multipart_form_data.pony

  1
  2
  3
  4
  5
  6
  7
  8
  9
 10
 11
 12
 13
 14
 15
 16
 17
 18
 19
 20
 21
 22
 23
 24
 25
 26
 27
 28
 29
 30
 31
 32
 33
 34
 35
 36
 37
 38
 39
 40
 41
 42
 43
 44
 45
 46
 47
 48
 49
 50
 51
 52
 53
 54
 55
 56
 57
 58
 59
 60
 61
 62
 63
 64
 65
 66
 67
 68
 69
 70
 71
 72
 73
 74
 75
 76
 77
 78
 79
 80
 81
 82
 83
 84
 85
 86
 87
 88
 89
 90
 91
 92
 93
 94
 95
 96
 97
 98
 99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
use "format"
use "random"
use "time"

class ref MultipartFormData
  """
  Build a `multipart/form-data` body for file uploads and mixed form
  submissions (RFC 7578).

  Use `field()` for plain text values and `file()` for file attachments.
  After adding all parts, pass the builder to `multipart_body()` on the
  request builder, which sets both the body and `Content-Type` header.

  For simple key-value form data without files, use `FormEncoder` with
  `form_body()` instead — it produces the more compact
  `application/x-www-form-urlencoded` format.

  ```pony
  let form = MultipartFormData
    .> field("username", "alice")
    .> file("avatar", "photo.jpg", "image/jpeg", image_data)
  let req = Request.post("/upload")
    .multipart_body(form)
    .build()
  ```
  """
  let _boundary: String
  embed _parts: Array[_MultipartPart]

  new ref create() =>
    """
    Create a new builder with a randomly generated boundary string.
    """
    _parts = Array[_MultipartPart]
    (let secs, let nanos) = Time.now()
    let rand = Rand(secs.u64(), nanos.u64())
    let a = rand.next()
    let b = rand.next()
    _boundary = "----pony" +
      Format.int[U64](a, FormatHexSmallBare where width = 16, fill = '0') +
      Format.int[U64](b, FormatHexSmallBare where width = 16, fill = '0')

  fun ref field(name: String, value: String): MultipartFormData ref =>
    """
    Add a text field to the form.

    `"` and `\` in the name are automatically backslash-escaped in the
    serialized `Content-Disposition` quoted-string.
    """
    _parts.push(_MultipartField(name, value))
    this

  fun ref file(
    name: String,
    filename: String,
    file_content_type: String,
    data: Array[U8] val)
    : MultipartFormData ref
  =>
    """
    Add a file attachment to the form.

    `"` and `\` in the name and filename are automatically backslash-escaped
    in the serialized `Content-Disposition` quoted-string.
    """
    _parts.push(_MultipartFile(name, filename, file_content_type, data))
    this

  fun content_type(): String =>
    """
    Return the `Content-Type` header value including the boundary parameter.

    Pass this to the request's `Content-Type` header so the server knows how
    to parse the body. The `multipart_body()` method on the request builder
    does this automatically.
    """
    "multipart/form-data; boundary=" + _boundary

  fun body(): Array[U8] val =>
    """
    Serialize all parts into the `multipart/form-data` wire format.

    Each part is delimited by the boundary string. Field parts include a
    `Content-Disposition` header; file parts additionally include a `filename`
    parameter and a `Content-Type` header. The body ends with a closing
    boundary.

    Field names and filenames are backslash-escaped (`"` becomes `\"`, `\`
    becomes `\\`) within `Content-Disposition` quoted-strings.
    """
    let buf = recover iso Array[U8] end
    for part in _parts.values() do
      buf.append("--")
      buf.append(_boundary)
      buf.append("\r\n")
      match \exhaustive\ part
      | let f: _MultipartField val =>
        buf.append("Content-Disposition: form-data; name=\"")
        buf.append(_escape_quoted(f.name))
        buf.append("\"\r\n\r\n")
        buf.append(f.value)
      | let f: _MultipartFile val =>
        buf.append("Content-Disposition: form-data; name=\"")
        buf.append(_escape_quoted(f.name))
        buf.append("\"; filename=\"")
        buf.append(_escape_quoted(f.filename))
        buf.append("\"\r\nContent-Type: ")
        buf.append(f.content_type)
        buf.append("\r\n\r\n")
        buf.append(f.data)
      end
      buf.append("\r\n")
    end
    buf.append("--")
    buf.append(_boundary)
    buf.append("--\r\n")
    consume buf

  fun _escape_quoted(input: String): String iso^ =>
    let buf = recover iso String(input.size()) end
    for byte in input.values() do
      if (byte == '"') or (byte == '\\') then
        buf.push('\\')
      end
      buf.push(byte)
    end
    consume buf