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package com.sun.jersey.server.impl.uri.rules.automata;
import com.sun.jersey.server.impl.uri.PathPattern;
import com.sun.jersey.server.impl.uri.rules.PatternRulePair;
import com.sun.jersey.spi.uri.rules.UriMatchResultContext;
import com.sun.jersey.spi.uri.rules.UriRules;
import java.util.ArrayList;
import java.util.HashSet;
import java.util.Iterator;
import java.util.List;
import java.util.Set;
import java.util.Stack;
/**
* UriRules implementation based on a TRIE/Finite Automata.
*
* This class has been made abstract because it needs to fixed in terms
* of supporting the UriRules interface and matching using more general regular
* expressions.
*
* @author Frank D. Martinez. fmartinez@asimovt.com
*/
public class AutomataMatchingUriTemplateRules<R> implements UriRules<R> {
/** Trie/Automata Index */
private final TrieNode<R> automata;
public AutomataMatchingUriTemplateRules(List<PatternRulePair<R>> rules) {
this.automata = initTrie(rules);
}
public Iterator<R> match(CharSequence path, UriMatchResultContext resultContext) {
List<String> capturingGroupValues = new ArrayList<String>();
TrieNode<R> node = find(path, capturingGroupValues);
if (node != null) {
return node.getValue();
}
return new TrieNodeValue.EmptyIterator<R>();
}
/**
* Trie initialization
*/
private TrieNode<R> initTrie(List<PatternRulePair<R>> rules) {
TrieNode<R> a = new TrieNode<R>();
for (PatternRulePair<R> prp : rules) {
if (prp.p instanceof PathPattern) {
PathPattern p = (PathPattern)prp.p;
a.add(p.getTemplate().getTemplate(), prp.r, prp.p);
} else {
throw new IllegalArgumentException(
"The automata matching algorithm currently only works" +
"for UriPattern instance that are instances of " +
"PathPattern");
}
}
a.pack();
return a;
}
/**
* Backtracking state struct
*/
private static final class SearchState<E> {
// Saved node
final TrieNode<E> node;
// Saved arch
final TrieArc<E> arc;
// Saved input position
final int i;
/** Constructor */
public SearchState(TrieNode<E> node, TrieArc<E> arc, int i) {
this.node = node;
this.arc = arc;
this.i = i;
}
}
/**
* Trie/Automata search algorithm.
*/
private TrieNode<R> find(CharSequence uri, List<String> templateValues) {
// URI Length
final int length = uri.length();
// Backtracking stack
final Stack<SearchState<R>> stack = new Stack<SearchState<R>>();
// Candidates saved by the way
final Stack<TrieNode<R>> candidates = new Stack<TrieNode<R>>();
// Arcs marked as visited
final Set<TrieArc<R>> visitedArcs = new HashSet<TrieArc<R>>();
// Actual node
TrieNode<R> node = automata;
// Actual matching arc
TrieArc<R> nextArc = node.getFirstArc();
// URI character pointer
int i = 0;
// =====================================================================
// Trie Search with backtracking
// NFA simulation
// =====================================================================
while (true) {
// End of input reached
if (i >= length) {
// Resource matched
if (node.hasValue()) break; // <<< EXIT POINT <<<<<<<<<<<<<<<<<<
// Restore backtracking state
nextArc = null;
while (!stack.isEmpty() && nextArc == null) {
SearchState<R> state = stack.pop();
nextArc = state.arc.next;
node = state.node;
i = state.i;
}
// Skip visited arcs if necesary
if (nextArc != null) {
while (visitedArcs.contains(nextArc)) {
nextArc = nextArc.next;
}
if (nextArc != null) visitedArcs.add(nextArc);
}
// No more chance to match
if (nextArc == null) break; // <<< EXIT POINT <<<<<<<<<<<<<<<<<<
// Go backtrack
continue;
}
// Accept a wildcard (Parameter)
if (nextArc == null && node.isWildcard()) {
int p = 0;
TrieArc<R> exitArc = null;
while ((i+p) < length &&
(exitArc = node.matchExitArc(uri, i+p)) == null) p++;
if (exitArc != null) {
nextArc = exitArc;
}
i = i+p;
continue;
}
// No wildcard and no more paths, end.
else if (nextArc == null && !node.isWildcard()) {
break; // <<< EXIT POINT <<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<
}
// Save backtracking point
if (nextArc.next != null && node.isWildcard()) {
stack.push(new SearchState<R>(node, nextArc, i));
}
// Save candidate
if (node.hasValue()) {
candidates.push(node);
}
// Matching cases ==================================================
// CASE 0 ----------------------------------------------------------
// If wildcard matches, exit wildcard.
if (node.isWildcard() && nextArc.match(uri, i) > 0) {
i += nextArc.length();
node = nextArc.target;
nextArc = node.getFirstArc();
continue;
}
// CASE 1 ----------------------------------------------------------
// If wildcard does not match, try another escape sequence.
// if nothing matches, consume input.
else if (node.isWildcard() && nextArc.match(uri, i) == 0) {
nextArc = nextArc.next;
if (nextArc == null) {
i++;
}
continue;
}
// CASE 2 ----------------------------------------------------------
// Fixed sequence matches, consume input and follow the arc.
else if (!node.isWildcard() && nextArc.match(uri, i) > 0) {
i += nextArc.length();
node = nextArc.target;
nextArc = node.getFirstArc();
continue;
}
// CASE 3 ----------------------------------------------------------
// Fixed sequence does not match, try the next.
else if (!node.isWildcard() && nextArc.match(uri, i) == 0) {
nextArc = nextArc.next;
continue;
}
}
// =====================================================================
// Select a matching candidate
// =====================================================================
// A perfect match
if (node.hasValue()) {
if (node.getPattern().match(uri, templateValues)) {
return node;
}
}
// No direct matches, looking for a secondary candidate
while (!candidates.isEmpty()) {
TrieNode<R> s = candidates.pop();
if (s.getPattern().match(uri, templateValues)) {
return s;
}
}
// Definitively it does not match
templateValues.clear();
return null;
}
}