// Copyright © Microsoft Corporation.
// This source file is subject to the Microsoft Permissive License.
// See http://www.microsoft.com/resources/sharedsource/licensingbasics/sharedsourcelicenses.mspx.
// All other rights reserved.

using System;
using System.Collections.Generic;
using System.Configuration;
using System.Xml;
using System.Xml.XPath;

namespace Microsoft.Ddue.Tools {

	public class ForEachComponent : BuildComponent {

		public ForEachComponent (BuildAssembler assembler, XPathNavigator configuration) : base(assembler, configuration) {

            // set up the context
            XPathNodeIterator context_nodes = configuration.Select("context");
            foreach (XPathNavigator context_node in context_nodes)
            {
                string prefix = context_node.GetAttribute("prefix", String.Empty);
                string name = context_node.GetAttribute("name", String.Empty);
                context.AddNamespace(prefix, name);
            }

			// load the expression format
			XPathNavigator variable_node = configuration.SelectSingleNode("variable");
			if (variable_node == null) throw new ConfigurationErrorsException("When instantiating a ForEach component, you must specify a variable using the <variable> element.");
			string xpath_format = variable_node.GetAttribute("expression", String.Empty);
			if ((xpath_format == null) || (xpath_format.Length == 0)) throw new ConfigurationErrorsException("When instantiating a ForEach component, you must specify a variable expression using the expression attribute");
			xpath = XPathExpression.Compile(xpath_format);

			// load the subcomponents
			WriteMessage(MessageLevel.Info, "Loading subcomponents.");
			XPathNavigator components_node = configuration.SelectSingleNode("components");
			if (components_node == null) throw new ConfigurationErrorsException("When instantiating a ForEach component, you must specify subcomponents using the <components> element.");
			
			components = BuildAssembler.LoadComponents(components_node);

			WriteMessage(MessageLevel.Info, String.Format("Loaded {0} subcomponents.", components.Count));

		}

		// the format string for the variable expression
		private XPathExpression xpath;

		// the xpath context
		private CustomContext context = new CustomContext();

		// the subcomponents
		private ICollection<BuildComponent> components;

		// the work of the component

		public override void Apply (XmlDocument document, string key) {

			// adjust the context
			context["key"] = key;

			// evaluate the condition
			XPathExpression xpath_local = xpath.Clone();
			xpath_local.SetContext(context);
            
			Object result = document.CreateNavigator().Evaluate(xpath_local);
           
			// try to intrepret the result as a node set
			XPathNodeIterator result_node_iterator = result as XPathNodeIterator;

			if (result_node_iterator != null) {
                XPathNavigator[] result_nodes = BuildComponentUtilities.ConvertNodeIteratorToArray(result_node_iterator);
				//Console.WriteLine("{0} node-set result", result_nodes.Length);
				// if it is, apply the child components to each node value
				foreach (XPathNavigator result_node in result_nodes) {
                    // Console.WriteLine(result_node.Value);
					ApplyComponents(document, result_node.Value);
				}
			} else {
				//Console.WriteLine("non-node-set result");
				// if it isn't, apply the child components to the string value of the result
				ApplyComponents(document, result.ToString());

			}


		}

		private void ApplyComponents (XmlDocument document, string key) {
			foreach (BuildComponent component in components) {
				component.Apply(document, key);
			}
		}

        protected override void Dispose(bool disposing) {
            if (disposing) {
                foreach (BuildComponent component in components) {
                    component.Dispose();
                }
            }
            base.Dispose(disposing);
        }
		
	}

}