Crystal-lang HTTP Multipart/form-data POST

http_multipart_post.cr

require "http/client"

class MultiPartFormData
  property io : IO::Memory
  property size : Int32
  def initialize(name, filename, file, boundary=nil)
    @boundary = boundary || "boundary"
    first = [boundary_line, content_disposition(name, filename), "", ""].join("\r\n")
    last = ["", boundary_last, ""].join("\r\n")
    @io = IO::Memory.new
    @io << IO::Memory.new(first)
    IO.copy(file, @io)
    @io << IO::Memory.new(last)
    @size = @io.size
  end
  def content_type
    "multipart/form-data; boundary=#{@boundary}"
  end
  def boundary_line
    "--#{@boundary}"
  end
  def boundary_last
    "--#{@boundary}--"
  end
  def content_disposition(name, filename)
    "content-disposition: form-data; name=\"#{name}\"; filename=\"#{filename}\""
  end
  def size
    @size
  end
end

path = "./image.png"
url = URI.parse("http://httpbin.org")

HTTP::Client.new(url) do |client|
  req = HTTP::Request.new("POST", "/post")
  File.open(path, "rb") do |f|
    form_data = MultiPartFormData.new("file", File.basename(path), f)
    req.body = form_data.io.to_slice
    req.content_length = form_data.size
    req.headers = HTTP::Headers{
      "Host" => "#{url.host}",
      "Content-Length" => form_data.size.to_s,
      "Content-Type" => form_data.content_type
    }
    client.exec(req) do |response|
      puts response.body_io.gets_to_end
    end
  end
end