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    ji is a JSON Inspector for the command line.


    ji handles its input much like grep. Data can be passed to it through stdin or by providing a list of filenames. Globbing works.

    The Reader class reads from the standard input or a list of files, and emits events when a JSON document is read, and when it's finished reading documents.

    {EventEmitter} = require 'events'
    fs = require 'fs'
    querystring = require 'querystring'
    class Reader extends EventEmitter

    Read the standard input, by resuming the standard input stream and calling @readStream on it.

      readStandardInput: ->
        process.stdin.setEncoding 'utf8'
        @readStream '(standard input)'process.stdin=>
          @emit 'end'

    Read the next file from the @filenames array which contains the remaining files to be read.

      _readNextFile: () ->
        filename = @_filenames.shift()
        if filename
          stream = fs.createReadStream filename
          stream.setEncoding 'utf8'
          @readStream filenamestream=>
          @emit 'end'

    Read a list of files. Makes a copy of the filenames so it can be modified without modifying the value passed in by reference.

      readFiles: (filenames) ->
        @_filenames = filenames.slice()

    Read data from a stream. At present only one document per stream is permitted.

      readStream: (name, stream, done) ->
        data = ''
        stream.on 'data'(chunk) ->
          data += chunk
        stream.on 'end'=>
          document = JSON.parse(data)
          @emit 'data'namedocument

    Selecting Nodes

    JSON Pointer is used for selecting nodes. It uses the same syntax as URLs. This differs from the spec in that you're allowed to omit the leading slash ('/').

    class Pointer

    To decode, split a string on slashes and unescape each component.

      @decode: (path) ->
        (querystring.unescape(component) for component in path.split '/')

    To encode, escape each component and join it with a slash.

      @encode: (components) ->
        escaped = (querystring.escape(component) for component in components)
        escaped.join '/'

    Get a value at a jsonpointer path.

      @get: (document, path) ->
        value = document
        components = Pointer.decode path
        for component in components
          if typeof value == 'object' and value != null
            value = value[component]
            value = undefined

    Printing Data

    class Printer
      print: (data) ->
        str = JSON.stringify datanull2
        console.log str

    Gluing It Together

    A Program class interprets the command-line arguments and runs commands.

    class Program

    Construct the object instances.

      constructor: ->
        @reader = new Reader
        @printer = new Printer

    The options are specified here. The key is both the key that will be set on the Program instance and the default long option name. A boolean option won't use a parameter; all other options will.

          short: 'p'
        #  short: 'r' 
        #  short: 'f' 
        #  boolean: true 

    Build the options into a more searchable format.

      buildOptions: ->
        @_options = {}
        for nameoption of @options
 = name
          option.long or= name
          @_options[option.long= option
          @_options[option.short= option if option.short

    Parse the arguments using the options table. Make a lookup table for short options.

      parse: (argv) ->
        args = argv.slice(2)
        @filenames = []
        = 0
        while i < args.length
          if /^-/.test(args[i])
            option = @_options[args[i][1]]
            @exitWithError 'unrecognized option: ' + args[iunless option
            if option.boolean
              @[ true
              if typeof args[i+1== 'undefined'
                @exitWithError 'value required for option ' + args[i]
              @[ args[i+1]
              += 1
            @filenames.push args[i]
          += 1

    Parse the options and execute the command.

      run: ->
        @parse process.argv
        @reader.on 'data'(name, document) =>
          value = document
          if @path
            value = Pointer.get document@path
          @printer.print value unless typeof value == 'undefined'
        if @filenames.length > 0
          @reader.readFiles @filenames

    Display errors.

      showError: (message) ->
        console.error 'error: ' + message
      exitWithError: (message) ->
        @showError message
        process.exit 1

    Run the program, unless this is being imported from another module.

    unless module.parent
      program = new Program()

    Export the classes.

    exports.Reader = Reader
    exports.Pointer = Pointer
    exports.Printer = Printer
    exports.Program = Program




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