using NubLang.Common;
using NubLang.Diagnostics;
using NubLang.Syntax.Binding.Node;
using NubLang.Syntax.Parsing.Node;
using NubLang.Syntax.Tokenization;

namespace NubLang.Syntax.Binding;

public sealed class Binder
{
    private readonly SyntaxTree _syntaxTree;
    private readonly DefinitionTable _definitionTable;

    private readonly Stack<Scope> _scopes = [];
    private readonly Stack<NubType> _funcReturnTypes = [];

    private Scope Scope => _scopes.Peek();

    public Binder(SyntaxTree syntaxTree, DefinitionTable definitionTable)
    {
        _syntaxTree = syntaxTree;
        _definitionTable = definitionTable;
    }

    public BoundSyntaxTree Bind()
    {
        _funcReturnTypes.Clear();
        _scopes.Clear();

        var diagnostics = new List<Diagnostic>();
        var definitions = new List<BoundDefinition>();

        foreach (var definition in _syntaxTree.Definitions)
        {
            try
            {
                definitions.Add(BindDefinition(definition));
            }
            catch (BindException e)
            {
                diagnostics.Add(e.Diagnostic);
            }
        }

        return new BoundSyntaxTree(_syntaxTree.Namespace, definitions, diagnostics);
    }

    private BoundDefinition BindDefinition(DefinitionSyntax node)
    {
        return node switch
        {
            ExternFuncSyntax definition => BindExternFuncDefinition(definition),
            InterfaceSyntax definition => BindTraitDefinition(definition),
            LocalFuncSyntax definition => BindLocalFuncDefinition(definition),
            StructSyntax definition => BindStruct(definition),
            _ => throw new ArgumentOutOfRangeException(nameof(node))
        };
    }

    private BoundTrait BindTraitDefinition(InterfaceSyntax node)
    {
        var functions = new List<BoundTraitFunc>();

        foreach (var function in node.Functions)
        {
            functions.Add(new BoundTraitFunc(function.Name, BindFuncSignature(function.Signature)));
        }

        return new BoundTrait(node.Namespace, node.Name, functions);
    }

    private BoundStruct BindStruct(StructSyntax node)
    {
        var structFields = new List<BoundStructField>();

        foreach (var field in node.Fields)
        {
            var value = Optional.Empty<BoundExpression>();

            if (field.Value.HasValue)
            {
                value = BindExpression(field.Value.Value, BindType(field.Type));
            }

            structFields.Add(new BoundStructField(field.Index, field.Name, BindType(field.Type), value));
        }

        return new BoundStruct(node.Namespace, node.Name, structFields);
    }

    private BoundExternFunc BindExternFuncDefinition(ExternFuncSyntax node)
    {
        return new BoundExternFunc(node.Namespace, node.Name, node.CallName, BindFuncSignature(node.Signature));
    }

    private BoundLocalFunc BindLocalFuncDefinition(LocalFuncSyntax node)
    {
        var signature = BindFuncSignature(node.Signature);
        var body = BindFuncBody(node.Body, signature.ReturnType, signature.Parameters);

        return new BoundLocalFunc(node.Namespace, node.Name, signature, body);
    }

    private BoundStatement BindStatement(StatementSyntax node)
    {
        return node switch
        {
            AssignmentSyntax statement => BindAssignment(statement),
            BreakSyntax => new BoundBreak(),
            ContinueSyntax => new BoundContinue(),
            IfSyntax statement => BindIf(statement),
            ReturnSyntax statement => BindReturn(statement),
            StatementExpressionSyntax statement => BindStatementExpression(statement),
            VariableDeclarationSyntax statement => BindVariableDeclaration(statement),
            WhileSyntax statement => BindWhile(statement),
            _ => throw new ArgumentOutOfRangeException(nameof(node))
        };
    }

    private BoundStatement BindAssignment(AssignmentSyntax statement)
    {
        var expression = BindExpression(statement.Target);
        var value = BindExpression(statement.Value, expression.Type);
        return new BoundAssignment(expression, value);
    }

    private BoundIf BindIf(IfSyntax statement)
    {
        var elseStatement = Optional.Empty<Variant<BoundIf, BoundBlock>>();

        if (statement.Else.HasValue)
        {
            elseStatement = statement.Else.Value.Match<Variant<BoundIf, BoundBlock>>
            (
                elseIf => BindIf(elseIf),
                @else => BindBlock(@else)
            );
        }

        return new BoundIf(BindExpression(statement.Condition, new NubPrimitiveType(PrimitiveTypeKind.Bool)), BindBlock(statement.Body), elseStatement);
    }

    private BoundReturn BindReturn(ReturnSyntax statement)
    {
        var value = Optional.Empty<BoundExpression>();

        if (statement.Value.HasValue)
        {
            value = BindExpression(statement.Value.Value, _funcReturnTypes.Peek());
        }

        return new BoundReturn(value);
    }

    private BoundStatementExpression BindStatementExpression(StatementExpressionSyntax statement)
    {
        return new BoundStatementExpression(BindExpression(statement.Expression));
    }

    private BoundVariableDeclaration BindVariableDeclaration(VariableDeclarationSyntax statement)
    {
        NubType? type = null;

        if (statement.ExplicitType.HasValue)
        {
            type = BindType(statement.ExplicitType.Value);
        }

        var assignment = Optional<BoundExpression>.Empty();
        if (statement.Assignment.HasValue)
        {
            var boundValue = BindExpression(statement.Assignment.Value, type);
            assignment = boundValue;
            type = boundValue.Type;
        }

        if (type == null)
        {
            throw new NotImplementedException("Diagnostics not implemented");
        }

        Scope.Declare(new Variable(statement.Name, type));

        return new BoundVariableDeclaration(statement.Name, assignment, type);
    }

    private BoundWhile BindWhile(WhileSyntax statement)
    {
        return new BoundWhile(BindExpression(statement.Condition, new NubPrimitiveType(PrimitiveTypeKind.Bool)), BindBlock(statement.Body));
    }

    private BoundExpression BindExpression(ExpressionSyntax node, NubType? expectedType = null)
    {
        return node switch
        {
            AddressOfSyntax expression => BindAddressOf(expression),
            ArrowFuncSyntax expression => BindArrowFunc(expression, expectedType),
            ArrayIndexAccessSyntax expression => BindArrayIndexAccess(expression),
            ArrayInitializerSyntax expression => BindArrayInitializer(expression),
            BinaryExpressionSyntax expression => BindBinaryExpression(expression),
            DereferenceSyntax expression => BindDereference(expression),
            FuncCallSyntax expression => BindFuncCall(expression),
            IdentifierSyntax expression => BindIdentifier(expression),
            LiteralSyntax expression => BindLiteral(expression, expectedType),
            MemberAccessSyntax expression => BindMemberAccess(expression),
            StructInitializerSyntax expression => BindStructInitializer(expression),
            UnaryExpressionSyntax expression => BindUnaryExpression(expression),
            _ => throw new ArgumentOutOfRangeException(nameof(node))
        };
    }

    private BoundAddressOf BindAddressOf(AddressOfSyntax expression)
    {
        var inner = BindExpression(expression.Expression);
        return new BoundAddressOf(new NubPointerType(inner.Type), inner);
    }

    private BoundArrowFunc BindArrowFunc(ArrowFuncSyntax expression, NubType? expectedType = null)
    {
        if (expectedType == null)
        {
            throw new BindException(Diagnostic.Error("Cannot infer argument types for arrow function").Build());
        }

        if (expectedType is not NubFuncType funcType)
        {
            throw new BindException(Diagnostic.Error($"Expected {expectedType}, but got arrow function").Build());
        }

        var parameters = new List<BoundFuncParameter>();

        for (var i = 0; i < expression.Parameters.Count; i++)
        {
            if (i >= funcType.Parameters.Count)
            {
                throw new BindException(Diagnostic.Error($"Arrow function expected a maximum of {funcType.Parameters.Count} arguments").Build());
            }

            var expectedParameterType = funcType.Parameters[i];
            var parameter = expression.Parameters[i];
            parameters.Add(new BoundFuncParameter(parameter.Name, expectedParameterType));
        }

        var body = BindFuncBody(expression.Body, funcType.ReturnType, parameters);

        return new BoundArrowFunc(new NubFuncType(parameters.Select(x => x.Type).ToList(), funcType.ReturnType), parameters, funcType.ReturnType, body);
    }

    private BoundArrayIndexAccess BindArrayIndexAccess(ArrayIndexAccessSyntax expression)
    {
        var boundArray = BindExpression(expression.Target);
        var elementType = ((NubArrayType)boundArray.Type).ElementType;
        return new BoundArrayIndexAccess(elementType, boundArray, BindExpression(expression.Index, new NubPrimitiveType(PrimitiveTypeKind.U64)));
    }

    private BoundArrayInitializer BindArrayInitializer(ArrayInitializerSyntax expression)
    {
        var capacity = BindExpression(expression.Capacity, new NubPrimitiveType(PrimitiveTypeKind.U64));
        var type = new NubArrayType(BindType(expression.ElementType));
        return new BoundArrayInitializer(type, capacity, BindType(expression.ElementType));
    }

    private BoundBinaryExpression BindBinaryExpression(BinaryExpressionSyntax expression)
    {
        var boundLeft = BindExpression(expression.Left);
        var boundRight = BindExpression(expression.Right, boundLeft.Type);
        return new BoundBinaryExpression(boundLeft.Type, boundLeft, BindBinaryOperator(expression.Operator), boundRight);
    }

    private BoundDereference BindDereference(DereferenceSyntax expression)
    {
        var boundExpression = BindExpression(expression.Expression);
        var dereferencedType = ((NubPointerType)boundExpression.Type).BaseType;
        return new BoundDereference(dereferencedType, boundExpression);
    }

    private BoundFuncCall BindFuncCall(FuncCallSyntax expression)
    {
        var boundExpression = BindExpression(expression.Expression);

        var funcType = (NubFuncType)boundExpression.Type;

        var parameters = new List<BoundExpression>();

        foreach (var (i, parameter) in expression.Parameters.Index())
        {
            if (i >= funcType.Parameters.Count)
            {
                throw new NotImplementedException("Diagnostics not implemented");
            }

            var expectedType = funcType.Parameters[i];

            parameters.Add(BindExpression(parameter, expectedType));
        }

        return new BoundFuncCall(funcType.ReturnType, boundExpression, parameters);
    }

    private BoundExpression BindIdentifier(IdentifierSyntax expression)
    {
        var @namespace = expression.Namespace.Or(_syntaxTree.Namespace);
        var localFuncs = _definitionTable.LookupLocalFunc(@namespace, expression.Name).ToArray();
        if (localFuncs.Length > 0)
        {
            if (localFuncs.Length > 1)
            {
                throw new BindException(Diagnostic.Error($"Extern func {expression.Namespace}::{expression.Name} has multiple definitions").Build());
            }

            var localFunc = localFuncs[0];

            var returnType = BindType(localFunc.Signature.ReturnType);
            var parameterTypes = localFunc.Signature.Parameters.Select(p => BindType(p.Type)).ToList();
            var type = new NubFuncType(parameterTypes, returnType);
            return new BoundLocalFuncIdent(type, @namespace, expression.Name);
        }

        var externFuncs = _definitionTable.LookupExternFunc(@namespace, expression.Name).ToArray();
        if (externFuncs.Length > 0)
        {
            if (externFuncs.Length > 1)
            {
                throw new BindException(Diagnostic.Error($"Extern func {expression.Namespace}::{expression.Name} has multiple definitions").Build());
            }

            var externFunc = externFuncs[0];

            var returnType = BindType(externFunc.Signature.ReturnType);
            var parameterTypes = externFunc.Signature.Parameters.Select(p => BindType(p.Type)).ToList();
            var type = new NubFuncType(parameterTypes, returnType);
            return new BoundExternFuncIdent(type, @namespace, expression.Name);
        }

        if (!expression.Namespace.HasValue)
        {
            var variable = Scope.Lookup(expression.Name);
            if (variable != null)
            {
                return new BoundVariableIdent(variable.Type, variable.Name);
            }
        }

        throw new BindException(Diagnostic.Error($"No identifier with the name {(expression.Namespace.HasValue ? $"{expression.Namespace.Value}::" : "")}{expression.Name} exists").Build());
    }

    private BoundLiteral BindLiteral(LiteralSyntax expression, NubType? expectedType = null)
    {
        var type = expectedType ?? expression.Kind switch
        {
            LiteralKind.Integer => new NubPrimitiveType(PrimitiveTypeKind.I64),
            LiteralKind.Float => new NubPrimitiveType(PrimitiveTypeKind.F64),
            LiteralKind.String => new NubStringType(),
            LiteralKind.Bool => new NubPrimitiveType(PrimitiveTypeKind.Bool),
            _ => throw new ArgumentOutOfRangeException()
        };

        return new BoundLiteral(type, expression.Value, expression.Kind);
    }

    private BoundExpression BindMemberAccess(MemberAccessSyntax expression)
    {
        var boundExpression = BindExpression(expression.Target);

        // var traitFuncImpls = _definitionTable.LookupTraitFuncImpl(boundExpression.Type, expression.Member).ToArray();
        // if (traitFuncImpls.Length > 0)
        // {
        //     if (traitFuncImpls.Length > 1)
        //     {
        //         throw new BindException(Diagnostic.Error($"Type {boundExpression.Type} implements multiple traits  with the function {expression.Member}").Build());
        //     }
        //
        //     var impl = traitFuncImpls[0];
        //
        //     var returnType = BindType(impl.Signature.ReturnType);
        //     var parameterTypes = impl.Signature.Parameters.Select(p => BindType(p.Type)).ToList();
        //     var type = new NubFuncType(parameterTypes, returnType);
        //     return new BoundTraitImplFuncAccess(type, boundExpression, expression.Member);
        // }

        if (boundExpression.Type is NubCustomType customType)
        {
            var traits = _definitionTable.LookupTrait(customType).ToArray();
            if (traits.Length > 0)
            {
                if (traits.Length > 1)
                {
                    throw new BindException(Diagnostic.Error($"Trait {customType} has multiple definitions").Build());
                }

                var trait = traits[0];

                var traitFuncs = _definitionTable.LookupTraitFunc(trait, expression.Member).ToArray();
                if (traits.Length > 0)
                {
                    if (traits.Length > 1)
                    {
                        throw new BindException(Diagnostic.Error($"Trait {customType} has multiple functions with the name {expression.Member}").Build());
                    }

                    var traitFunc = traitFuncs[0];

                    var returnType = BindType(traitFunc.Signature.ReturnType);
                    var parameterTypes = traitFunc.Signature.Parameters.Select(p => BindType(p.Type)).ToList();
                    var type = new NubFuncType(parameterTypes, returnType);
                    return new BoundInterfaceFuncAccess(type, customType, boundExpression, expression.Member);
                }
            }

            var structs = _definitionTable.LookupStruct(customType).ToArray();
            if (structs.Length > 0)
            {
                if (structs.Length > 1)
                {
                    throw new BindException(Diagnostic.Error($"Struct {customType} has multiple definitions").Build());
                }

                var @struct = structs[0];

                var fields = _definitionTable.LookupStructField(@struct, expression.Member).ToArray();
                if (fields.Length > 0)
                {
                    if (fields.Length > 1)
                    {
                        throw new BindException(Diagnostic.Error($"Struct {customType} has multiple fields with the name {expression.Member}").Build());
                    }

                    var field = fields[0];

                    return new BoundStructFieldAccess(BindType(field.Type), customType, boundExpression, expression.Member);
                }
            }
        }

        throw new BindException(Diagnostic.Error($"{boundExpression.Type} does not have a member with the name {expression.Member}").Build());
    }

    private BoundStructInitializer BindStructInitializer(StructInitializerSyntax expression)
    {
        var boundType = BindType(expression.StructType);

        if (boundType is not NubCustomType structType)
        {
            throw new BindException(Diagnostic.Error($"Cannot initialize non-struct type {expression.StructType}").Build());
        }

        var structs = _definitionTable.LookupStruct(structType).ToArray();

        if (structs.Length == 0)
        {
            throw new BindException(Diagnostic.Error($"Struct {structType} is not defined").Build());
        }

        if (structs.Length > 1)
        {
            throw new BindException(Diagnostic.Error($"Struct {structType} has multiple definitions").Build());
        }

        var @struct = structs[0];

        var initializers = new Dictionary<string, BoundExpression>();

        foreach (var (field, initializer) in expression.Initializers)
        {
            var fields = _definitionTable.LookupStructField(@struct, field).ToArray();

            if (fields.Length == 0)
            {
                throw new BindException(Diagnostic.Error($"Struct {structType} does not have a field with the name {field}").Build());
            }

            if (fields.Length > 1)
            {
                throw new BindException(Diagnostic.Error($"Struct {structType} has multiple fields with the name {field}").Build());
            }

            initializers[field] = BindExpression(initializer, BindType(fields[0].Type));
        }

        return new BoundStructInitializer(structType, initializers);
    }

    private BoundUnaryExpression BindUnaryExpression(UnaryExpressionSyntax expression)
    {
        var boundOperand = BindExpression(expression.Operand);

        NubType? type = null;

        switch (expression.Operator)
        {
            case UnaryOperator.Negate:
            {
                boundOperand = BindExpression(expression.Operand, new NubPrimitiveType(PrimitiveTypeKind.I64));

                if (boundOperand.Type.IsNumber)
                {
                    type = boundOperand.Type;
                }

                break;
            }
            case UnaryOperator.Invert:
            {
                boundOperand = BindExpression(expression.Operand, new NubPrimitiveType(PrimitiveTypeKind.Bool));

                type = new NubPrimitiveType(PrimitiveTypeKind.Bool);
                break;
            }
        }

        if (type == null)
        {
            throw new NotImplementedException("Diagnostics not implemented");
        }

        return new BoundUnaryExpression(type, BindBinaryOperator(expression.Operator), boundOperand);
    }

    private BoundFuncSignature BindFuncSignature(FuncSignatureSyntax node)
    {
        var parameters = new List<BoundFuncParameter>();

        foreach (var parameter in node.Parameters)
        {
            parameters.Add(new BoundFuncParameter(parameter.Name, BindType(parameter.Type)));
        }

        return new BoundFuncSignature(parameters, BindType(node.ReturnType));
    }

    private BoundBinaryOperator BindBinaryOperator(BinaryOperator op)
    {
        return op switch
        {
            BinaryOperator.Equal => BoundBinaryOperator.Equal,
            BinaryOperator.NotEqual => BoundBinaryOperator.NotEqual,
            BinaryOperator.GreaterThan => BoundBinaryOperator.GreaterThan,
            BinaryOperator.GreaterThanOrEqual => BoundBinaryOperator.GreaterThanOrEqual,
            BinaryOperator.LessThan => BoundBinaryOperator.LessThan,
            BinaryOperator.LessThanOrEqual => BoundBinaryOperator.LessThanOrEqual,
            BinaryOperator.Plus => BoundBinaryOperator.Plus,
            BinaryOperator.Minus => BoundBinaryOperator.Minus,
            BinaryOperator.Multiply => BoundBinaryOperator.Multiply,
            BinaryOperator.Divide => BoundBinaryOperator.Divide,
            _ => throw new ArgumentOutOfRangeException(nameof(op), op, null)
        };
    }

    private BoundUnaryOperator BindBinaryOperator(UnaryOperator op)
    {
        return op switch
        {
            UnaryOperator.Negate => BoundUnaryOperator.Negate,
            UnaryOperator.Invert => BoundUnaryOperator.Invert,
            _ => throw new ArgumentOutOfRangeException(nameof(op), op, null)
        };
    }

    private BoundBlock BindBlock(BlockSyntax node, Scope? scope = null)
    {
        var statements = new List<BoundStatement>();

        _scopes.Push(scope ?? Scope.SubScope());

        foreach (var statement in node.Statements)
        {
            statements.Add(BindStatement(statement));
        }

        _scopes.Pop();

        return new BoundBlock(statements);
    }

    private BoundBlock BindFuncBody(BlockSyntax block, NubType returnType, IReadOnlyList<BoundFuncParameter> parameters)
    {
        _funcReturnTypes.Push(returnType);

        var scope = new Scope();
        foreach (var parameter in parameters)
        {
            scope.Declare(new Variable(parameter.Name, parameter.Type));
        }

        var body = BindBlock(block, scope);
        _funcReturnTypes.Pop();
        return body;
    }

    private NubType BindType(TypeSyntax node)
    {
        return node switch
        {
            ArrayTypeSyntax type => new NubArrayType(BindType(type.BaseType)),
            CStringTypeSyntax => new NubCStringType(),
            CustomTypeSyntax type => new NubCustomType(type.Namespace, type.MangledName()),
            FuncTypeSyntax type => new NubFuncType(type.Parameters.Select(BindType).ToList(), BindType(type.ReturnType)),
            PointerTypeSyntax type => new NubPointerType(BindType(type.BaseType)),
            PrimitiveTypeSyntax type => new NubPrimitiveType(type.SyntaxKind switch
            {
                PrimitiveTypeSyntaxKind.I64 => PrimitiveTypeKind.I64,
                PrimitiveTypeSyntaxKind.I32 => PrimitiveTypeKind.I32,
                PrimitiveTypeSyntaxKind.I16 => PrimitiveTypeKind.I16,
                PrimitiveTypeSyntaxKind.I8 => PrimitiveTypeKind.I8,
                PrimitiveTypeSyntaxKind.U64 => PrimitiveTypeKind.U64,
                PrimitiveTypeSyntaxKind.U32 => PrimitiveTypeKind.U32,
                PrimitiveTypeSyntaxKind.U16 => PrimitiveTypeKind.U16,
                PrimitiveTypeSyntaxKind.U8 => PrimitiveTypeKind.U8,
                PrimitiveTypeSyntaxKind.F64 => PrimitiveTypeKind.F64,
                PrimitiveTypeSyntaxKind.F32 => PrimitiveTypeKind.F32,
                PrimitiveTypeSyntaxKind.Bool => PrimitiveTypeKind.Bool,
                _ => throw new ArgumentOutOfRangeException()
            }),
            StringTypeSyntax => new NubStringType(),
            VoidTypeSyntax => new NubVoidType(),
            _ => throw new ArgumentOutOfRangeException(nameof(node))
        };
    }
}

public record Variable(string Name, NubType Type);

public class Scope(Scope? parent = null)
{
    private readonly List<Variable> _variables = [];

    public Variable? Lookup(string name)
    {
        var variable = _variables.FirstOrDefault(x => x.Name == name);
        if (variable != null)
        {
            return variable;
        }

        return parent?.Lookup(name);
    }

    public void Declare(Variable variable)
    {
        _variables.Add(variable);
    }

    public Scope SubScope()
    {
        return new Scope(this);
    }
}

public class BindException : Exception
{
    public Diagnostic Diagnostic { get; }

    public BindException(Diagnostic diagnostic) : base(diagnostic.Message)
    {
        Diagnostic = diagnostic;
    }
}