csv-sql/src/parser.js at master · DavidTimms/csv-sql · GitHub

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import {merge} from './utils';

import {tokenize} from './tokenizer';

import {LEFT, RIGHT} from './operators';

import * as ast from './ast';

export function parseQuery(query) {

const {node, rest} = parseSubQuery(query).ifNextToken(isType('semicolon'), curr =>

curr.then(semicolon)

);

if (rest.length > 0) {

const restString = rest.map(token => token.string).join(' ');

throw SyntaxError(`Parser completed with input remaining: "${restString}"`);

}

return node;

}

function parseSubQuery(query) {

const tokens = tokenize(query);

return parser(tokens)

.then(keyword('SELECT'))

.bind('select', outputColumns)

.bind('from', fromClause)

.bind('where', createConditionClause('WHERE'))

.map(parseGroupByHaving)

.bind('orderBy', orderByClause)

.bind('limit', limitClause)

.bind('offset', offsetClause)

.mapNode(ast.query);

}

function fromClause(rest) {

return parser(rest).ifNextToken(isKeyword('FROM'), curr =>

curr.then(keyword('FROM'))

.just(tableName)

);

}

function parseGroupByHaving(parser) {

return parser

.ifNextToken(isKeyword('GROUP'), curr =>

curr.then(keyword('GROUP'))

.then(keyword('BY'))

.bind('groupBy', many(expression, {separator: comma}))

.bind('having', createConditionClause('HAVING'))

)

.mapNode(node => merge({groupBy: null, having: null}, node));

}

function createConditionClause(conditionType) {

return tokens =>

parser(tokens).ifNextToken(isKeyword(conditionType), curr =>

curr.then(keyword(conditionType))

.just(expression)

);

}

function orderByClause(tokens) {

return parser(tokens).ifNextToken(isKeyword('ORDER'), curr =>

curr.then(keyword('ORDER'))

.then(keyword('BY'))

.just(many(orderingTerm, {separator: comma}))

);

}

function orderingTerm(tokens) {

return parser(tokens)

.bind('expression', expression)

.bind('direction', tokens => {

const [first, ...rest] = tokens;

if (isKeyword('ASC', first) || isKeyword('DESC', first)) {

return parser(rest, first.string);

}

return parser(tokens, 'ASC');

})

.mapNode(node => ast.orderingTerm(node.expression, node.direction));

}

function limitClause(tokens) {

return parser(tokens).ifNextToken(isKeyword('LIMIT'), curr =>

curr.then(keyword('LIMIT')).just(number)

);

}

function offsetClause(tokens) {

return parser(tokens).ifNextToken(isKeyword('OFFSET'), curr =>

curr.then(keyword('OFFSET')).just(number)

);

}

function atom([first, ...rest]) {

// grouped expression

if (isType('parOpen', first)) {

return expression(rest).then(parClose);

}

// literal TRUE, FALSE, or NULL

else if (isType('keyword', first)) {

const s = first.string;

if (s === 'TRUE' || s === 'FALSE' || s === 'NULL') {

return parser(rest, ast.literal(JSON.parse(s.toLowerCase())));

}

else if (first.string === 'CASE') {

return caseExpression(rest);

}

// function call

else if (isType('identifier', first) && isType('parOpen', rest[0])) {

const functionName = first.value;

if (functionName.toUpperCase() === 'COUNT' && isStar(rest[1])) {

return parser(rest.slice(2))

.then(parClose)

.mapNode(node => ast.call(functionName, [ast.star()]));

}

return parser(rest.slice(1))

.bind('arguments', many(expression, {separator: comma, min: 0}))

.then(parClose)

.mapNode(node => ast.call(functionName, node.arguments))

}

// identifier, number, or string

else if (isType(['identifier', 'number', 'string'], first)) {

return parser(rest, first);

}

throw SyntaxError(

`Expected an expression, found "${first.string || '(end of input)'}"`);

}

function caseExpression(tokens) {

return parser(tokens)

.ifNextToken(not(isKeyword('WHEN')), curr =>

curr.bind('switchExpression', expression)

)

.bind('cases', many(whenThen, {min: 1}))

.ifNextToken(isKeyword('ELSE'), curr =>

curr.then(keyword('ELSE'))

.bind('elseExpression', expression)

)

.then(keyword('END'))

.mapNode(({switchExpression, cases, elseExpression}) =>

switchExpression ?

ast.caseSwitch(switchExpression, cases, elseExpression) :

ast.caseIf(cases, elseExpression)

);

}

function whenThen(tokens) {

return parser(tokens)

.then(keyword('WHEN'))

.bind('when', expression)

.then(keyword('THEN'))

.bind('then', expression)

.mapNode(node => ast.whenThen(node.when, node.then));

}

function expression(tokens, controlOperator=null) {

let parser = atom(tokens);

while (true) {

const token = parser.rest[0];

const tokenIsLesserOperator = (

token &&

token.type === 'operator' && (

controlOperator === null ||

token.precedence > controlOperator.precedence || (

token.precedence === controlOperator.precedence &&

controlOperator.associativity === RIGHT

)

);

if (!tokenIsLesserOperator) return parser;

parser = parser

.mapNode(left => ({left}))

.bind('operator', operator)

.bind('right', tokens => expression(tokens, token))

.mapNode(node => ast.binaryExpression(node.operator, node.left, node.right));

}

function namedExpression(tokens) {

return expression(tokens)

.mapNode(expression => ({expression}))

.ifNextToken(isKeyword('AS'), curr =>

curr.then(keyword('AS'))

.bind('name', atom)

)

.mapNode(({expression, name}) => {

return ast.namedExpression(expression, name ? name.value : null)

});

}

function outputColumns(tokens) {

if (isStar(tokens[0])) {

return parser(tokens.slice(1), '*');

}

return many(namedExpression, {separator: comma})(tokens);

}

function keyword(word) {

return tokens => {

const first = tokens[0];

if (isKeyword(word, first)) {

return parser(tokens.slice(1), word);

}

else {

throw SyntaxError(

`Expected "${word}", found "${first.string || '(end of input)'}"`);

}

};

}

const tableName = parseTokenType('string', {expected: 'a table name'});

const identifier = parseTokenType('identifier', 'an identifier');

const operator = parseTokenType('operator', {expected: 'an operator'});

const comma = parseTokenType('comma');

const number = parseTokenType('number');

const semicolon = parseTokenType('semicolon');

const parOpen = parseTokenType('parOpen', {expected: 'an opening parenthesis'});

const parClose = parseTokenType('parClose', {expected: 'a closing parenthesis'});

function parseTokenType(typeName, {expected}={expected: 'a ' + typeName}) {

return ([first, ...rest]) => {

if (isType(typeName, first)) {

return parser(rest, first.value);

}

const found = first && first.string || '(end of input)';

throw SyntaxError(`Expected ${expected}, found "${found}"`);

};

}

function isKeyword(keyword, token) {

if (arguments.length < 2) {

return token => isKeyword(keyword, token);

}

return token && token.type === 'keyword' && token.string === keyword;

}

function isType(types, token) {

if (arguments.length < 2) {

return token => isType(types, token);

}

if (!Array.isArray(types)) types = [types];

return token && types.some(type => token.type === type);

}

function isStar(token) {

return token && token.string === '*';

}

function many(parseFunc, {separator, min}={}) {

if (min === undefined) min = 1;

return tokens => {

let node, rest = tokens;

const parts = [];

// TODO refactor this function to provide better error messages for

// sequences with a minimum - i.e. don't swallow the errors until

// the minimum is reached

try {

for (let i = 0; rest.length > 0; i ++) {

if (separator && i > 0) {

({rest} = separator(rest));

}

({node, rest} = parseFunc(rest));

parts.push(node);

}

catch (e) {

if (!(e instanceof SyntaxError)) {

throw e;

}

if (parts.length < min) {

throwUnexpected(rest[0]);

}

return parser(rest, parts);

};

}

function not(predicate) {

return (...args) => !predicate(...args);

}

function and(predicate1, predicate2) {

return (...args) => predicate1(...args) && predicate2(...args);

}

function throwUnexpected(token) {

throw SyntaxError(`Unexpected token: "${token.string}"`);

}

function printRest(parser) {

console.log(parser.rest.map(token => ({[token.type]: token.string})));

return parser;

}

function parser(rest, node=null) {

return {

rest,

node,

bind(key, parseFunc) {

const {rest, node} = parseFunc(this.rest);

return parser(rest, merge(this.node, {[key]: node}));

just(parseFunc) {

return parseFunc(this.rest);

then(parseFunc) {

const {rest} = parseFunc(this.rest);

return parser(rest, this.node);

ifNextToken(predicate, ifFunc, elseFunc) {

if (predicate(this.rest[0])) {

return ifFunc(this);

}

else if (elseFunc) {

return elseFunc(this);

}

else return this;

mapNode(func) {

const mapped = func(this.node);

return parser(this.rest, mapped === undefined ? this.node : mapped);

map(func) {

return func(this);

};

}

csv-sql/src/parser.js at master · DavidTimms/csv-sql · GitHub

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