# NAME

API::Client - General-Purpose API Client Abstraction

# VERSION

version 0.02

# SYNOPSIS

    use API::Client;
    use Mojo::URL;

    my $url = "https://api.example.com";
    my $client = API::Client->new(url => Mojo::URL->new($url));

    $client->debug(1);
    $client->fatal(1);

    my $resource = $client->resource;
    my $results  = $resource->fetch;

    # after some introspection

    $resource->update(...);

# DESCRIPTION

This distribution provides an API client abstraction for rapidly developing
client to interact with web services. Although this module can be used to
interact with APIs directly, API::Client was designed to be consumed
(subclassed) by higher-level purpose-specific API client code.

# THIN CLIENT

The thin api-client library is advantageous as it has complete API coverage and
can easily adapt to changes in the API with minimal effort. As a thin-client
library, this module does not map specific HTTP requests to specific routines,
nor does it provide parameter validation, pagination, or other conventions
found in typical API client implementations; Instead, it simply provides a
simple and consistent mechanism for dynamically generating HTTP requests.
Additionally, this module has support for debugging and retrying API calls as
well as throwing exceptions when 4xx and 5xx server response codes are
returned.

## Building

    my $user = $client->users('c09e91a');

    $user->action; # GET /users/c09e91a
    $user->action('head'); # HEAD /users/c09e91a
    $user->action('patch'); # PATCH /users/c09e91a

Building up an HTTP request object is extremely easy, simply call method names
which correspond to the API's path segments in the resource you wish to execute
a request against. This module uses autoloading and returns a new instance with
each method call. The following is the equivalent:

## Chaining

    my $user = $client->resource('users', 'c09e91a');

    # or

    my $users = $client->users;
    my $user  = $users->resource('c09e91a');

    # then

    $user->action('put', %args); # PUT /users/c09e91a

Because each call returns a new API instance configured with a resource locator
based on the supplied parameters, reuse and request isolation are made simple,
i.e., you will only need to configure the client once in your application.

## Fetching

    my $users = $client->users;

    # query-string parameters

    $users->fetch( query => { ... } );

    # equivalent to

    my $users = $client->resource('users');

    $users->action( get => ( query => { ... } ) );

This example illustrates how you might fetch an API resource.

## Creating

    my $users = $client->users;

    # content-body parameters

    $users->create( data => { ... } );

    # query-string parameters

    $users->create( query => { ... } );

    # equivalent to

    $client->resource('users')->action(
        post => ( query => { ... }, data => { ... } )
    );

This example illustrates how you might create a new API resource.

## Updating

    my $users = $client->users;
    my $user  = $users->resource('c09e91a');

    # content-body parameters

    $user->update( data => { ... } );

    # query-string parameters

    $user->update( query => { ... } );

    # or

    my $user = $client->users('c09e91a');

    $user->update(...);

    # equivalent to

    $client->resource('users')->action(
        put => ( query => { ... }, data => { ... } )
    );

This example illustrates how you might update a new API resource.

## Deleting

    my $users = $client->users;
    my $user  = $users->resource('c09e91a');

    # content-body parameters

    $user->delete( data => { ... } );

    # query-string parameters

    $user->delete( query => { ... } );

    # or

    my $user = $client->users('c09e91a');

    $user->delete(...);

    # equivalent to

    $client->resource('users')->action(
        delete => ( query => { ... }, data => { ... } )
    );

This example illustrates how you might delete an API resource.

## Transacting

    my $users = $client->resource('users', 'c09e91a');

    my ($results, $transaction) = $users->action( ... );

    my $request  = $transaction->req;
    my $response = $transaction->res;

    my $headers;

    $headers = $request->headers;
    $headers = $response->headers;

    # etc

This example illustrates how you can access the transaction object used to
represent and process the HTTP transaction.

## Casing

    $client->casing('lowercase');

    my $settings = $client->users('c09e91a')->profile_settings;

    # given casing as 'lowercase'
    $settings->fetch( ... ); # GET /users/c09e91a/profile_settings

    # given casing as 'uppercase'
    $settings->fetch( ... ); # GET /USERS/C09E91A/PROFILE_SETTINGS

    # given casing as 'camelcase'
    $settings->fetch( ... ); # GET /users/c09e91a/profileSettings

    # given casing as 'snakecase'
    $settings->fetch( ... ); # GET /users/c09e91a/profileSettings

    # given casing as 'pascalcase'
    $settings->fetch( ... ); # GET /Users/c09e91a/ProfileSettings

This example illustrates how you can configure the client to automatically
handle the casing of path segments while continuing to use lowercase-userscore 
separated string in your code. This is useful when interacting with an API that
uses convetions foreign to that of your codebase.

# ATTRIBUTES

## identifier

    $client->identifier;
    $client->identifier('IDENTIFIER');

The identifier attribute should be set to a string that identifies your
application.

## debug

    $client->debug;
    $client->debug(1);

The debug attribute if true prints HTTP requests and responses to standard out.

## fatal

    $client->fatal;
    $client->fatal(1);

The fatal attribute if true promotes 4xx and 5xx server response codes to
exceptions, a [API::Client::Exception](https://metacpan.org/pod/API::Client::Exception) object.

## retries

    $client->retries;
    $client->retries(10);

The retries attribute determines how many times an HTTP request should be
retried if a 4xx or 5xx response is received. This attribute defaults to 0.

## timeout

    $client->timeout;
    $client->timeout(5);

The timeout attribute determines how long an HTTP connection should be kept
alive. This attribute defaults to 10.

## url

    $client->url;
    $client->url(Mojo::URL->new('https://api.example.com'));

The url attribute sets the base/pre-configured URL object that will be used in
all HTTP requests. This attribute expects a [Mojo::URL](https://metacpan.org/pod/Mojo::URL) object.

## user\_agent

    $client->user_agent;
    $client->user_agent(Mojo::UserAgent->new);

The user\_agent attribute sets the pre-configured UserAgent object that will be
used in all HTTP requests. This attribute expects a [Mojo::UserAgent](https://metacpan.org/pod/Mojo::UserAgent) object.

# METHODS

## action

    my $result = $client->action($verb, %args);

    # e.g.

    $client->action('head', %args);    # HEAD request
    $client->action('options', %args); # OPTIONS request
    $client->action('patch', %args);   # PATCH request

The action method issues a request to the API resource represented by the
object. The first parameter will be used as the HTTP request method. The
arguments, expected to be a list of key/value pairs, will be included in the
request if the key is either `data` or `query`.

## create

    my $results = $client->create(%args);

    # or

    $client->POST(%args);

The create method issues a `POST` request to the API resource represented by
the object. The arguments, expected to be a list of key/value pairs, will be
included in the request if the key is either `data` or `query`.

## delete

    my $results = $client->delete(%args);

    # or

    $client->DELETE(%args);

The delete method issues a `DELETE` request to the API resource represented by
the object. The arguments, expected to be a list of key/value pairs, will be
included in the request if the key is either `data` or `query`.

## fetch

    my $results = $client->fetch(%args);

    # or

    $client->GET(%args);

The fetch method issues a `GET` request to the API resource represented by the
object. The arguments, expected to be a list of key/value pairs, will be
included in the request if the key is either `data` or `query`.

## update

    my $results = $client->update(%args);

    # or

    $client->PUT(%args);

The update method issues a `PUT` request to the API resource represented by
the object. The arguments, expected to be a list of key/value pairs, will be
included in the request if the key is either `data` or `query`.

# AUTHOR

Al Newkirk <anewkirk@ana.io>

# COPYRIGHT AND LICENSE

This software is copyright (c) 2014 by Al Newkirk.

This is free software; you can redistribute it and/or modify it under
the same terms as the Perl 5 programming language system itself.