package Trog::Log::Metrics;

use strict;
use warnings;

no warnings 'experimental';
use feature qw{signatures state};

use Trog::SQLite;

=head1 Trog::Log::Metrics

A means for acquiring time-series representations of the data recorded by Trog::Log::DBI,
and for reasoning about the various things that it's Urchin-compatible data can give you.

=cut

sub _dbh {
    return Trog::SQLite::dbh( 'schema/log.schema', "logs/log.db" );
}

=head2 requests_per(ENUM period{second,minute,hour,day,month,year}, INTEGER num_periods, [TIME_T before], INTEGER[] @codes)

Returns a data structure of the following form

    {
        labels => [TIME_STR, TIME_STR, ...],
        data   => [INT, INT,...]
    }

Describing the # of requests for the requested $num_periods $period(s) before $before.

'month' and 'year' are approximations for performance reasons; 30 day and 365 day periods.

Optionally filter by response code(s).

=cut

sub requests_per ( $period, $num_periods, $before, @codes ) {
    $before ||= time;

    # Build our periods in seconds.
    state %period2time = (
        second => 1,
        minute => 60,
        hour   => 3600,
        day    => 86400,
        week   => 604800,
        month  => 2592000,
        year   => 31356000,
    );

    my $interval = $period2time{$period};
    die "Invalid time interval passed." unless $interval;

    my @input;
    my $whereclause = '';
    if (@codes) {
        my $bind = join( ',', ( map { '?' } @codes ) );
        $whereclause = "WHERE code IN ($bind)";
        push( @input, @codes );
    }
    push( @input, $interval, $before, $num_periods );

    my $query = "SELECT count(*) FROM all_requests $whereclause GROUP BY date / ? HAVING date < ? LIMIT ?";

    my @results = map { $_->[0] } @{ _dbh()->selectall_arrayref( $query, undef, @input ) };
    my $np      = @results < $num_periods ? @results : $num_periods;
    my @labels  = reverse map { "$_ $period(s) ago" } ( 1 .. $np );

    return {
        labels => \@labels,
        data   => \@results,
    };
}

1;