// 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 CopyFromFileComponent : BuildComponent {

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

			if (configuration == null) throw new ArgumentNullException("configuration");

			string data_name = null;

			// get information about the data file
			XPathNodeIterator data_nodes = configuration.Select("data");
			foreach (XPathNavigator data_node in data_nodes) {
				string data_file = data_node.GetAttribute("file", String.Empty);
				if (String.IsNullOrEmpty(data_file)) WriteMessage(MessageLevel.Error, "Data elements must have a file attribute specifying a file from which to load data.");
				data_file = Environment.ExpandEnvironmentVariables(data_file);

				data_name = data_node.GetAttribute("name", String.Empty);
				if (String.IsNullOrEmpty(data_name)) data_name = Guid.NewGuid().ToString();

				// load a schema, if one is specified
				string schema_file = data_node.GetAttribute("schema", String.Empty);
				XmlReaderSettings settings = new XmlReaderSettings();
				if (!String.IsNullOrEmpty(schema_file)) {
					settings.Schemas.Add(null, schema_file);
				}

				// load the document
				WriteMessage(MessageLevel.Info, String.Format("Loading data file '{0}'.", data_file) );
				using (XmlReader reader = XmlReader.Create(data_file, settings)) {
					XPathDocument data_document = new XPathDocument(reader);
					Data.Add(data_name, data_document);
				}
			}
			

			// get the source and target expressions for each copy command
			XPathNodeIterator copy_nodes = configuration.Select("copy");
			foreach (XPathNavigator copy_node in copy_nodes) {
				string source_name = copy_node.GetAttribute("name", String.Empty);
				if (String.IsNullOrEmpty(source_name)) source_name = data_name;

				XPathDocument source_document = (XPathDocument) Data[source_name];

				string source_xpath = copy_node.GetAttribute("source", String.Empty);
				if (String.IsNullOrEmpty(source_xpath)) throw new ConfigurationErrorsException("When instantiating a CopyFromFile component, you must specify a source xpath format using the source attribute.");
				string target_xpath = copy_node.GetAttribute("target", String.Empty);
				if (String.IsNullOrEmpty(target_xpath)) throw new ConfigurationErrorsException("When instantiating a CopyFromFile component, you must specify a target xpath format using the target attribute.");
				copy_commands.Add( new CopyFromFileCommand(source_document, source_xpath, target_xpath) );
			}

		}

		// private XPathDocument data_document;

		private List<CopyFromFileCommand> copy_commands = new List<CopyFromFileCommand>();

		private CustomContext context = new CustomContext();

		// the work of the component

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

			// set the key in the XPath context
			context["key"] = key;

			// iterate over the copy commands
			foreach (CopyFromFileCommand copy_command in copy_commands) {

				// extract the target node
				XPathExpression target_xpath = copy_command.Target.Clone();
				target_xpath.SetContext(context);
				XPathNavigator target = document.CreateNavigator().SelectSingleNode(target_xpath);

				// warn if target not found?
				if (target == null) {
					continue;
				}

				// extract the source nodes
				XPathExpression source_xpath = copy_command.Source.Clone();
				source_xpath.SetContext(context);
				XPathNodeIterator sources = copy_command.SourceDocument.CreateNavigator().Select(source_xpath);

				// warn if source not found?
				
				// append the source nodes to the target node
				foreach (XPathNavigator source in sources) {
					target.AppendChild(source);
				}

			}

		}

	}


	// a representation of a copying operation

	internal class CopyFromFileCommand {

		public CopyFromFileCommand (XPathDocument source_document, string source_xpath, string target_xpath) {
			this.source_document = source_document;
			source = XPathExpression.Compile(source_xpath);
			target = XPathExpression.Compile(target_xpath);
		}

		private XPathDocument source_document;

		private XPathExpression source;

		private XPathExpression target;

		public XPathDocument SourceDocument {
			get {
				return(source_document);
			}
		}

		public XPathExpression Source {
			get {
				return(source);
			}
		}

		public XPathExpression Target {
			get {
				return(target);
			}
		}

	}

}