using Common;
using Syntax.Diagnostics;
using Syntax.Node;
using Syntax.Tokenization;
using UnaryExpressionNode = Syntax.Node.UnaryExpressionNode;

namespace Syntax.Binding;

// TODO: Currently anonymous function does not get a new scope
public static class Binder
{
    private static SyntaxTree _syntaxTree = null!;
    private static DefinitionTable _definitionTable = null!;

    private static Dictionary<string, NubType> _variables = new();
    private static NubType? _funcReturnType;

    public static BoundSyntaxTree Bind(SyntaxTree syntaxTree, DefinitionTable definitionTable, out IEnumerable<Diagnostic> diagnostics)
    {
        _syntaxTree = syntaxTree;
        _definitionTable = definitionTable;

        _variables = [];
        _funcReturnType = null;

        var definitions = new List<BoundTopLevelNode>();

        foreach (var topLevel in syntaxTree.TopLevelNodes)
        {
            definitions.Add(BindTopLevel(topLevel));
        }

        diagnostics = [];
        return new BoundSyntaxTree(syntaxTree.Namespace, definitions);
    }

    private static BoundTopLevelNode BindTopLevel(TopLevelNode node)
    {
        return node switch
        {
            ExternFuncNode definition => BindExternFuncDefinition(definition),
            TraitImplNode definition => BindTraitImplementation(definition),
            TraitNode definition => BindTraitDefinition(definition),
            LocalFuncNode definition => BindLocalFuncDefinition(definition),
            StructNode definition => BindStruct(definition),
            _ => throw new ArgumentOutOfRangeException(nameof(node))
        };
    }

    private static BoundTraitImplNode BindTraitImplementation(TraitImplNode node)
    {
        _variables.Clear();
        var functions = new List<BoundTraitFuncImplNode>();

        foreach (var function in node.Functions)
        {
            foreach (var parameter in function.Parameters)
            {
                _variables[parameter.Name] = parameter.Type;
            }

            functions.Add(new BoundTraitFuncImplNode(function.Tokens, function.Name, function.Parameters, function.ReturnType, BindBlock(function.Body)));
        }

        return new BoundTraitImplNode(node.Tokens, node.Namespace, node.TraitType, node.ForType, functions);
    }

    private static BoundTraitNode BindTraitDefinition(TraitNode node)
    {
        var functions = new List<BoundTraitFuncNode>();

        foreach (var func in node.Functions)
        {
            functions.Add(new BoundTraitFuncNode(node.Tokens, func.Name, func.Parameters, func.ReturnType));
        }

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

    private static BoundStructNode BindStruct(StructNode node)
    {
        var defOpt = _definitionTable.LookupStruct(node.Namespace, node.Name);
        if (!defOpt.TryGetValue(out var definition))
        {
            throw new NotImplementedException("Diagnostics not implemented");
        }

        var structFields = new List<BoundStructFieldNode>();

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

            if (structField.Value.HasValue)
            {
                var definitionField = definition.Fields.FirstOrDefault(f => f.Name == structField.Name);
                if (definitionField == null)
                {
                    throw new NotImplementedException("Diagnostics not implemented");
                }

                value = BindExpression(structField.Value.Value, definitionField.Type);
            }

            structFields.Add(new BoundStructFieldNode(structField.Tokens, structField.Name, structField.Type, value));
        }

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

    private static BoundExternFuncNode BindExternFuncDefinition(ExternFuncNode node)
    {
        return new BoundExternFuncNode(node.Tokens, node.Namespace, node.Name, node.CallName, node.Parameters, node.ReturnType);
    }

    private static BoundLocalFuncNode BindLocalFuncDefinition(LocalFuncNode node)
    {
        _variables.Clear();
        _funcReturnType = node.ReturnType;

        foreach (var parameter in node.Parameters)
        {
            _variables[parameter.Name] = parameter.Type;
        }

        var body = BindBlock(node.Body);

        return new BoundLocalFuncNode(node.Tokens, node.Namespace, node.Name, node.Parameters, body, node.ReturnType, node.Exported);
    }

    private static BoundBlock BindBlock(BlockNode node)
    {
        var statements = new List<BoundStatementNode>();

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

        return new BoundBlock(node.Tokens, statements);
    }

    private static BoundStatementNode BindStatement(StatementNode node)
    {
        return node switch
        {
            AssignmentNode statement => BindAssignment(statement),
            BreakNode statement => BindBreak(statement),
            ContinueNode statement => BindContinue(statement),
            IfNode statement => BindIf(statement),
            ReturnNode statement => BindReturn(statement),
            StatementExpressionNode statement => BindStatementExpression(statement),
            VariableDeclarationNode statement => BindVariableDeclaration(statement),
            WhileNode statement => BindWhile(statement),
            _ => throw new ArgumentOutOfRangeException(nameof(node))
        };
    }

    private static BoundStatementNode BindAssignment(AssignmentNode statement)
    {
        var expression = BindExpression(statement.Expression);
        var value = BindExpression(statement.Value, expression.Type);
        return new BoundAssignmentNode(statement.Tokens, expression, value);
    }

    private static BoundBreakNode BindBreak(BreakNode statement)
    {
        return new BoundBreakNode(statement.Tokens);
    }

    private static BoundContinueNode BindContinue(ContinueNode statement)
    {
        return new BoundContinueNode(statement.Tokens);
    }

    private static BoundIfNode BindIf(IfNode statement)
    {
        var elseStatement = Optional.Empty<Variant<BoundIfNode, BoundBlock>>();

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

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

    private static BoundReturnNode BindReturn(ReturnNode statement)
    {
        var value = Optional.Empty<BoundExpressionNode>();

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

        return new BoundReturnNode(statement.Tokens, value);
    }

    private static BoundStatementExpressionNode BindStatementExpression(StatementExpressionNode statement)
    {
        return new BoundStatementExpressionNode(statement.Tokens, BindExpression(statement.Expression));
    }

    private static BoundVariableDeclarationNode BindVariableDeclaration(VariableDeclarationNode statement)
    {
        NubType? type = null;

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

        var assignment = Optional<BoundExpressionNode>.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");
        }

        _variables[statement.Name] = type;

        return new BoundVariableDeclarationNode(statement.Tokens, statement.Name, statement.ExplicitType, assignment, type);
    }

    private static BoundWhileNode BindWhile(WhileNode statement)
    {
        return new BoundWhileNode(statement.Tokens, BindExpression(statement.Condition, NubPrimitiveType.Bool), BindBlock(statement.Body));
    }

    private static BoundExpressionNode BindExpression(ExpressionNode node, NubType? expectedType = null)
    {
        return node switch
        {
            AddressOfNode expression => BindAddressOf(expression),
            AnonymousFuncNode expression => BindAnonymousFunc(expression),
            ArrayIndexAccessNode expression => BindArrayIndexAccess(expression),
            ArrayInitializerNode expression => BindArrayInitializer(expression),
            BinaryExpressionNode expression => BindBinaryExpression(expression),
            DereferenceNode expression => BindDereference(expression),
            FuncCallNode expression => BindFuncCall(expression),
            IdentifierNode expression => BindIdentifier(expression),
            LiteralNode expression => BindLiteral(expression, expectedType),
            MemberAccessNode expression => BindMemberAccess(expression),
            StructInitializerNode expression => BindStructInitializer(expression),
            UnaryExpressionNode expression => BindUnaryExpression(expression),
            _ => throw new ArgumentOutOfRangeException(nameof(node))
        };
    }

    private static BoundAddressOfNode BindAddressOf(AddressOfNode expression)
    {
        var inner = BindExpression(expression.Expression);
        return new BoundAddressOfNode(expression.Tokens, new NubPointerType(inner.Type), inner);
    }

    private static BoundAnonymousFuncNode BindAnonymousFunc(AnonymousFuncNode expression)
    {
        var parameterTypes = expression.Parameters.Select(x => x.Type).ToList();

        var body = BindBlock(expression.Body);

        return new BoundAnonymousFuncNode(expression.Tokens, new NubFuncType(expression.ReturnType, parameterTypes), expression.Parameters, body, expression.ReturnType);
    }

    private static BoundArrayIndexAccessNode BindArrayIndexAccess(ArrayIndexAccessNode expression)
    {
        var boundArray = BindExpression(expression.Array);
        var elementType = ((NubArrayType)boundArray.Type).ElementType;
        return new BoundArrayIndexAccessNode(expression.Tokens, elementType, boundArray, BindExpression(expression.Index, NubPrimitiveType.U64));
    }

    private static BoundArrayInitializerNode BindArrayInitializer(ArrayInitializerNode expression)
    {
        return new BoundArrayInitializerNode(expression.Tokens, new NubArrayType(expression.ElementType), BindExpression(expression.Capacity, NubPrimitiveType.U64), expression.ElementType);
    }

    private static BoundBinaryExpressionNode BindBinaryExpression(BinaryExpressionNode expression)
    {
        var boundLeft = BindExpression(expression.Left);
        var boundRight = BindExpression(expression.Right, boundLeft.Type);
        return new BoundBinaryExpressionNode(expression.Tokens, boundLeft.Type, boundLeft, expression.Operator, boundRight);
    }

    private static BoundDereferenceNode BindDereference(DereferenceNode expression)
    {
        var boundExpression = BindExpression(expression.Expression);
        var dereferencedType = ((NubPointerType)boundExpression.Type).BaseType;
        return new BoundDereferenceNode(expression.Tokens, dereferencedType, boundExpression);
    }

    private static BoundFuncCallNode BindFuncCall(FuncCallNode expression)
    {
        var boundExpression = BindExpression(expression.Expression);

        var funcType = (NubFuncType)boundExpression.Type;
        var returnType = ((NubFuncType)boundExpression.Type).ReturnType;

        var parameters = new List<BoundExpressionNode>();

        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 BoundFuncCallNode(expression.Tokens, returnType, boundExpression, parameters);
    }

    private static BoundIdentifierNode BindIdentifier(IdentifierNode expression)
    {
        NubType? type = null;

        var definition = _definitionTable.LookupFunction(expression.Namespace.Or(_syntaxTree.Namespace), expression.Name);
        if (definition.HasValue)
        {
            type = new NubFuncType(definition.Value.ReturnType, definition.Value.Parameters.Select(p => p.Type).ToList());
        }

        if (type == null && !expression.Namespace.HasValue)
        {
            type = _variables[expression.Name];
        }

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

        return new BoundIdentifierNode(expression.Tokens, type, expression.Namespace, expression.Name);
    }

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

        return new BoundLiteralNode(expression.Tokens, type, expression.Literal, expression.Kind);
    }

    private static BoundMemberAccessNode BindMemberAccess(MemberAccessNode expression)
    {
        var boundExpression = BindExpression(expression.Expression);

        var implementation = _definitionTable.LookupTraitImplementationForType(boundExpression.Type, expression.Member);
        if (implementation.HasValue)
        {
            var type = new NubFuncType(implementation.Value.Item2.ReturnType, implementation.Value.Item2.Parameters.Select(p => p.Type).ToList());
            return new BoundMemberAccessNode(expression.Tokens, type, boundExpression, expression.Member);
        }

        if (boundExpression.Type is NubCustomType customType)
        {
            var function = _definitionTable.LookupFunctionOnTrait(customType.Namespace, customType.Name, expression.Member);
            if (function.HasValue)
            {
                var type = new NubFuncType(function.Value.ReturnType, function.Value.Parameters.Select(p => p.Type).ToList());
                return new BoundMemberAccessNode(expression.Tokens, type, boundExpression, expression.Member);
            }

            var structDef = _definitionTable.LookupStruct(customType.Namespace, customType.Name);
            if (structDef.HasValue)
            {
                var matchingFields = structDef.Value.Fields.Where(f => f.Name == expression.Member).ToList();

                if (matchingFields.Count > 1)
                {
                    throw new NotImplementedException("Diagnostics not implemented");
                }

                if (matchingFields.Count == 1)
                {
                    return new BoundMemberAccessNode(expression.Tokens, matchingFields[0].Type, boundExpression, expression.Member);
                }
            }
        }

        if (boundExpression.Type is NubStringType or NubCStringType or NubArrayType && expression.Member == "count")
        {
            return new BoundMemberAccessNode(expression.Tokens, NubPrimitiveType.I64, boundExpression, expression.Member);
        }

        throw new NotImplementedException("Diagnostics not implemented");
    }

    private static BoundStructInitializerNode BindStructInitializer(StructInitializerNode expression)
    {
        if (expression.StructType is not NubCustomType structType)
        {
            throw new NotImplementedException("Diagnostics not implemented");
        }

        var defOpt = _definitionTable.LookupStruct(structType.Namespace, structType.Name);
        if (!defOpt.TryGetValue(out var definition))
        {
            throw new NotImplementedException("Diagnostics not implemented");
        }

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

        foreach (var (member, initializer) in expression.Initializers)
        {
            var definitionField = definition.Fields.FirstOrDefault(x => x.Name == member);
            if (definitionField == null)
            {
                throw new NotImplementedException("Diagnostics not implemented");
            }

            initializers[member] = BindExpression(initializer, definitionField.Type);
        }

        return new BoundStructInitializerNode(expression.Tokens, structType, structType, initializers);
    }

    private static BoundUnaryExpressionNode BindUnaryExpression(UnaryExpressionNode expression)
    {
        var boundOperand = BindExpression(expression.Operand);

        NubType? type = null;

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

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

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

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

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

        return new BoundUnaryExpressionNode(expression.Tokens, type, expression.Operator, boundOperand);
    }
}