package Mojo::Pg;
use Mojo::Base 'Mojo::EventEmitter';

use Carp 'croak';
use DBI;
use Mojo::Pg::Database;
use Mojo::Pg::Migrations;
use Mojo::Pg::PubSub;
use Mojo::URL;
use Scalar::Util qw(blessed weaken);
use SQL::Abstract;

has abstract => sub {
  SQL::Abstract->new(array_datatypes => 1, name_sep => '.', quote_char => '"');
};
has [qw(auto_migrate parent search_path)];
has database_class  => 'Mojo::Pg::Database';
has dsn             => 'dbi:Pg:';
has max_connections => 1;
has migrations      => sub {
  my $migrations = Mojo::Pg::Migrations->new(pg => shift);
  weaken $migrations->{pg};
  return $migrations;
};
has options => sub {
  {
    AutoCommit          => 1,
    AutoInactiveDestroy => 1,
    PrintError          => 0,
    PrintWarn           => 0,
    RaiseError          => 1
  };
};
has [qw(password username)] => '';
has pubsub => sub {
  my $pubsub = Mojo::Pg::PubSub->new(pg => shift);
  weaken $pubsub->{pg};
  return $pubsub;
};

our $VERSION = '4.04';

sub db { $_[0]->database_class->new(dbh => $_[0]->_prepare, pg => $_[0]) }

sub from_string {
  my ($self, $str) = @_;

  # Parent
  return $self unless $str;
  return $self->parent($str) if blessed $str && $str->isa('Mojo::Pg');

  # Protocol
  my $url = Mojo::URL->new($str);
  croak qq{Invalid PostgreSQL connection string "$str"}
    unless $url->protocol =~ /^postgres(?:ql)?$/;

  # Connection information
  my $db = $url->path->parts->[0];
  my $dsn = defined $db ? "dbi:Pg:dbname=$db" : 'dbi:Pg:';
  if (my $host = $url->host) { $dsn .= ";host=$host" }
  if (my $port = $url->port) { $dsn .= ";port=$port" }
  if (defined(my $username = $url->username)) { $self->username($username) }
  if (defined(my $password = $url->password)) { $self->password($password) }

  # Service and search_path
  my $hash = $url->query->to_hash;
  if (my $service = delete $hash->{service}) { $dsn .= "service=$service" }
  if (my $path = delete $hash->{search_path}) {
    $self->search_path(ref $path ? $path : [$path]);
  }

  # Options
  @{$self->options}{keys %$hash} = values %$hash;

  return $self->dsn($dsn);
}

sub new { @_ > 1 ? shift->SUPER::new->from_string(@_) : shift->SUPER::new }

sub _dequeue {
  my $self = shift;

  # Fork-safety
  delete @$self{qw(pid queue)} unless ($self->{pid} //= $$) eq $$;

  while (my $dbh = shift @{$self->{queue} || []}) { return $dbh if $dbh->ping }
  my $dbh = DBI->connect(map { $self->$_ } qw(dsn username password options));

  # Search path
  if (my $path = $self->search_path) {
    my $search_path = join ', ', map { $dbh->quote_identifier($_) } @$path;
    $dbh->do("set search_path to $search_path");
  }

  $self->emit(connection => $dbh);

  return $dbh;
}

sub _enqueue {
  my ($self, $dbh) = @_;

  if (my $parent = $self->parent) { return $parent->_enqueue($dbh) }

  my $queue = $self->{queue} ||= [];
  push @$queue, $dbh if $dbh->{Active};
  shift @$queue while @$queue > $self->max_connections;
}

sub _prepare {
  my $self = shift;

  # Automatic migrations
  ++$self->{migrated} and $self->migrations->migrate
    if !$self->{migrated} && $self->auto_migrate;

  my $parent = $self->parent;
  return $parent ? $parent->_prepare : $self->_dequeue;
}

1;

=encoding utf8

=head1 NAME

Mojo::Pg - Mojolicious ♥ PostgreSQL

=head1 SYNOPSIS

  use Mojo::Pg;

  # Use a PostgreSQL connection string for configuration
  my $pg = Mojo::Pg->new('postgresql://postgres@/test');

  # Select the server version
  say $pg->db->query('select version() as version')->hash->{version};

  # Use migrations to create a table
  $pg->migrations->name('my_names_app')->from_string(<<EOF)->migrate;
  -- 1 up
  create table names (id serial primary key, name text);
  -- 1 down
  drop table names;
  EOF

  # Use migrations to drop and recreate the table
  $pg->migrations->migrate(0)->migrate;

  # Get a database handle from the cache for multiple queries
  my $db = $pg->db;

  # Use SQL::Abstract to generate simple CRUD queries for you
  $db->insert('names', {name => 'Isabell'});
  my $id = $db->select('names', ['id'], {name => 'Isabell'})->hash->{id};
  $db->update('names', {name => 'Belle'}, {id => $id});
  $db->delete('names', {name => 'Belle'});

  # Insert a few rows in a transaction with SQL and placeholders
  eval {
    my $tx = $db->begin;
    $db->query('insert into names (name) values (?)', 'Sara');
    $db->query('insert into names (name) values (?)', 'Stefan');
    $tx->commit;
  };
  say $@ if $@;

  # Insert another row with SQL::Abstract and return the generated id
  say $db->insert('names', {name => 'Daniel'}, {returning => 'id'})->hash->{id};

  # JSON roundtrip
  say $db->query('select ?::json as foo', {json => {bar => 'baz'}})
    ->expand->hash->{foo}{bar};

  # Select all rows blocking with SQL::Abstract
  say $_->{name} for $db->select('names')->hashes->each;

  # Select all rows non-blocking with SQL::Abstract
  $db->select('names' => sub {
    my ($db, $err, $results) = @_;
    die $err if $err;
    say $_->{name} for $results->hashes->each;
  });
  Mojo::IOLoop->start unless Mojo::IOLoop->is_running;

  # Concurrent non-blocking queries (synchronized with promises)
  my $now   = $pg->db->query_p('select now() as now');
  my $names = $pg->db->query_p('select * from names');
  Mojo::Promise->all($now, $names)->then(sub {
    my ($now, $names) = @_;
    say $now->[0]->hash->{now};
    say $_->{name} for $names->[0]->hashes->each;
  })->catch(sub {
    my $err = shift;
    warn "Something went wrong: $err";
  })->wait;

  # Send and receive notifications non-blocking
  $pg->pubsub->listen(foo => sub {
    my ($pubsub, $payload) = @_;
    say "foo: $payload";
    $pubsub->notify(bar => $payload);
  });
  $pg->pubsub->listen(bar => sub {
    my ($pubsub, $payload) = @_;
    say "bar: $payload";
  });
  $pg->pubsub->notify(foo => 'PostgreSQL rocks!');
  Mojo::IOLoop->start unless Mojo::IOLoop->is_running;

=head1 DESCRIPTION

L<Mojo::Pg> is a tiny wrapper around L<DBD::Pg> that makes
L<PostgreSQL|http://www.postgresql.org> a lot of fun to use with the
L<Mojolicious|http://mojolicious.org> real-time web framework. Perform queries
blocking and non-blocking, use all
L<SQL features|https://www.postgresql.org/docs/current/static/sql.html>
PostgreSQL has to offer, generate CRUD queries from data structures, manage your
database schema with migrations and build scalable real-time web applications
with the publish/subscribe pattern.

=head1 BASICS

Database and statement handles are cached automatically, and will be reused
transparently to increase performance. You can handle connection timeouts
gracefully by holding on to them only for short amounts of time.

  use Mojolicious::Lite;
  use Mojo::Pg;

  helper pg => sub { state $pg = Mojo::Pg->new('postgresql://postgres@/test') };

  get '/' => sub {
    my $c  = shift;
    my $db = $c->pg->db;
    $c->render(json => $db->query('select now() as now')->hash);
  };

  app->start;

In this example application, we create a C<pg> helper to store a L<Mojo::Pg>
object. Our action calls that helper and uses the method L<Mojo::Pg/"db"> to
dequeue a L<Mojo::Pg::Database> object from the connection pool. Then we use the
method L<Mojo::Pg::Database/"query"> to execute an
L<SQL|http://www.postgresql.org/docs/current/static/sql.html> statement, which
returns a L<Mojo::Pg::Results> object. And finally we call the method
L<Mojo::Pg::Results/"hash"> to retrieve the first row as a hash reference.

While all I/O operations are performed blocking, you can wait for long running
queries asynchronously, allowing the L<Mojo::IOLoop> event loop to perform
other tasks in the meantime. Since database connections usually have a very low
latency, this often results in very good performance.

Every database connection can only handle one active query at a time, this
includes asynchronous ones. To perform multiple queries concurrently, you have
to use multiple connections.

  # Performed concurrently (5 seconds)
  $pg->db->query('select pg_sleep(5)' => sub {...});
  $pg->db->query('select pg_sleep(5)' => sub {...});

All cached database handles will be reset automatically if a new process has
been forked, this allows multiple processes to share the same L<Mojo::Pg>
object safely.

=head1 GROWING

And as your application grows, you can move queries into model classes.

  package MyApp::Model::Time;
  use Mojo::Base -base;

  has 'pg';

  sub now { shift->pg->db->query('select now() as now')->hash }

  1;

Which get integrated into your application with helpers.

  use Mojolicious::Lite;
  use Mojo::Pg;
  use MyApp::Model::Time;

  helper pg => sub { state $pg = Mojo::Pg->new('postgresql://postgres@/test') };
  helper time => sub { state $time = MyApp::Model::Time->new(pg => shift->pg) };

  get '/' => sub {
    my $c = shift;
    $c->render(json => $c->time->now);
  };

  app->start;

=head1 EXAMPLES

This distribution also contains two great
L<example applications|https://github.com/kraih/mojo-pg/tree/master/examples/>
you can use for inspiration. The minimal
L<chat|https://github.com/kraih/mojo-pg/tree/master/examples/chat.pl>
application will show you how to scale WebSockets to multiple servers, and the
well-structured
L<blog|https://github.com/kraih/mojo-pg/tree/master/examples/blog> application
how to apply the MVC design pattern in practice.

=head1 EVENTS

L<Mojo::Pg> inherits all events from L<Mojo::EventEmitter> and can emit the
following new ones.

=head2 connection

  $pg->on(connection => sub {
    my ($pg, $dbh) = @_;
    ...
  });

Emitted when a new database connection has been established.

  $pg->on(connection => sub {
    my ($pg, $dbh) = @_;
    $dbh->do('set search_path to my_schema');
  });

=head1 ATTRIBUTES

L<Mojo::Pg> implements the following attributes.

=head2 abstract

  my $abstract = $pg->abstract;
  $pg          = $pg->abstract(SQL::Abstract->new);

L<SQL::Abstract> object used to generate CRUD queries for L<Mojo::Pg::Database>,
defaults to enabling C<array_datatypes> and setting C<name_sep> to C<.> and
C<quote_char> to C<">.

  # Generate WHERE clause and bind values
  my($stmt, @bind) = $pg->abstract->where({foo => 'bar', baz => 'yada'});

=head2 auto_migrate

  my $bool = $pg->auto_migrate;
  $pg      = $pg->auto_migrate($bool);

Automatically migrate to the latest database schema with L</"migrations">, as
soon as L</"db"> has been called for the first time.

=head2 database_class

  my $class = $pg->database_class;
  $pg       = $pg->database_class('MyApp::Database');

Class to be used by L</"db">, defaults to L<Mojo::Pg::Database>. Note that this
class needs to have already been loaded before L</"db"> is called.

=head2 dsn

  my $dsn = $pg->dsn;
  $pg     = $pg->dsn('dbi:Pg:dbname=foo');

Data source name, defaults to C<dbi:Pg:>.

=head2 max_connections

  my $max = $pg->max_connections;
  $pg     = $pg->max_connections(3);

Maximum number of idle database handles to cache for future use, defaults to
C<1>.

=head2 migrations

  my $migrations = $pg->migrations;
  $pg            = $pg->migrations(Mojo::Pg::Migrations->new);

L<Mojo::Pg::Migrations> object you can use to change your database schema more
easily.

  # Load migrations from file and migrate to latest version
  $pg->migrations->from_file('/home/sri/migrations.sql')->migrate;

=head2 options

  my $options = $pg->options;
  $pg         = $pg->options({AutoCommit => 1, RaiseError => 1});

Options for database handles, defaults to activating C<AutoCommit>,
C<AutoInactiveDestroy> as well as C<RaiseError> and deactivating C<PrintError>
as well as C<PrintWarn>. Note that C<AutoCommit> and C<RaiseError> are
considered mandatory, so deactivating them would be very dangerous.

=head2 parent

  my $parent = $pg->parent;
  $pg        = $pg->parent(Mojo::Pg->new);

Another L<Mojo::Pg> object to use for connection management, instead of
establishing and caching our own database connections.

=head2 password

  my $password = $pg->password;
  $pg          = $pg->password('s3cret');

Database password, defaults to an empty string.

=head2 pubsub

  my $pubsub = $pg->pubsub;
  $pg        = $pg->pubsub(Mojo::Pg::PubSub->new);

L<Mojo::Pg::PubSub> object you can use to send and receive notifications very
efficiently, by sharing a single database connection with many consumers.

  # Subscribe to a channel
  $pg->pubsub->listen(news => sub {
    my ($pubsub, $payload) = @_;
    say "Received: $payload";
  });

  # Notify a channel
  $pg->pubsub->notify(news => 'PostgreSQL rocks!');

=head2 search_path

  my $path = $pg->search_path;
  $pg      = $pg->search_path(['$user', 'foo', 'public']);

Schema search path assigned to all new connections.

  # Isolate tests and avoid race conditions when running them in parallel
  my $pg = Mojo::Pg->new('postgresql:///test')->search_path(['test_one']);
  $pg->db->query('drop schema if exists test_one cascade');
  $pg->db->query('create schema test_one');
  ...
  $pg->db->query('drop schema test_one cascade');

=head2 username

  my $username = $pg->username;
  $pg          = $pg->username('sri');

Database username, defaults to an empty string.

=head1 METHODS

L<Mojo::Pg> inherits all methods from L<Mojo::EventEmitter> and implements the
following new ones.

=head2 db

  my $db = $pg->db;

Get a database object based on L</"database_class"> (which is usually
L<Mojo::Pg::Database>) for a cached or newly established database connection.
The L<DBD::Pg> database handle will be automatically cached again when that
object is destroyed, so you can handle problems like connection timeouts
gracefully by holding on to it only for short amounts of time.

  # Add up all the money
  say $pg->db->select('accounts')
    ->hashes->reduce(sub { $a->{money} + $b->{money} });

=head2 from_string

  $pg = $pg->from_string('postgresql://postgres@/test');
  $pg = $pg->from_string(Mojo::Pg->new);

Parse configuration from connection string or use another L<Mojo::Pg> object as
L</"parent">.

  # Just a database
  $pg->from_string('postgresql:///db1');

  # Just a service
  $pg->from_string('postgresql://?service=foo');

  # Username and database
  $pg->from_string('postgresql://sri@/db2');

  # Short scheme, username, password, host and database
  $pg->from_string('postgres://sri:s3cret@localhost/db3');

  # Username, domain socket and database
  $pg->from_string('postgresql://sri@%2ftmp%2fpg.sock/db4');

  # Username, database and additional options
  $pg->from_string('postgresql://sri@/db5?PrintError=1&pg_server_prepare=0');

  # Service and additional options
  $pg->from_string('postgresql://?service=foo&PrintError=1&RaiseError=0');

  # Username, database, an option and search_path
  $pg->from_string('postgres://sri@/db6?&PrintError=1&search_path=test_schema');

=head2 new

  my $pg = Mojo::Pg->new;
  my $pg = Mojo::Pg->new('postgresql://postgres@/test');
  my $pg = Mojo::Pg->new(Mojo::Pg->new);

Construct a new L<Mojo::Pg> object and parse connection string with
L</"from_string"> if necessary.

  # Customize configuration further
  my $pg = Mojo::Pg->new->dsn('dbi:Pg:service=foo');

=head1 DEBUGGING

You can set the C<DBI_TRACE> environment variable to get some advanced
diagnostics information printed by L<DBI>.

  DBI_TRACE=1
  DBI_TRACE=15
  DBI_TRACE=SQL

=head1 REFERENCE

This is the class hierarchy of the L<Mojo::Pg> distribution.

=over 2

=item * L<Mojo::Pg>

=item * L<Mojo::Pg::Database>

=item * L<Mojo::Pg::Migrations>

=item * L<Mojo::Pg::PubSub>

=item * L<Mojo::Pg::Results>

=item * L<Mojo::Pg::Transaction>

=back

=head1 AUTHOR

Sebastian Riedel, C<sri@cpan.org>.

=head1 CREDITS

In alphabetical order:

=over 2

Christopher Eveland

Dan Book

Flavio Poletti

Hernan Lopes

William Lindley

=back

=head1 COPYRIGHT AND LICENSE

Copyright (C) 2014-2017, Sebastian Riedel and others.

This program is free software, you can redistribute it and/or modify it under
the terms of the Artistic License version 2.0.

=head1 SEE ALSO

L<https://github.com/kraih/mojo-pg>, L<Mojolicious::Guides>,
L<http://mojolicious.org>.

=cut
