCopyOrInitialize(BoundExpression source)
    {
        // If the source is a value which is not used yet such as an array/struct initializer or literal, we can skip copying
        if (EmitTryCreateWithoutCopy(source, out var uncopiedValue))
        {
            return uncopiedValue;
        }

        var value = EmitUnwrap(EmitExpression(source));

        if (source.Type.IsSimpleType(out _, out var complexType))
        {
            // Simple types are passed in registers and are therefore always copied
            return value;
        }

        var size = complexType switch
        {
            NubArrayType arrayType => EmitArraySizeInBytes(arrayType, value),
            NubCStringType => EmitCStringSizeInBytes(value),
            NubStringType => EmitStringSizeInBytes(value),
            NubCustomType customType => customType.Size(_definitionTable).ToString(),
            _ => throw new ArgumentOutOfRangeException(nameof(source.Type))
        };

        var destination = TmpName();
        _writer.Indented($"{destination} =l alloc8 {size}");
        EmitMemcpy(value, destination, size);
        return destination;
    }

    private static string QBEAssign(NubType type)
    {
        return type switch
        {
            NubComplexType => "=l",
            NubSimpleType simpleType => simpleType switch
            {
                NubFuncType or NubFuncType => "=l",
                NubPrimitiveType primitiveType => primitiveType.Kind switch
                {
                    PrimitiveTypeKind.I64 or PrimitiveTypeKind.U64 => "=l",
                    PrimitiveTypeKind.I32 or PrimitiveTypeKind.U32 => "=w",
                    PrimitiveTypeKind.I16 or PrimitiveTypeKind.U16 => "=w",
                    PrimitiveTypeKind.I8 or PrimitiveTypeKind.U8 or PrimitiveTypeKind.Bool => "=w",
                    PrimitiveTypeKind.F64 => "=d",
                    PrimitiveTypeKind.F32 => "=s",
                    _ => throw new ArgumentOutOfRangeException()
                },
                _ => throw new NotSupportedException($"'{type}' type cannot be used in variables")
            },
            _ => throw new UnreachableException()
        };
    }

    // Utility to create QBE type names for function parameters and return types
    private static string FuncQBETypeName(NubType type)
    {
        if (type.IsSimpleType(out var simpleType, out var complexType))
        {
            return simpleType.StorageSize switch
            {
                StorageSize.I64 or StorageSize.U64 => "l",
                StorageSize.I32 or StorageSize.U32 => "w",
                StorageSize.I16 => "sh",
                StorageSize.I8 => "sb",
                StorageSize.U16 => "uh",
                StorageSize.U8 => "ub",
                StorageSize.F64 => "d",
                StorageSize.F32 => "s",
                _ => throw new ArgumentOutOfRangeException()
            };
        }

        if (complexType is NubCustomType customType)
        {
            return CustomTypeName(customType);
        }

        return "l";
    }

    private static void EmitFuncDefinition(BoundNode debugNode, string name, List<BoundFuncParameter> parameters, NubType returnType, BoundBlock body, bool exported)
    {
        _variables.Clear();
        _variableScopes.Clear();
        _labelIndex = 0;
        _tmpIndex = 0;

        var builder = new StringBuilder();

        if (exported)
        {
            builder.Append("export ");
        }

        builder.Append("function ");
        if (returnType is not NubVoidType)
        {
            builder.Append(FuncQBETypeName(returnType) + ' ');
        }

        builder.Append(name);

        var parameterStrings = parameters.Select(x => FuncQBETypeName(x.Type) + $" %{x.Name}");

        builder.Append($"({string.Join(", ", parameterStrings)})");

        _writer.StartFunction(builder.ToString());
        _writer.WriteDebugLocation(debugNode);

        var parameterVars = parameters.Select(parameter => new Variable(parameter.Name, new Val("%" + parameter.Name, parameter.Type, ValKind.Direct))).ToList();

        EmitBlock(body, parameterVars);

        if (body.Statements.LastOrDefault() is not BoundReturn)
        {
            if (returnType is NubVoidType)
            {
                _writer.Indented("ret");
            }
        }

        _writer.EndFunction();
    }

    private static void EmitStructDefinition(BoundStruct structDef)
    {
        _writer.WriteLine($"type {CustomTypeName(structDef.Namespace, structDef.Name)} = {{ ");

        var types = new Dictionary<string, string>();

        foreach (var field in structDef.Fields)
        {
            types.Add(field.Name, StructDefQBEType(field));
        }

        var longest = types.Values.Max(x => x.Length);
        foreach (var (name, type) in types)
        {
            var padding = longest - type.Length;
            _writer.Indented($"{type},{new string(' ', padding)} # {name}");
        }

        _writer.WriteLine("}");
        return;

        string StructDefQBEType(BoundStructField field)
        {
            if (field.Type.IsSimpleType(out var simpleType, out var complexType))
            {
                return simpleType.StorageSize switch
                {
                    StorageSize.I64 or StorageSize.U64 => "l",
                    StorageSize.I32 or StorageSize.U32 => "w",
                    StorageSize.I16 or StorageSize.U16 => "h",
                    StorageSize.I8 or StorageSize.U8 => "b",
                    StorageSize.F64 => "d",
                    StorageSize.F32 => "s",
                    _ => throw new ArgumentOutOfRangeException()
                };
            }

            if (complexType is NubCustomType customType)
            {
                return CustomTypeName(customType);
            }

            return "l";
        }
    }

    private static void EmitTraitVTable(BoundTrait traitDef)
    {
        _writer.WriteLine($"type {CustomTypeName(traitDef.Namespace, traitDef.Name)} = {{");

        foreach (var func in traitDef.Functions)
        {
            _writer.Indented($"l, # func {func.Name}({string.Join(", ", func.Parameters.Select(x => $"{x.Name}: {x.Type}"))}): {func.ReturnType}");
        }

        _writer.WriteLine("}");
    }

    private static void EmitStatement(BoundStatement statement)
    {
        _writer.WriteDebugLocation(statement);

        switch (statement)
        {
            case BoundAssignment assignment:
                EmitAssignment(assignment);
                break;
            case BoundBreak:
                EmitBreak();
                break;
            case BoundContinue:
                EmitContinue();
                break;
            case BoundIf ifStatement:
                EmitIf(ifStatement);
                break;
            case BoundReturn @return:
                EmitReturn(@return);
                break;
            case BoundStatementExpression statementExpression:
                EmitExpression(statementExpression.Expression);
                break;
            case BoundVariableDeclaration variableDeclaration:
                EmitVariableDeclaration(variableDeclaration);
                break;
            case BoundWhile whileStatement:
                EmitWhile(whileStatement);
                break;
            default:
                throw new ArgumentOutOfRangeException(nameof(statement));
        }
    }

    private static void EmitAssignment(BoundAssignment assignment)
    {
        var destination = EmitExpression(assignment.Target);
        Debug.Assert(destination.Kind == ValKind.Pointer);
        EmitCopyIntoOrInitialize(assignment.Value, destination.Name);
    }

    private static void EmitBlock(BoundBlock block, List<Variable>? variables = null)
    {
        _variableScopes.Push(_variables.Count);
        if (variables != null)
        {
            foreach (var variable in variables)
            {
                _variables.Push(variable);
            }
        }

        foreach (var statement in block.Statements.Where(_ => _codeIsReachable))
        {
            EmitStatement(statement);
        }

        var count = _variableScopes.Pop();
        while (_variableScopes.Count > count)
        {
            _variableScopes.Pop();
        }

        _codeIsReachable = true;
    }

    private static void EmitBreak()
    {
        _writer.Indented($"jmp {_breakLabels.Peek()}");
        _codeIsReachable = false;
    }

    private static void EmitContinue()
    {
        _writer.Indented($"jmp {_continueLabels.Peek()}");
        _codeIsReachable = false;
    }

    private static void EmitIf(BoundIf ifStatement)
    {
        var trueLabel = LabelName();
        var falseLabel = LabelName();
        var endLabel = LabelName();

        var result = EmitUnwrap(EmitExpression(ifStatement.Condition));
        _writer.Indented($"jnz {result}, {trueLabel}, {falseLabel}");
        _writer.WriteLine(trueLabel);
        EmitBlock(ifStatement.Body);
        _writer.Indented($"jmp {endLabel}");
        _writer.WriteLine(falseLabel);
        if (ifStatement.Else.HasValue)
        {
            ifStatement.Else.Value.Match
            (
                elseIfNode => EmitIf(elseIfNode),
                elseNode => EmitBlock(elseNode)
            );
        }

        _writer.WriteLine(endLabel);
    }

    private static void EmitReturn(BoundReturn @return)
    {
        if (@return.Value.HasValue)
        {
            var result = EmitUnwrap(EmitExpression(@return.Value.Value));
            _writer.Indented($"ret {result}");
        }
        else
        {
            _writer.Indented("ret");
        }
    }

    private static void EmitVariableDeclaration(BoundVariableDeclaration variableDeclaration)
    {
        var name = $"%{variableDeclaration.Name}";
        _writer.Indented($"{name} =l alloc8 8");

        if (variableDeclaration.Assignment.HasValue)
        {
            var value = EmitCreateCopyOrInitialize(variableDeclaration.Assignment.Value);
            EmitStore(variableDeclaration.Assignment.Value.Type, value, name);
        }

        _variables.Push(new Variable(variableDeclaration.Name, new Val(name, variableDeclaration.Type, ValKind.Pointer)));
    }

    private static void EmitWhile(BoundWhile whileStatement)
    {
        var conditionLabel = LabelName();
        var iterationLabel = LabelName();
        var endLabel = LabelName();

        _breakLabels.Push(endLabel);
        _continueLabels.Push(conditionLabel);

        _writer.Indented($"jmp {conditionLabel}");
        _writer.WriteLine(iterationLabel);
        EmitBlock(whileStatement.Body);
        _writer.WriteLine(conditionLabel);
        var result = EmitUnwrap(EmitExpression(whileStatement.Condition));
        _writer.Indented($"jnz {result}, {iterationLabel}, {endLabel}");
        _writer.WriteLine(endLabel);

        _continueLabels.Pop();
        _breakLabels.Pop();
    }

    private static Val EmitExpression(BoundExpression expression)
    {
        _writer.WriteDebugLocation(expression);
        return expression switch
        {
            BoundArrayInitializer arrayInitializer => EmitArrayInitializer(arrayInitializer),
            BoundStructInitializer structInitializer => EmitStructInitializer(structInitializer),
            BoundAddressOf addressOf => EmitAddressOf(addressOf),
            BoundDereference dereference => EmitDereference(dereference),
            BoundAnonymousFunc anonymousFunc => EmitAnonymousFunc(anonymousFunc),
            BoundBinaryExpression binaryExpression => EmitBinaryExpression(binaryExpression),
            BoundFuncCall funcCallExpression => EmitFuncCall(funcCallExpression),
            BoundExternFuncIdent externFuncIdent => EmitExternFuncIdent(externFuncIdent),
            BoundLocalFuncIdent localFuncIdent => EmitLocalFuncIdent(localFuncIdent),
            BoundVariableIdent variableIdent => EmitVariableIdent(variableIdent),
            BoundLiteral literal => EmitLiteral(literal),
            BoundUnaryExpression unaryExpression => EmitUnaryExpression(unaryExpression),
            BoundStructFieldAccess structFieldAccess => EmitStructFieldAccess(structFieldAccess),
            BoundTraitFuncAccess traitFuncAccess => EmitTraitFuncAccess(traitFuncAccess),
            BoundTraitImplFuncAccess traitImplFuncAccess => EmitTraitImplFuncAccess(traitImplFuncAccess),
            BoundArrayIndexAccess arrayIndex => EmitArrayIndexAccess(arrayIndex),
            _ => throw new ArgumentOutOfRangeException(nameof(expression))
        };
    }

    private static Val EmitAnonymousFunc(BoundAnonymousFunc anonymousFunc)
    {
        var name = $"$anon_func{++_anonymousFuncIndex}";
        _anonymousFunctions.Enqueue((anonymousFunc, name));
        return new Val(name, anonymousFunc.Type, ValKind.Direct);
    }

    private static Val EmitArrayIndexAccess(BoundArrayIndexAccess arrayIndexAccess)
    {
        var array = EmitUnwrap(EmitExpression(arrayIndexAccess.Target));
        var index = EmitUnwrap(EmitExpression(arrayIndexAccess.Index));

        EmitArrayBoundsCheck(array, index);

        var elementType = ((NubArrayType)arrayIndexAccess.Target.Type).ElementType;

        var pointer = TmpName();
        _writer.Indented($"{pointer} =l mul {index}, {elementType.Size(_definitionTable)}");
        _writer.Indented($"{pointer} =l add {pointer}, 8");
        _writer.Indented($"{pointer} =l add {array}, {pointer}");
        return new Val(pointer, arrayIndexAccess.Type, ValKind.Pointer);
    }

    private static void EmitArrayBoundsCheck(string array, string index)
    {
        var count = TmpName();
        _writer.Indented($"{count} =l loadl {array}");

        var isNegative = TmpName();
        _writer.Indented($"{isNegative} =w csltl {index}, 0");

        var isOob = TmpName();
        _writer.Indented($"{isOob} =w csgel {index}, {count}");

        var anyOob = TmpName();
        _writer.Indented($"{anyOob} =w or {isNegative}, {isOob}");

        var oobLabel = LabelName();
        var notOobLabel = LabelName();
        _writer.Indented($"jnz {anyOob}, {oobLabel}, {notOobLabel}");

        _writer.Indented(oobLabel);
        _writer.Indented($"call $nub_panic_array_oob()");

        _writer.Indented(notOobLabel);
    }

    private static Val EmitArrayInitializer(BoundArrayInitializer arrayInitializer)
    {
        var capacity = EmitUnwrap(EmitExpression(arrayInitializer.Capacity));
        var elementSize = arrayInitializer.ElementType.Size(_definitionTable);

        var capacityInBytes = TmpName();
        _writer.Indented($"{capacityInBytes} =l mul {capacity}, {elementSize}");
        var totalSize = TmpName();
        _writer.Indented($"{totalSize} =l add {capacityInBytes}, 8");

        var arrayPointer = TmpName();
        _writer.Indented($"{arrayPointer} =l alloc8 {totalSize}");
        _writer.Indented($"storel {capacity}, {arrayPointer}");

        var dataPointer = TmpName();
        _writer.Indented($"{dataPointer} =l add {arrayPointer}, 8");
        _writer.Indented($"call $nub_memset(l {dataPointer}, w 0, l {capacityInBytes})");

        return new Val(arrayPointer, arrayInitializer.Type, ValKind.Direct);
    }

    private static Val EmitDereference(BoundDereference dereference)
    {
        return EmitLoad(dereference.Type, EmitUnwrap(EmitExpression(dereference.Expression)));
    }

    private static Val EmitAddressOf(BoundAddressOf addressOf)
    {
        var value = EmitExpression(addressOf.Expression);
        if (value.Kind != ValKind.Pointer)
        {
            throw new UnreachableException("Tried to take address of non-pointer type. This should have been causht in the type checker");
        }

        return new Val(value.Name, addressOf.Type, ValKind.Direct);
    }

    private static Val EmitBinaryExpression(BoundBinaryExpression binaryExpression)
    {
        var left = EmitUnwrap(EmitExpression(binaryExpression.Left));
        var right = EmitUnwrap(EmitExpression(binaryExpression.Right));

        var outputName = TmpName();

        var instruction = EmitBinaryInstructionFor(binaryExpression.Operator, binaryExpression.Left.Type, left, right);

        _writer.Indented($"{outputName} {QBEAssign(binaryExpression.Left.Type)} {instruction} {left}, {right}");
        return new Val(outputName, binaryExpression.Type, ValKind.Direct);
    }

    private static string EmitBinaryInstructionFor(BoundBinaryOperator op, NubType type, string left, string right)
    {
        if (op is
            BoundBinaryOperator.Equal or
            BoundBinaryOperator.NotEqual or
            BoundBinaryOperator.GreaterThan or
            BoundBinaryOperator.GreaterThanOrEqual or
            BoundBinaryOperator.LessThan or
            BoundBinaryOperator.LessThanOrEqual)
        {
            char suffix;

            if (!type.IsSimpleType(out var simpleType, out _))
            {
                throw new NotSupportedException("Binary operations is only supported for simple types.");
            }

            switch (simpleType.StorageSize)
            {
                case StorageSize.I8:
                    _writer.Indented($"{left} =w extsb {left}");
                    _writer.Indented($"{right} =w extsb {right}");
                    suffix = 'w';
                    break;
                case StorageSize.U8:
                    _writer.Indented($"{left} =w extub {left}");
                    _writer.Indented($"{right} =w extub {right}");
                    suffix = 'w';
                    break;
                case StorageSize.I16:
                    _writer.Indented($"{left} =w extsh {left}");
                    _writer.Indented($"{right} =w extsh {right}");
                    suffix = 'w';
                    break;
                case StorageSize.U16:
                    _writer.Indented($"{left} =w extuh {left}");
                    _writer.Indented($"{right} =w extuh {right}");
                    suffix = 'w';
                    break;
                case StorageSize.I32 or StorageSize.U32:
                    suffix = 'w';
                    break;
                case StorageSize.I64 or StorageSize.U64:
                    suffix = 'l';
                    break;
                default:
                    throw new NotSupportedException($"Unsupported type '{simpleType}' for binary operator '{op}'");
            }

            if (op is BoundBinaryOperator.Equal)
            {
                return "ceq" + suffix;
            }

            if (op is BoundBinaryOperator.NotEqual)
            {
                return "cne" + suffix;
            }

            string sign;

            if (simpleType is NubPrimitiveType { Kind: PrimitiveTypeKind.I8 or PrimitiveTypeKind.I16 or PrimitiveTypeKind.I32 or PrimitiveTypeKind.I64 })
            {
                sign = "s";
            }
            else if (simpleType is NubPrimitiveType { Kind: PrimitiveTypeKind.U8 or PrimitiveTypeKind.U16 or PrimitiveTypeKind.U32 or PrimitiveTypeKind.U64 })
            {
                sign = "u";
            }
            else
            {
                throw new NotSupportedException($"Unsupported type '{type}' for binary operator '{op}'");
            }

            return op switch
            {
                BoundBinaryOperator.GreaterThan => 'c' + sign + "gt" + suffix,
                BoundBinaryOperator.GreaterThanOrEqual => 'c' + sign + "ge" + suffix,
                BoundBinaryOperator.LessThan => 'c' + sign + "lt" + suffix,
                BoundBinaryOperator.LessThanOrEqual => 'c' + sign + "le" + suffix,
                _ => throw new ArgumentOutOfRangeException(nameof(op), op, null)
            };
        }

        return op switch
        {
            BoundBinaryOperator.Plus => "add",
            BoundBinaryOperator.Minus => "sub",
            BoundBinaryOperator.Multiply => "mul",
            BoundBinaryOperator.Divide => "div",
            _ => throw new ArgumentOutOfRangeException(nameof(op))
        };
    }

    private static Val EmitExternFuncIdent(BoundExternFuncIdent externFuncIdent)
    {
        var func = _definitionTable.LookupExternFunc(externFuncIdent.Namespace, externFuncIdent.Name);
        return new Val(ExternFuncName(func), externFuncIdent.Type, ValKind.Direct);
    }

    private static Val EmitLocalFuncIdent(BoundLocalFuncIdent localFuncIdent)
    {
        var func = _definitionTable.LookupExternFunc(localFuncIdent.Namespace, localFuncIdent.Name);
        return new Val(ExternFuncName(func), localFuncIdent.Type, ValKind.Direct);
    }

    private static Val EmitVariableIdent(BoundVariableIdent variableIdent)
    {
        return _variables.Single(v => v.Name == variableIdent.Name).Val;
    }

    private static Val EmitLiteral(BoundLiteral literal)
    {
        switch (literal.Kind)
        {
            case LiteralKind.Integer:
            {
                if (literal.Type is NubPrimitiveType { Kind: PrimitiveTypeKind.F32 })
                {
                    var value = float.Parse(literal.Literal, CultureInfo.InvariantCulture);
                    var bits = BitConverter.SingleToInt32Bits(value);
                    return new Val(bits.ToString(), literal.Type, ValKind.Direct);
                }

                if (literal.Type is NubPrimitiveType { Kind: PrimitiveTypeKind.F64 })
                {
                    var value = double.Parse(literal.Literal, CultureInfo.InvariantCulture);
                    var bits = BitConverter.DoubleToInt64Bits(value);
                    return new Val(bits.ToString(), literal.Type, ValKind.Direct);
                }

                if (literal.Type is NubPrimitiveType { Kind: PrimitiveTypeKind.I8 or PrimitiveTypeKind.U8 or PrimitiveTypeKind.I16 or PrimitiveTypeKind.U16 or PrimitiveTypeKind.I32 or PrimitiveTypeKind.U32 or PrimitiveTypeKind.I64 or PrimitiveTypeKind.U64 })
                {
                    return new Val(literal.Literal, literal.Type, ValKind.Direct);
                }

                break;
            }
            case LiteralKind.Float:
            {
                if (literal.Type is NubPrimitiveType { Kind: PrimitiveTypeKind.I8 or PrimitiveTypeKind.U8 or PrimitiveTypeKind.I16 or PrimitiveTypeKind.U16 or PrimitiveTypeKind.I32 or PrimitiveTypeKind.U32 or PrimitiveTypeKind.I64 or PrimitiveTypeKind.U64 })
                {
                    return new Val(literal.Literal.Split(".").First(), literal.Type, ValKind.Direct);
                }

                if (literal.Type is NubPrimitiveType { Kind: PrimitiveTypeKind.F32 })
                {
                    var value = float.Parse(literal.Literal, CultureInfo.InvariantCulture);
                    var bits = BitConverter.SingleToInt32Bits(value);
                    return new Val(bits.ToString(), literal.Type, ValKind.Direct);
                }

                if (literal.Type is NubPrimitiveType { Kind: PrimitiveTypeKind.F64 })
                {
                    var value = double.Parse(literal.Literal, CultureInfo.InvariantCulture);
                    var bits = BitConverter.DoubleToInt64Bits(value);
                    return new Val(bits.ToString(), literal.Type, ValKind.Direct);
                }

                break;
            }
            case LiteralKind.String:
            {
                if (literal.Type is NubStringType)
                {
                    var stringLiteral = new StringLiteral(literal.Literal, StringName());
                    _stringLiterals.Add(stringLiteral);
                    return new Val(stringLiteral.Name, literal.Type, ValKind.Direct);
                }

                if (literal.Type is NubCStringType)
                {
                    var cStringLiteral = new CStringLiteral(literal.Literal, CStringName());
                    _cStringLiterals.Add(cStringLiteral);
                    return new Val(cStringLiteral.Name, literal.Type, ValKind.Direct);
                }

                break;
            }
            case LiteralKind.Bool:
            {
                if (literal.Type is NubPrimitiveType { Kind: PrimitiveTypeKind.Bool })
                {
                    return new Val(bool.Parse(literal.Literal) ? "1" : "0", literal.Type, ValKind.Direct);
                }

                break;
            }
        }

        throw new NotSupportedException($"Cannot create literal of kind '{literal.Kind}' for type {literal.Type}");
    }

    private static Val EmitStructInitializer(BoundStructInitializer structInitializer, string? destination = null)
    {
        var @struct = _definitionTable.LookupStruct(structInitializer.StructType.Namespace, structInitializer.StructType.Name);

        if (destination == null)
        {
            destination = TmpName();
            var size = structInitializer.StructType.Size(_definitionTable);
            _writer.Indented($"{destination} =l alloc8 {size}");
        }

        foreach (var field in @struct.Fields)
        {
            if (!structInitializer.Initializers.TryGetValue(field.Name, out var valueExpression))
            {
                valueExpression = field.Value.Value;
            }

            Debug.Assert(valueExpression != null);

            var offset = TmpName();
            _writer.Indented($"{offset} =l add {destination}, {OffsetOf(@struct, field.Name)}");
            EmitCopyIntoOrInitialize(valueExpression, offset);
        }

        return new Val(destination, structInitializer.StructType, ValKind.Direct);
    }

    private static Val EmitUnaryExpression(BoundUnaryExpression unaryExpression)
    {
        var operand = EmitUnwrap(EmitExpression(unaryExpression.Operand));
        var outputName = TmpName();

        switch (unaryExpression.Operator)
        {
            case BoundUnaryOperator.Negate:
            {
                switch (unaryExpression.Operand.Type)
                {
                    case NubPrimitiveType { Kind: PrimitiveTypeKind.I64 }:
                        _writer.Indented($"{outputName} =l neg {operand}");
                        return new Val(outputName, unaryExpression.Type, ValKind.Direct);
                    case NubPrimitiveType { Kind: PrimitiveTypeKind.I32 or PrimitiveTypeKind.I16 or PrimitiveTypeKind.I8 }:
                        _writer.Indented($"{outputName} =w neg {operand}");
                        return new Val(outputName, unaryExpression.Type, ValKind.Direct);
                    case NubPrimitiveType { Kind: PrimitiveTypeKind.F64 }:
                        _writer.Indented($"{outputName} =d neg {operand}");
                        return new Val(outputName, unaryExpression.Type, ValKind.Direct);
                    case NubPrimitiveType { Kind: PrimitiveTypeKind.F32 }:
                        _writer.Indented($"{outputName} =s neg {operand}");
                        return new Val(outputName, unaryExpression.Type, ValKind.Direct);
                }

                break;
            }
            case BoundUnaryOperator.Invert:
            {
                switch (unaryExpression.Operand.Type)
                {
                    case NubPrimitiveType { Kind: PrimitiveTypeKind.Bool }:
                        _writer.Indented($"{outputName} =w xor {operand}, 1");
                        return new Val(outputName, unaryExpression.Type, ValKind.Direct);
                }

                break;
            }
            default:
            {
                throw new ArgumentOutOfRangeException();
            }
        }

        throw new NotSupportedException($"Unary operator {unaryExpression.Operator} for type {unaryExpression.Operand.Type} not supported");
    }

    private static Val EmitStructFieldAccess(BoundStructFieldAccess structFieldAccess)
    {
        var target = EmitUnwrap(EmitExpression(structFieldAccess.Target));

        var structDef = _definitionTable.LookupStruct(structFieldAccess.StructType.Namespace, structFieldAccess.StructType.Name);
        var offset = OffsetOf(structDef, structFieldAccess.Field);

        var output = TmpName();
        _writer.Indented($"{output} =l add {target}, {offset}");

        // If the accessed member is an inline struct, it will not be a pointer
        if (structFieldAccess.Type is NubCustomType customType && customType.Kind(_definitionTable) == CustomTypeKind.Struct)
        {
            return new Val(output, structFieldAccess.Type, ValKind.Direct);
        }

        return new Val(output, structFieldAccess.Type, ValKind.Pointer);
    }

    private static Val EmitTraitFuncAccess(BoundTraitFuncAccess traitFuncAccess)
    {
        throw new NotImplementedException();
    }

    private static Val EmitTraitImplFuncAccess(BoundTraitImplFuncAccess traitImplFuncAccess)
    {
        var target = EmitExpression(traitImplFuncAccess.Target);

        var funcImpl = _definitionTable.LookupTraitFuncImpl(traitImplFuncAccess.Target.Type, traitImplFuncAccess.FuncName);

        var name = ImplFuncName();
        _implFunctions.TryAdd(funcImpl, name);
        return new Val(name, traitImplFuncAccess.Type, ValKind.Direct, new MethodCallContext(target));
    }

    private static Val EmitFuncCall(BoundFuncCall funcCall)
    {
        var expression = EmitExpression(funcCall.Expression);
        var funcPointer = EmitUnwrap(expression);

        var parameterStrings = new List<string>();

        if (expression.FuncCallContext != null)
        {
            var thisArg = EmitUnwrap(expression.FuncCallContext.ThisArg);
            parameterStrings.Add($"{FuncQBETypeName(expression.FuncCallContext.ThisArg.Type)} {thisArg}");
        }

        foreach (var parameter in funcCall.Parameters)
        {
            var copy = EmitCreateCopyOrInitialize(parameter);
            parameterStrings.Add($"{FuncQBETypeName(parameter.Type)} {copy}");
        }

        if (funcCall.Type is NubVoidType)
        {
            _writer.Indented($"call {funcPointer}({string.Join(", ", parameterStrings)})");
            return new Val(string.Empty, funcCall.Type, ValKind.Direct);
        }
        else
        {
            var outputName = TmpName();
            _writer.Indented($"{outputName} {QBEAssign(funcCall.Type)} call {funcPointer}({string.Join(", ", parameterStrings)})");
            return new Val(outputName, funcCall.Type, ValKind.Direct);
        }
    }

    private static string EmitUnwrap(Val val)
    {
        return val.Kind switch
        {
            ValKind.Direct => val.Name,
            ValKind.Pointer => EmitLoad(val.Type, val.Name).Name,
            _ => throw new ArgumentOutOfRangeException()
        };
    }

    private static int OffsetOf(BoundStruct structDefinition, string member)
    {
        var offset = 0;

        foreach (var field in structDefinition.Fields)
        {
            if (field.Name == member)
            {
                return offset;
            }

            var fieldAlignment = field.Type.Alignment(_definitionTable);

            offset = NubType.AlignTo(offset, fieldAlignment);
            offset += field.Type.Size(_definitionTable);
        }

        throw new UnreachableException($"Member '{member}' not found in struct");
    }
}

internal class StringLiteral(string value, string name)
{
    public string Value { get; } = value;
    public string Name { get; } = name;
}

internal class CStringLiteral(string value, string name)
{
    public string Value { get; } = value;
    public string Name { get; } = name;
}

internal class Variable(string name, Val val)
{
    public string Name { get; } = name;
    public Val Val { get; } = val;
}

internal record Val(string Name, NubType Type, ValKind Kind, MethodCallContext? FuncCallContext = null);

internal record MethodCallContext(Val ThisArg);

internal enum ValKind
{
    Pointer,
    Direct,
}