Mini Shell

#!/usr/bin/node

'use strict'

var Parser = require('jsonparse')
  , through = require('through')

/*

  the value of this.stack that creationix's jsonparse has is weird.

  it makes this code ugly, but his problem is way harder that mine,
  so i'll forgive him.

*/

exports.parse = function (path, map) {
  var header, footer
  var parser = new Parser()
  var stream = through(function (chunk) {
    if('string' === typeof chunk)
      chunk = new Buffer(chunk)
    parser.write(chunk)
  },
  function (data) {
    if(data)
      stream.write(data)
    if (header)
        stream.emit('header', header)
    if (footer)
      stream.emit('footer', footer)
    stream.queue(null)
  })

  if('string' === typeof path)
    path = path.split('.').map(function (e) {
      if (e === '$*')
        return {emitKey: true}
      else if (e === '*')
        return true
      else if (e === '') // '..'.split('.') returns an empty string
        return {recurse: true}
      else
        return e
    })


  var count = 0, _key
  if(!path || !path.length)
    path = null

  parser.onValue = function (value) {
    if (!this.root)
      stream.root = value

    if(! path) return

    var i = 0 // iterates on path
    var j  = 0 // iterates on stack
    var emitKey = false;
    var emitPath = false;
    while (i < path.length) {
      var key = path[i]
      var c
      j++

      if (key && !key.recurse) {
        c = (j === this.stack.length) ? this : this.stack[j]
        if (!c) return
        if (! check(key, c.key)) {
          setHeaderFooter(c.key, value)
          return
        }
        emitKey = !!key.emitKey;
        emitPath = !!key.emitPath;
        i++
      } else {
        i++
        var nextKey = path[i]
        if (! nextKey) return
        while (true) {
          c = (j === this.stack.length) ? this : this.stack[j]
          if (!c) return
          if (check(nextKey, c.key)) {
            i++;
            if (!Object.isFrozen(this.stack[j]))
              this.stack[j].value = null
            break
          } else {
            setHeaderFooter(c.key, value)
          }
          j++
        }
      }

    }

    // emit header
    if (header) {
      stream.emit('header', header);
      header = false;
    }
    if (j !== this.stack.length) return

    count ++
    var actualPath = this.stack.slice(1).map(function(element) { return element.key }).concat([this.key])
    var data = this.value[this.key]
    if(null != data)
      if(null != (data = map ? map(data, actualPath) : data)) {
        if (emitKey || emitPath) {
          data = { value: data };
          if (emitKey)
            data["key"] = this.key;
          if (emitPath)
            data["path"] = actualPath;
        }

        stream.queue(data)
      }
    delete this.value[this.key]
    for(var k in this.stack)
      if (!Object.isFrozen(this.stack[k]))
        this.stack[k].value = null
  }
  parser._onToken = parser.onToken;

  parser.onToken = function (token, value) {
    parser._onToken(token, value);
    if (this.stack.length === 0) {
      if (stream.root) {
        if(!path)
          stream.queue(stream.root)
        count = 0;
        stream.root = null;
      }
    }
  }

  parser.onError = function (err) {
    if(err.message.indexOf("at position") > -1)
      err.message = "Invalid JSON (" + err.message + ")";
    stream.emit('error', err)
  }

  return stream

  function setHeaderFooter(key, value) {
    // header has not been emitted yet
    if (header !== false) {
      header = header || {}
      header[key] = value
    }

    // footer has not been emitted yet but header has
    if (footer !== false && header === false) {
      footer = footer || {}
      footer[key] = value
    }
  }
}

function check (x, y) {
  if ('string' === typeof x)
    return y == x
  else if (x && 'function' === typeof x.exec)
    return x.exec(y)
  else if ('boolean' === typeof x || 'object' === typeof x)
    return x
  else if ('function' === typeof x)
    return x(y)
  return false
}

exports.stringify = function (op, sep, cl, indent) {
  indent = indent || 0
  if (op === false){
    op = ''
    sep = '\n'
    cl = ''
  } else if (op == null) {

    op = '[\n'
    sep = '\n,\n'
    cl = '\n]\n'

  }

  //else, what ever you like

  var stream
    , first = true
    , anyData = false
  stream = through(function (data) {
    anyData = true
    try {
      var json = JSON.stringify(data, null, indent)
    } catch (err) {
      return stream.emit('error', err)
    }
    if(first) { first = false ; stream.queue(op + json)}
    else stream.queue(sep + json)
  },
  function (data) {
    if(!anyData)
      stream.queue(op)
    stream.queue(cl)
    stream.queue(null)
  })

  return stream
}

exports.stringifyObject = function (op, sep, cl, indent) {
  indent = indent || 0
  if (op === false){
    op = ''
    sep = '\n'
    cl = ''
  } else if (op == null) {

    op = '{\n'
    sep = '\n,\n'
    cl = '\n}\n'

  }

  //else, what ever you like

  var first = true
  var anyData = false
  var stream = through(function (data) {
    anyData = true
    var json = JSON.stringify(data[0]) + ':' + JSON.stringify(data[1], null, indent)
    if(first) { first = false ; this.queue(op + json)}
    else this.queue(sep + json)
  },
  function (data) {
    if(!anyData) this.queue(op)
    this.queue(cl)

    this.queue(null)
  })

  return stream
}

if(!module.parent && process.title !== 'browser') {
  process.stdin
    .pipe(exports.parse(process.argv[2]))
    .pipe(exports.stringify('[', ',\n', ']\n', 2))
    .pipe(process.stdout)
}