namespace Tanshu.Accounts.SqlDAO
{
    using System.Collections;
    using System.Collections.Generic;
    using System.Text.RegularExpressions;

    /// <summary>
    /// The Inflector class transforms words from one 
    /// form to another. For example, from singular to plural.
    /// </summary>
    public class Inflector
    {
        private static readonly List<Rule> plurals = new List<Rule>();

        private static readonly List<Rule> singulars = new List<Rule>();

        private static readonly List<string> uncountables = new List<string>();

        /// <summary>
        /// Initializes static members of the <see cref="Inflector"/> class. 
        /// </summary>
        static Inflector()
        {
            AddPlural("$", "s");
            AddPlural("s$", "s");
            AddPlural("(ax|test)is$", "$1es");
            AddPlural("(octop|vir)us$", "$1i");
            AddPlural("(alias|status)$", "$1es");
            AddPlural("(bu)s$", "$1ses");
            AddPlural("(buffal|tomat)o$", "$1oes");
            AddPlural("([ti])um$", "$1a");
            AddPlural("sis$", "ses");
            AddPlural("(?:([^f])fe|([lr])f)$", "$1$2ves");
            AddPlural("(hive)$", "$1s");
            AddPlural("([^aeiouy]|qu)y$", "$1ies");
            AddPlural("(x|ch|ss|sh)$", "$1es");
            AddPlural("(matr|vert|ind)ix|ex$", "$1ices");
            AddPlural("([m|l])ouse$", "$1ice");
            AddPlural("^(ox)$", "$1en");
            AddPlural("(quiz)$", "$1zes");

            AddSingular("s$", string.Empty);
            AddSingular("(n)ews$", "$1ews");
            AddSingular("([ti])a$", "$1um");
            AddSingular("((a)naly|(b)a|(d)iagno|(p)arenthe|(p)rogno|(s)ynop|(t)he)ses$", "$1$2sis");
            AddSingular("(^analy)ses$", "$1sis");
            AddSingular("([^f])ves$", "$1fe");
            AddSingular("(hive)s$", "$1");
            AddSingular("(tive)s$", "$1");
            AddSingular("([lr])ves$", "$1f");
            AddSingular("([^aeiouy]|qu)ies$", "$1y");
            AddSingular("(s)eries$", "$1eries");
            AddSingular("(m)ovies$", "$1ovie");
            AddSingular("(x|ch|ss|sh)es$", "$1");
            AddSingular("([m|l])ice$", "$1ouse");
            AddSingular("(bus)es$", "$1");
            AddSingular("(o)es$", "$1");
            AddSingular("(shoe)s$", "$1");
            AddSingular("(cris|ax|test)es$", "$1is");
            AddSingular("(octop|vir)i$", "$1us");
            AddSingular("(alias|status)es$", "$1");
            AddSingular("^(ox)en", "$1");
            AddSingular("(vert|ind)ices$", "$1ex");
            AddSingular("(matr)ices$", "$1ix");
            AddSingular("(quiz)zes$", "$1");

            AddIrregular("person", "people");
            AddIrregular("man", "men");
            AddIrregular("child", "children");
            AddIrregular("sex", "sexes");
            AddIrregular("move", "moves");

            AddUncountable("equipment");
            AddUncountable("information");
            AddUncountable("rice");
            AddUncountable("money");
            AddUncountable("species");
            AddUncountable("series");
            AddUncountable("fish");
            AddUncountable("sheep");
        }

        /// <summary>
        /// Prevents a default instance of the <see cref="Inflector"/> class from being created. 
        /// </summary>
        private Inflector()
        {
        }

        /// <summary>
        /// Capitalizes a word.
        /// </summary>
        /// <param name="word">
        /// The word to be capitalized.
        /// </param>
        /// <returns>
        /// <paramref name="word"/> capitalized.
        /// </returns>
        public static string Capitalize(string word)
        {
            return word.Substring(0, 1).ToUpper() + word.Substring(1).ToLower();
        }

        /// <summary>
        /// Return the plural of a word.
        /// </summary>
        /// <param name="word">
        /// The singular form
        /// </param>
        /// <returns>
        /// The plural form of <paramref name="word"/>
        /// </returns>
        public static string Pluralize(string word)
        {
            return ApplyRules(plurals, word);
        }

        /// <summary>
        /// Return the singular of a word.
        /// </summary>
        /// <param name="word">
        /// The plural form
        /// </param>
        /// <returns>
        /// The singular form of <paramref name="word"/>
        /// </returns>
        public static string Singularize(string word)
        {
            return ApplyRules(singulars, word);
        }

        /// <summary>
        /// Adds the irregular.
        /// </summary>
        /// <param name="singular">The singular.</param>
        /// <param name="plural">The plural.</param>
        private static void AddIrregular(string singular, string plural)
        {
            AddPlural("(" + singular[0] + ")" + singular.Substring(1) + "$", "$1" + plural.Substring(1));
            AddSingular("(" + plural[0] + ")" + plural.Substring(1) + "$", "$1" + singular.Substring(1));
        }

        /// <summary>
        /// Adds the plural.
        /// </summary>
        /// <param name="rule">The replacement rule.</param>
        /// <param name="replacement">The replacement.</param>
        private static void AddPlural(string rule, string replacement)
        {
            plurals.Add(new Rule(rule, replacement));
        }

        /// <summary>
        /// Adds the singular.
        /// </summary>
        /// <param name="rule">The replacement rule.</param>
        /// <param name="replacement">The replacement.</param>
        private static void AddSingular(string rule, string replacement)
        {
            singulars.Add(new Rule(rule, replacement));
        }

        /// <summary>
        /// Adds the uncountable.
        /// </summary>
        /// <param name="word">The uncountable word.</param>
        private static void AddUncountable(string word)
        {
            uncountables.Add(word.ToLower());
        }

        /// <summary>
        /// Applies the rules.
        /// </summary>
        /// <param name="rules">The replacement rules.</param>
        /// <param name="word">The word to be replaced.</param>
        /// <returns>String resulting from rules being applied.</returns>
        private static string ApplyRules(IList rules, string word)
        {
            string result = word;

            if (!uncountables.Contains(word.ToLower()))
            {
                for (int i = rules.Count - 1; i >= 0; i--)
                {
                    var rule = (Rule)rules[i];

                    if ((result = rule.Apply(word)) != null)
                    {
                        break;
                    }
                }
            }

            return result;
        }

        /// <summary>
        /// Replacement rule.
        /// </summary>
        private class Rule
        {
            private readonly Regex regex;

            private readonly string replacement;

            /// <summary>
            /// Initializes a new instance of the <see cref="Rule"/> class. 
            /// </summary>
            /// <param name="pattern">
            /// The pattern.
            /// </param>
            /// <param name="replacement">
            /// The replacement.
            /// </param>
            public Rule(string pattern, string replacement)
            {
                this.regex = new Regex(pattern, RegexOptions.IgnoreCase);
                this.replacement = replacement;
            }

            /// <summary>
            /// Applies the specified word.
            /// </summary>
            /// <param name="word">The word to be replaced.</param>
            /// <returns>Regex replaced word.</returns>
            public string Apply(string word)
            {
                if (!this.regex.IsMatch(word))
                {
                    return null;
                }

                return this.regex.Replace(word, this.replacement);
            }
        }
    }
}