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package bjc.utils.parserutils;
import java.io.InputStream;
import java.util.InputMismatchException;
import java.util.Scanner;
import java.util.function.BiConsumer;
import java.util.function.Consumer;
import bjc.utils.data.IHolder;
import bjc.utils.data.IPair;
import bjc.utils.data.Identity;
import bjc.utils.data.Pair;
import bjc.utils.exceptions.UnknownPragmaException;
import bjc.utils.funcdata.FunctionalMap;
import bjc.utils.funcdata.FunctionalStringTokenizer;
import bjc.utils.funcdata.IMap;
/**
* This class parses a rules based config file, and uses it to drive a
* provided set of actions
*
* @author ben
*
* @param <E>
* The type of the state object to use
*
*/
public class RuleBasedConfigReader<E> {
private BiConsumer<FunctionalStringTokenizer, IPair<String,
E>> startRule;
private BiConsumer<FunctionalStringTokenizer,
E> continueRule;
private Consumer<
E> endRule;
private IMap<String, BiConsumer<FunctionalStringTokenizer,
E>> pragmas;
/**
* Create a new rule-based config reader
*
* @param startRule
* The action to fire when starting a rule
* @param continueRule
* The action to fire when continuing a rule
* @param endRule
* The action to fire when ending a rule
*/
public RuleBasedConfigReader(
BiConsumer<FunctionalStringTokenizer,
IPair<String, E>> startRule,
BiConsumer<FunctionalStringTokenizer, E> continueRule,
Consumer<E> endRule) {
this.startRule = startRule;
this.continueRule = continueRule;
this.endRule = endRule;
this.pragmas = new FunctionalMap<>();
}
/**
* Add a pragma to this reader
*
* @param pragmaName
* The name of the pragma to add
* @param pragmaAction
* The function to execute when this pragma is read
*/
public void addPragma(String pragmaName,
BiConsumer<FunctionalStringTokenizer, E> pragmaAction) {
if (pragmaName == null) {
throw new NullPointerException("Pragma name must not be null");
} else if (pragmaAction == null) {
throw new NullPointerException(
"Pragma action must not be null");
}
pragmas.put(pragmaName, pragmaAction);
}
private void continueRule(E state, boolean ruleOpen, String line) {
if (ruleOpen == false) {
throw new InputMismatchException(
"Can't continue rule with no rule currently open");
}
if (continueRule == null) {
throw new InputMismatchException(
"Attempted to continue rule with rule continuation disabled."
+ " Check for extraneous tabs");
}
continueRule.accept(
new FunctionalStringTokenizer(line.substring(1), " "),
state);
}
private boolean endRule(E state, boolean ruleOpen) {
if (ruleOpen == false) {
// Ignore blank line without an open rule
} else {
if (endRule == null) {
// Nothing happens on rule end
ruleOpen = false;
} else {
endRule.accept(state);
}
ruleOpen = false;
}
return ruleOpen;
}
/**
* Run a stream through this reader
*
* @param inputStream
* The stream to get input
* @param initialState
* The initial state of the reader
* @return The final state of the reader
*/
public E fromStream(InputStream inputStream, E initialState) {
if (inputStream == null) {
throw new NullPointerException(
"Input stream must not be null");
}
E state;
try (Scanner inputSource = new Scanner(inputStream, "\n")) {
state = initialState;
IHolder<Boolean> ruleOpen = new Identity<>(false);
inputSource.forEachRemaining((line) -> {
if (line.startsWith("#") || line.startsWith("//")) {
// It's a comment
return;
} else if (line.equals("")) {
ruleOpen.replace(endRule(state, ruleOpen.getValue()));
return;
} else if (line.startsWith("\t")) {
continueRule(state, ruleOpen.getValue(), line);
} else {
ruleOpen.replace(
startRule(state, ruleOpen.getValue(), line));
}
});
}
return state;
}
/**
* Set the action to execute when continuing a rule
*
* @param continueRule
* The action to execute on continuation of a rule
*/
public void setContinueRule(
BiConsumer<FunctionalStringTokenizer, E> continueRule) {
this.continueRule = continueRule;
}
/**
* Set the action to execute when ending a rule
*
* @param endRule
* The action to execute on ending of a rule
*/
public void setEndRule(Consumer<E> endRule) {
this.endRule = endRule;
}
/**
* Set the action to execute when starting a rule
*
* @param startRule
* The action to execute on starting of a rule
*/
public void setStartRule(BiConsumer<FunctionalStringTokenizer,
IPair<String, E>> startRule) {
if (startRule == null) {
throw new NullPointerException(
"Action on rule start must be non-null");
}
this.startRule = startRule;
}
private boolean startRule(E state, boolean ruleOpen, String line) {
FunctionalStringTokenizer tokenizer = new FunctionalStringTokenizer(
line, " ");
String nextToken = tokenizer.nextToken();
if (nextToken.equals("pragma")) {
String token = tokenizer.nextToken();
pragmas.getOrDefault(token, (tokenzer, stat) -> {
throw new UnknownPragmaException(
"Unknown pragma " + token);
}).accept(tokenizer, state);
} else {
if (ruleOpen == true) {
throw new InputMismatchException("Attempted to open a"
+ " rule with a rule already open. Make sure rules are"
+ " seperated by blank lines");
}
startRule.accept(tokenizer, new Pair<>(nextToken, state));
ruleOpen = true;
}
return ruleOpen;
}
}
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