//---------------------------------------------------------------------
// <copyright file="StringUtil.cs" company="Microsoft">
//      Copyright (c) Microsoft Corporation.  All rights reserved.
// </copyright>
//
// @owner Microsoft
// @backupOwner Microsoft
//---------------------------------------------------------------------


using System;
using System.Collections;
using System.Collections.Generic;
using System.Text;
using System.Globalization;
using System.Diagnostics;

namespace System.Data.Common.Utils {

    // This class provides some useful string utilities, e.g., converting a
    // list to string.
    internal static class StringUtil {
        private const string s_defaultDelimiter = ", ";

        #region String Conversion - Unsorted
        /// <summary>
        /// Converts an enumeration of values to a delimited string list.
        /// </summary>
        /// <typeparam name="T">Type of elements to convert.</typeparam>
        /// <param name="values">Values. If null, returns empty string.</param>
        /// <param name="converter">Converter. If null, uses default invariant culture converter.</param>
        /// <param name="delimiter">Delimiter. If null, uses default (', ')</param>
        /// <returns>Delimited list of values in string.</returns>
        internal static string BuildDelimitedList<T>(IEnumerable<T> values, ToStringConverter<T> converter, string delimiter) {
            if (null == values) { return String.Empty; }
            if (null == converter) { converter = new ToStringConverter<T>(InvariantConvertToString<T>); }
            if (null == delimiter) { delimiter = s_defaultDelimiter; }

            StringBuilder sb = new StringBuilder();
            bool first = true;
            foreach (T value in values) {
                if (first) { first = false; }
                else { sb.Append(delimiter); }
                sb.Append(converter(value));
            }

            return sb.ToString();
        }

        // effects: Converts list to a string separated by a comma with
        // string.Empty used for null values
        internal static string ToCommaSeparatedString(IEnumerable list) {
            return ToSeparatedString(list, s_defaultDelimiter, string.Empty);
        }

        // effects: Converts list to a string separated by "separator" with
        // "nullValue" used for null values
        internal static string ToSeparatedString(IEnumerable list, string separator, string nullValue) {
            StringBuilder builder = new StringBuilder();
            ToSeparatedString(builder, list, separator, nullValue);
            return builder.ToString();
        }
        #endregion

        #region String Conversion - Sorted
        // effects: Converts the list to a list of strings, sorts its
        // and then converts to a string separated by a comma with
        // string.Empty used for null values
        internal static string ToCommaSeparatedStringSorted(IEnumerable list) {
            return ToSeparatedStringSorted(list, s_defaultDelimiter, string.Empty);
        }

        // effects: Converts the list to a list of strings, sorts its using
        // StringComparer.Ordinal
        // and then converts to a string separated by  "separator" with
        // with "nullValue" used for null values
        internal static string ToSeparatedStringSorted(IEnumerable list, string separator, string nullValue) {
            StringBuilder builder = new StringBuilder();
            ToSeparatedStringPrivate(builder, list, separator, nullValue, true);
            return builder.ToString();
        }
        #endregion

        #region StringBuilder routines

        internal static string MembersToCommaSeparatedString(IEnumerable members)
        {
            StringBuilder builder = new StringBuilder();
            builder.Append("{");
            StringUtil.ToCommaSeparatedString(builder, members);
            builder.Append("}");
            return builder.ToString();
        }

        internal static void ToCommaSeparatedString(StringBuilder builder, IEnumerable list) {
            ToSeparatedStringPrivate(builder, list, s_defaultDelimiter, string.Empty, false);
        }

        internal static void ToCommaSeparatedStringSorted(StringBuilder builder, IEnumerable list) {
            ToSeparatedStringPrivate(builder, list, s_defaultDelimiter, string.Empty, true);
        }

        internal static void ToSeparatedString(StringBuilder builder, IEnumerable list, string separator) {
            ToSeparatedStringPrivate(builder, list, separator, string.Empty, false);
        }

        internal static void ToSeparatedStringSorted(StringBuilder builder, IEnumerable list, string separator) {
            ToSeparatedStringPrivate(builder, list, separator, string.Empty, true);
        }

        // effects: Modifies stringBuilder to contain a string of values from list
        // separated by "separator" with "nullValue" used for null values
        internal static void ToSeparatedString(StringBuilder stringBuilder, IEnumerable list, string separator,
                                               string nullValue) {
            ToSeparatedStringPrivate(stringBuilder, list, separator, nullValue, false);
        }

        // effects: Converts the list to a list of strings, sorts its (if
        // toSort is true) and then converts to a string separated by
        // "separator" with "nullValue" used for null values.
        private static void ToSeparatedStringPrivate(StringBuilder stringBuilder, IEnumerable list, string separator,
                                                     string nullValue, bool toSort) {
            if (null == list) {
                return;
            }
            bool isFirst = true;
            // Get the list of strings first
            List<string> elementStrings = new List<string>();
            foreach (object element in list) {
                string str;
                // Get the element or its default null value
                if (element == null) {
                    str = nullValue;
                } else {
                    str = FormatInvariant("{0}", element);
                }
                elementStrings.Add(str);
            }            

            if (toSort == true) {
                // Sort the list
                elementStrings.Sort(StringComparer.Ordinal);
            }

            // Now add the strings to the stringBuilder
            foreach (string str in elementStrings) {
                if (false == isFirst) {
                    stringBuilder.Append(separator);
                }
                stringBuilder.Append(str);
                isFirst = false;
            }
        }
        #endregion

        #region Some Helper routines
        /// <summary>
        ///   This private static method checks a string to make sure that it is not empty.
        ///   Comparing with String.Empty is not sufficient since a string with nothing
        ///   but white space isn't considered "empty" by that rationale.
        /// </summary>
        internal static bool IsNullOrEmptyOrWhiteSpace(string value)
        {
            return IsNullOrEmptyOrWhiteSpace(value, 0);
        }
        
        internal static bool IsNullOrEmptyOrWhiteSpace(string value, int offset)
        {
            // don't use Trim(), which will copy the string, which may be large, just to test for emptyness
            //return String.IsNullOrEmpty(value) || String.IsNullOrEmpty(value.Trim());
            if (null != value)
            {
                for(int i = offset; i < value.Length; ++i)
                {
                    if (!Char.IsWhiteSpace(value[i]))
                    {
                        return false;
                    }
                }
            }
            return true;
        }
        
        // separate implementation from IsNullOrEmptyOrWhiteSpace(string, int) because that one will
        // pick up the jit optimization to avoid boundary checks and the this won't is unknown (most likely not)
        [System.Diagnostics.CodeAnalysis.SuppressMessage("Microsoft.Performance", "CA1811:AvoidUncalledPrivateCode")] // referenced by System.Data.Entity.Design.dll
        internal static bool IsNullOrEmptyOrWhiteSpace(string value, int offset, int length)
        {
            // don't use Trim(), which will copy the string, which may be large, just to test for emptyness
            //return String.IsNullOrEmpty(value) || String.IsNullOrEmpty(value.Trim());
            if (null != value)
            {
                length = Math.Min(value.Length, length);
                for(int i = offset; i < length; ++i)
                {
                    if (!Char.IsWhiteSpace(value[i]))
                    {
                        return false;
                    }
                }
            }
            return true;
        }

        internal static string FormatInvariant(string format, params object[] args) {
            Debug.Assert(args.Length > 0, "Formatting utilities must be called with at least one argument");
            return String.Format(CultureInfo.InvariantCulture, format, args);
        }

        // effects: Formats args according to the format string and adds it
        // to builder. Returns the modified builder
        internal static StringBuilder FormatStringBuilder(StringBuilder builder, string format, params object[] args) {
            Debug.Assert(args.Length > 0, "Formatting utilities must be called with at least one argument");
            builder.AppendFormat(CultureInfo.InvariantCulture, format, args);
            return builder;
        }
        
        // effects: Generates a new line and then indents the new line by
        // indent steps in builder -- indent steps are determined internally
        // by this method. Returns the modified builder
        internal static StringBuilder IndentNewLine(StringBuilder builder, int indent) {
            builder.AppendLine();
            for (int i = 0; i < indent; i++) {
                builder.Append("    ");
            }
            return builder;
        }

        // effects: returns a string of the form 'arrayVarName[index]'
        internal static string FormatIndex(string arrayVarName, int index) {
            System.Text.StringBuilder builder = new System.Text.StringBuilder(arrayVarName.Length + 10 + 2);
            return builder.Append(arrayVarName).Append('[').Append(index).Append(']').ToString();
        }

        private static string InvariantConvertToString<T>(T value) {
            return String.Format(CultureInfo.InvariantCulture, "{0}", value);
        }
        #endregion

        #region Delegates
        internal delegate string ToStringConverter<T>(T value);
        #endregion
    }
}