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*/
package com.google.refine.expr;
import java.io.StringReader;
import java.util.HashMap;
import java.util.Map;
import java.util.Properties;
import java.util.Set;
import clojure.lang.IFn;
import com.google.refine.grel.Parser;
abstract public class MetaParser {
static public class LanguageInfo {
final public String name;
final public LanguageSpecificParser parser;
final public String defaultExpression;
LanguageInfo(String name, LanguageSpecificParser parser, String defaultExpression) {
this.name = name;
this.parser = parser;
this.defaultExpression = defaultExpression;
}
}
static final protected Map<String, LanguageInfo> s_languages = new HashMap<String, LanguageInfo>();
static {
registerLanguageParser("grel", "Google Refine Expression Language (GREL)", new LanguageSpecificParser() {
@Override
public Evaluable parse(String s) throws ParsingException {
return parseGREL(s);
}
}, "value");
registerLanguageParser("clojure", "Clojure", new LanguageSpecificParser() {
@Override
public Evaluable parse(String s) throws ParsingException {
try {
IFn fn = (IFn) clojure.lang.Compiler.load(new StringReader(
"(fn [value cell cells row rowIndex] " + s + ")"
));
return new Evaluable() {
private IFn _fn;
public Evaluable init(IFn fn) {
_fn = fn;
return this;
}
@Override
public Object evaluate(Properties bindings) {
try {
return _fn.invoke(
bindings.get("value"),
bindings.get("cell"),
bindings.get("cells"),
bindings.get("row"),
bindings.get("rowIndex")
);
} catch (Exception e) {
return new EvalError(e.getMessage());
}
}
}.init(fn);
} catch (Exception e) {
throw new ParsingException(e.getMessage());
}
}
}, "value");
}
static public void registerLanguageParser(String languagePrefix, String name, LanguageSpecificParser parser, String defaultExpression) {
s_languages.put(languagePrefix, new LanguageInfo(name, parser, defaultExpression));
}
static public LanguageInfo getLanguageInfo(String languagePrefix) {
return s_languages.get(languagePrefix.toLowerCase());
}
static public Set<String> getLanguagePrefixes() {
return s_languages.keySet();
}
/**
* Parse an expression that might have a language prefix into an Evaluable.
* Expressions without valid prefixes or without any prefix are assumed to be
* GREL expressions.
*
* @param s
* @return
* @throws ParsingException
*/
static public Evaluable parse(String s) throws ParsingException {
String language = "grel";
int colon = s.indexOf(':');
if (colon >= 0) {
language = s.substring(0, colon).toLowerCase();
if ("gel".equals(language)) {
language = "grel";
}
}
LanguageInfo info = s_languages.get(language.toLowerCase());
if (info != null) {
return info.parser.parse(s.substring(colon + 1));
} else {
return parseGREL(s);
}
}
static protected Evaluable parseGREL(String s) throws ParsingException {
Parser parser = new Parser(s);
return parser.getExpression();
}
}