MpcNET/LibMpc/MpdResponse.cs

using System;
using System.Collections.Generic;
using System.Collections.ObjectModel;
using System.Text;
using System.Text.RegularExpressions;

namespace LibMpc
{
    /// <summary>
    /// The MpdResponse class parses the response to an MPD command in it's most
    /// basic structure.
    /// </summary>
    public class MpdResponse : IEnumerable<KeyValuePair<string, string>>
    {
        private const string OK = "OK";
        private const string ACK = "ACK";

        private static readonly Regex LINE_REGEX = new Regex("^(?<key>[A-Za-z]*):[ ]{0,1}(?<value>.*)$");

        private readonly bool isError;
        private readonly int errorCode;
        private readonly int commandListNum;
        private readonly string currentCommand;
        private readonly string errorMessage;
        private readonly ReadOnlyCollection<string> message;

        private Dictionary<string, string> dictionary = null;
        /// <summary>
        /// If the response denotes an error in the last command.
        /// </summary>
        public bool IsError { get { return this.isError; } }
        /// <summary>
        /// The error code if an error occured.
        /// </summary>
        public int ErrorCode { get { return this.errorCode; } }
        /// <summary>
        /// If an error occured the index of the invalid command in a command list.
        /// </summary>
        public int CommandListNum { get { return this.commandListNum; } }
        /// <summary>
        /// The command executed.
        /// </summary>
        public string CurrentCommand { get { return this.currentCommand; } }
        /// <summary>
        /// The description of the error, if occured.
        /// </summary>
        public string ErrorMessage { get { return this.errorMessage; } }
        /// <summary>
        /// The lines of the response message.
        /// </summary>
        public ReadOnlyCollection<string> Message { get { return this.message; } }
        /// <summary>
        /// The value of an attribute in the MPD response.
        /// </summary>
        /// <param name="key">The name of the attribute.</param>
        /// <returns>The value of the attribute</returns>
        public string this[string key]
        {
            get
            {
                if (this.dictionary == null)
                {
                    this.dictionary = new Dictionary<string,string>();

                    foreach (string line in this.message)
                    {
                        Match match = LINE_REGEX.Match(line);
                        if (match.Success)
                            this.dictionary[match.Result("$key")] = match.Result("$value");
                    }
                }

                return this.dictionary[key];
            }
        }
        /// <summary>
        /// The number of lines in the response message.
        /// </summary>
        public int Count { get { return this.message.Count; } }
        /// <summary>
        /// A line in the MPD response as KeyValuePair. If the message cannot be separated
        /// into key and value according to the MPD protocol spec, a KeyValuePair is returned
        /// with the key null and the value the whole text of the line.
        /// </summary>
        /// <param name="line">The index of the line.</param>
        /// <returns>The requested line as KeyValuePair.</returns>
        public KeyValuePair<string, string> this[int line]
        {
            get
            {
                Match match = LINE_REGEX.Match(this.message[line]);
                if (match.Success)
                    return new KeyValuePair<string, string>(match.Result("${key}"), match.Result("${value}"));
                else
                    return new KeyValuePair<string,string>(null, this.message[line]);
            }
        }
        /// <summary>
        /// Creates a new MpdResponse from a list of lines in case no error occured.
        /// </summary>
        /// <param name="message">The response to an MPD command.</param>
        public MpdResponse( ReadOnlyCollection<string> message )
        {
            if (message == null)
                throw new ArgumentNullException("message");

            this.isError = false;
            this.errorCode = -1;
            this.commandListNum = 0;
            this.currentCommand = null;
            this.errorMessage = null;
            this.message = message;
        }
        /// <summary>
        /// Creates a new MpdResponse in case an error occured.
        /// </summary>
        /// <param name="errorCode">The code of the error.</param>
        /// <param name="commandListNum">The index of the command which raised the error.</param>
        /// <param name="currentCommand">The command that raised the error.</param>
        /// <param name="errorMessage">The message describing the error.</param>
        /// <param name="message">The text of the standard MPD response.</param>
        public MpdResponse( int errorCode, int commandListNum, string currentCommand, string errorMessage, ReadOnlyCollection<string> message)
        {
            if (currentCommand == null)
                throw new ArgumentNullException("currentCommand");
            if (errorMessage == null)
                throw new ArgumentNullException("errorMessage");
            if (message == null)
                throw new ArgumentNullException("message");

            this.isError = true;
            this.errorCode = errorCode;
            this.commandListNum = commandListNum;
            this.currentCommand = currentCommand;
            this.errorMessage = errorMessage;
            this.message = message;
        }
        /// <summary>
        /// Returns the values in all lines with the given attribute.
        /// </summary>
        /// <param name="attribute">The attribute who's values are reguested.</param>
        /// <returns>The values in all lines with the given attribute.</returns>
        public List<string> getAttributeValueList(string attribute)
        {
            List<string> ret = new List<string>();

            foreach (string line in this.message)
            {
                Match match = LINE_REGEX.Match(line);
                if (match.Success)
                {
                    string key = match.Result("${key}");
                    if( ( key != null ) && key.Equals( attribute ) )
                    {
                        string value = match.Result("${value}");
                        if( value != null )
                            ret.Add( value );
                    }
                }
            }

            return ret;
        }
        /// <summary>
        /// Returns only the value parts in all key/value pairs in the response.
        /// </summary>
        /// <returns>The list of values in all key/value pairs in the response.</returns>
        public List<string> getValueList()
        {
            List<string> ret = new List<string>();

            foreach (string line in this.message)
            {
                Match match = LINE_REGEX.Match(line);
                if (match.Success)
                {
                    string value = match.Result("${value}");
                    if (value != null)
                        ret.Add(value);
                }
            }

            return ret;
        }
        /// <summary>
        /// Builds the response text of the MPD server from the object.
        /// </summary>
        /// <returns>The response text of the MPD server from the object.</returns>
        public override string ToString()
        {
            StringBuilder builder = new StringBuilder();
            foreach (string line in this.message)
                builder.AppendLine(line);

            if (this.isError)
            {
                builder.Append(ACK);
                builder.Append(" [");
                builder.Append(this.errorMessage);
                builder.Append('@');
                builder.Append(this.commandListNum);
                builder.Append("] {");
                builder.Append(this.currentCommand);
                builder.Append("} ");
                builder.Append(this.errorMessage);
                //ACK [50@1] {play} song doesn't exist: "10240"
            }
            else
                builder.Append(OK);

            return builder.ToString();
        }

        #region IEnumerable<KeyValuePair<string,string>> Members
        /// <summary>
        /// Returns an enumerator for all KeyValuePairs in the MPD response.
        /// </summary>
        /// <returns>An enumerator for all KeyValuePairs in the MPD response.</returns>
        IEnumerator<KeyValuePair<string, string>> IEnumerable<KeyValuePair<string, string>>.GetEnumerator()
        {
            return new MpdResponseEnumerator(this);
        }

        #endregion

        #region IEnumerable Members
        /// <summary>
        /// Returns an enumerator for all KeyValuePairs in the MPD response.
        /// </summary>
        /// <returns>An enumerator for all KeyValuePairs in the MPD response.</returns>
        System.Collections.IEnumerator System.Collections.IEnumerable.GetEnumerator()
        {
            return new MpdResponseEnumerator(this);
        }

        #endregion
    }
    /// <summary>
    /// A class for enumerating over the KeyValuePairs in the response.
    /// </summary>
    public class MpdResponseEnumerator :IEnumerator<KeyValuePair<string, string>>
    {
        private readonly MpdResponse response;
        private int position = -1;
        private KeyValuePair<string, string> current;
        /// <summary>
        /// Creates a new MpdResponseEnumerator.
        /// </summary>
        /// <param name="response">The response to enumerate over.</param>
        protected internal MpdResponseEnumerator(MpdResponse response)
        {
            this.response = response;
        }

        #region IEnumerator<KeyValuePair<string,string>> Members
        /// <summary>
        /// Returns the current element of the enumerator.
        /// </summary>
        KeyValuePair<string, string> IEnumerator<KeyValuePair<string, string>>.Current
        {
            get { return this.current; }
        }

        #endregion

        #region IDisposable Members

        void IDisposable.Dispose()
        {
            this.position = -1;
        }

        #endregion

        #region IEnumerator Members
        /// <summary>
        /// Returns the current element of the enumerator.
        /// </summary>
        object System.Collections.IEnumerator.Current
        {
            get { return this.current; }
        }
        /// <summary>
        /// Moves the enumerator to the next KeyValuePair in the MPD response.
        /// </summary>
        /// <returns>If the enumerator has any values left.</returns>
        bool System.Collections.IEnumerator.MoveNext()
        {
            this.position++;
            if (this.position < this.response.Count)
            {
                this.current = this.response[this.position];
                return true;
            }
            else
                return false;
        }
        /// <summary>
        /// Sets the enumerator to it's initial state.
        /// </summary>
        void System.Collections.IEnumerator.Reset()
        {
            this.position = -1;
        }

        #endregion
    }
}