module Middleware

module Versioner

# This middleware sets various version related rack environment variables

# based on the HTTP Accept header with the pattern:

# application/vnd.:vendor-:version+:format

#

# Example: For request header

# Accept: application/vnd.mycompany-v1+json

#

# The following rack env variables are set:

#

# env['api.type'] => 'application'

# env['api.subtype'] => 'vnd.mycompany-v1+json'

# env['api.vendor] => 'mycompany'

# env['api.version] => 'v1'

# env['api.format] => 'format'

#

# If version does not match this route, then a 406 is raised with

# X-Cascade header to alert Rack::Mount to attempt the next matched

# route.

class Header < Base

def before

begin

header = Rack::Accept::MediaType.new env['HTTP_ACCEPT']

rescue RuntimeError => e

throw :error, status: 406, headers: error_headers, message: e.message

end

if strict?

# If no Accept header:

if header.qvalues.empty?

throw :error, status: 406, headers: error_headers, message: 'Accept header must be set.'

end

# Remove any acceptable content types with ranges.

header.qvalues.reject! do |media_type, _|

Rack::Accept::Header.parse_media_type(media_type).find { |s| s == '*' }

end

# If all Accept headers included a range:

if header.qvalues.empty?

throw :error, status: 406, headers: error_headers, message: 'Accept header must not contain ranges ("*").'

end

end

media_type = header.best_of available_media_types

if media_type

type, subtype = Rack::Accept::Header.parse_media_type media_type

env['api.type'] = type

env['api.subtype'] = subtype

if /\Avnd\.([a-z0-9*.]+)(?:-([a-z0-9*\-.]+))?(?:\+([a-z0-9*\-.+]+))?\z/ =~ subtype

env['api.vendor'] = $1

env['api.version'] = $2

env['api.format'] = $3 # weird that Grape::Middleware::Formatter also does this

end

# If none of the available content types are acceptable:

elsif strict?

throw :error, status: 406, headers: error_headers, message: '406 Not Acceptable'

# If all acceptable content types specify a vendor or version that doesn't exist:

elsif header.values.all? { |header_value| has_vendor?(header_value) || has_version?(header_value) }

throw :error, status: 406, headers: error_headers, message: 'API vendor or version not found.'

end

end

private

def available_media_types

available_media_types = []

content_types.each do |extension, media_type|

versions.reverse.each do |version|

available_media_types += ["application/vnd.#{vendor}-#{version}+#{extension}", "application/vnd.#{vendor}-#{version}"]

end

available_media_types << "application/vnd.#{vendor}+#{extension}"

end

available_media_types << "application/vnd.#{vendor}"

content_types.each do |_, media_type|

available_media_types << media_type

end

available_media_types = available_media_types.flatten

end

def versions

options[:versions] || []

end

def vendor

options[:version_options] && options[:version_options][:vendor]

end

def strict?

options[:version_options] && options[:version_options][:strict]

end

# By default those errors contain an `X-Cascade` header set to `pass`, which allows nesting and stacking

# of routes (see [Rack::Mount](https://github.com/josh/rack-mount) for more information). To prevent

# this behavior, and not add the `X-Cascade` header, one can set the `:cascade` option to `false`.

def cascade?

if options[:version_options] && options[:version_options].has_key?(:cascade)

!!options[:version_options][:cascade]

else

true

end

end

def error_headers

cascade? ? { 'X-Cascade' => 'pass' } : {}

end

# @param [String] media_type a content type

# @return [Boolean] whether the content type sets a vendor

def has_vendor?(media_type)

_, subtype = Rack::Accept::Header.parse_media_type media_type

subtype[/\Avnd\.[a-z0-9*.]+/]

end

# @param [String] media_type a content type

# @return [Boolean] whether the content type sets an API version

def has_version?(media_type)

_, subtype = Rack::Accept::Header.parse_media_type media_type

subtype[/\Avnd\.[a-z0-9*.]+-[a-z0-9*\-.]+/]

end

end

end

end