// This file is part of YamlDotNet - A .NET library for YAML.
// Copyright (c) Antoine Aubry and contributors
//
// Permission is hereby granted, free of charge, to any person obtaining a copy of
// this software and associated documentation files (the "Software"), to deal in
// the Software without restriction, including without limitation the rights to
// use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies
// of the Software, and to permit persons to whom the Software is furnished to do
// so, subject to the following conditions:
//
// The above copyright notice and this permission notice shall be included in all
// copies or substantial portions of the Software.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
// SOFTWARE.

namespace YamlDotNet.RepresentationModel
{
    /// <summary>
    /// Abstract implementation of <see cref="IYamlVisitor"/> that knows how to walk a complete YAML object model.
    /// </summary>
    public abstract class YamlVisitorBase : IYamlVisitor
    {
        /// <summary>
        /// Called when this object is visiting a <see cref="YamlStream"/>.
        /// </summary>
        /// <param name="stream">
        /// The <see cref="YamlStream"/> that is being visited.
        /// </param>
        public virtual void Visit(YamlStream stream)
        {
            VisitChildren(stream);
        }

        /// <summary>
        /// Called when this object is visiting a <see cref="YamlDocument"/>.
        /// </summary>
        /// <param name="document">
        /// The <see cref="YamlDocument"/> that is being visited.
        /// </param>
        public virtual void Visit(YamlDocument document)
        {
            VisitChildren(document);
        }

        /// <summary>
        /// Called when this object is visiting a <see cref="YamlScalarNode"/>.
        /// </summary>
        /// <param name="scalar">
        /// The <see cref="YamlScalarNode"/> that is being visited.
        /// </param>
        public virtual void Visit(YamlScalarNode scalar)
        {
            // Do nothing.
        }

        /// <summary>
        /// Called when this object is visiting a <see cref="YamlSequenceNode"/>.
        /// </summary>
        /// <param name="sequence">
        /// The <see cref="YamlSequenceNode"/> that is being visited.
        /// </param>
        public virtual void Visit(YamlSequenceNode sequence)
        {
            VisitChildren(sequence);
        }

        /// <summary>
        /// Called when this object is visiting a <see cref="YamlMappingNode"/>.
        /// </summary>
        /// <param name="mapping">
        /// The <see cref="YamlMappingNode"/> that is being visited.
        /// </param>
        public virtual void Visit(YamlMappingNode mapping)
        {
            VisitChildren(mapping);
        }

        /// <summary>
        /// Called when this object is visiting a key-value pair.
        /// </summary>
        /// <param name="key">The left (key) <see cref="YamlNode"/> that is being visited.</param>
        /// <param name="value">The right (value) <see cref="YamlNode"/> that is being visited.</param>
        protected virtual void VisitPair(YamlNode key, YamlNode value)
        {
            key.Accept(this);
            value.Accept(this);
        }

        /// <summary>
        /// Visits every child of a <see cref="YamlStream"/>.
        /// </summary>
        /// <param name="stream">
        /// The <see cref="YamlStream"/> that is being visited.
        /// </param>
        protected virtual void VisitChildren(YamlStream stream)
        {
            foreach (var document in stream.Documents)
            {
                document.Accept(this);
            }
        }

        /// <summary>
        /// Visits every child of a <see cref="YamlDocument"/>.
        /// </summary>
        /// <param name="document">
        /// The <see cref="YamlDocument"/> that is being visited.
        /// </param>
        protected virtual void VisitChildren(YamlDocument document)
        {
            if (document.RootNode != null)
            {
                document.RootNode.Accept(this);
            }
        }

        /// <summary>
        /// Visits every child of a <see cref="YamlSequenceNode"/>.
        /// </summary>
        /// <param name="sequence">
        /// The <see cref="YamlSequenceNode"/> that is being visited.
        /// </param>
        protected virtual void VisitChildren(YamlSequenceNode sequence)
        {
            foreach (var node in sequence.Children)
            {
                node.Accept(this);
            }
        }

        /// <summary>
        /// Visits every child of a <see cref="YamlMappingNode"/>.
        /// </summary>
        /// <param name="mapping">
        /// The <see cref="YamlMappingNode"/> that is being visited.
        /// </param>
        protected virtual void VisitChildren(YamlMappingNode mapping)
        {
            foreach (var pair in mapping.Children)
            {
                VisitPair(pair.Key, pair.Value);
            }
        }
    }
}
