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org.h2.bnf.Bnf Maven / Gradle / Ivy
/*
* Copyright 2004-2019 H2 Group. Multiple-Licensed under the MPL 2.0,
* and the EPL 1.0 (https://h2database.com/html/license.html).
* Initial Developer: H2 Group
*/
package org.h2.bnf;
import java.io.ByteArrayInputStream;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.Reader;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.StringTokenizer;
import org.h2.bnf.context.DbContextRule;
import org.h2.tools.Csv;
import org.h2.util.StringUtils;
import org.h2.util.Utils;
/**
* This class can read a file that is similar to BNF (Backus-Naur form).
* It is made specially to support SQL grammar.
*/
public class Bnf {
/**
* The rule map. The key is lowercase, and all spaces
* are replaces with underscore.
*/
private final HashMap ruleMap = new HashMap<>();
private String syntax;
private String currentToken;
private String[] tokens;
private char firstChar;
private int index;
private Rule lastRepeat;
private ArrayList statements;
private String currentTopic;
/**
* Create an instance using the grammar specified in the CSV file.
*
* @param csv if not specified, the help.csv is used
* @return a new instance
*/
public static Bnf getInstance(Reader csv) throws SQLException, IOException {
Bnf bnf = new Bnf();
if (csv == null) {
byte[] data = Utils.getResource("/org/h2/res/help.csv");
csv = new InputStreamReader(new ByteArrayInputStream(data));
}
bnf.parse(csv);
return bnf;
}
/**
* Add an alias for a rule.
*
* @param name for example "procedure"
* @param replacement for example "@func@"
*/
public void addAlias(String name, String replacement) {
RuleHead head = ruleMap.get(replacement);
ruleMap.put(name, head);
}
private void addFixedRule(String name, int fixedType) {
Rule rule = new RuleFixed(fixedType);
addRule(name, "Fixed", rule);
}
private RuleHead addRule(String topic, String section, Rule rule) {
RuleHead head = new RuleHead(section, topic, rule);
String key = StringUtils.toLowerEnglish(topic.trim().replace(' ', '_'));
if (ruleMap.get(key) != null) {
throw new AssertionError("already exists: " + topic);
}
ruleMap.put(key, head);
return head;
}
private void parse(Reader reader) throws SQLException, IOException {
Rule functions = null;
statements = new ArrayList<>();
Csv csv = new Csv();
csv.setLineCommentCharacter('#');
ResultSet rs = csv.read(reader, null);
while (rs.next()) {
String section = rs.getString("SECTION").trim();
if (section.startsWith("System")) {
continue;
}
String topic = rs.getString("TOPIC");
syntax = rs.getString("SYNTAX").trim();
currentTopic = section;
tokens = tokenize();
index = 0;
Rule rule = parseRule();
if (section.startsWith("Command")) {
rule = new RuleList(rule, new RuleElement(";\n\n", currentTopic), false);
}
RuleHead head = addRule(topic, section, rule);
if (section.startsWith("Function")) {
if (functions == null) {
functions = rule;
} else {
functions = new RuleList(rule, functions, true);
}
} else if (section.startsWith("Commands")) {
statements.add(head);
}
}
addRule("@func@", "Function", functions);
addFixedRule("@ymd@", RuleFixed.YMD);
addFixedRule("@hms@", RuleFixed.HMS);
addFixedRule("@nanos@", RuleFixed.NANOS);
addFixedRule("anything_except_single_quote", RuleFixed.ANY_EXCEPT_SINGLE_QUOTE);
addFixedRule("anything_except_double_quote", RuleFixed.ANY_EXCEPT_DOUBLE_QUOTE);
addFixedRule("anything_until_end_of_line", RuleFixed.ANY_UNTIL_EOL);
addFixedRule("anything_until_end_comment", RuleFixed.ANY_UNTIL_END);
addFixedRule("anything_except_two_dollar_signs", RuleFixed.ANY_EXCEPT_2_DOLLAR);
addFixedRule("anything", RuleFixed.ANY_WORD);
addFixedRule("@hex_start@", RuleFixed.HEX_START);
addFixedRule("@concat@", RuleFixed.CONCAT);
addFixedRule("@az_@", RuleFixed.AZ_UNDERSCORE);
addFixedRule("@af@", RuleFixed.AF);
addFixedRule("@digit@", RuleFixed.DIGIT);
addFixedRule("@open_bracket@", RuleFixed.OPEN_BRACKET);
addFixedRule("@close_bracket@", RuleFixed.CLOSE_BRACKET);
addFixedRule("json_text", RuleFixed.JSON_TEXT);
}
/**
* Parse the syntax and let the rule call the visitor.
*
* @param visitor the visitor
* @param s the syntax to parse
*/
public void visit(BnfVisitor visitor, String s) {
this.syntax = s;
tokens = tokenize();
index = 0;
Rule rule = parseRule();
rule.setLinks(ruleMap);
rule.accept(visitor);
}
/**
* Check whether the statement starts with a whitespace.
*
* @param s the statement
* @return if the statement is not empty and starts with a whitespace
*/
public static boolean startWithSpace(String s) {
return s.length() > 0 && Character.isWhitespace(s.charAt(0));
}
/**
* Convert convert ruleLink to rule_link.
*
* @param token the token
* @return the rule map key
*/
public static String getRuleMapKey(String token) {
StringBuilder buff = new StringBuilder();
for (char ch : token.toCharArray()) {
if (Character.isUpperCase(ch)) {
buff.append('_').append(Character.toLowerCase(ch));
} else {
buff.append(ch);
}
}
return buff.toString();
}
/**
* Get the rule head for the given title.
*
* @param title the title
* @return the rule head, or null
*/
public RuleHead getRuleHead(String title) {
return ruleMap.get(title);
}
private Rule parseRule() {
read();
return parseOr();
}
private Rule parseOr() {
Rule r = parseList();
if (firstChar == '|') {
read();
r = new RuleList(r, parseOr(), true);
}
lastRepeat = r;
return r;
}
private Rule parseList() {
Rule r = parseToken();
if (firstChar != '|' && firstChar != ']' && firstChar != '}'
&& firstChar != 0) {
r = new RuleList(r, parseList(), false);
}
lastRepeat = r;
return r;
}
private Rule parseToken() {
Rule r;
if ((firstChar >= 'A' && firstChar <= 'Z')
|| (firstChar >= 'a' && firstChar <= 'z')) {
// r = new RuleElement(currentToken+ " syntax:" + syntax);
r = new RuleElement(currentToken, currentTopic);
} else if (firstChar == '[') {
read();
Rule r2 = parseOr();
r = new RuleOptional(r2);
if (firstChar != ']') {
throw new AssertionError("expected ], got " + currentToken
+ " syntax:" + syntax);
}
} else if (firstChar == '{') {
read();
r = parseOr();
if (firstChar != '}') {
throw new AssertionError("expected }, got " + currentToken
+ " syntax:" + syntax);
}
} else if ("@commaDots@".equals(currentToken)) {
r = new RuleList(new RuleElement(",", currentTopic), lastRepeat, false);
r = new RuleRepeat(r, true);
} else if ("@dots@".equals(currentToken)) {
r = new RuleRepeat(lastRepeat, false);
} else {
r = new RuleElement(currentToken, currentTopic);
}
lastRepeat = r;
read();
return r;
}
private void read() {
if (index < tokens.length) {
currentToken = tokens[index++];
firstChar = currentToken.charAt(0);
} else {
currentToken = "";
firstChar = 0;
}
}
private String[] tokenize() {
ArrayList list = new ArrayList<>();
syntax = StringUtils.replaceAll(syntax, "yyyy-MM-dd", "@ymd@");
syntax = StringUtils.replaceAll(syntax, "hh:mm:ss", "@hms@");
syntax = StringUtils.replaceAll(syntax, "hh:mm", "@hms@");
syntax = StringUtils.replaceAll(syntax, "mm:ss", "@hms@");
syntax = StringUtils.replaceAll(syntax, "nnnnnnnnn", "@nanos@");
syntax = StringUtils.replaceAll(syntax, "function", "@func@");
syntax = StringUtils.replaceAll(syntax, "0x", "@hexStart@");
syntax = StringUtils.replaceAll(syntax, ",...", "@commaDots@");
syntax = StringUtils.replaceAll(syntax, "...", "@dots@");
syntax = StringUtils.replaceAll(syntax, "||", "@concat@");
syntax = StringUtils.replaceAll(syntax, "a-z|_", "@az_@");
syntax = StringUtils.replaceAll(syntax, "A-Z|_", "@az_@");
syntax = StringUtils.replaceAll(syntax, "A-F", "@af@");
syntax = StringUtils.replaceAll(syntax, "0-9", "@digit@");
syntax = StringUtils.replaceAll(syntax, "'['", "@openBracket@");
syntax = StringUtils.replaceAll(syntax, "']'", "@closeBracket@");
StringTokenizer tokenizer = getTokenizer(syntax);
while (tokenizer.hasMoreTokens()) {
String s = tokenizer.nextToken();
// avoid duplicate strings
s = StringUtils.cache(s);
if (s.length() == 1) {
if (" \r\n".indexOf(s.charAt(0)) >= 0) {
continue;
}
}
list.add(s);
}
return list.toArray(new String[0]);
}
/**
* Get the list of tokens that can follow.
* This is the main autocomplete method.
* The returned map for the query 'S' may look like this:
*
* key: 1#SELECT, value: ELECT
* key: 1#SET, value: ET
*
*
* @param query the start of the statement
* @return the map of possible token types / tokens
*/
public HashMap getNextTokenList(String query) {
Sentence sentence = new Sentence();
sentence.setQuery(query);
try {
for (RuleHead head : statements) {
if (!head.getSection().startsWith("Commands")) {
continue;
}
sentence.start();
if (head.getRule().autoComplete(sentence)) {
break;
}
}
} catch (IllegalStateException e) {
// ignore
}
return sentence.getNext();
}
/**
* Cross-link all statements with each other.
* This method is called after updating the topics.
*/
public void linkStatements() {
for (RuleHead r : ruleMap.values()) {
r.getRule().setLinks(ruleMap);
}
}
/**
* Update a topic with a context specific rule.
* This is used for autocomplete support.
*
* @param topic the topic
* @param rule the database context rule
*/
public void updateTopic(String topic, DbContextRule rule) {
topic = StringUtils.toLowerEnglish(topic);
RuleHead head = ruleMap.get(topic);
if (head == null) {
head = new RuleHead("db", topic, rule);
ruleMap.put(topic, head);
statements.add(head);
} else {
head.setRule(rule);
}
}
/**
* Get the list of possible statements.
*
* @return the list of statements
*/
public ArrayList getStatements() {
return statements;
}
/**
* Get the tokenizer for the given syntax.
*
* @param s the syntax
* @return the tokenizer
*/
public static StringTokenizer getTokenizer(String s) {
return new StringTokenizer(s, " [](){}|.,\r\n<>:-+*/=\"!'$", true);
}
}
