using System.Diagnostics;
using System.Globalization;
using System.Text;
using NubLang.Tokenization;
using NubLang.TypeChecking;
using NubLang.TypeChecking.Node;

namespace NubLang.Generation.QBE;

public class QBEGenerator
{
    private readonly QBEWriter _writer;
    private readonly TypedModule _module;
    private readonly IReadOnlyDictionary<string, ModuleSignature> _moduleSignatures;

    private readonly List<CStringLiteral> _cStringLiterals = [];
    private readonly List<StringLiteral> _stringLiterals = [];
    private readonly Stack<string> _breakLabels = [];
    private readonly Stack<string> _continueLabels = [];
    private int _tmpIndex;
    private int _labelIndex;
    private int _cStringLiteralIndex;
    private int _stringLiteralIndex;
    private bool _codeIsReachable = true;

    public QBEGenerator(TypedModule module, IReadOnlyDictionary<string, ModuleSignature> moduleSignatures)
    {
        _module = module;
        _moduleSignatures = moduleSignatures;
        _writer = new QBEWriter();
    }

    public string Emit()
    {
        _cStringLiterals.Clear();
        _stringLiterals.Clear();
        _breakLabels.Clear();
        _continueLabels.Clear();
        _tmpIndex = 0;
        _labelIndex = 0;
        _cStringLiteralIndex = 0;
        _stringLiteralIndex = 0;
        _codeIsReachable = true;

        foreach (var (module, signature) in _moduleSignatures)
        {
            foreach (var structType in signature.StructTypes)
            {
                EmitStructType(module, structType);
                _writer.NewLine();
            }
        }

        foreach (var structDef in _module.Definitions.OfType<StructNode>())
        {
            EmitStructDefinition(structDef);
            _writer.NewLine();
        }

        foreach (var funcDef in _module.Definitions.OfType<FuncNode>())
        {
            EmitFuncDefinition(funcDef);
            _writer.NewLine();
        }

        // foreach (var structDef in _module.Definitions.OfType<StructNode>().Where(x => x.InterfaceImplementations.Count > 0))
        // {
        //     _writer.Write($"data {StructVtableName(_module.Name, structDef.Name)} = {{ ");
        //
        //     foreach (var interfaceImplementation in structDef.InterfaceImplementations)
        //     {
        //         var interfaceDef = _definitionTable.LookupInterface(interfaceImplementation.Name);
        //         foreach (var func in interfaceDef.Functions)
        //         {
        //             _writer.Write($"l {StructFuncName(_module.Name, structDef.Name, func.Name)}, ");
        //         }
        //     }
        //
        //     _writer.WriteLine("}");
        // }

        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 QBEAssign(TypeNode type)
    {
        if (type.IsSimpleType(out var simpleType, out _))
        {
            return simpleType.StorageSize switch
            {
                StorageSize.I8 or StorageSize.U8 or StorageSize.I16 or StorageSize.U16 or StorageSize.I32 or StorageSize.U32 => "=w",
                StorageSize.I64 or StorageSize.U64 => "=l",
                StorageSize.F32 => "=s",
                StorageSize.F64 => "=d",
                _ => throw new ArgumentOutOfRangeException(nameof(simpleType.StorageSize))
            };
        }

        return "=l";
    }

    private void EmitStore(TypeNode 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 string EmitLoad(TypeNode 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 into;
    }

    private void EmitMemset(string destination, int value, string length)
    {
        var count = TmpName();
        _writer.Indented($"{count} =l copy 0");

        var loopLabel = LabelName();
        _writer.WriteLine(loopLabel);

        var continueLabel = LabelName();
        var doneLabel = LabelName();
        var condition = TmpName();
        _writer.Indented($"{condition} =w cultl {count}, {length}");
        _writer.Indented($"jnz {condition}, {continueLabel}, {doneLabel}");

        _writer.WriteLine(continueLabel);

        var destinationAddress = TmpName();
        _writer.Indented($"{destinationAddress} =l add {destination}, {count}");

        _writer.Indented($"storeb {value}, {destinationAddress}");

        _writer.Indented($"{count} =l add {count}, 1");
        _writer.Indented($"jmp {loopLabel}");

        _writer.WriteLine(doneLabel);
    }

    private void EmitMemcpy(string source, string destination, string length)
    {
        var count = TmpName();
        _writer.Indented($"{count} =l copy 0");

        var loopLabel = LabelName();
        _writer.WriteLine(loopLabel);

        var continueLabel = LabelName();
        var doneLabel = LabelName();
        var condition = TmpName();
        _writer.Indented($"{condition} =w cultl {count}, {length}");
        _writer.Indented($"jnz {condition}, {continueLabel}, {doneLabel}");

        _writer.WriteLine(continueLabel);

        var sourceAddress = TmpName();
        _writer.Indented($"{sourceAddress} =l add {source}, {count}");

        var destinationAddress = TmpName();
        _writer.Indented($"{destinationAddress} =l add {destination}, {count}");

        var value = TmpName();
        _writer.Indented($"{value} =w loadub {sourceAddress}");
        _writer.Indented($"storeb {value}, {destinationAddress}");

        _writer.Indented($"{count} =l add {count}, 1");
        _writer.Indented($"jmp {loopLabel}");

        _writer.WriteLine(doneLabel);
    }

    private string EmitArraySizeInBytes(ArrayTypeNode 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 string EmitCStringSizeInBytes(string cstring)
    {
        var count = TmpName();
        _writer.Indented($"{count} =l copy 0");

        var loopLabel = LabelName();
        _writer.WriteLine(loopLabel);

        var address = TmpName();
        _writer.Indented($"{address} =l add {cstring}, {count}");

        var value = TmpName();
        _writer.Indented($"{value} =w loadub {address}");

        var notZeroLabel = LabelName();
        var zeroLabel = LabelName();
        _writer.Indented($"jnz {value}, {notZeroLabel}, {zeroLabel}");
        _writer.WriteLine(notZeroLabel);
        _writer.Indented($"{count} =l add {count}, 1");
        _writer.Indented($"jmp {loopLabel}");
        _writer.WriteLine(zeroLabel);

        return count;
    }

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

    private void EmitCopyInto(ExpressionNode source, string destination)
    {
        // Simple types are passed in registers and can therefore just be stored
        if (source.Type.IsSimpleType(out var simpleType, out var complexType))
        {
            var value = EmitExpression(source);
            EmitStore(simpleType, value, destination);
            return;
        }

        // Structs and interfaces has known sizes at compile time
        if (complexType is StructTypeNode or InterfaceTypeNode)
        {
            var value = EmitExpression(source);
            _writer.Indented($"blit {value}, {destination}, {SizeOf(complexType)}");
        }
        // The rest of the complex types has unknown sizes
        else
        {
            var value = EmitExpression(source);
            var size = complexType switch
            {
                ArrayTypeNode arrayType => EmitArraySizeInBytes(arrayType, value),
                CStringTypeNode => EmitCStringSizeInBytes(value),
                StringTypeNode => EmitStringSizeInBytes(value),
                _ => throw new ArgumentOutOfRangeException(nameof(source.Type))
            };

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

    private string EmitCopy(ExpressionNode source)
    {
        // Allowlist for types which are safe to not copy
        if (source is ArrayInitializerNode or StructInitializerNode or ConvertToInterfaceNode or LiteralNode)
        {
            return EmitExpression(source);
        }

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

        // For the rest, we figure out the size of the type and shallow copy them
        var value = EmitExpression(source);
        var destination = TmpName();

        // Structs and interfaces has known sizes at compile time
        if (complexType is StructTypeNode or InterfaceTypeNode)
        {
            var size = SizeOf(complexType);
            _writer.Indented($"{destination} =l alloc8 {size}");
            _writer.Indented($"blit {value}, {destination}, {size}");
        }
        // The rest of the complex types has unknown sizes
        else
        {
            var size = complexType switch
            {
                ArrayTypeNode arrayType => EmitArraySizeInBytes(arrayType, value),
                CStringTypeNode => EmitCStringSizeInBytes(value),
                StringTypeNode => EmitStringSizeInBytes(value),
                _ => throw new ArgumentOutOfRangeException(nameof(source.Type))
            };

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

        return destination;
    }

    // Utility to create QBE type names for function parameters and return types
    private string FuncQBETypeName(TypeNode 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 StructTypeNode structType)
        {
            return StructTypeName(structType.Module, structType.Name);
        }

        return "l";
    }

    private void EmitFuncDefinition(FuncNode funcDef)
    {
        if (funcDef.Body == null) return;

        _labelIndex = 0;
        _tmpIndex = 0;

        _writer.Write("export function ");

        if (funcDef.Signature.ReturnType is not VoidTypeNode)
        {
            _writer.Write(FuncQBETypeName(funcDef.Signature.ReturnType) + ' ');
        }

        _writer.Write(FuncName(_module.Name, funcDef.Name));

        _writer.Write("(");
        foreach (var parameter in funcDef.Signature.Parameters)
        {
            _writer.Write(FuncQBETypeName(parameter.Type) + $" %{parameter.Name}");
        }

        _writer.WriteLine(") {");
        _writer.WriteLine("@start");

        EmitBlock(funcDef.Body);

        // Implicit return for void functions if no explicit return has been set
        if (funcDef.Signature.ReturnType is VoidTypeNode && funcDef.Body.Statements.LastOrDefault() is not ReturnNode)
        {
            _writer.Indented("ret");
        }

        _writer.WriteLine("}");
    }

    private void EmitStructDefinition(StructNode structDef)
    {
        var type = TypeResolver.ResolveStructType(_module.Name, structDef.Name, _moduleSignatures);

        // _writer.WriteLine($"export function {StructCtorName(_module.Name, structDef.Name)}() {{");
        // _writer.WriteLine("@start");
        // _writer.Indented($"%struct =l alloc8 {SizeOf(type)}");
        // // todo(nub31): Finish constructor
        // _writer.Indented("ret %struct");
        // _writer.WriteLine("}");

        foreach (var function in structDef.Functions)
        {
            _labelIndex = 0;
            _tmpIndex = 0;

            _writer.NewLine();
            _writer.Write("export function ");

            if (function.Signature.ReturnType is not VoidTypeNode)
            {
                _writer.Write(FuncQBETypeName(function.Signature.ReturnType) + ' ');
            }

            _writer.Write(StructFuncName(_module.Name, structDef.Name, function.Name));

            _writer.Write("(l %this, ");
            foreach (var parameter in function.Signature.Parameters)
            {
                _writer.Write(FuncQBETypeName(parameter.Type) + $" %{parameter.Name}, ");
            }

            _writer.WriteLine(") {");
            _writer.WriteLine("@start");

            EmitBlock(function.Body);

            // Implicit return for void functions if no explicit return has been set
            if (function.Signature.ReturnType is VoidTypeNode && function.Body.Statements.LastOrDefault() is not ReturnNode)
            {
                _writer.Indented("ret");
            }

            _writer.WriteLine("}");
        }
    }

    private void EmitStructType(string module, StructTypeNode structType)
    {
        _writer.WriteLine($"type {StructTypeName(module, structType.Name)} = {{ ");

        foreach (var field in structType.Fields)
        {
            _writer.Indented($"{StructDefQBEType(field.Type)},");
        }

        _writer.WriteLine("}");
        return;

        string StructDefQBEType(TypeNode 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 or StorageSize.U16 => "h",
                    StorageSize.I8 or StorageSize.U8 => "b",
                    StorageSize.F64 => "d",
                    StorageSize.F32 => "s",
                    _ => throw new ArgumentOutOfRangeException()
                };
            }

            if (complexType is StructTypeNode childStructType)
            {
                return StructTypeName(childStructType.Module, childStructType.Name);
            }

            return "l";
        }
    }

    private void EmitBlock(BlockNode block)
    {
        foreach (var statement in block.Statements)
        {
            if (_codeIsReachable)
            {
                EmitStatement(statement);
            }
        }

        _codeIsReachable = true;
    }

    private void EmitStatement(StatementNode statement)
    {
        // var tokens = statement.Tokens.ToArray();
        // if (tokens.Length != 0)
        // {
        //     _writer.WriteLine($"dbgloc {tokens[0].FileSpan.Span.Start.Line}");
        // }

        switch (statement)
        {
            case AssignmentNode assignment:
                EmitAssignment(assignment);
                break;
            case BreakNode:
                EmitBreak();
                break;
            case ContinueNode:
                EmitContinue();
                break;
            case IfNode ifStatement:
                EmitIf(ifStatement);
                break;
            case ReturnNode @return:
                EmitReturn(@return);
                break;
            case StatementExpressionNode statementExpression:
                EmitExpression(statementExpression.Expression);
                break;
            case VariableDeclarationNode variableDeclaration:
                EmitVariableDeclaration(variableDeclaration);
                break;
            case WhileNode whileStatement:
                EmitWhile(whileStatement);
                break;
            default:
                throw new ArgumentOutOfRangeException(nameof(statement));
        }
    }

    private void EmitAssignment(AssignmentNode assignment)
    {
        EmitCopyInto(assignment.Value, EmitAddressOfLValue(assignment.Target));
    }

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

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

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

        var result = 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(EmitIf, EmitBlock);
        }

        _writer.WriteLine(endLabel);
    }

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

    private void EmitVariableDeclaration(VariableDeclarationNode variableDeclaration)
    {
        var name = $"%{variableDeclaration.Name}";
        _writer.Indented($"{name} =l alloc8 {SizeOf(variableDeclaration.Type)}");

        if (variableDeclaration.Assignment.HasValue)
        {
            EmitCopyInto(variableDeclaration.Assignment.Value, name);
        }
    }

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

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

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

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

    private string EmitExpression(ExpressionNode expression)
    {
        // var tokens = expression.Tokens.ToArray();
        // if (tokens.Length != 0)
        // {
        //     _writer.WriteLine($"dbgloc {tokens[0].FileSpan.Span.Start.Line}");
        // }

        return expression switch
        {
            ArrayInitializerNode arrayInitializer => EmitArrayInitializer(arrayInitializer),
            StructInitializerNode structInitializer => EmitStructInitializer(structInitializer),
            AddressOfNode addressOf => EmitAddressOf(addressOf),
            DereferenceNode dereference => EmitDereference(dereference),
            BinaryExpressionNode binary => EmitBinaryExpression(binary),
            FuncCallNode funcCall => EmitFuncCall(funcCall),
            InterfaceFuncCallNode interfaceFuncCall => EmitInterfaceFuncCall(interfaceFuncCall),
            ConvertToInterfaceNode convertToInterface => EmitConvertToInterface(convertToInterface),
            ConvertIntNode convertInt => EmitConvertInt(convertInt),
            ConvertFloatNode convertFloat => EmitConvertFloat(convertFloat),
            VariableIdentifierNode identifier => EmitVariableIdentifier(identifier),
            FuncIdentifierNode funcIdentifier => EmitFuncIdentifier(funcIdentifier),
            FuncParameterIdentifierNode funcParameterIdentifier => EmitParameterFuncIdentifier(funcParameterIdentifier),
            LiteralNode literal => EmitLiteral(literal),
            UnaryExpressionNode unaryExpression => EmitUnaryExpression(unaryExpression),
            StructFieldAccessNode structFieldAccess => EmitStructFieldAccess(structFieldAccess),
            StructFuncCallNode structFuncCall => EmitStructFuncCall(structFuncCall),
            ArrayIndexAccessNode arrayIndex => EmitArrayIndexAccess(arrayIndex),
            _ => throw new ArgumentOutOfRangeException(nameof(expression))
        };
    }

    private string EmitFuncIdentifier(FuncIdentifierNode funcIdent)
    {
        // todo(nub31): Support for extern funcs
        return FuncName(funcIdent.Module, funcIdent.Name);
    }

    private string EmitVariableIdentifier(VariableIdentifierNode variableIdent)
    {
        var address = EmitAddressOfVariableIdent(variableIdent);

        return variableIdent.Type.IsSimpleType(out _, out _)
            ? EmitLoad(variableIdent.Type, address)
            : address;
    }

    private string EmitParameterFuncIdentifier(FuncParameterIdentifierNode funcParameterIdent)
    {
        return "%" + funcParameterIdent.Name;
    }

    private string EmitArrayIndexAccess(ArrayIndexAccessNode arrayIndexAccess)
    {
        // var address = EmitAddressOfArrayIndexAccess(arrayIndexAccess);
        // if (arrayIndexAccess.Type is StructTypeNode)
        // {
        //     return address;
        // }
        //
        // return EmitLoad(arrayIndexAccess.Type, address);
        throw new NotImplementedException();
    }

    private string EmitArrayInitializer(ArrayInitializerNode arrayInitializer)
    {
        var capacity = 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");
        EmitMemset(dataPointer, 0, capacityInBytes);

        return arrayPointer;
    }

    private string EmitDereference(DereferenceNode dereference)
    {
        var address = EmitExpression(dereference.Expression);
        if (dereference.Type is StructTypeNode)
        {
            return address;
        }

        return EmitLoad(dereference.Type, address);
    }

    private string EmitAddressOf(AddressOfNode addressOf)
    {
        return EmitAddressOfLValue(addressOf.LValue);
    }

    private string EmitAddressOfLValue(LValueExpressionNode addressOf)
    {
        return addressOf switch
        {
            ArrayIndexAccessNode arrayIndexAccess => EmitAddressOfArrayIndexAccess(arrayIndexAccess),
            StructFieldAccessNode structFieldAccess => EmitAddressOfStructFieldAccess(structFieldAccess),
            VariableIdentifierNode variableIdent => EmitAddressOfVariableIdent(variableIdent),
            _ => throw new ArgumentOutOfRangeException(nameof(addressOf))
        };
    }

    private string EmitAddressOfArrayIndexAccess(ArrayIndexAccessNode arrayIndexAccess)
    {
        var array = EmitExpression(arrayIndexAccess.Target);
        var index = EmitExpression(arrayIndexAccess.Index);

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

        var offset = TmpName();
        _writer.Indented($"{offset} =l mul {index}, {SizeOf(elementType)}");
        _writer.Indented($"{offset} =l add {offset}, 8");
        _writer.Indented($"{offset} =l add {array}, {offset}");
        return offset;
    }

    private string EmitAddressOfStructFieldAccess(StructFieldAccessNode structFieldAccess)
    {
        var target = EmitExpression(structFieldAccess.Target);

        var structType = TypeResolver.ResolveStructType(structFieldAccess.StructType.Module, structFieldAccess.StructType.Name, _moduleSignatures);
        var offset = OffsetOf(structType, structFieldAccess.Field);

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

    private string EmitAddressOfVariableIdent(VariableIdentifierNode variableIdent)
    {
        return "%" + variableIdent.Name;
    }

    private string EmitBinaryExpression(BinaryExpressionNode binaryExpression)
    {
        var left = EmitExpression(binaryExpression.Left);
        var right = EmitExpression(binaryExpression.Right);

        var outputName = TmpName();

        var instruction = EmitBinaryInstructionForOperator(binaryExpression.Operator, binaryExpression.Left.Type);

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

    private static string EmitBinaryInstructionForOperator(BinaryOperator op, TypeNode type)
    {
        return op switch
        {
            BinaryOperator.RightShift => type switch
            {
                IntTypeNode { Signed: true } => "sar",
                IntTypeNode { Signed: false } => "shr",
                _ => throw new NotSupportedException($"Right shift not supported for type '{type}'")
            },
            BinaryOperator.BitwiseAnd => "and",
            BinaryOperator.BitwiseOr => "or",
            BinaryOperator.BitwiseXor => "xor",
            BinaryOperator.LeftShift => "shl",
            BinaryOperator.Divide => type switch
            {
                IntTypeNode { Signed: true } => "div",
                IntTypeNode { Signed: false } => "udiv",
                FloatTypeNode => "div",
                _ => throw new NotSupportedException($"Division not supported for type '{type}'")
            },
            BinaryOperator.Modulo => type switch
            {
                IntTypeNode { Signed: true } => "rem",
                IntTypeNode { Signed: false } => "urem",
                _ => throw new NotSupportedException($"Modulo not supported for type '{type}'")
            },
            BinaryOperator.Plus => "add",
            BinaryOperator.Minus => "sub",
            BinaryOperator.Multiply => "mul",
            BinaryOperator.Equal => type switch
            {
                IntTypeNode intType => intType.Width switch
                {
                    <= 32 => "ceqw",
                    64 => "ceql",
                    _ => throw new ArgumentOutOfRangeException()
                },
                FloatTypeNode floatType => floatType.Width switch
                {
                    32 => "ceqs",
                    64 => "ceqd",
                    _ => throw new ArgumentOutOfRangeException()
                },
                _ => throw new NotSupportedException($"Equality comparison not supported for type '{type}'")
            },
            BinaryOperator.NotEqual => type switch
            {
                IntTypeNode intType => intType.Width switch
                {
                    <= 32 => "cnew",
                    64 => "cnel",
                    _ => throw new ArgumentOutOfRangeException()
                },
                FloatTypeNode floatType => floatType.Width switch
                {
                    32 => "cnes",
                    64 => "cned",
                    _ => throw new ArgumentOutOfRangeException()
                },
                _ => throw new NotSupportedException($"Inequality comparison not supported for type '{type}'")
            },
            BinaryOperator.LessThan => type switch
            {
                IntTypeNode { Signed: true } intType => intType.Width switch
                {
                    <= 32 => "csltw",
                    64 => "csltl",
                    _ => throw new ArgumentOutOfRangeException()
                },
                IntTypeNode { Signed: false } intType => intType.Width switch
                {
                    <= 32 => "cultw",
                    64 => "cultl",
                    _ => throw new ArgumentOutOfRangeException()
                },
                FloatTypeNode floatType => floatType.Width switch
                {
                    32 => "clts",
                    64 => "cltd",
                    _ => throw new ArgumentOutOfRangeException()
                },
                _ => throw new NotSupportedException($"Less than comparison not supported for type '{type}'")
            },
            BinaryOperator.LessThanOrEqual => type switch
            {
                IntTypeNode { Signed: true } intType => intType.Width switch
                {
                    <= 32 => "cslew",
                    64 => "cslel",
                    _ => throw new ArgumentOutOfRangeException()
                },
                IntTypeNode { Signed: false } intType => intType.Width switch
                {
                    <= 32 => "culew",
                    64 => "culel",
                    _ => throw new ArgumentOutOfRangeException()
                },
                FloatTypeNode floatType => floatType.Width switch
                {
                    32 => "cles",
                    64 => "cled",
                    _ => throw new ArgumentOutOfRangeException()
                },
                _ => throw new NotSupportedException($"Less than or equal comparison not supported for type '{type}'")
            },
            BinaryOperator.GreaterThan => type switch
            {
                IntTypeNode { Signed: true } intType => intType.Width switch
                {
                    <= 32 => "csgtw",
                    64 => "csgtl",
                    _ => throw new ArgumentOutOfRangeException()
                },
                IntTypeNode { Signed: false } intType => intType.Width switch
                {
                    <= 32 => "cugtw",
                    64 => "cugtl",
                    _ => throw new ArgumentOutOfRangeException()
                },
                FloatTypeNode floatType => floatType.Width switch
                {
                    32 => "cgts",
                    64 => "cgtd",
                    _ => throw new ArgumentOutOfRangeException()
                },
                _ => throw new NotSupportedException($"Greater than comparison not supported for type '{type}'")
            },
            BinaryOperator.GreaterThanOrEqual => type switch
            {
                IntTypeNode { Signed: true } intType => intType.Width switch
                {
                    <= 32 => "csgew",
                    64 => "csgel",
                    _ => throw new ArgumentOutOfRangeException()
                },
                IntTypeNode { Signed: false } intType => intType.Width switch
                {
                    <= 32 => "cugew",
                    64 => "cugel",
                    _ => throw new ArgumentOutOfRangeException()
                },
                FloatTypeNode floatType => floatType.Width switch
                {
                    32 => "cges",
                    64 => "cged",
                    _ => throw new ArgumentOutOfRangeException()
                },
                _ => throw new NotSupportedException($"Greater than or equal comparison not supported for type '{type}'")
            },
            // todo(nub31): Implement short circuiting
            BinaryOperator.LogicalAnd => "and",
            BinaryOperator.LogicalOr => "or",
            _ => throw new ArgumentOutOfRangeException(nameof(op))
        };
    }

    private string EmitLiteral(LiteralNode literal)
    {
        switch (literal.Kind)
        {
            case LiteralKind.Integer:
            {
                if (literal.Type is FloatTypeNode { Width: 32 })
                {
                    var value = float.Parse(literal.Value, CultureInfo.InvariantCulture);
                    var bits = BitConverter.SingleToInt32Bits(value);
                    return bits.ToString();
                }

                if (literal.Type is FloatTypeNode { Width: 64 })
                {
                    var value = double.Parse(literal.Value, CultureInfo.InvariantCulture);
                    var bits = BitConverter.DoubleToInt64Bits(value);
                    return bits.ToString();
                }

                if (literal.Type is IntTypeNode)
                {
                    return literal.Value;
                }

                break;
            }
            case LiteralKind.Float:
            {
                if (literal.Type is IntTypeNode)
                {
                    return literal.Value.Split(".").First();
                }

                if (literal.Type is FloatTypeNode { Width: 32 })
                {
                    var value = float.Parse(literal.Value, CultureInfo.InvariantCulture);
                    var bits = BitConverter.SingleToInt32Bits(value);
                    return bits.ToString();
                }

                if (literal.Type is FloatTypeNode { Width: 64 })
                {
                    var value = double.Parse(literal.Value, CultureInfo.InvariantCulture);
                    var bits = BitConverter.DoubleToInt64Bits(value);
                    return bits.ToString();
                }

                break;
            }
            case LiteralKind.String:
            {
                if (literal.Type is StringTypeNode)
                {
                    var stringLiteral = new StringLiteral(literal.Value, StringName());
                    _stringLiterals.Add(stringLiteral);
                    return stringLiteral.Name;
                }

                if (literal.Type is CStringTypeNode)
                {
                    var cStringLiteral = new CStringLiteral(literal.Value, CStringName());
                    _cStringLiterals.Add(cStringLiteral);
                    return cStringLiteral.Name;
                }

                break;
            }
            case LiteralKind.Bool:
            {
                if (literal.Type is BoolTypeNode)
                {
                    return bool.Parse(literal.Value) ? "1" : "0";
                }

                break;
            }
        }

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

    private string EmitStructInitializer(StructInitializerNode structInitializer)
    {
        var destination = TmpName();
        var size = SizeOf(structInitializer.StructType);
        _writer.Indented($"{destination} =l alloc8 {size}");

        foreach (var (field, value) in structInitializer.Initializers)
        {
            var offset = TmpName();
            _writer.Indented($"{offset} =l add {destination}, {OffsetOf(structInitializer.StructType, field)}");
            EmitCopyInto(value, offset);
        }

        return destination;
    }

    private string EmitUnaryExpression(UnaryExpressionNode unaryExpression)
    {
        var operand = EmitExpression(unaryExpression.Operand);
        var outputName = TmpName();

        switch (unaryExpression.Operator)
        {
            case UnaryOperator.Negate:
            {
                switch (unaryExpression.Operand.Type)
                {
                    case IntTypeNode { Signed: true, Width: 64 }:
                        _writer.Indented($"{outputName} =l neg {operand}");
                        return outputName;
                    case IntTypeNode { Signed: true, Width: 8 or 16 or 32 }:
                        _writer.Indented($"{outputName} =w neg {operand}");
                        return outputName;
                    case FloatTypeNode { Width: 64 }:
                        _writer.Indented($"{outputName} =d neg {operand}");
                        return outputName;
                    case FloatTypeNode { Width: 32 }:
                        _writer.Indented($"{outputName} =s neg {operand}");
                        return outputName;
                }

                break;
            }
            case UnaryOperator.Invert:
            {
                switch (unaryExpression.Operand.Type)
                {
                    case BoolTypeNode:
                        _writer.Indented($"{outputName} =w xor {operand}, 1");
                        return outputName;
                }

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

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

    private string EmitStructFieldAccess(StructFieldAccessNode structFieldAccess)
    {
        var address = EmitAddressOfStructFieldAccess(structFieldAccess);
        if (structFieldAccess.Type is StructTypeNode)
        {
            return address;
        }

        return EmitLoad(structFieldAccess.Type, address);
    }

    private string EmitStructFuncCall(StructFuncCallNode structFuncCall)
    {
        var func = StructFuncName(structFuncCall.StructType.Module, structFuncCall.StructType.Name, structFuncCall.Name);

        var thisParameter = EmitExpression(structFuncCall.StructExpression);

        List<string> parameterStrings = [$"l {thisParameter}"];

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

        if (structFuncCall.Type is VoidTypeNode)
        {
            _writer.Indented($"call {func}({string.Join(", ", parameterStrings)})");
            return string.Empty;
        }
        else
        {
            var outputName = TmpName();
            _writer.Indented($"{outputName} {QBEAssign(structFuncCall.Type)} call {func}({string.Join(", ", parameterStrings)})");
            return outputName;
        }
    }

    private string EmitInterfaceFuncCall(InterfaceFuncCallNode interfaceFuncCall)
    {
        var target = EmitExpression(interfaceFuncCall.InterfaceExpression);

        var functionIndex = interfaceFuncCall.InterfaceType.Functions.ToList().FindIndex(x => x.Name == interfaceFuncCall.Name);
        var offset = functionIndex * 8;

        var vtable = TmpName();
        _writer.Indented($"{vtable} =l loadl {target}");

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

        var func = TmpName();
        _writer.Indented($"{func} =l loadl {funcOffset}");

        var data = TmpName();
        _writer.Indented($"{data} =l add {target}, 8");
        _writer.Indented($"{data} =l loadl {data}");

        List<string> parameterStrings = [$"l {data}"];

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

        if (interfaceFuncCall.Type is VoidTypeNode)
        {
            _writer.Indented($"call {func}({string.Join(", ", parameterStrings)})");
            return string.Empty;
        }
        else
        {
            var outputName = TmpName();
            _writer.Indented($"{outputName} {QBEAssign(interfaceFuncCall.Type)} call {func}({string.Join(", ", parameterStrings)})");
            return outputName;
        }
    }

    private string EmitConvertToInterface(ConvertToInterfaceNode convertToInterface)
    {
        var implementation = EmitExpression(convertToInterface.Implementation);

        var vtableOffset = 0;
        foreach (var interfaceImplementation in convertToInterface.StructType.InterfaceImplementations)
        {
            if (interfaceImplementation == convertToInterface.InterfaceType)
            {
                break;
            }

            vtableOffset += interfaceImplementation.Functions.Count * 8;
        }

        var destination = TmpName();
        _writer.Indented($"{destination} =l alloc8 {SizeOf(convertToInterface.InterfaceType)}");

        var interfaceVtablePointer = TmpName();
        _writer.Indented($"{interfaceVtablePointer} =l add {StructVtableName(convertToInterface.StructType.Module, convertToInterface.StructType.Name)}, {vtableOffset}");
        _writer.Indented($"storel {interfaceVtablePointer}, {destination}");

        var objectPointer = TmpName();
        _writer.Indented($"{objectPointer} =l add {destination}, 8");
        _writer.Indented($"storel {implementation}, {objectPointer}");

        return destination;
    }

    private string EmitConvertInt(ConvertIntNode convertInt)
    {
        var value = EmitExpression(convertInt.Value);

        if (convertInt.ValueType.Width >= convertInt.TargetType.Width)
        {
            return value;
        }

        var method = convertInt.ValueType.Signed switch
        {
            true => convertInt.ValueType.Width switch
            {
                8 => "extsb",
                16 => "extsh",
                32 => "extsw",
                _ => throw new ArgumentOutOfRangeException()
            },
            false => convertInt.ValueType.Width switch
            {
                8 => "extub",
                16 => "extuh",
                32 => "extuw",
                _ => throw new ArgumentOutOfRangeException()
            }
        };

        var result = TmpName();
        _writer.Indented($"{result} {QBEAssign(convertInt.TargetType)} {method} {value}");
        return result;
    }

    private string EmitConvertFloat(ConvertFloatNode convertFloat)
    {
        var value = EmitExpression(convertFloat.Value);

        if (convertFloat.ValueType.Width == convertFloat.TargetType.Width)
        {
            return value;
        }

        var method = convertFloat.ValueType.Width switch
        {
            32 => "exts",
            64 => "truncd",
            _ => throw new ArgumentOutOfRangeException()
        };

        var result = TmpName();
        _writer.Indented($"{result} {QBEAssign(convertFloat.TargetType)} {method} {value}");
        return result;
    }

    private string EmitFuncCall(FuncCallNode funcCall)
    {
        var funcPointer = EmitExpression(funcCall.Expression);

        var parameterStrings = new List<string>();

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

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

    private static int SizeOf(TypeNode type)
    {
        return type switch
        {
            SimpleTypeNode simple => simple.StorageSize switch
            {
                StorageSize.Void => 0,
                StorageSize.I8 or StorageSize.U8 => 1,
                StorageSize.I16 or StorageSize.U16 => 2,
                StorageSize.I32 or StorageSize.U32 or StorageSize.F32 => 4,
                StorageSize.I64 or StorageSize.U64 or StorageSize.F64 => 8,
                _ => throw new ArgumentOutOfRangeException(nameof(type), $"Unknown storage size: {simple.StorageSize}")
            },
            CStringTypeNode => 8,
            StringTypeNode => 8,
            ArrayTypeNode => 8,
            StructTypeNode structType => CalculateStructSize(structType),
            InterfaceTypeNode => 16,
            _ => throw new ArgumentOutOfRangeException(nameof(type), $"Unknown type: {type.GetType()}")
        };
    }

    private static int CalculateStructSize(StructTypeNode structType)
    {
        var offset = 0;

        var fields = new List<TypeNode>(structType.Fields.Count);

        foreach (var field in structType.Fields)
        {
            var fieldAlignment = AlignmentOf(field.Type);
            offset = AlignTo(offset, fieldAlignment);
            offset += SizeOf(field.Type);
        }

        var structAlignment = CalculateStructAlignment(structType);
        return AlignTo(offset, structAlignment);
    }

    private static int AlignmentOf(TypeNode type)
    {
        return type switch
        {
            SimpleTypeNode simple => simple.StorageSize switch
            {
                StorageSize.Void => 1,
                StorageSize.I8 or StorageSize.U8 => 1,
                StorageSize.I16 or StorageSize.U16 => 2,
                StorageSize.I32 or StorageSize.U32 or StorageSize.F32 => 4,
                StorageSize.I64 or StorageSize.U64 or StorageSize.F64 => 8,
                _ => throw new ArgumentOutOfRangeException(nameof(type), $"Unknown storage size: {simple.StorageSize}")
            },
            CStringTypeNode => 8,
            StringTypeNode => 8,
            ArrayTypeNode => 8,
            StructTypeNode structType => CalculateStructAlignment(structType),
            InterfaceTypeNode => 8,
            _ => throw new ArgumentOutOfRangeException(nameof(type), $"Unknown type: {type.GetType()}")
        };
    }

    private static int CalculateStructAlignment(StructTypeNode structType)
    {
        var maxAlignment = 1;

        if (structType.InterfaceImplementations.Any())
        {
            maxAlignment = Math.Max(maxAlignment, 8);
        }

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

        return maxAlignment;
    }

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

    private static int OffsetOf(StructTypeNode structDef, string member)
    {
        var offset = 0;

        foreach (var field in structDef.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");
    }

    #region Naming utilities

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

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

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

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

    private string FuncName(string module, string name)
    {
        var type = TypeResolver.ResolveFunctionType(module, name, _moduleSignatures);
        var symbol = type.ExternSymbol ?? $"{module}.{name}";
        return "$" + symbol;
    }

    private string StructTypeName(string module, string name)
    {
        return $":{module}.{name}";
    }

    private string StructFuncName(string module, string structName, string funcName)
    {
        return $"${module}.{structName}_func.{funcName}";
    }

    private string StructCtorName(string module, string structName)
    {
        return $"${module}.{structName}_ctor";
    }

    private string StructVtableName(string module, string structName)
    {
        return $"${module}.{structName}_vtable";
    }

    #endregion
}

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

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