fs = require 'fs'
Stream = require 'stream'
utils = require './utils'

###

Writing data to a destination
=============================

The `csv().to` property provides functions to read from a CSV instance and
to write to an external destination. The destination may be a stream, a file
or a callback. 

You may call the `to` function or one of its sub function. For example, 
here are two identical ways to write to a file:

    csv.from(data).to('/tmp/data.csv');
    csv.from(data).to.path('/tmp/data.csv');

###
module.exports = (csv) ->

  ###

  `to(mixed)`
  -----------

  Write from any sort of destination. It should be considered as a convenient function 
  which will discover the nature of the destination where to write the CSV data.   

  If is an function, then the csv will be provided as the first argument 
  of the callback. If it is a string, then it is expected to be a 
  file path. If it is an instance of stream, it consider the object to be an  
  output stream. 

  Here's some examples on how to use this function:

      csv()
      .from('"1","2","3","4","5"')
      .to(function(data){ console.log(data) })

      csv()
      .from('"1","2","3","4","5"')
      .to('./path/to/file.csv')

      csv()
      .from('"1","2","3","4","5"')
      .to(fs.createWriteStream('./path/to/file.csv'))

  ###
  to = (mixed, options) ->
    error = false
    switch typeof mixed
      when 'string'
        to.path mixed, options
      when 'object'
        if mixed instanceof Stream
        then to.stream mixed, options
        else error = true
      when 'function'
        to.string mixed, options
      else
        error = true
    csv.error new Error "Invalid mixed argument in from" if error
    csv

  ###

  `to.options([options])`
  -----------------------

  Update and retrieve options relative to the output. Return the options 
  as an object if no argument is provided.

  *   `delimiter`   Set the field delimiter, one character only, defaults to `options.from.delimiter` which is a comma.
  *   `quote`       Defaults to the quote read option.
  *   `quoted`      Boolean, default to false, quote all the fields even if not required.
  *   `escape`      Defaults to the escape read option.
  *   `columns`     List of fields, applied when `transform` returns an object, order matters, see the transform and the columns sections below.
  *   `header`      Display the column names on the first line if the columns option is provided.
  *   `lineBreaks`  String used to delimit record rows or a special value; special values are 'auto', 'unix', 'mac', 'windows', 'unicode'; defaults to 'auto' (discovered in source or 'unix' if no source is specified).
  *   `flags`       Defaults to 'w', 'w' to create or overwrite an file, 'a' to append to a file. Applied when using the `toPath` method.
  *   `newColumns`  If the `columns` option is not specified (which means columns will be taken from the reader options, will automatically append new columns if they are added during `transform()`.
  *   `end`         Prevent calling `end` on the destination, so that destination is no longer writable.
  *   `eof`         Add a linebreak on the last line, default to false, expect a charactere or use '\n' if value is set to "true"

  The end options is similar to passing `{end: false}` option in `stream.pipe()`. According to the Node.js documentation:
  > By default end() is called on the destination when the source stream emits end, so that destination is no longer writable. Pass { end: false } as options to keep the destination stream open. 

  ###
  to.options = (options) ->
    if options?
      utils.merge csv.options.to, options
      if csv.options.to.lineBreaks
        console.log 'To options linebreaks is replaced by rowDelimiter'
        unless csv.options.to.rowDelimiter
          csv.options.to.rowDelimiter = csv.options.to.lineBreaks
      switch csv.options.to.rowDelimiter
        when 'auto'
          csv.options.to.rowDelimiter = null
        when 'unix'
          csv.options.to.rowDelimiter = "\n"
        when 'mac'
          csv.options.to.rowDelimiter = "\r"
        when 'windows'
          csv.options.to.rowDelimiter = "\r\n"
        when 'unicode'
          csv.options.to.rowDelimiter = "\u2028"
      csv
    else
      csv.options.to
  
  ###

  `to.string(callback, [options])`
  ------------------------------

  Provide the output string to a callback.

      csv()
      .from( '"1","2","3"\n"a","b","c"' )
      .to.string( function(data, count){} )

  Callback is called with 2 arguments:
  *   data      Entire CSV as a string
  *   count     Number of stringified records
  
  ###
  to.string = (callback, options) ->
    @options options
    data = ''
    stream = new Stream
    stream.writable = true
    stream.write = (d) ->
        data += d
        true
    stream.end = ->
        callback data, csv.state.countWriten
    csv.pipe stream
    csv

  ###

  `to.stream(stream, [options])`
  ------------------------------

  Write to a stream. Take a writable stream as first argument and  
  optionally an object of options as a second argument.
  
  ###
  to.stream = (stream, options) ->
    @options options
    csv.pipe stream, csv.options.to
    stream.on 'error', (e) ->
      csv.error e
    stream.on 'close', ->
      csv.emit 'close', csv.state.count
    csv
  
  ###

  `to.path(path, [options])`
  --------------------------

  Write to a path. Take a file path as first argument and optionally an object of 
  options as a second argument. The `close` event is sent after the file is written. 
  Relying on the `end` event is incorrect because it is sent when parsing is done 
  but before the file is written.
  
  ###
  to.path = (path, options) ->
    # Merge user provided options
    @options options
    # Clone options
    options = utils.merge {}, csv.options.to
    # Delete end property which otherwise overwrite `stream.end()`
    delete options.end
    # Create the write stream
    stream = fs.createWriteStream path, options
    csv.to.stream stream, null
    csv
  
  ###

  `to.array(path, [options])`
  --------------------------

  Provide the output string to a callback.

      csv()
      .from( '"1","2","3"\n"a","b","c"' )
      .to.array( function(data, count){} )

  Callback is called with 2 arguments:
  *   data      Entire CSV as an array of records
  *   count     Number of stringified records
  
  ###
  to.array = (callback, options) ->
    @options options
    records = []
    csv.on 'record', (record) ->
      records.push record
    csv.on 'end', ->
      callback records, csv.state.countWriten
    csv

  to