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Stringer.js
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Stringer.js
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'use strict';
const {Transform} = require('stream');
const noCommaAfter = {startObject: 1, startArray: 1, endKey: 1, keyValue: 1},
noSpaceAfter = {endObject: 1, endArray: 1, '': 1},
noSpaceBefore = {startObject: 1, startArray: 1},
depthIncrement = {startObject: 1, startArray: 1},
depthDecrement = {endObject: 1, endArray: 1},
values = {startKey: 'keyValue', startString: 'stringValue', startNumber: 'numberValue'},
stopNames = {startKey: 'endKey', startString: 'endString', startNumber: 'endNumber'},
symbols = {
startObject: '{',
endObject: '}',
startArray: '[',
endArray: ']',
startKey: '"',
endKey: '":',
startString: '"',
endString: '"',
startNumber: '',
endNumber: '',
nullValue: 'null',
trueValue: 'true',
falseValue: 'false'
};
const skipValue = endName =>
function (chunk, encoding, callback) {
if (chunk.name === endName) {
this._transform = this._prev_transform;
}
callback(null);
};
const replaceSymbols = {'\b': '\\b', '\f': '\\f', '\n': '\\n', '\r': '\\r', '\t': '\\t', '"': '\\"', '\\': '\\\\'};
const sanitizeString = value =>
value.replace(/[\b\f\n\r\t\"\\\u0000-\u001F\u007F-\u009F]/g, match =>
replaceSymbols.hasOwnProperty(match) ? replaceSymbols[match] : '\\u' + ('0000' + match.charCodeAt(0).toString(16)).slice(-4)
);
const doNothing = () => {};
class Stringer extends Transform {
static make(options) {
return new Stringer(options);
}
constructor(options) {
super(Object.assign({}, options, {writableObjectMode: true, readableObjectMode: false}));
this._values = {};
if (options) {
'useValues' in options && (this._values.keyValue = this._values.stringValue = this._values.numberValue = options.useValues);
'useKeyValues' in options && (this._values.keyValue = options.useKeyValues);
'useStringValues' in options && (this._values.stringValue = options.useStringValues);
'useNumberValues' in options && (this._values.numberValue = options.useNumberValues);
this._makeArray = options.makeArray;
}
this._prev = '';
this._depth = 0;
if (this._makeArray) {
this._transform = this._arrayTransform;
this._flush = this._arrayFlush;
}
}
_arrayTransform(chunk, encoding, callback) {
// it runs once
delete this._transform;
this._transform({name: 'startArray'}, encoding, doNothing);
this._transform(chunk, encoding, callback);
}
_arrayFlush(callback) {
if (this._transform === this._arrayTransform) {
delete this._transform;
this._transform({name: 'startArray'}, null, doNothing);
}
this._transform({name: 'endArray'}, null, callback);
}
_transform(chunk, _, callback) {
if (this._values[chunk.name]) {
if (this._depth && noCommaAfter[this._prev] !== 1) this.push(',');
switch (chunk.name) {
case 'keyValue':
this.push('"' + sanitizeString(chunk.value) + '":');
break;
case 'stringValue':
this.push('"' + sanitizeString(chunk.value) + '"');
break;
case 'numberValue':
this.push(chunk.value);
break;
}
} else {
// filter out values
switch (chunk.name) {
case 'endObject':
case 'endArray':
case 'endKey':
case 'endString':
case 'endNumber':
this.push(symbols[chunk.name]);
break;
case 'stringChunk':
this.push(sanitizeString(chunk.value));
break;
case 'numberChunk':
this.push(chunk.value);
break;
case 'keyValue':
case 'stringValue':
case 'numberValue':
// skip completely
break;
case 'startKey':
case 'startString':
case 'startNumber':
if (this._values[values[chunk.name]]) {
this._prev_transform = this._transform;
this._transform = skipValue(stopNames[chunk.name]);
return callback(null);
}
// intentional fall down
default:
// case 'startObject': case 'startArray': case 'startKey': case 'startString':
// case 'startNumber': case 'nullValue': case 'trueValue': case 'falseValue':
if (this._depth) {
if (noCommaAfter[this._prev] !== 1) this.push(',');
} else {
if (noSpaceAfter[this._prev] !== 1 && noSpaceBefore[chunk.name] !== 1) this.push(' ');
}
this.push(symbols[chunk.name]);
break;
}
if (depthIncrement[chunk.name]) {
++this._depth;
} else if (depthDecrement[chunk.name]) {
--this._depth;
}
}
this._prev = chunk.name;
callback(null);
}
}
Stringer.stringer = Stringer.make;
Stringer.make.Constructor = Stringer;
module.exports = Stringer;