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/**
* (C) Copyright 2022 Benjamin Culkin.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package bjc.inflexion;
import java.util.Iterator;
/**
* Performs the parsing of directives from a string.
*
* @author bjculkin
*/
public class DirectiveIterator implements Iterator<String> {
private String strang;
private int pos;
/**
* Create a new directive iterator over a string.
*
* @param strang
* The string to parse directives from.
*/
public DirectiveIterator(String strang) {
this.strang = strang;
}
@Override
public boolean hasNext() {
return pos < strang.length();
}
@Override
public String next() {
if (!hasNext())
return null;
// Directive nesting level
int level = 0;
int prevPos = pos;
char prevChar = ' ';
boolean parsingVar = false;
for (; pos < strang.length(); pos++) {
// Backslash escapes a character
if (prevChar == '\\')
continue;
char c = strang.charAt(pos);
switch (c) {
case '<':
// Stop parsing at the start of a
// directive, unless the directive is
// the first thing in the string.
if (level == 0 && prevPos != pos) {
return strang.substring(prevPos, pos);
}
level += 1;
break;
case '>':
// :ErrorHandling 11/19/18
if (level == 0)
throw new IllegalArgumentException(
"Attempted to close inflection directive without one open at position "
+ prevPos + " in string '" + strang
+ "', current token is '"
+ strang.substring(prevPos, pos) + "'");
// Denest a level
level = Math.max(0, level - 1);
// Stop parsing at the end of a
// directive.
if (level == 0) {
// Advance past the '>'
pos += 1;
return strang.substring(prevPos, pos);
}
break;
case '$':
// Ignore v-refs when inside a directive
if (level > 0)
break;
// Stop parsing if this isn't at the
// start of a string
if (prevPos != pos)
return strang.substring(prevPos, pos);
parsingVar = true;
break;
case ' ':
// If we're parsing a v-ref, this
// finishes it.
if (parsingVar)
return strang.substring(prevPos, pos);
break;
default:
// Do nothing for ordinary characters
break;
}
}
/*
* @TODO 11/19/18 Ben Culkin :ErrorHandling Do something better than this
* exception, if possible.
*
* In the rest of the inflection string code, we use the whole 'list of
* errors/warnings' thing. Is there a way to do something similar here?
*/
if (level > 0)
throw new IllegalArgumentException(
"Unclosed inflection directive, starting at position " + prevPos
+ " in string '" + strang + "'");
return strang.substring(prevPos, pos);
}
}
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