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package Torello.Java;

import Torello.Java.Function.IntCharFunction;

class Indent
{
    // Uses this array as a parameter to StrReplace
    private static final char[] cArrIndent = { '\n' };

    static String run
        (final String s, int n, boolean spaceOrTab, boolean trimBlankLines)
    {
        if (n < 1) throw new NException(
            "The value passed to parameter 'n' was [" + n + "], but this is expected to be an " +
            "integer greater than or equal to 1."
        );

        if (s.length() == 0) return "";

        final String padding = String.format("%1$"+ n + "s", spaceOrTab ? " " : "\t");


        // This replacement-function does a 'look-ahead'.  If the next character after a newline
        // character '\n' is *also* a '\n', then the first '\n' is left alone (not indented)

        IntCharFunction<String> replFunc = (int i, char c) ->
        {
            while (i < (s.length() - 1))
            {
                c = s.charAt(++i);
                if (c == '\n')                  return "\n";
                if ((c != ' ') && (c != '\t'))  return "\n" + padding;
            }

            return "\n";
        };

        // NOTE: private static final char[] cArrIndent = { '\n' };
        String ret = StrReplace.r(s, cArrIndent, replFunc);

        if (trimBlankLines) ret = StrIndent.trimWhiteSpaceOnlyLines(ret);


        // Indent the first line of text - insert the padding before the final returned string.
        // 
        // NOTE: This is somewhat inefficient, because the whole array needs to be copied again.
        //       Perhaps switching to RegEx and matching '^' is better (because of this reason).
        // 
        // Special Case:    The first character, itself, is a new-line.

        return (ret.charAt(0) != '\n') ? (padding + ret) : ret;
    }    
}