using System;

namespace Microsoft.PowerShell
{
    public partial class PSConsoleReadLine
    {
        /// <summary>
        /// Returns the position of the beginning of line
        /// starting from the specified "current" position.
        /// </summary>
        /// <param name="current">The position in the current logical line.</param>
        private static int GetBeginningOfLinePos(int current)
        {
            int i = Math.Max(0, current);
            while (i > 0)
            {
                if (_singleton._buffer[--i] == '\n')
                {
                    i += 1;
                    break;
                }
            }

            return i;
        }

        /// <summary>
        /// Returns the position of the beginning of line
        /// for the 0-based specified line number.
        /// </summary>
        private static int GetBeginningOfNthLinePos(int lineIndex)
        {
            System.Diagnostics.Debug.Assert(lineIndex >= 0 || lineIndex < _singleton.GetLogicalLineCount());

            var nth = 0;
            var index = 0;
            var result = 0;

            for (; index < _singleton._buffer.Length; index++)
            {
                if (nth == lineIndex)
                {
                    result = index;
                    break;
                }

                if (_singleton._buffer[index] == '\n')
                {
                    nth++;
                }
            }

            if (nth == lineIndex)
            {
                result = index;
            }


            return result;
        }

        /// <summary>
        /// Returns the position of the end of the logical line
        /// as specified by the "current" position.
        /// </summary>
        /// <param name="current"></param>
        /// <returns></returns>
        private static int GetEndOfLogicalLinePos(int current)
        {
            var newCurrent = current;

            for (var position = current; position < _singleton._buffer.Length; position++)
            {
                if (_singleton._buffer[position] == '\n')
                {
                    break;
                }

                newCurrent = position;
            }

            return newCurrent;
        }

        /// <summary>
        /// Returns the position of the end of the logical line
        /// for the 0-based specified line number.
        /// </summary>
        private static int GetEndOfNthLogicalLinePos(int lineIndex)
        {
            return GetEndOfLogicalLinePos(
                GetBeginningOfNthLinePos(lineIndex));
        }

        /// <summary>
        /// Returns the position of the first non whitespace character in
        /// the current logical line as specified by the "current" position.
        /// </summary>
        /// <param name="current">The position in the current logical line.</param>
        private static int GetFirstNonBlankOfLogicalLinePos(int current)
        {
            var beginningOfLine = GetBeginningOfLinePos(current);

            var newCurrent = beginningOfLine;
            var buffer = _singleton._buffer;

            while (newCurrent < buffer.Length && buffer.IsVisibleBlank(newCurrent))
            {
                newCurrent++;
            }

            return newCurrent;
        }
    }
}