using System;

using System.Collections.Generic;

using Xunit;

​

namespace CustomCollection.Tests

{

    public class TestClass {

        public static void Main() {

            var stringMap = new StringMap<TestClass>();

            var result = false;

            var exception = Record.Exception(() => result = stringMap.AddElement(null, new TestClass()));

            Assert.IsType<ArgumentNullException>(exception);

            exception = Record.Exception(() => result = stringMap.AddElement("test", null));

            Assert.IsType<ArgumentNullException>(exception);

            exception = Record.Exception(() => result = stringMap.AddElement("", new TestClass()));

            Assert.IsType<ArgumentException>(exception);

            exception = Record.Exception(() => result = stringMap.AddElement("test", new TestClass()));

            Assert.Null(exception);

            Assert.False(result);

            exception = Record.Exception(() => result = stringMap.AddElement("test", new TestClass()));

            Assert.Null(exception);

            Assert.True(result);

            Console.WriteLine("All passed");

        }

    }

​

    //STRINGMAP

​

    // Do not change the name of this class

    public class StringMap<TValue> : IStringMap<TValue>

        where TValue: class

    {

        private Dictionary<string, TValue> _mapper = new Dictionary<string, TValue>();

​

        /// <summary> Returns number of elements in a map</summary>

        public int Count => _mapper.Count;

​

        /// <summary>

        /// If <c>GetValue</c> method is called but a given key is not in a map then <c>DefaultValue</c> is returned.

        /// </summary>

        // Do not change this property

        public TValue DefaultValue { get; set; }

​

        /// <summary>

        /// Adds a given key and value to a map.

        /// If the given key already exists in a map, then the value associated with this key should be overriden.

        /// </summary>

        /// <returns>true if the value for the key was overriden otherwise false</returns>

        /// <exception cref="System.ArgumentNullException">If the key is null</exception>

        /// <exception cref="System.ArgumentException">If the key is an empty string</exception>

        /// <exception cref="System.ArgumentNullException">If the value is null</exception>

        public bool AddElement(string key, TValue value)

        {

            ValidateKey(key);

            ValidateValue(value);

​

            bool overrideNeeded = _mapper.ContainsKey(key);

            _mapper[key] = value;

            return overrideNeeded;

        }

​

        /// <summary>

        /// Removes a given key and associated value from a map.

        /// </summary>

        /// <returns>true if the key was in the map and was removed otherwise false</returns>

        /// <exception cref="System.ArgumentNullException">If the key is null</exception>

        /// <exception cref="System.ArgumentException">If the key is an empty string</exception>

        public bool RemoveElement(string key)

        {

            ValidateKey(key);

​

            if (_mapper.ContainsKey(key)) {

                _mapper.Remove(key);

                return true;

            }

            return false;

        }

​

        /// <summary>

        /// Returns the value associated with a given key.

        /// </summary>

        /// <returns>The value associated with a given key or <c>DefaultValue</c> if the key does not exist in a map</returns>

        /// <exception cref="System.ArgumentNullException">If a key is null</exception>

        /// <exception cref="System.ArgumentException">If a key is an empty string</exception>

        public TValue GetValue(string key)

        {

            ValidateKey(key);

​

            if (_mapper.ContainsKey(key)) {

                return _mapper[key];

            } 

​

            return DefaultValue;

        }

​

        private void ValidateKey(string key) {

            if (key == null) {

                throw new ArgumentNullException("Key must not be null");

            }

​

            if (key == "") {

                throw new ArgumentException("Key must not be empty string");

            }

        }

​

        private void ValidateValue(TValue value) {

            if (value == null) {

                throw new ArgumentNullException("Value must not be null");

            }

        }

    }

    //ISTRINGMAP

​

    ///<summary>

    /// The interface for <see cref="StringMap" > collection </see>

    ///</summary>

    public interface IStringMap<TValue> where TValue: class

    {

        /// <summary>Returns number of elements in a map</summary>

        int Count { get; }

​

        /// <summary>

        /// If <c>GetValue</c> method is called but a given key is not in a map then <c>DefaultValue</c> is returned.

        /// </summary>

        TValue DefaultValue { get; set; }

​

        /// <summary>

        /// Adds a given key and value to a map.

        /// If the given key already exists in the map, then the value associated with this key should be overridden.

        /// </summary>

        /// <returns>true if the value for the key was overridden, otherwise false</returns>

        /// <exception cref="System.ArgumentNullException">If the key is null</exception>

        /// <exception cref="System.ArgumentException">If the key is an empty string</exception>

        /// <exception cref="System.ArgumentNullException">If the value is null</exception>

        bool AddElement(string key, TValue value);

​

        /// <summary>

        /// Removes a given key and associated value from a map.

        /// </summary>

        /// <returns>true if the key was in the map and was removed, otherwise false</returns>

        /// <exception cref="System.ArgumentNullException">If the key is null</exception>

        /// <exception cref="System.ArgumentException">If the key is an empty string</exception>

        bool RemoveElement(string key);

​

        /// <summary>

        /// Returns the value associated with a given key.

        /// </summary>

        /// <returns>The value associated with a given key or <c>DefaultValue</c> if the key does not exist in a map</returns>

        /// <exception cref="System.ArgumentNullException">If the key is null</exception>

        /// <exception cref="System.ArgumentException">If the key is an empty string</exception>

        TValue GetValue(string key);

    }

}

​