using System;
using System.Collections.Generic;

namespace MsgReader.Mime.Decode
{
	/// <summary>
	/// Contains common operations needed while decoding.
	/// </summary>
	internal static class Utility
    {
        #region RemoveQuotesIfAny
        /// <summary>
	    /// Remove quotes, if found, around the string.
	    /// </summary>
	    /// <param name="text">Text with quotes or without quotes</param>
	    /// <returns>Text without quotes</returns>
	    /// <exception cref="ArgumentNullException">If <paramref name="text"/> is <see langword="null"/></exception>
	    public static string RemoveQuotesIfAny(string text)
	    {
	        if (text == null)
	            throw new ArgumentNullException(nameof(text));

	        // Check if there are quotes at both ends and have at least two characters
	        if (text.Length > 1 && text[0] == '"' && text[text.Length - 1] == '"')
	        {
	            // Remove quotes at both ends
	            return text.Substring(1, text.Length - 2);
	        }

	        // If no quotes were found, the text is just returned
	        return text;
	    }
	    #endregion

        #region SplitStringWithCharNotInsideQuotes
        /// <summary>
	    /// Split a string into a list of strings using a specified character.<br/>
	    /// Everything inside quotes are ignored.
	    /// </summary>
	    /// <param name="input">A string to split</param>
	    /// <param name="toSplitAt">The character to use to split with</param>
	    /// <returns>A List of strings that was delimited by the <paramref name="toSplitAt"/> character</returns>
	    public static List<string> SplitStringWithCharNotInsideQuotes(string input, char toSplitAt)
	    {
	        var elements = new List<string>();

	        var lastSplitLocation = 0;
	        var insideQuote = false;

	        var characters = input.ToCharArray();

	        for (var i = 0; i < characters.Length; i++)
	        {
	            var character = characters[i];
	            if (character == '\"')
	                insideQuote = !insideQuote;

	            // Only split if we are not inside quotes
	            if (character != toSplitAt || insideQuote) continue;
	            // We need to split
	            var length = i - lastSplitLocation;
	            elements.Add(input.Substring(lastSplitLocation, length));

	            // Update last split location
	            // + 1 so that we do not include the character used to split with next time
	            lastSplitLocation = i + 1;
	        }

	        // Add the last part
	        elements.Add(input.Substring(lastSplitLocation, input.Length - lastSplitLocation));

	        return elements;
	    }
	    #endregion
	}
}