csv

stream = require 'stream' ### Transforming data ================= Transformations may occur synchronously or asynchronously depending on the provided transform callback and its declared arguments length. Callback are called for each line and its arguments are : * *row* CSV record * *index* Incremented counter * *callback* Callback function to be called in asynchronous mode Unless you specify the `columns` read option, the `row` argument will be provided as an array, otherwise it will be provided as an object with keys matching columns names. In synchronous mode, the contract is quite simple, you will receive an array of fields for each record and the transformed array should be returned. In asynchronous mode, it is your responsibility to call the callback provided as the third argument. It must be called with two arguments, the first one is an error if any, the second is the transformed record. Transformed records may be an array, an associative array, a string or null. If null, the record will simply be skipped. When the returned value is an array, the fields are merged in order. When the returned value is an object, it will search for the `columns` property in the write or in the read options and smartly order the values. If no `columns` options are found, it will merge the values in their order of appearance. When the returned value is a string, it is directly sent to the destination source and it is your responsibility to delimit, quote, escape or define line breaks. Transform callback run synchronously: csv() .from('82,Preisner,Zbigniew\n94,Gainsbourg,Serge') .to(console.log) .transform(function(row, index){ return row.reverse() }); // Executing `node samples/transform.js`, print: // 94,Gainsbourg,Serge\n82,Preisner,Zbigniew Transform callback run asynchronously: csv() .from('82,Preisner,Zbigniew\n94,Gainsbourg,Serge') .to(console.log) .transform(function(row, index, callback){ process.nextTick(function(){ callback(null, row.reverse()); }); }); // Executing `node samples/transform.js`, print: // 94,Gainsbourg,Serge\n82,Preisner,Zbigniew Transform callback returning a string: csv() .from('82,Preisner,Zbigniew\n94,Gainsbourg,Serge') .to(console.log) .transform(function(row, index){ return (index>0 ? ',' : '') + row[0] + ":" + row[2] + ' ' + row[1]; }); // Executing `node samples/transform.js`, print: // 82:Zbigniew Preisner,94:Serge Gainsbourg ### Transformer = (csv) -> @csv = csv @running = 0 @options = parallel: 100 @todo = [] @ Transformer.prototype.__proto__ = stream.prototype ### no doc `headers()` ---------------------------- Print headers. ### Transformer.prototype.headers = -> labels = @csv.options.to.columns or @csv.options.from.columns # If columns is an object, keys are fields and values are labels if typeof labels is 'object' then labels = for k, label of labels then label @csv.stringifier.write labels ### no doc `write(line)` ---------------------------------- Call a callback to transform a line. Called for each line after being parsed. It is responsible for transforming the data and finally calling `write`. ### Transformer.prototype.write = (line) -> self = @ csv = @csv # Sanitize columns option into state and cache the result if not @columns? columns = csv.options.from.columns if typeof columns is 'object' and columns isnt null and not Array.isArray columns columns = Object.keys columns # Extract column names from the first line if csv.state.count is 0 and columns is true columns = csv.options.from.columns = line return @columns = if columns? then columns else false else columns = @columns # Convert line to an object if columns # Line provided as an array and stored as an object, keys are column names if Array.isArray line lineAsObject = {} for column, i in columns lineAsObject[column] = if line[i]? then line[i] else null line = lineAsObject # Line was provided as an object, we create a new one with only the defined columns else lineAsObject = {} for column, i in columns lineAsObject[column] = if line[column]? then line[column] else null line = lineAsObject finish = (line) -> # Print header on first line to we need to self.headers() if csv.options.to.header is true and (csv.state.count - self.running) is 1 # Stringify the transformed line csv.stringifier.write line # Pick line if any line = self.todo.shift() return run line if line # Emit end event if we are closed and we have no more transformation going on self.emit 'end', csv.state.count if csv.state.transforming is 0 and self.closed is true csv.state.count++ return finish line unless @callback sync = @callback.length isnt 3 csv.state.transforming++ self = @ done = (err, line) -> self.running-- return csv.error err if err isObject = typeof line is 'object' and not Array.isArray line if isObject and csv.options.to.newColumns and not csv.options.to.columns Object.keys(line) .filter( (column) -> self.columns.indexOf(column) is -1 ) .forEach( (column) -> self.columns.push(column) ) csv.state.transforming-- finish line run = (line) -> self.running++ try if sync then done null, self. callback line, csv.state.count - 1 else self.callback line, csv.state.count - 1, done catch err done err # Apply back pressure if @running is @options.parallel @todo.push line return false # Work on current line run line true ### no doc `end()` ------------------------ A transformer instance extends the EventEmitter and emit the 'end' event when the last callback is called. ### Transformer.prototype.end = -> return @csv.error new Error 'Transformer already closed' if @closed @closed = true @emit 'end' if @csv.state.transforming is 0 module.exports = (csv) -> new Transformer csv module.exports.Transformer = Transformer