/**
* Licensed to the Apache Software Foundation (ASF) under one
* or more contributor license agreements. See the NOTICE file
* distributed with this work for additional information
* regarding copyright ownership. The ASF licenses this file
* to you 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 org.apache.ambari.server.api.predicate;
import org.apache.ambari.server.api.predicate.expressions.Expression;
import org.apache.ambari.server.api.predicate.expressions.LogicalExpressionFactory;
import org.apache.ambari.server.api.predicate.expressions.RelationalExpression;
import org.apache.ambari.server.api.predicate.operators.*;
import org.apache.ambari.server.controller.spi.Predicate;
import java.util.*;
/**
* Parser which produces a predicate instance from an array of tokens,
* which is generated by the lexer.
*/
public class QueryParser {
/**
* Map of token type to token handlers.
*/
private static final Map<Token.TYPE, TokenHandler> TOKEN_HANDLERS =
new HashMap<Token.TYPE, TokenHandler>();
/**
* Constructor.
* Register token handlers.
*
*/
public QueryParser() {
TOKEN_HANDLERS.put(Token.TYPE.BRACKET_OPEN, new BracketOpenTokenHandler());
TOKEN_HANDLERS.put(Token.TYPE.BRACKET_CLOSE, new BracketCloseTokenHandler());
TOKEN_HANDLERS.put(Token.TYPE.RELATIONAL_OPERATOR, new RelationalOperatorTokenHandler());
TOKEN_HANDLERS.put(Token.TYPE.LOGICAL_OPERATOR, new LogicalOperatorTokenHandler());
TOKEN_HANDLERS.put(Token.TYPE.LOGICAL_UNARY_OPERATOR, new LogicalUnaryOperatorTokenHandler());
TOKEN_HANDLERS.put(Token.TYPE.PROPERTY_OPERAND, new PropertyOperandTokenHandler());
TOKEN_HANDLERS.put(Token.TYPE.VALUE_OPERAND, new ValueOperandTokenHandler());
TOKEN_HANDLERS.put(Token.TYPE.RELATIONAL_OPERATOR_FUNC, new RelationalOperatorFuncTokenHandler());
}
/**
* Generate a Predicate instance from an array of tokens.
* Each input token contains a type and a value.
*
* Based on the token type and location, the tokens are first translated into a list of
* expressions, both relational and logical. These expressions are then merged into a tree
* of expressions with a single root following operator precedence and explicit grouping rules.
* Depending on the query, this merging of expressions into a tree of expressions may occur in
* several passes, one pass per level of precedence starting at the highest level of precedence.
*
* The predicate is built by traversing the expression tree in-order with each node expressing itself
* as a predicate.
*
* @param tokens an array of tokens which represent the query,
* each token contains type and value information
*
* @return a new predicate instance based on the supplied tokens
* @throws InvalidQueryException if unable to parse the tokens and produce a predicate
*/
public Predicate parse(Token[] tokens) throws InvalidQueryException {
ParseContext ctx = parseExpressions(tokens);
List<Expression> listExpressions = ctx.getExpressions();
List<Expression> listMergedExpressions = mergeExpressions(listExpressions, ctx.getMaxPrecedence());
return listMergedExpressions.isEmpty() ? null :
listMergedExpressions.get(0).toPredicate();
}
/**
* Create parse context from an array of tokens. The parse context contains a list of expressions
* and other information about the expressions an parsed tokens.
*
* @param tokens an array of tokens which represent the query,
* each token contains type and value information
*
* @return a parse context which contains a list of expressions
* @throws InvalidQueryException if unable to properly parse the tokens into a parse context
*/
private ParseContext parseExpressions(Token[] tokens) throws InvalidQueryException {
ParseContext ctx = new ParseContext(tokens);
while (ctx.getCurrentTokensIndex() < tokens.length) {
TOKEN_HANDLERS.get(tokens[ctx.getCurrentTokensIndex()].getType()).handleToken(ctx);
}
if (ctx.getPrecedenceLevel() != 0) {
throw new InvalidQueryException("Invalid query string: mismatched parentheses.");
}
return ctx;
}
/**
* Merge list of expressions into a tree of logical/relational expressions.
* This is done recursively in several passes, one per level of precedence starting at the
* highest precedence level. Recursion exits when a single expression remains.
*
* @param listExpressions list of expressions to merge
* @param precedenceLevel the precedence level that is to be merged
*
* @return tree of expressions with a single root expression
*/
private List<Expression> mergeExpressions(List<Expression> listExpressions, int precedenceLevel) {
if (listExpressions.size() > 1) {
Stack<Expression> stack = new Stack<Expression>();
stack.push(listExpressions.remove(0));
while (! listExpressions.isEmpty()) {
Expression exp = stack.pop();
Expression left = stack.empty() ? null : stack.pop();
Expression right = listExpressions.remove(0);
stack.addAll(exp.merge(left, right, precedenceLevel));
}
return mergeExpressions(new ArrayList<Expression>(stack), precedenceLevel - 1);
}
return listExpressions;
}
/**
* A parse context which contains information related to parsing the provided tokens into expressions.
*/
private class ParseContext {
/**
* The current context precedence level. This is dictated by bracket tokens.
*/
private int m_precedence = 0;
/**
* Current position in tokens array
*/
private int m_tokensIdx = 0;
/**
* Tokens
*/
private Token[] m_tokens;
/**
* The type of the previous token used in validation.
*/
private Token.TYPE m_previousTokenType = null;
/**
* The list of expressions which are generated from the tokens.
*/
private List<Expression> m_listExpressions = new ArrayList<Expression>();
/**
* Highest precedence level in expression.
*/
int m_maxPrecedence = 0;
public ParseContext(Token[] tokens) {
m_tokens = tokens;
}
/**
* Get array of all tokens.
* @return token array
*/
public Token[] getTokens() {
return m_tokens;
}
/**
* Get the current position in the tokens array.
* @return the current tokens index
*/
public int getCurrentTokensIndex() {
return m_tokensIdx;
}
/**
* Set the current position in the tokens array.
* Each handler should set this value after processing a token(s).
* @param idx current tokens index
*/
public void setCurrentTokensIndex(int idx) {
m_tokensIdx = idx;
}
/**
* Increment the context precedence level.
*
* @param val how much the level is increased by
*/
public void incPrecedenceLevel(int val) {
m_precedence += val;
}
/**
* Decrement the context precedence level.
*
* @param val how much the level is decremented by
* @throws InvalidQueryException if the level is decremented below 0
*/
public void decPrecedenceLevel(int val) throws InvalidQueryException {
m_precedence -= val;
if (m_precedence < 0) {
throw new InvalidQueryException("Invalid query string: mismatched parentheses.");
}
}
/**
* Get the current context precedence level.
*
* @return current context precedence level
*/
public int getPrecedenceLevel() {
return m_precedence;
}
/**
* Get the list of generated expressions.
*
* @return the list of generated expressions
*/
public List<Expression> getExpressions() {
return m_listExpressions;
}
/**
* Get the last expression.
*
* @return the last expression
*/
public Expression getPrecedingExpression() {
return m_listExpressions == null ? null :
m_listExpressions.get(m_listExpressions.size() - 1);
}
/**
* Get the highest operator precedence in the list of generated expressions.
*
* @return the max operator precedence
*/
public int getMaxPrecedence() {
return m_maxPrecedence;
}
/**
* Update the max precedence level.
* The max precedence level is only updated if the provided level > the current level.
*
* @param precedenceLevel the new value
*/
public void updateMaxPrecedence(int precedenceLevel) {
if (precedenceLevel > m_maxPrecedence) {
m_maxPrecedence = precedenceLevel;
}
}
/**
* Add a generated expression.
*
* @param exp the expression to add
*/
public void addExpression(Expression exp) {
m_listExpressions.add(exp);
}
/**
* Set the token type of the current token
*
* @param type type of the current token
*/
private void setTokenType(Token.TYPE type) {
m_previousTokenType = type;
}
/**
* Get the last token type set.
*
* @return the last token type set
*/
public Token.TYPE getPreviousTokenType() {
return m_previousTokenType;
}
}
/**
* Base token handler.
* Token handlers are responsible for handling the processing of a specific token type.
*/
private abstract class TokenHandler {
/**
* Process a token. Handles common token processing functionality then delegates to the individual
* concrete handlers.
*
* @param ctx the current parse context
* @throws InvalidQueryException if unable to process the token
*/
public void handleToken(ParseContext ctx) throws InvalidQueryException {
Token token = ctx.getTokens()[ctx.getCurrentTokensIndex()];
if (! validate(ctx.getPreviousTokenType())) {
throw new InvalidQueryException("Unexpected token encountered in query string. Last Token Type=" +
ctx.getPreviousTokenType() + ", Current Token[type=" + token.getType() +
", value='" + token.getValue() + "']");
}
ctx.setTokenType(token.getType());
int idxIncrement = _handleToken(ctx);
ctx.setCurrentTokensIndex(ctx.getCurrentTokensIndex() + idxIncrement);
}
/**
* Process a token.
*
* @param ctx the current parse context
* @throws InvalidQueryException if unable to process the token
*/
public abstract int _handleToken(ParseContext ctx) throws InvalidQueryException;
/**
* Validate the token based on the previous token.
*
* @param previousTokenType the type of the previous token
* @return true if validation is successful, false otherwise
*/
public abstract boolean validate(Token.TYPE previousTokenType);
}
/**
* Open Bracket token handler.
*/
private class BracketOpenTokenHandler extends TokenHandler {
@Override
public int _handleToken(ParseContext ctx) {
ctx.incPrecedenceLevel(Operator.MAX_OP_PRECEDENCE);
return 1;
}
@Override
public boolean validate(Token.TYPE previousTokenType) {
return previousTokenType == null ||
previousTokenType == Token.TYPE.BRACKET_OPEN ||
previousTokenType == Token.TYPE.LOGICAL_OPERATOR ||
previousTokenType == Token.TYPE.LOGICAL_UNARY_OPERATOR;
}
}
/**
* Close Bracket token handler
*/
private class BracketCloseTokenHandler extends TokenHandler {
@Override
public int _handleToken(ParseContext ctx) throws InvalidQueryException{
ctx.decPrecedenceLevel(Operator.MAX_OP_PRECEDENCE);
return 1;
}
@Override
public boolean validate(Token.TYPE previousTokenType) {
return previousTokenType == Token.TYPE.VALUE_OPERAND ||
previousTokenType == Token.TYPE.BRACKET_CLOSE;
}
}
/**
* Relational Operator token handler
*/
private class RelationalOperatorTokenHandler extends TokenHandler {
@Override
public int _handleToken(ParseContext ctx) throws InvalidQueryException {
Token token = ctx.getTokens()[ctx.getCurrentTokensIndex()];
RelationalOperator relationalOp = RelationalOperatorFactory.createOperator(token.getValue());
//todo: use factory to create expression
ctx.addExpression(new RelationalExpression(relationalOp));
return 1;
}
@Override
public boolean validate(Token.TYPE previousTokenType) {
return previousTokenType == null ||
previousTokenType == Token.TYPE.BRACKET_OPEN ||
previousTokenType == Token.TYPE.LOGICAL_OPERATOR ||
previousTokenType == Token.TYPE.LOGICAL_UNARY_OPERATOR;
}
}
/**
* Relational Operator function token handler
*/
private class RelationalOperatorFuncTokenHandler extends TokenHandler {
@Override
public int _handleToken(ParseContext ctx) throws InvalidQueryException {
Token[] tokens = ctx.getTokens();
int idx = ctx.getCurrentTokensIndex();
Token token = tokens[idx];
RelationalOperator relationalOp = RelationalOperatorFactory.createOperator(token.getValue());
ctx.addExpression(new RelationalExpression(relationalOp));
ctx.setCurrentTokensIndex(++idx);
TokenHandler propertyHandler = new PropertyOperandTokenHandler();
propertyHandler.handleToken(ctx);
// handle right operand if applicable to operator
idx = ctx.getCurrentTokensIndex();
if (ctx.getCurrentTokensIndex() < tokens.length &&
tokens[idx].getType().equals(Token.TYPE.VALUE_OPERAND)) {
TokenHandler valueHandler = new ValueOperandTokenHandler();
valueHandler.handleToken(ctx);
}
// skip closing bracket
idx = ctx.getCurrentTokensIndex();
if (idx >= tokens.length || tokens[idx].getType() != Token.TYPE.BRACKET_CLOSE) {
throw new InvalidQueryException("Missing closing bracket for in expression.") ;
}
return 1;
}
@Override
public boolean validate(Token.TYPE previousTokenType) {
return previousTokenType == null ||
previousTokenType == Token.TYPE.BRACKET_OPEN ||
previousTokenType == Token.TYPE.LOGICAL_OPERATOR ||
previousTokenType == Token.TYPE.LOGICAL_UNARY_OPERATOR;
}
}
/**
* Logical Operator token handler
*/
private class LogicalOperatorTokenHandler extends TokenHandler {
@Override
public int _handleToken(ParseContext ctx) throws InvalidQueryException {
Token token = ctx.getTokens()[ctx.getCurrentTokensIndex()];
LogicalOperator logicalOp = LogicalOperatorFactory.createOperator(token.getValue(), ctx.getPrecedenceLevel());
ctx.updateMaxPrecedence(logicalOp.getPrecedence());
ctx.addExpression(LogicalExpressionFactory.createLogicalExpression(logicalOp));
return 1;
}
@Override
public boolean validate(Token.TYPE previousTokenType) {
return previousTokenType == Token.TYPE.VALUE_OPERAND ||
previousTokenType == Token.TYPE.BRACKET_CLOSE;
}
}
/**
* Logical Unary Operator token handler
*/
private class LogicalUnaryOperatorTokenHandler extends LogicalOperatorTokenHandler {
@Override
public boolean validate(Token.TYPE previousTokenType) {
return previousTokenType == null ||
previousTokenType == Token.TYPE.BRACKET_OPEN ||
previousTokenType == Token.TYPE.LOGICAL_OPERATOR;
}
}
/**
* Property Operand token handler
*/
private class PropertyOperandTokenHandler extends TokenHandler {
@Override
public int _handleToken(ParseContext ctx) throws InvalidQueryException {
Token token = ctx.getTokens()[ctx.getCurrentTokensIndex()];
ctx.getPrecedingExpression().setLeftOperand(token.getValue());
return 1;
}
@Override
public boolean validate(Token.TYPE previousTokenType) {
return previousTokenType == Token.TYPE.RELATIONAL_OPERATOR ||
previousTokenType == Token.TYPE.RELATIONAL_OPERATOR_FUNC;
}
}
/**
* Value Operand token handler
*/
private class ValueOperandTokenHandler extends TokenHandler {
@Override
public int _handleToken(ParseContext ctx) throws InvalidQueryException {
Token token = ctx.getTokens()[ctx.getCurrentTokensIndex()];
ctx.getPrecedingExpression().setRightOperand(token.getValue());
return 1;
}
@Override
public boolean validate(Token.TYPE previousTokenType) {
return previousTokenType == Token.TYPE.PROPERTY_OPERAND;
}
}
}