NAME
    DotCloud::Environment - easy handling of environment in dotcloud

VERSION
    version 0.9.0

SYNOPSIS
       # Most typical usage, suppose you have a shared 'lib' directory
       # under the root of your dotCloud directory hierarchy
       use DotCloud::Environment 'path_for';
       use lib path_for('lib');
       use My::Shared::Module; # in your project-root/lib directory

       # Most typical usage when you set a default environment.json file
       # in the root of your project and you need to access the variables
       # of the 'redis' service
       use DotCloud::Environment 'dotvars';
       my $redis_vars = dotvars('redis');

       # Not-very-typical usage examples from now on!

       # get an object, fallback to $path if not in dotCloud deploy
       my $dcenv = DotCloud::Environment->new(fallback_file => $path);

       # you should now which services make part of your stack!
       my $nosqldb_conf = $dcenv->service('nosqldb');
       my $type = $nosqldb_conf->{type}; # e.g. mysql, redis, etc.
       my $vars = $nosqldb_conf->{vars}; # e.g. login, password, host...

       # suppose your nosqldb service is redis...
       require Redis;
       my $redis = Redis->new(server => "$vars->{host}:$vars->{port}");
       $redis->auth($vars->{password});

       # another service, similar approach
       my $conf = $dcenv->service('database');
       die 'not MySQL?!?' unless $conf->{type} eq 'mysql';

       my ($host, $port, $user, $pass)
          = @{$conf->{vars}}{qw< host port login password >}
       require DBI;
       my $dbh = DBI->connect("dbi:mysql:host=$host;port=$port;database=db",
          $user, $pass, {RaiseError => 1});

DESCRIPTION
    DotCloud::Environment is useful when you design applications to be
    deployed in the dotCloud platform. It is assumed that you know what
    dotCloud is (anyway, see <http://www.dotcloud.com/>).

    In general you will have multiple services in your application, and when
    you are in one instance inside dotCloud you can access the configuration
    of the relevant ones reading either /home/dotcloud/environment.yml or
    /home/dotcloud/environment.json. For example, this lets your frontend or
    backend applications know where the data services are, e.g. a Redis
    database or a MySQL one.

    This modules serves to two main goals:

    *   it reads either file to load the configuration of each service, so
        that you can access this configuration easily as a hash of hashes;

    *   it lets you abstract from the assumption that you're actually in a
        dotCloud instance, allowing you to use the same interface also in
        your development environment.

    With respect to the second goal, it should be observed that most of the
    times in your development environment you don't have the same exact
    situation as in dotCloud, e.g. it's improbable that you have a
    /home/dotcloud directory around. With this module you can set a fallback
    to be used in different ways, e.g.:

    *   providing a fallback file path to be loaded if
        "/home/dotcloud/environment.json" is not found;

    *   setting up the "DOTCLOUD_ENVIRONMENT" environment variable to point
        to the file to be used.

  Suggested/Typical Usage
    In order to keep your code clean, you will probably be dividing it
    depending on the functional block that will be deployed as a service in
    dotCloud. Suppose that you have a frontend service, a backend service
    and a database; you probably have the following directory layout:

       project
       +- dotcloud.yml
       +- backend
       |  | ...
       |  +- lib
       |     +- Backend.pm
       +- frontend
       |  | ...
       |  +- lib
       |     +- FrontEnd.pm
       +- lib
          +- Shared.pm

    Each service is put into a separate directory and all the code that they
    both use (e.g. functions to connect to databases) is put in a common
    "lib" directory.

    How should you use DotCloud::Environment?

    The main goal is to let it find the right "environment.json" (or,
    equivalently, "environment.yml") depending on the environment you are
    into. If you are in dotCloud there is actually no problem, because by
    default the *right* "/home/dotcloud/environment.json" file is selected;
    for your local development the best thing to do is to put the
    configuration file in the project's root directory, which becomes like
    this:

       project
       +- dotcloud.yml
       +- backend
       |  | ...
       |  +- lib
       |     +- Backend.pm
       +- frontend
       |  | ...
       |  +- lib
       |     +- FrontEnd.pm
       +- lib
       |  +- Shared.pm
       |
       +- environment.json

    Putting the file in that position lets DotCloud::Environment find it by
    default when no "/home/dotcloud/environment.json" file (or the
    equivalent YAML file) is found in the system. Which hopefully is the
    case of your development environment.

    In this case, you would have this in each service:

       # -- in BackEnd.pm and FrontEnd.pm --
       use DotCloud::Environment 'path_for';
       use lib path_for('lib');
       use Shared ...;

    The function "path_for" helps you to set up the right path in @INC so
    that the module can find the shared code.

    In the shared module you can do this:

       # -- in Shared.pm --
       use DotCloud::Environment 'dotenv';

       # ... when you need it...
       my $service = dotenv()->service('service-name');
       my $type = $service->{type}; # e.g. mysql, redis, etc.
       my $vars = $service->{vars}; # e.g. login, password, host...

    Most of the time all you need is to access the variables related to a
    specific service, so there's a shortcut for this:

       use DotCloud::Environment 'dotvars';
       my %vars = dotvars('service-name');

    For example, suppose that you want to implement a function to connect to
    a Redis service called "redisdb":

       sub get_redis {
          my %vars = dotvars('redisdb');

          require Redis;
          my $redis = Redis->new(server => "$vars{host}:$vars{port}");
          $redis->auth($vars{password});
          return $redis;
       }

    Of course you can use "dotenv"/"dotvars" directly in "FrontEnd.pm" and
    "BackEnd.pm", but you will probably benefit from refactoring your common
    code to avoid duplications.

METHODS
  new
       $dcenv = DotCloud::Environment->new(%params);
       $dcenv = DotCloud::Environment->new({%params});

    Create a new object. Parameters are:

    no_load
        don't attempt to load the configuration

    environment_string
        unconditionally use the provided string, ignoring everything else;

    environment_file
        unconditionally use the provided file, ignoring everything else;

    fallback_string
        use the provided string if other methods fail;

    fallback_file
        use the provided file if other methods fail.

    backtrack
        if nothing works and no fallback is set, look for suitable files in
        filesystem. This option is activated by default, so you can use it
        to *disable* it (e.g. with "backtrack => 0").

    Unless "no_load" is passed and set to true, the object creation also
    calls the "load" method.

    Returns the new object or "croak"s if errors occur.

  load
       $dcenv->load(%params);
       $dcenv->load({%params});

    Load the configuration for an application. The accepted parameters are
    "environment_string", "environment_file", "fallback_string",
    "fallback_file" and "backtrack" with the same meaning as in the
    constructor (see "new").

    The sequence to get the configuration string is the following:

    environment_string
        from parameter passed to the method

    environment_file
        from parameter passed to the method

    environment_string
        from parameter set in the constructor

    environment_file
        from parameter set in the constructor

    DOTCLOUD_ENVIRONMENT
        environment variable (i.e. $ENV{DOTCLOUD_ENVIRONMENT})

    $DotCloud::Environment::main_file_path
        which defaults to /home/dotcloud/environment.json (you SHOULD NOT
        change this variable unless you really know what you're doing)

    fallback_string
        from parameter passed to the method

    fallback_file
        from parameter passed to the method

    fallback_string
        from parameter set in the constructor

    fallback_file
        from parameter set in the constructor

    If none of the above works there's still some hope in case there is
    option "backtrack" (or it was specified to the constructor). In this
    case, either file is searched recursively starting from the following
    directories:

    *   the one returned by "find_code_dir" (but as if it were called by the
        caller of "load", i.e. with a value of "n" equal to 1)

    *   the current working directory

    *   the directory of the file that called us.

    Actually, option "backtrack" is enabled by default, so if you do not
    want the behaviour above you have to explicitly disable it (e.g. passing
    "backtrack => 0" in the constructor).

    It is possible to load multiple configuration files from multiple
    applications.

    Returns a reference to the object itself.

  as_json
       %json_for = $dcenv->as_json();
       $json_for = $dcenv->as_json();

    Rebuild the JSON representations of all the applications.

    Returns a hash (in list context) or an anonymous hash (in scalar
    context) with each application name pointing to the relevant JSON
    string.

  as_yaml
       %yaml_for = $dcenv->as_yaml();
       $yaml_for = $dcenv->as_yaml();

    Rebuild the YAML representations of all the applications.

    Returns a hash (in list context) or an anonymous hash (in scalar
    context) with each application name pointing to the relevant YAML
    string.

  merge_json
       $dcenv->merge_json($json_string);

    Add (or replace) the configuration of an application, provided as JSON
    string. You should not need to do this explicitly, because this does the
    same for you with autodetection of the format:

       $dcenv->load(environment_string => $json_or_yaml_string);

    Return a reference to the object itself.

  merge_yaml
       $dcenv->merge_yaml($yaml_string);

    Add (or replace) the configuration of an application, provided as YAML
    string. You should not need to do this explicitly, because this does the
    same for you with autodetection of the format:

       $dcenv->load(environment_string => $json_or_yaml_string);

  application_names
       my @names = $dcenv->application_names();

    Returns the names of the applications loaded. Generally only one
    application will be available, i.e. the one of the stack you're working
    with.

  applications
       my %conf_for = $dcenv->applications();
       my $conf_for = $dcenv->applications();

    Get a hash (in list context) or anonymous hash (in scalar context) with
    the relevant data of all the applications. Example:

       {
          app1 => {
             project      => 'app1',
             environment  => 'default',
             service_id   => 0,
             service_name => 'www',
             services     => {
                nosqldb => {
                   type => 'redis',
                   vars => {
                      login    => 'redis',
                      password => 'wafadsfsdfdsfdas',
                      host     => 'data.app1.dotcloud.com',
                      port     => '12345',
                   }
                }
                sqldb => {
                   type => 'mysql',
                   vars => {
                      login    => 'mysql',
                      password => 'wafadsfsdfdsfdas',
                      host     => 'data.app1.dotcloud.com',
                      port     => '54321',
                   }
                }
             }
          },
          app2 => {
             # ...
          }
       }

  application
       my %conf_for = $dcenv->application($appname);
       my $conf_for = $dcenv->application($appname);

    Get a hash (in list context) or anonymous hash (in scalar context) with
    the relevant data for the requested application. Example:

       {
          project      => 'app1',
          environment  => 'default',
          service_id   => 0,
          service_name => 'www',
          services     => {
             nosqldb => {
                type => 'redis',
                vars => {
                   login    => 'redis',
                   password => 'wafadsfsdfdsfdas',
                   host     => 'data.app1.dotcloud.com',
                   port     => '12345',
                }
             }
             sqldb => {
                type => 'mysql',
                vars => {
                   login    => 'mysql',
                   password => 'wafadsfsdfdsfdas',
                   host     => 'data.app1.dotcloud.com',
                   port     => '54321',
                }
             }
          }
       }

  service
       my %conf_for = $dcenv->service(%params); # also with \%params
       my $conf_for = $dcenv->service(%params); # also with \%params

    Get a hash (in list context) or anonymous hash (in scalar context) with
    the relevant data for the requested service. Example:

       {
          type => 'redis',
          vars => {
             login    => 'redis',
             password => 'wafadsfsdfdsfdas',
             host     => 'data.app1.dotcloud.com',
             port     => '12345',
          }
       }

    The parameters are the following:

    service
        (Required) the name of the service.

    application
        (Optional) the name of the application.

    The name of the application is optional because in most cases it can be
    omitted, e.g. because there is only one application. The name can be
    also provided in the service name, in line with what normally happens in
    dotCloud where the complete name of a service is something like
    "application.service".

    This is the algorithm:

    *   if the name of the service is of the form "application.service", the
        name is split into the two components;

    *   otherwise, if the application parameter is present it is used

    *   otherwise the service is searched among all the services of all the
        applications.

    If exactly one service is found it is returned, otherwise this method
    "croak"s.

  service_vars
       my %vars   = $dcenv->service_vars('service-name');
       my $vars   = $dcenv->service_vars('service-name');
       my %vars   = $dcenv->service_vars(%params); # also \%params
       my $vars   = $dcenv->service_vars(%params); # also \%params
       my @values = $dcenv->service_vars(%params); # also \%params
       my $values = $dcenv->service_vars(%params); # also \%params

    Shorthand to get the configuration variables of a single service.

    The input parameter list can be a single string with the name of the
    service, or a hash/anonymous hash with parameters. Depending on the
    input, the return value might be structured like a hash or like an
    array:

    service
        the name of the service, see "service"

    application
        the name of the application, see "service"

    list
        (Optional) if a list is provided, then the values corresponding to
        each item in order is returned. This allows writing things like
        this:

           my ($host, $port, $password) = $dcenv->service_list(
              service => 'nosqldb',
              list => [ qw< host port password > ],
           );

        and get directly the values to put into variables. In this case, the
        return value can be a list of values or an anonymous array with the
        values.

        If this parameter is not present, the whole name/value hash is
        returned, either as a list or as an anonymous hash depending on the
        context.

FUNCTIONS
    Nothing is exported by default, but you can import the following
    functions. If you need both, you can use the ":all" tag, e.g.:

       use DotCloud::Environment ':all';

    This module uses Sub::Exporter under the hood; this means that if you're
    not happy with the name of the imported subroutines you can provide your
    own names, e.g.:

       use DotCloud::Environment
          dotvars => { -as => 'dotcloud_variables_for' };
       my $vars = dotcloud_variables_for('my-service');

  dotenv
       my $singleton = dotenv();

    This function returns a default instance of DotCloud::Environment that
    should suit the needs for the typical/suggested usage. Subsequent calls
    to the function always return the same object.

    It can be useful if you don't want a global variable in your code, e.g.:

       my @application_names = dotenv()->application_names();
       # ...
       my $vars = dotenv()->service_vars('my-sql-db');

  dotvars
       my $vars = dotvars('service-name');

    This function gets the configuration variables for the provided service
    using the default singleton instance. Most of the time this is exactly
    what you want, and nothing more.

    This function actually calls "service_vars" behind the scenes, you can
    pass all the parameters that the method accepts.

  find_code_dir
       my $code_directory = find_code_dir(%params);

    This function tries to find the file dotcloud.yml that describes the
    application backtracking from the current working directory and from the
    directory containing the file that called us (i.e. what happens to be
    "(caller($n))[1]").

    Parameters:

    n   an integer, defaulting to 0, that tells how to call "caller()". You
        shouldn't need to set it, anyway.

    unix
        when set, the name of the directory will be returned in Unix format,
        so that you can use it with "use lib". By default the format is the
        same as the system.

    This should be useful if you want to put a default configuration file
    there or if you want to set up a shared library directory. If you are
    interested into this feature, anyway, look at "path_for" which is easier
    to use.

  path_for
       use lib path_for('lib');

    This function produces a list of paths that are suitable for "use lib".
    It uses "find_code_dir" internally, see it for details.

    You should pass a list of subdirectories which will be rebased using the
    result of "find_code_dir" as a parent directory. If you are actually in
    the dotCloud enviroment, the example above produces the path
    "/home/dotcloud/code/lib".

    Returns a list of Unix paths, one element for each input directory.

AUTHOR
    Flavio Poletti <polettix@cpan.org>

COPYRIGHT AND LICENSE
    Copyright (C) 2011 by Flavio Poletti polettix@cpan.org.

    This module is free software. You can redistribute it and/or modify it
    under the terms of the Artistic License 2.0.

    This program is distributed in the hope that it will be useful, but
    without any warranty; without even the implied warranty of
    merchantability or fitness for a particular purpose.