using System.Collections.Generic;
using Microsoft.CodeAnalysis;
using Microsoft.CodeAnalysis.CSharp;
using Microsoft.CodeAnalysis.CSharp.Syntax;

namespace StardewModdingAPI.ModBuildConfig.Analyzer
{
    /// <summary>Provides generic utilities for SMAPI's Roslyn analyzers.</summary>
    internal static class AnalyzerUtilities
    {
        /*********
        ** Public methods
        *********/
        /// <summary>Get the metadata for an explicit cast or 'x as y' expression.</summary>
        /// <param name="node">The member access expression.</param>
        /// <param name="semanticModel">provides methods for asking semantic questions about syntax nodes.</param>
        /// <param name="fromExpression">The expression whose value is being converted.</param>
        /// <param name="fromType">The type being converted from.</param>
        /// <param name="toType">The type being converted to.</param>
        /// <returns>Returns true if the node is a matched expression, else false.</returns>
        public static bool TryGetCastOrAsInfo(SyntaxNode node, SemanticModel semanticModel, out ExpressionSyntax fromExpression, out TypeInfo fromType, out TypeInfo toType)
        {
            // (type)x
            if (node is CastExpressionSyntax cast)
            {
                fromExpression = cast.Expression;
                fromType = semanticModel.GetTypeInfo(fromExpression);
                toType = semanticModel.GetTypeInfo(cast.Type);
                return true;
            }

            // x as y
            if (node is BinaryExpressionSyntax binary && binary.Kind() == SyntaxKind.AsExpression)
            {
                fromExpression = binary.Left;
                fromType = semanticModel.GetTypeInfo(fromExpression);
                toType = semanticModel.GetTypeInfo(binary.Right);
                return true;
            }

            // invalid
            fromExpression = null;
            fromType = default(TypeInfo);
            toType = default(TypeInfo);
            return false;
        }

        /// <summary>Get the metadata for a member access expression.</summary>
        /// <param name="node">The member access expression.</param>
        /// <param name="semanticModel">provides methods for asking semantic questions about syntax nodes.</param>
        /// <param name="declaringType">The object type which has the member.</param>
        /// <param name="memberType">The type of the accessed member.</param>
        /// <param name="memberName">The name of the accessed member.</param>
        /// <returns>Returns true if the node is a member access expression, else false.</returns>
        public static bool TryGetMemberInfo(SyntaxNode node, SemanticModel semanticModel, out ITypeSymbol declaringType, out TypeInfo memberType, out string memberName)
        {
            // simple access
            if (node is MemberAccessExpressionSyntax memberAccess)
            {
                declaringType = semanticModel.GetTypeInfo(memberAccess.Expression).Type;
                memberType = semanticModel.GetTypeInfo(node);
                memberName = memberAccess.Name.Identifier.Text;
                return true;
            }

            // conditional access
            if (node is ConditionalAccessExpressionSyntax conditionalAccess && conditionalAccess.WhenNotNull is MemberBindingExpressionSyntax conditionalBinding)
            {
                declaringType = semanticModel.GetTypeInfo(conditionalAccess.Expression).Type;
                memberType = semanticModel.GetTypeInfo(node);
                memberName = conditionalBinding.Name.Identifier.Text;
                return true;
            }

            // invalid
            declaringType = null;
            memberType = default(TypeInfo);
            memberName = null;
            return false;
        }

        /// <summary>Get the class types in a type's inheritance chain, including itself.</summary>
        /// <param name="type">The initial type.</param>
        public static IEnumerable<ITypeSymbol> GetConcreteTypes(ITypeSymbol type)
        {
            while (type != null)
            {
                yield return type;
                type = type.BaseType;
            }
        }
    }
}