// Copyright (c) Microsoft Corporation.  All rights reserved.
//
using System;
using System.Collections.Generic;
using System.Configuration;
using System.IO;
using System.Reflection;
using System.Xml;
using System.Xml.XPath;

using Microsoft.Ddue.Tools.CommandLine;

namespace Microsoft.Ddue.Tools {

	public class BuildAssembler : IDisposable {

        // the built context
        public BuildAssembler()
        {
            this.handler = BuildAssembler.ConsoleMessageHandler;
            
        }

         // the built context
        public BuildAssembler(MessageHandler messageHandler)
        {
            if (messageHandler == null) throw new ArgumentNullException("messageHandler");
            this.handler = messageHandler;
 
        }

        // private data

        private BuildContext context = new BuildContext();
        
        public List<BuildComponent> components = new List<BuildComponent>();

        private MessageHandler handler;

        // data accessors

        public BuildContext Context {
            get {
                return (context);
            }
        }

        public BuildComponent[] BuildComponents {
            get {
                return (components.ToArray());
            }
        }

        public MessageHandler MessageHandler {
            get {
                return (handler);
            }
        }

        // component communication mechanism

        public event EventHandler ComponentEvent;

        internal void OnComponentEvent (Object o, EventArgs e) {
            if (ComponentEvent != null) ComponentEvent(o, e);
        }

        // operations

        public int Apply(IEnumerable<string> topics)
        {
            int count = 0;

            foreach (string topic in topics)
            {

                // create the document
                XmlDocument document = new XmlDocument();
                document.PreserveWhitespace = true;

                // write a log message
                WriteMessage(MessageLevel.Info, String.Format("Building topic {0}", topic));

                // apply the component stack
                foreach (BuildComponent component in components)
                {

                    component.Apply(document, topic);
                }

                count++;
            }

            return (count);
        }

        public int Apply (string manifestFile) {
            return (Apply(new TopicManifest(manifestFile)));
        }

        public virtual void Dispose () {
            foreach (BuildComponent component in components) {
                ((IDisposable) component).Dispose();
            }
        }

        private class TopicManifest : IEnumerable<string> {

            public TopicManifest (string manifest) {
                this.manifest = manifest;
            }

            private string manifest;

            public IEnumerator<string> GetEnumerator () {
                return (new TopicEnumerator(manifest));
            }

            System.Collections.IEnumerator System.Collections.IEnumerable.GetEnumerator () {
                return (GetEnumerator());
            }

        }

        private class TopicEnumerator : IEnumerator<string> {

            public TopicEnumerator (string manifest) {
                reader = XmlReader.Create(manifest);
                reader.MoveToContent();
            }

            private XmlReader reader;

            public bool MoveNext () {
                while (reader.Read()) {
                    if ((reader.NodeType == XmlNodeType.Element) && (reader.LocalName == "topic")) return (true);
                }
                return (false);
            }

            public string Current {
                get {
                    string id = reader.GetAttribute("id");
                    return(id);
                }
            }

            Object System.Collections.IEnumerator.Current {
                get {
                    return (Current);
                }
            }

            public void Reset () {
                throw new InvalidOperationException();
            }

            public virtual void Dispose () {
                reader.Close();
            }

        }

        public IEnumerable<BuildContext> GetFileManifestBuildContextEnumerator(string manifestFilename)
        {
            using (XmlReader reader = XmlReader.Create(manifestFilename))
            {
                reader.MoveToContent();
                while (reader.Read())
                {
                    if ((reader.NodeType == XmlNodeType.Element) && (reader.LocalName == "topic"))
                    {
                        BuildContext thisContext = new BuildContext();

                        try
                        {
                            string id = reader.GetAttribute("id");

                            while (reader.MoveToNextAttribute())
                            {
                                string name = reader.Name;
                                string value = reader.Value;
                                thisContext.AddVariable(name, value);
                            }
                        }
                        catch (XmlException e)
                        {
                            throw new XmlException(String.Format("The manifest file: '{0}' is not well-formed. The error message is: {1}", manifestFilename, e.Message), e);
                        }

                        yield return thisContext;
                    }
                }
            }
        }

        public BuildComponent LoadComponent (XPathNavigator configuration) {

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

            // get the component infomation
            string assemblyName = configuration.GetAttribute("assembly", String.Empty);
            if (String.IsNullOrEmpty(assemblyName)) {
                WriteMessage(MessageLevel.Error, "Each component element must have an assembly attribute that specifys a path to the component assembly.");
            }

            string typeName = configuration.GetAttribute("type", String.Empty);
            if (String.IsNullOrEmpty(typeName)) {
                WriteMessage(MessageLevel.Error, "Each component element must have a type attribute that specifys the fully qualified name of a component type.");
            }

            // expand environmet variables in path of assembly name
            assemblyName = Environment.ExpandEnvironmentVariables(assemblyName);

            // load and instantiate the component
            BuildComponent component = null;
            try {

                Assembly assembly = Assembly.LoadFrom(assemblyName);
                component = (BuildComponent) assembly.CreateInstance(typeName, false, BindingFlags.Public | BindingFlags.Instance, null, new Object[2] { this, configuration }, null, null);

            } catch (IOException e) {
                WriteMessage(MessageLevel.Error, String.Format("A file access error occured while attempting to load the build component assembly '{0}'. The error message is: {1}", assemblyName, e.Message));
            } catch (BadImageFormatException e) {
                WriteMessage(MessageLevel.Error, String.Format("The build component assembly '{0}' is not a valid managed assembly. The error message is: {1}", assemblyName, e.Message));
            } catch (TypeLoadException) {
                WriteMessage(MessageLevel.Error, String.Format("The build component '{0}' was not found in the assembly '{1}'.", typeName, assemblyName));
            } catch (MissingMethodException e) {
                WriteMessage(MessageLevel.Error, String.Format("No appropriate constructor exists for the build component '{0}' in the component assembly '{1}'. The error message is: {1}", typeName, assemblyName, e.Message));
            } catch (TargetInvocationException e) {
                WriteMessage(MessageLevel.Error, String.Format("An error occured while initializing the build component '{0}' in the component assembly '{1}'. The error message and stack trace follows: {2}", typeName, assemblyName, e.InnerException.ToString()));
            } catch (InvalidCastException) {
                WriteMessage(MessageLevel.Error, String.Format("The type '{0}' in the component assembly '{1}' is not a build component.", typeName, assemblyName));
            }

            if (component == null) {
                WriteMessage(MessageLevel.Error, String.Format("The type '{0}' was not found in the component assembly '{1}'.", typeName, assemblyName));
            }

            return (component);


        }

        public BuildComponent[] LoadComponents (XPathNavigator configuration) {

            XPathNodeIterator componentNodes = configuration.Select("component");

            List<BuildComponent> components = new List<BuildComponent>();

            foreach (XPathNavigator componentNode in componentNodes) {
                components.Add(LoadComponent(componentNode));
            }

            return(components.ToArray());

        }

        // routines to add and remove components from the 

        public void AddComponents (XPathNavigator configuration) {
            BuildComponent[] componentsToAdd = LoadComponents(configuration);
            foreach (BuildComponent componentToAdd in componentsToAdd) {
                components.Add(componentToAdd);
            }
        }

        public void ClearComponents () {
            components.Clear();
        }
        private void WriteMessage(MessageLevel level, string message)
        {
            handler(this.GetType(), level, message);
        }

        // the default message handler

        public static MessageHandler ConsoleMessageHandler {
            get {
                return (new MessageHandler(WriteComponentMessageToConsole));
            }
        }

        private static void WriteComponentMessageToConsole(Type type, MessageLevel level, string message)
        {
            string text = String.Format("{0}: {1}", type.Name, message);
            switch (level)
            {
                case MessageLevel.Info:
                    ConsoleApplication.WriteMessage(LogLevel.Info, text);
                break;
                case MessageLevel.Warn:
                    ConsoleApplication.WriteMessage(LogLevel.Warn, text);
                break;
                case MessageLevel.Error:
                    ConsoleApplication.WriteMessage(LogLevel.Error, text);
                    Environment.Exit(1);
                break;
            }
        }
        
        private void SetupContextFromConfiguration(XPathDocument configuration)
        {
            // Load namespaces into context
            XPathNodeIterator namespace_nodes = configuration.CreateNavigator().Select("/configuration/dduetools/builder/context/namespace");
            foreach (XPathNavigator namespace_node in namespace_nodes)
            {
                string prefix = namespace_node.GetAttribute("prefix", String.Empty);
                string uri = namespace_node.GetAttribute("uri", String.Empty);
                context.AddNamespace(prefix, uri);
            }
        }

	}

}