Provided by: tcllib_1.19-dfsg-2_all 
NAME
rest - define REST web APIs and call them inline or asychronously
SYNOPSIS
package require Tcl 8.5
package require rest ?1.3.1?
::rest::simple url query ?config? ?body?
::rest::get url query ?config? ?body?
::rest::post url query ?config? ?body?
::rest::patch url query ?config? ?body?
::rest::head url query ?config? ?body?
::rest::put url query ?config? ?body?
::rest::delete url query ?config? ?body?
::rest::save name file
::rest::describe name
::rest::parameters url ?key?
::rest::parse_opts static required optional words
::rest::substitute string var
::rest::create_interface name
________________________________________________________________________________________________________________
DESCRIPTION
There are two types of usage this package supports: simple calls, and complete interfaces. In an
interface you specify a set of rules and then the package builds the commands which correspond to the
REST methods. These commands can have many options such as input and output transformations and data type
specific formatting. This results in a cleaner and simpler script. On the other hand, while a simple
call is easier and quicker to implement it is also less featureful. It takes the url and a few options
about the command and returns the result directly. Any formatting or checking is up to rest of the
script.
SIMPLE USAGE
In simple usage you make calls using the http method procedures and then check or process the returned
data yourself
::rest::simple url query ?config? ?body?
::rest::get url query ?config? ?body?
::rest::post url query ?config? ?body?
::rest::patch url query ?config? ?body?
::rest::head url query ?config? ?body?
::rest::put url query ?config? ?body?
::rest::delete url query ?config? ?body?
These commands are all equivalent except for the http method used. If you use simple then the
method should be specified as an option in the config dictionary. If that is not done it defaults
to get. If a body is needed then the config dictionary must be present, however it is allowed to
be empty.
The config dictionary supports the following keys
auth
content-type
cookie
error-body
format
headers
method
Two quick examples:
Example 1, Yahoo Boss:
set appid APPID
set search tcl
set res [rest::get http://boss.yahooapis.com/ysearch/web/v1/$search [list appid $appid]]
set res [rest::format_json $res]
Example 2, Twitter:
set url http://twitter.com/statuses/update.json
set query [list status $text]
set res [rest::simple $url $query {
method post
auth {basic user password}
format json
}]
INTERFACE USAGE
An interface to a REST API consists of a series of definitions of REST calls contained in an array. The
name of that array becomes a namespace containing the defined commands. Each key of the array specifies
the name of the call, with the associated configuration a dictionary, i.e. key/value pairs. The
acceptable keys, i.e. legal configuration options are described below. After creating the definitions in
the array simply calling rest::create_interface with the array as argument will then create the desired
commands.
Example, Yahoo Weather:
package require rest
set yweather(forecast) {
url http://weather.yahooapis.com/forecastrss
req_args { p: }
opt_args { u: }
}
rest::create_interface yweather
puts [yweather::forecast -p 94089]
::rest::save name file
This command saves a copy of the dynamically created procedures for all the API calls specified in
the array variable name to the file, for later loading.
The result of the command is the empty string
::rest::describe name
This command prints a description of all API calls specified in the array variable name to the
channel stdout.
The result of the command is the empty string.
::rest::parameters url ?key?
This command parses an url query string into a dictionary and returns said dictionary as its
result.
If key is specified the command will not return the entire dictionary, but only the value of that
key.
::rest::parse_opts static required optional words
This command implements a custom parserfor command options.
dict static
A dictionary of options and their values that are always present in the output.
list required
A list of options that must be supplied by words
list optional
A list of options that may appear in the words, but are not required. The elements must be
in one of three forms:
name The option may be present or not, no default.
name: When present the option requires an argument.
name:value
When not present use value as default.
list words
The words to parse into options and values.
The result of the command is a list containing two elements. The first element is a dictionary
containing the parsed options and their values. The second element is a list of the remaining words.
::rest::substitute string var
This command takes a string, substitutes values for any option identifiers found inside and
returns the modified string as its results.
The values to substitute are found in the variable var, which is expected to contain a dictionary
mapping from the option identifiers to replace to their values. Note that option identifiers
which have no key in var are replaced with the empty string.
The option identifiers in string have to follow the syntax %...% where ... may contain any
combination of lower-case alphanumeric characters, plus underscore, colon and dash.
::rest::create_interface name
This command creates procedures for all the API calls specified in the array variable name.
The name of that array becomes a namespace containing the defined commands. Each key of the array
specifies the name of the call, with the associated configuration a dictionary, i.e. key/value
pairs. The legal keys and their meanings are:
url The value of this required option must be the target of the http request.
description
The value of this option must be a short string describing the call. Default to the empty
string, if not specified. Used only by ::rest::describe.
body The value of this option indicates if arguments are required for the call's request body or
not. The acceptable values are listed below. Defaults to optional if not specified.
none The call has no request body, none must be supplied.
optional
A request body can be supplied, but is not required.
required
A request body must be supplied.
argument
This value must be followed by the name of an option, treating the entire string as
a list. The request body will be used as the value of that option.
mime_multipart
A request body must be supplied and will be interpreted as each argument
representing one part of a mime/multipart document. Arguments must be lists
containing 2 elements, a list of header keys and values, and the mime part body, in
this order.
method The value of this option must be the name of the HTTP method to call on the url. Defaults
to GET, if not specified. The acceptable values are GET, POST, and PUT, regardless of
letter-case.
copy When present the value of this option specifies the name of a previously defined call. The
definition of that call is copied to the current call, except for the options specified by
the current call itself.
unset When present the value of this option contains a list of options in the current call. These
options are removed from the definition. Use this after copying an existing definition to
remove options, instead of overriding their value.
headers
Specification of additional header fields. The value of this option must be a dictionary,
interpreted to contain the new header fields and their values. The default is to not add
any additional headers.
content-type
The value of this option specifies the content type for the request data.
req_args
The value of this option is a list naming the required arguments of the call. Names ending
in a colon will require a value.
opt_args
The value of this option a list naming the arguments that may be present for a call but are
not required.
static_args
The value of this option a list naming the arguments that are always the same. No sense in
troubling the user with these. A leading dash (-) is allowed but not required to maintain
consistency with the command line.
auth The value of this option specifies how to authenticate the calls. No authentication is
done if the option is not specified.
basic The user may configure the basic authentication by overriding the procedure
basic_auth in the namespace of interface. This procedure takes two arguments, the
username and password, in this order.
sign The value must actually be a list with the second element the name of a procedure
which will be called to perform request signing.
callback
If this option is present then the method will be created as an async call. Such calls will
return immediately with the value of the associated http token instead of the call's
result. The event loop must be active to use this option.
The value of this option is treated as a command prefix which is invoked when the HTTP call
is complete. The prefix will receive at least two additional arguments, the name of the
calling procedure and the status of the result (one of OK or ERROR), in this order.
In case of OK a third argument is added, the data associated with the result.
If and only if the ERROR is a redirection, the location redirected to will be added as
argument. Further, if the configuration key error-body is set to true the data associated
with the result will be added as argument as well.
The http request header will be available in that procedure via upvar token token.
cookie The value of this option is a list of cookies to be passed in the http header. This is a
shortcut to the headers option.
input_transform
The value of this option is a command prefix or script to perform a transformation on the
query before invoking the call. A script transform is wrapped into an automatically
generated internal procedure.
If not specified no transformation is done.
The command (prefix) must accept a single argument, the query (a dictionary) to transform,
and must return the modified query (again as dictionary) as its result. The request body
is accessible in the transform command via upvar body body.
format
result The value of this option specifies the format of the returned data. Defaults to auto if
not specified. The acceptable values are:
auto Auto detect between xml and json.
discard
json
raw
rss This is formatted as a special case of xml.
tdom
xml
pre_transform
The value of this option is a command prefix or script to perform a transformation on the
result of a call (before the application of the output transform as per format). A script
transform is wrapped into an automatically generated internal procedure.
If not specified no transformation is done.
The command (prefix) must accept a single argument, the result to transform, and must
return the modified result as its result.
The http request header is accessible in the transform command via upvar token token
post_transform
The value of this option is a command prefix or script to perform a transformation on the
result of a call (after the application of the output transform as per format). A script
transform is wrapped into an automatically generated internal procedure.
If not specified no transformation is done.
The command (prefix) must accept a single argument, the result to transform, and must
return the modified result as its result.
The http request header is accessible in the transform command via upvar token token
check_result
The value of this option must be list of two expressions, either of which may be empty.
The first expression is checks the OK condition, it must return true when the result is
satisfactory, and false otherwise.
The second expression is the ERROR condition, it must return false unless there is an
error, then it has to return true.
error_body
The value of this option determines whether to return the response when encountering an
HTTP error, or not. The default is to not return the response body on error.
See callback above for more information.
EXAMPLES
Yahoo Geo:
set ygeo(parse) {
url http://wherein.yahooapis.com/v1/document
method post
body { arg documentContent }
}
ygeo::parse "san jose ca"
# "san jose ca" will be interpreted as if it were specified as the -documentContent option
Google Docs:
set gdocs(upload) {
url http://docs.google.com/feeds/default/private/full
body mime_multipart
}
gdocs::upload [list {Content-Type application/atom+xml} $xml] [list {Content-Type image/jpeg} $filedata]
Delicious:
set delicious(updated) {
url https://api.del.icio.us/v1/posts/update
auth basic
}
rest::create_interface flickr
flickr::basic_auth username password
Flickr:
set flickr(auth.getToken) {
url http://api.flickr.com/services/rest/
req_args { api_key: secret: }
auth { sign do_signature }
}
rest::create_interface flickr
proc ::flickr::do_signature {query} {
# perform some operations on the query here
return $query
}
INCLUDED
The package provides functional but incomplete implementations for the following services:
del.icio.us
facebook
flickr
twitter
google calendar
yahoo boss
yahoo weather
Please either read the package's implementation, or use rest::describe after loading it for their
details.
Do not forget developers' documentation on the respective sites either.
TLS
The rest package can be used with https-secured services, by requiring the TLS package and then
registering it with the http package it is sitting on top of. Example
package require tls
http::register https 443 ::tls::socket
TLS SECURITY CONSIDERATIONS
This package uses the TLS package to handle the security for https urls and other socket connections.
Policy decisions like the set of protocols to support and what ciphers to use are not the responsibility
of TLS, nor of this package itself however. Such decisions are the responsibility of whichever
application is using the package, and are likely influenced by the set of servers the application will
talk to as well.
For example, in light of the recent POODLE attack
[http://googleonlinesecurity.blogspot.co.uk/2014/10/this-poodle-bites-exploiting-ssl-30.html] discovered
by Google many servers will disable support for the SSLv3 protocol. To handle this change the
applications using TLS must be patched, and not this package, nor TLS itself. Such a patch may be as
simple as generally activating tls1 support, as shown in the example below.
package require tls
tls::init -tls1 1 ;# forcibly activate support for the TLS1 protocol
... your own application code ...
BUGS, IDEAS, FEEDBACK
This document, and the package it describes, will undoubtedly contain bugs and other problems. Please
report such in the category rest of the Tcllib Trackers [http://core.tcl.tk/tcllib/reportlist]. Please
also report any ideas for enhancements you may have for either package and/or documentation.
When proposing code changes, please provide unified diffs, i.e the output of diff -u.
Note further that attachments are strongly preferred over inlined patches. Attachments can be made by
going to the Edit form of the ticket immediately after its creation, and then using the left-most button
in the secondary navigation bar.
tcllib 1.3.1 rest(3tcl)