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

namespace NubLang.Generation.QBE;

public partial class QBEGenerator
{
    private Val EmitExpression(Expression expression)
    {
        return expression switch
        {
            ArrayInitializer arrayInitializer => EmitArrayInitializer(arrayInitializer),
            StructInitializer structInitializer => EmitStructInitializer(structInitializer),
            AddressOf addressOf => EmitAddressOf(addressOf),
            Dereference dereference => EmitDereference(dereference),
            ArrowFunc arrowFunc => EmitArrowFunc(arrowFunc),
            BinaryExpression binaryExpression => EmitBinaryExpression(binaryExpression),
            FuncCall funcCallExpression => EmitFuncCall(funcCallExpression),
            ExternFuncIdent externFuncIdent => EmitExternFuncIdent(externFuncIdent),
            LocalFuncIdent localFuncIdent => EmitLocalFuncIdent(localFuncIdent),
            VariableIdent variableIdent => EmitVariableIdent(variableIdent),
            Literal literal => EmitLiteral(literal),
            UnaryExpression unaryExpression => EmitUnaryExpression(unaryExpression),
            StructFieldAccess structFieldAccess => EmitStructFieldAccess(structFieldAccess),
            InterfaceFuncAccess traitFuncAccess => EmitTraitFuncAccess(traitFuncAccess),
            ArrayIndexAccess arrayIndex => EmitArrayIndexAccess(arrayIndex),
            _ => throw new ArgumentOutOfRangeException(nameof(expression))
        };
    }

    private Val EmitArrowFunc(ArrowFunc arrowFunc)
    {
        var name = $"$arrow_func{++_arrowFuncIndex}";
        _arrowFunctions.Enqueue((arrowFunc, name));
        return new Val(name, arrowFunc.Type, ValKind.Direct);
    }

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

        EmitArraysCheck(array, index);

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

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

    private void EmitArraysCheck(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 Val EmitArrayInitializer(ArrayInitializer arrayInitializer)
    {
        var capacity = EmitUnwrap(EmitExpression(arrayInitializer.Capacity));
        var elementSize = arrayInitializer.ElementType.Size(_definitionTable);

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

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

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

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

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

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

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

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

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

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

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

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

            string sign;

            if (simpleType is NubIntType { Signed: true })
            {
                sign = "s";
            }
            else if (simpleType is NubIntType { Signed: false })
            {
                sign = "u";
            }
            else
            {
                throw new NotSupportedException($"Unsupported type '{type}' for binary operator '{op}'");
            }

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

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

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

    private Val EmitLocalFuncIdent(LocalFuncIdent localFuncIdent)
    {
        var func = _definitionTable.LookupLocalFunc(localFuncIdent.Name);
        return new Val(LocalFuncName(func), localFuncIdent.Type, ValKind.Direct);
    }

    private Val EmitVariableIdent(VariableIdent variableIdent)
    {
        return Scope.Lookup(variableIdent.Name);
    }

    private Val EmitLiteral(Literal literal)
    {
        switch (literal.Kind)
        {
            case LiteralKind.Integer:
            {
                if (literal.Type is NubFloatType { Width: 32 })
                {
                    var value = float.Parse(literal.Value, CultureInfo.InvariantCulture);
                    var bits = BitConverter.SingleToInt32Bits(value);
                    return new Val(bits.ToString(), literal.Type, ValKind.Direct);
                }

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

                if (literal.Type is NubIntType)
                {
                    return new Val(literal.Value, literal.Type, ValKind.Direct);
                }

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

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

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

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

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

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

                break;
            }
        }

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

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

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

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

            Debug.Assert(valueExpression != null);

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

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

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

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

                break;
            }
            case UnaryOperator.Invert:
            {
                switch (unaryExpression.Operand.Type)
                {
                    case NubBoolType:
                        _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 Val EmitStructFieldAccess(StructFieldAccess structFieldAccess)
    {
        var target = EmitUnwrap(EmitExpression(structFieldAccess.Target));

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

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

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

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

    private Val EmitTraitFuncAccess(InterfaceFuncAccess interfaceFuncAccess)
    {
        throw new NotImplementedException();
    }

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

        var parameterStrings = new List<string>();

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

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