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

namespace 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<(BoundAnonymousFuncNode Func, string Name)> _anonymousFunctions = [];
    private static Dictionary<BoundImplementationFuncNode, 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<BoundLocalFuncDefinitionNode>())
        {
            EmitFuncDefinition(funcDef, FuncName(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 FuncName(BoundFuncDefinition funcDef)
    {
        return funcDef switch
        {
            BoundExternFuncDefinitionNode externFuncDefinition => $"${externFuncDefinition.CallName}",
            BoundLocalFuncDefinitionNode localFuncDefinition => localFuncDefinition.Exported
                ? $"${localFuncDefinition.Name}"
                : $"${localFuncDefinition.Namespace}_{localFuncDefinition.Name}",
            _ => throw new ArgumentOutOfRangeException(nameof(funcDef))
        };
    }

    private static string ImplFuncName(BoundTraitImplementationDefinitionNode implDef, string funcName)
    {
        return $"$impl{++_implFuncNameIndex}";
    }

    private static string CustomTypeName(NubCustomType customType)
    {
        return $":{customType.Namespace}_{customType.Name}";
    }

    private static void EmitStore(NubType type, string value, string destination)
    {
        var store = type switch
        {
            NubComplexType => "storel",
            NubSimpleType simpleType => simpleType switch
            {
                NubFuncType or NubPointerType => "loadl",
                NubPrimitiveType primitiveType => primitiveType.Kind switch
                {
                    PrimitiveTypeKind.I64 or PrimitiveTypeKind.U64 => "storel",
                    PrimitiveTypeKind.I32 or PrimitiveTypeKind.U32 => "storew",
                    PrimitiveTypeKind.I16 or PrimitiveTypeKind.U16 => "storeh",
                    PrimitiveTypeKind.I8 or PrimitiveTypeKind.U8 or PrimitiveTypeKind.Bool => "storeb",
                    PrimitiveTypeKind.F64 => "stored",
                    PrimitiveTypeKind.F32 => "stores",
                    _ => throw new ArgumentOutOfRangeException()
                },
                _ => throw new ArgumentOutOfRangeException($"'{type}' type cannot be used in store instructions")
            },
            _ => throw new UnreachableException()
        };

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

    private static Val EmitLoad(NubType type, string from)
    {
        var into = TmpName();
        var load = type switch
        {
            NubComplexType => "loadl",
            NubSimpleType simpleType => simpleType switch
            {
                NubFuncType or NubPointerType => "loadl",
                NubPrimitiveType primitiveType => primitiveType.Kind switch
                {
                    PrimitiveTypeKind.I64 or PrimitiveTypeKind.U64 => "loadl",
                    PrimitiveTypeKind.I32 or PrimitiveTypeKind.U32 => "loadw",
                    PrimitiveTypeKind.I16 => "loadsh",
                    PrimitiveTypeKind.I8 => "loadsb",
                    PrimitiveTypeKind.U16 => "loaduh",
                    PrimitiveTypeKind.U8 or PrimitiveTypeKind.Bool => "loadub",
                    PrimitiveTypeKind.F64 => "loadd",
                    PrimitiveTypeKind.F32 => "loads",
                    _ => throw new ArgumentOutOfRangeException()
                },
                _ => throw new ArgumentOutOfRangeException($"'{type}' type cannot be used in load instructions")
            },
            _ => throw new UnreachableException()
        };

        _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}, {SizeOf(type.ElementType)}");
        _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(BoundExpressionNode source, string destinationPointer)
    {
        switch (source)
        {
            case BoundArrayInitializerNode arrayInitializer:
            {
                _writer.WriteDebugLocation(arrayInitializer);
                EmitStore(source.Type, EmitUnwrap(EmitArrayInitializer(arrayInitializer)), destinationPointer);
                return true;
            }
            case BoundStructInitializerNode structInitializer:
            {
                _writer.WriteDebugLocation(structInitializer);
                EmitStructInitializer(structInitializer, destinationPointer);
                return true;
            }
            case BoundLiteralNode { Kind: LiteralKind.String } literal:
            {
                _writer.WriteDebugLocation(literal);
                EmitStore(source.Type, EmitUnwrap(EmitLiteral(literal)), destinationPointer);
                return true;
            }
        }

        return false;
    }

    private static void EmitCopyIntoOrInitialize(BoundExpressionNode 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));

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

                switch (complexType)
                {
                    case NubArrayType:
                    case NubCStringType:
                    case NubStringType:
                    {
                        var buffer = TmpName();
                        _writer.Indented($"{buffer} =l alloc8 {size}");
                        EmitMemcpy(value, buffer, size);
                        EmitStore(source.Type, buffer, destinationPointer);
                        return;
                    }
                    case NubCustomType:
                    {
                        EmitMemcpy(value, destinationPointer, size);
                        return;
                    }
                    default:
                    {
                        throw new ArgumentOutOfRangeException(nameof(complexType));
                    }
                }
            }
            case NubSimpleType simpleType:
            {
                EmitStore(simpleType, value, destinationPointer);
                return;
            }
            default:
            {
                throw new ArgumentOutOfRangeException(nameof(source.Type));
            }
        }
    }

    private static bool EmitTryCreateWithoutCopy(BoundExpressionNode source, [NotNullWhen(true)] out string? destination)
    {
        switch (source)
        {
            case BoundArrayInitializerNode:
            case BoundStructInitializerNode:
            case BoundLiteralNode { Kind: LiteralKind.String }:
            {
                destination = EmitUnwrap(EmitExpression(source));
                return true;
            }
        }

        destination = null;
        return false;
    }

    private static string EmitCreateCopyOrInitialize(BoundExpressionNode 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));

        switch (source.Type)
        {
            case NubComplexType complexType:
            {
                var destination = TmpName();

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

                _writer.Indented($"{destination} =l alloc8 {size}");
                EmitMemcpy(value, destination, size);
                return destination;
            }
            case NubSimpleType:
            {
                return value;
            }
            default:
            {
                throw new ArgumentOutOfRangeException(nameof(source.Type));
            }
        }
    }

    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()
        };
    }

    private static int AlignmentOf(NubType type)
    {
        switch (type)
        {
            case NubPrimitiveType primitiveType:
            {
                return primitiveType.Kind switch
                {
                    PrimitiveTypeKind.I64 or PrimitiveTypeKind.U64 or PrimitiveTypeKind.F64 => 8,
                    PrimitiveTypeKind.I32 or PrimitiveTypeKind.U32 or PrimitiveTypeKind.F32 => 4,
                    PrimitiveTypeKind.I16 or PrimitiveTypeKind.U16 => 2,
                    PrimitiveTypeKind.I8 or PrimitiveTypeKind.U8 or PrimitiveTypeKind.Bool => 1,
                    _ => throw new ArgumentOutOfRangeException()
                };
            }
            case NubCustomType customType:
            {
                var structDef = _definitionTable.LookupStruct(customType.Namespace, customType.Name);
                if (structDef.HasValue)
                {
                    return structDef.Value.Fields.Max(f => AlignmentOf(f.Type));
                }

                var traitDef = _definitionTable.LookupTrait(customType.Namespace, customType.Name);
                if (traitDef.HasValue)
                {
                    return 8;
                }

                throw new UnreachableException();
            }
            case NubPointerType:
            case NubArrayType:
            case NubCStringType:
            case NubStringType:
            case NubFuncType:
                return 8;
            default:
                throw new ArgumentOutOfRangeException();
        }
    }

    private static int AlignTo(int offset, int alignment)
    {
        return (offset + alignment - 1) & ~(alignment - 1);
    }

    private static int SizeOf(NubType type)
    {
        switch (type)
        {
            case NubPrimitiveType primitiveType:
            {
                return primitiveType.Kind switch
                {
                    PrimitiveTypeKind.I64 or PrimitiveTypeKind.U64 or PrimitiveTypeKind.F64 => 8,
                    PrimitiveTypeKind.I32 or PrimitiveTypeKind.U32 or PrimitiveTypeKind.F32 => 4,
                    PrimitiveTypeKind.I16 or PrimitiveTypeKind.U16 => 2,
                    PrimitiveTypeKind.I8 or PrimitiveTypeKind.U8 or PrimitiveTypeKind.Bool => 1,
                    _ => throw new ArgumentOutOfRangeException()
                };
            }
            case NubCustomType customType:
            {
                var structDef = _definitionTable.LookupStruct(customType.Namespace, customType.Name);
                if (structDef.HasValue)
                {
                    var size = 0;
                    var maxAlignment = 1;

                    foreach (var field in structDef.Value.Fields)
                    {
                        var fieldAlignment = AlignmentOf(field.Type);
                        maxAlignment = Math.Max(maxAlignment, fieldAlignment);

                        size = AlignTo(size, fieldAlignment);
                        size += SizeOf(field.Type);
                    }

                    size = AlignTo(size, maxAlignment);

                    return size;
                }

                var traitDef = _definitionTable.LookupTrait(customType.Namespace, customType.Name);
                if (traitDef.HasValue)
                {
                    return 16;
                }

                throw new UnreachableException();
            }
            case NubPointerType:
            case NubArrayType:
            case NubCStringType:
            case NubStringType:
            case NubFuncType:
                return 8;
            default:
                throw new ArgumentOutOfRangeException();
        }
    }

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

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

            var fieldAlignment = AlignmentOf(field.Type);

            offset = AlignTo(offset, fieldAlignment);
            offset += SizeOf(field.Type);
        }

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

    private static string FuncQBETypeName(NubType type)
    {
        return type switch
        {
            NubCustomType customType => CustomTypeName(customType),
            NubComplexType => "l",
            NubSimpleType simpleType => simpleType switch
            {
                NubPointerType or NubFuncType => "l",
                NubPrimitiveType primitiveType => primitiveType.Kind switch
                {
                    PrimitiveTypeKind.I64 or PrimitiveTypeKind.U64 => "l",
                    PrimitiveTypeKind.I32 or PrimitiveTypeKind.U32 => "w",
                    PrimitiveTypeKind.I16 => "sh",
                    PrimitiveTypeKind.I8 => "sb",
                    PrimitiveTypeKind.U16 => "uh",
                    PrimitiveTypeKind.U8 or PrimitiveTypeKind.Bool => "ub",
                    PrimitiveTypeKind.F64 => "d",
                    PrimitiveTypeKind.F32 => "s",
                    _ => throw new ArgumentOutOfRangeException()
                },
                _ => throw new NotSupportedException($"'{type}' type cannot be used as a function definition type")
            },
            _ => throw new UnreachableException()
        };
    }

    private static void EmitFuncDefinition(BoundNode debugNode, string name, List<FuncParameter> 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 BoundReturnNode)
        {
            if (returnType is NubVoidType)
            {
                _writer.Indented("ret");
            }
        }

        _writer.EndFunction();
    }

    private static void EmitStructDefinition(BoundStructDefinitionNode structDef)
    {
        var structType = new NubCustomType(structDef.Namespace, structDef.Name);
        _writer.WriteLine($"type {CustomTypeName(structType)} = {{ ");

        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)
        {
            return field.Type switch
            {
                NubCustomType customType => CustomTypeName(customType),
                NubComplexType => "l",
                NubSimpleType simpleType => simpleType switch
                {
                    NubPointerType 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 => "h",
                        PrimitiveTypeKind.I8 or PrimitiveTypeKind.U8 or PrimitiveTypeKind.Bool => "b",
                        PrimitiveTypeKind.F64 => "d",
                        PrimitiveTypeKind.F32 => "s",
                        _ => throw new ArgumentOutOfRangeException()
                    },
                    _ => throw new NotSupportedException($"'{field.Type}' type cannot be used in structs")
                },
                _ => throw new UnreachableException()
            };
        }
    }

    private static void EmitTraitVTable(BoundTraitDefinitionNode traitDef)
    {
        _writer.WriteLine($"type {CustomTypeName(new NubCustomType(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(BoundStatementNode statement)
    {
        _writer.WriteDebugLocation(statement);

        switch (statement)
        {
            case BoundAssignmentNode assignment:
                EmitAssignment(assignment);
                break;
            case BoundBreakNode @break:
                EmitBreak(@break);
                break;
            case BoundContinueNode @continue:
                EmitContinue(@continue);
                break;
            case BoundIfNode ifStatement:
                EmitIf(ifStatement);
                break;
            case BoundReturnNode @return:
                EmitReturn(@return);
                break;
            case BoundStatementExpressionNode statementExpression:
                EmitExpression(statementExpression.Expression);
                break;
            case BoundVariableDeclarationNode variableDeclaration:
                EmitVariableDeclaration(variableDeclaration);
                break;
            case BoundWhileNode whileStatement:
                EmitWhile(whileStatement);
                break;
            default:
                throw new ArgumentOutOfRangeException(nameof(statement));
        }
    }

    private static void EmitAssignment(BoundAssignmentNode assignment)
    {
        var destination = EmitExpression(assignment.Expression);
        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(BoundBreakNode @break)
    {
        _writer.Indented($"jmp {_breakLabels.Peek()}");
        _codeIsReachable = false;
    }

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

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

    private static void EmitVariableDeclaration(BoundVariableDeclarationNode 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(BoundWhileNode 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(BoundExpressionNode expression)
    {
        _writer.WriteDebugLocation(expression);
        return expression switch
        {
            BoundAddressOfNode addressOf => EmitAddressOf(addressOf),
            BoundAnonymousFuncNode anonymousFunc => EmitAnonymousFunc(anonymousFunc),
            BoundArrayIndexAccessNode arrayIndex => EmitArrayIndexAccess(arrayIndex),
            BoundArrayInitializerNode arrayInitializer => EmitArrayInitializer(arrayInitializer),
            BoundBinaryExpressionNode binaryExpression => EmitBinaryExpression(binaryExpression),
            BoundDereferenceNode dereference => EmitDereference(dereference),
            BoundFuncCallNode funcCallExpression => EmitFuncCall(funcCallExpression),
            BoundIdentifierNode identifier => EmitIdentifier(identifier),
            BoundLiteralNode literal => EmitLiteral(literal),
            BoundStructInitializerNode structInitializer => EmitStructInitializer(structInitializer),
            BoundUnaryExpressionNode unaryExpression => EmitUnaryExpression(unaryExpression),
            BoundMemberAccessNode memberAccess => EmitMemberAccess(memberAccess),
            _ => throw new ArgumentOutOfRangeException(nameof(expression))
        };
    }

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

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

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

        var pointer = TmpName();
        _writer.Indented($"{pointer} =l mul {index}, {SizeOf(elementType)}");
        _writer.Indented($"{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(BoundArrayInitializerNode arrayInitializer)
    {
        var capacity = EmitUnwrap(EmitExpression(arrayInitializer.Capacity));
        var elementSize = SizeOf(arrayInitializer.ElementType);

        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(BoundDereferenceNode dereference)
    {
        return EmitLoad(dereference.Type, EmitUnwrap(EmitExpression(dereference.Expression)));
    }

    private static Val EmitAddressOf(BoundAddressOfNode addressOf)
    {
        var value = EmitExpression(addressOf.Expression);
        Debug.Assert(value.Kind == ValKind.Pointer);
        return new Val(value.Name, addressOf.Type, ValKind.Direct);
    }

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

            if (type.Is8BitInteger)
            {
                if (type.IsSignedInteger)
                {
                    _writer.Indented($"{left} =w extsb {left}");
                    _writer.Indented($"{right} =w extsb {right}");
                }
                else
                {
                    _writer.Indented($"{left} =w extub {left}");
                    _writer.Indented($"{right} =w extub {right}");
                }

                suffix = 'w';
            }
            else if (type.Is16BitInteger)
            {
                if (type.IsSignedInteger)
                {
                    _writer.Indented($"{left} =w extsh {left}");
                    _writer.Indented($"{right} =w extsh {right}");
                }
                else
                {
                    _writer.Indented($"{left} =w extuh {left}");
                    _writer.Indented($"{right} =w extuh {right}");
                }

                suffix = 'w';
            }
            else if (type.Is32BitInteger)
            {
                suffix = 'w';
            }
            else if (type.Is64BitInteger)
            {
                suffix = 'l';
            }
            else
            {
                throw new NotSupportedException($"Unsupported type '{type}' for binary operator '{op}'");
            }

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

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

            string sign;

            if (type.IsSignedInteger)
            {
                sign = "s";
            }
            else if (type.IsUnsignedInteger)
            {
                sign = "u";
            }
            else if (type.IsFloat)
            {
                sign = "";
            }
            else
            {
                throw new NotSupportedException($"Unsupported type '{type}' for binary operator '{op}'");
            }

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

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

    private static Val EmitIdentifier(BoundIdentifierNode identifier)
    {
        if (_definitionTable.LookupFunc(identifier.Namespace.Or(_syntaxTree.Namespace), identifier.Name).TryGetValue(out var func))
        {
            return new Val(FuncName(func), identifier.Type, ValKind.Direct);
        }

        if (!identifier.Namespace.HasValue)
        {
            return _variables.Single(v => v.Name == identifier.Name).Val;
        }

        throw new UnreachableException();
    }

    private static Val EmitLiteral(BoundLiteralNode literal)
    {
        switch (literal.Kind)
        {
            case LiteralKind.Integer:
            {
                if (literal.Type.IsFloat32)
                {
                    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.IsFloat64)
                {
                    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.IsInteger)
                {
                    return new Val(literal.Literal, literal.Type, ValKind.Direct);
                }

                break;
            }
            case LiteralKind.Float:
            {
                if (literal.Type.IsInteger)
                {
                    return new Val(literal.Literal.Split(".").First(), literal.Type, ValKind.Direct);
                }

                if (literal.Type.IsFloat32)
                {
                    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.IsFloat64)
                {
                    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.IsString)
                {
                    var stringLiteral = new StringLiteral(literal.Literal, StringName());
                    _stringLiterals.Add(stringLiteral);
                    return new Val(stringLiteral.Name, literal.Type, ValKind.Direct);
                }

                if (literal.Type.IsCString)
                {
                    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.IsBool)
                {
                    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(BoundStructInitializerNode structInitializer, string? destination = null)
    {
        if (structInitializer.StructType is not NubCustomType structType)
        {
            throw new UnreachableException();
        }

        var structDefinition = _definitionTable.LookupStruct(structType.Namespace, structType.Name).GetValue();

        if (destination == null)
        {
            destination = TmpName();
            var size = SizeOf(structType);
            _writer.Indented($"{destination} =l alloc8 {size}");
        }

        foreach (var field in structDefinition.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(structDefinition, field.Name)}");
            EmitCopyIntoOrInitialize(valueExpression, offset);
        }

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

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

        switch (unaryExpression.Operator)
        {
            case UnaryExpressionOperator.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 UnaryExpressionOperator.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 EmitMemberAccess(BoundMemberAccessNode memberAccess)
    {
        var item = EmitUnwrap(EmitExpression(memberAccess.Expression));

        var implementation = _definitionTable.LookupTraitImplementationForType(memberAccess.Expression.Type, memberAccess.Member);
        if (implementation.HasValue)
        {
            var name = ImplFuncName(implementation.Value.Item1, memberAccess.Member);
            _implFunctions.TryAdd(implementation.Value.Item2, name);
            return new Val(name, memberAccess.Type, ValKind.Direct, new MethodCallContext(item, memberAccess.Expression.Type));
        }

        var output = TmpName();

        if (memberAccess.Expression.Type is NubCustomType customType)
        {
            var function = _definitionTable.LookupFunctionOnTrait(customType.Namespace, customType.Name, memberAccess.Member);
            if (function.HasValue)
            {
                throw new NotImplementedException("VTable lookup is not implemented");
            }

            var structDef = _definitionTable.LookupStruct(customType.Namespace, customType.Name);
            if (structDef.HasValue)
            {
                var offset = OffsetOf(structDef.Value, memberAccess.Member);
                _writer.Indented($"{output} =l add {item}, {offset}");

                if (memberAccess.Type is NubCustomType inner)
                {
                    // If the accessed member is an inline struct, it will not be a pointer
                    if (_definitionTable.LookupStruct(inner.Namespace, inner.Name).HasValue)
                    {
                        return new Val(output, memberAccess.Type, ValKind.Direct);
                    }
                }

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

        if (memberAccess.Member == "count")
        {
            switch (memberAccess.Expression.Type)
            {
                case NubArrayType:
                {
                    _writer.Indented($"{output} =l loadl {item}");
                    return new Val(output, memberAccess.Type, ValKind.Direct);
                }
                case NubStringType:
                {
                    _writer.Indented($"{output} =l call $nub_string_length(l {item})");
                    return new Val(output, memberAccess.Type, ValKind.Direct);
                }
                case NubCStringType:
                {
                    _writer.Indented($"{output} =l call $nub_cstring_length(l {item})");
                    return new Val(output, memberAccess.Type, ValKind.Direct);
                }
            }
        }

        throw new UnreachableException();
    }

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

        var parameterStrings = new List<string>();

        if (expression.FuncCallContext != null)
        {
            parameterStrings.Add($"{FuncQBETypeName(expression.FuncCallContext.ThisArgType)} {expression.FuncCallContext.ThisArgName}");
        }

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

        if (funcCall.Type.IsVoid)
        {
            _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()
        };
    }
}

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(string ThisArgName, NubType ThisArgType);

internal enum ValKind
{
    Pointer,
    Direct,
}