org.jline.style.InterpolationHelper Maven / Gradle / Ivy
/*
* Copyright (c) 2002-2017, the original author or authors.
*
* This software is distributable under the BSD license. See the terms of the
* BSD license in the documentation provided with this software.
*
* http://www.opensource.org/licenses/bsd-license.php
*/
package org.jline.style;
import java.util.function.Function;
/**
* Interpolation.
* Borrowed and adapted from Apache Felix Utils module.
*/
public final class InterpolationHelper {
private InterpolationHelper() {
}
private static final char ESCAPE_CHAR = '\\';
private static final String DELIM_START = "@{";
private static final String DELIM_STOP = "}";
private static final String MARKER = "@__";
public static String substVars(String val,
Function callback,
boolean defaultsToEmptyString)
throws IllegalArgumentException {
return unescape(doSubstVars(val, callback, defaultsToEmptyString));
}
private static String doSubstVars(String val,
Function callback,
boolean defaultsToEmptyString)
throws IllegalArgumentException {
// Assume we have a value that is something like:
// "leading @{foo.@{bar}} middle @{baz} trailing"
// Find the first ending '}' variable delimiter, which
// will correspond to the first deepest nested variable
// placeholder.
int startDelim;
int stopDelim = -1;
do {
stopDelim = val.indexOf(DELIM_STOP, stopDelim + 1);
while (stopDelim > 0 && val.charAt(stopDelim - 1) == ESCAPE_CHAR) {
stopDelim = val.indexOf(DELIM_STOP, stopDelim + 1);
}
// Find the matching starting "@{" variable delimiter
// by looping until we find a start delimiter that is
// greater than the stop delimiter we have found.
startDelim = val.indexOf(DELIM_START);
while (stopDelim >= 0) {
int idx = val.indexOf(DELIM_START, startDelim + DELIM_START.length());
if ((idx < 0) || (idx > stopDelim)) {
break;
} else if (idx < stopDelim) {
startDelim = idx;
}
}
}
while (startDelim >= 0 && stopDelim >= 0 && stopDelim < startDelim + DELIM_START.length());
// If we do not have a start or stop delimiter, then just
// return the existing value.
if ((startDelim < 0) || (stopDelim < 0)) {
return val;
}
// At this point, we have found a variable placeholder so
// we must perform a variable substitution on it.
// Using the start and stop delimiter indices, extract
// the first, deepest nested variable placeholder.
String variable = val.substring(startDelim + DELIM_START.length(), stopDelim);
String substValue = null;
// Get the value of the deepest nested variable placeholder.
if (variable.length() > 0 && callback != null) {
substValue = callback.apply(variable);
}
if (substValue == null) {
if (defaultsToEmptyString) {
substValue = "";
} else {
// alters the original token to avoid infinite recursion
// altered tokens are reverted in unescape()
substValue = MARKER + "{" + variable + "}";
}
}
// Append the leading characters, the substituted value of
// the variable, and the trailing characters to get the new
// value.
val = val.substring(0, startDelim) + substValue + val.substring(stopDelim + DELIM_STOP.length(), val.length());
// Now perform substitution again, since there could still
// be substitutions to make.
val = doSubstVars(val, callback, defaultsToEmptyString);
// Return the value.
return val;
}
private static String unescape(String val) {
val = val.replaceAll(MARKER, "@");
int escape = val.indexOf(ESCAPE_CHAR);
while (escape >= 0 && escape < val.length() - 1) {
char c = val.charAt(escape + 1);
if (c == '{' || c == '}' || c == ESCAPE_CHAR) {
val = val.substring(0, escape) + val.substring(escape + 1);
}
escape = val.indexOf(ESCAPE_CHAR, escape + 1);
}
return val;
}
}