use 5.12.0;
use strict;
use warnings;
use Data::Dump qw/pp dd/;

use Benchmark qw/cmpthese/;




# --------- fetch all defined generators

my %generators;
for my $generator ( grep {/^gen_/} keys %Generators::) {
    my $g_generator = $Generators::{$generator};
    $generators{$generator} = $g_generator;
}

#warn pp \%generators;


# --------- init test data

my %hash;
my @entries = 0..1e3;

@hash{@entries} = reverse @entries;
my %copy = %hash;



# --------- run tests

while( my ($gen,$glob) = each %generators ) {
    say "\n*** Testing $gen";
    Tests::all(
               "$gen",
               $glob->(\%hash),
               \%copy
              );
}

Test::More::done_testing();


# --------- run benchmarks

# --- expand test data

@entries = 0..1e6;
@hash{@entries} = reverse @entries;

# --- init iterators

my %iterators;
while ( my ($gen,$glob) = each %generators ) {
    (my $name = $gen) =~ s/^gen_//;
    $iterators{$name} = $glob->(\%hash);
}
#warn pp \%iterators;

# --- benchmark
cmpthese(-1, \%iterators );







package Generators;


sub gen_copy_keys {
    my ($h_hash) = @_;
    my $idx = 0;
    my @keys = keys %$h_hash;

    return sub {

        # --- reset?
        if ($idx >= @keys) {
            $idx = 0;
            return;
        }

        # --- return key, value
        my $key = $keys[$idx++];
        return $key, $h_hash->{$key};
    }
}


sub gen_copy_hash_and_each {
    my ($h_hash) = @_;
    my %copy = %$h_hash;

    return sub {
        # --- return key, value
        return each %copy
    }
}

sub gen_each {
    my ($h_hash) = @_;

    return sub {
        # --- return key, value
        return each %$h_hash;
    }
}

sub gen_idx_keys {
    my ($h_hash) = @_;
    my $idx = 0;

    return sub {
        if ($idx >= keys %$h_hash) {
            $idx = 0;
            return;
        }

        # --- return key, value
        my $key = (keys %$h_hash)[$idx++];
        return $key, $h_hash->{$key};
    }
}




package Tests;
use Test::More;

sub all {
    my ( $name, $c_iter, $h_expected ) = @_;

    # --- gathers all entries
    my %got = ();

    while ( my ($k,$v) = &$c_iter ) {
        $got{$k} = $v;
    }

    is_deeply(\%got, $h_expected, "'$name' iterates over all entries");

    # --- cycles to restart
    %got = ();

    while ( my ($k,$v) = &$c_iter ) {
        $got{$k} = $v;
    }

    is_deeply(\%got, $h_expected, "'$name' cycles and iterates again");
}