#!/usr/local/bin/perl
# N.B.:  minimal included modules for portability
# (Could be more efficient with XML/Atom parsing and XPath.)
use Getopt::Long;
use LWP::Simple;
use Time::Local;
use strict;

# Parse command line
my ($osdd_url, $keywords, $bbox, $start, $end, $help);
my $result = GetOptions("osdd=s" => \$osdd_url, "keywords=s" => \$keywords,
   "bbox=s" => \$bbox, "start=s" => \$start, "end=s" => \$end, 
   "help" => \$help);

usage() if ($help || !$keywords);
$start ||= epoch2ccsds(time());
$end ||= epoch2ccsds(ccsds2epoch($start)+86400);
warn ("start: $start\nend:   $end\n");

# Get Dataset Open Search Description Document
my $datasets = opensearch($osdd_url, $keywords, $bbox, $start, $end);
my @osdd = extract_links($datasets, "search", "opensearchdescription");

# Loop through returned dataset OpenSearch Description Documents
foreach my $osdd (@osdd) {
    my $granules=opensearch($osdd, $keywords, $bbox, $start,$end);
    my @links = extract_links($granules, "/data#", '');
    print join("\n", @links, '');
}

# Extract links from Atom document based on rel and type values
sub extract_links {
    my ($doc, $rel_target, $type_target) = @_;
    my @links;
    # Loop through <entry> elements
    while ($doc =~ m/<entry>(.*?)<\/entry>/sg) {
        my $entry = $1;
        # Loop through <link> elements
        while ($entry =~ m/<link(.*?)>/sg) {
            my $link = $1;
            my $match = 1;
            my ($rel) = ($link =~ m/rel="(.*?)"/is);
            $match = 0 if ($rel_target && $rel !~ /$rel_target/);
            my ($type) = ($link =~ m/type="(.*?)"/is);
            $match = 0 if ($type_target && $type !~ /$type_target/);
            if ($match) {
                my ($link_href) = ($link =~ m/href="(.*?)"/);
                push @links, $link_href;
                last;
            }
        }
    }
    return @links;
}
# opensearch: given a URL to an OpenSearch Description Document and the search values,
# fetch the OSDD and execute the search
sub opensearch {
    my ($osdd_url, $keywords, $bbox, $start, $end) = @_;
    # Fetch OpenSearch Description Document
    my $osdd = get($osdd_url) or die "Could not get $osdd_url";
    # Extract template for Atom response
    my ($template) = ($osdd =~ /<[\w:]*Url .*atom.*template="(.*?)"/is);
    # Fill template in with values
    my $url = fill_template($template, $keywords, $bbox, $start, $end);
    # Fetch results
    my $results = get($url) or warn "No results returned for $url";
    return $results;
}
# fill_template:  fill in an OpenSearch template with values from command line
sub fill_template {
    my ($template, $keywords, $bbox, $start, $end) = @_;
    my $url = $template;
    $template =~ s/\{time:start\}/$start/ if ($start);
    $template =~ s/\{time:end\}/$end/ if ($end);
    $template =~ s/\{geo:box\}/$bbox/ if ($bbox);
    $template =~ s/\{searchTerms\}/$keywords/ if ($keywords);
    $template =~ s/(\&amp;|\?)\w+?=\{[\w:]+?\}//g;
    return $template;
}
sub ccsds2epoch {
    my ($y, $m, $d, $h, $min, $s) = ($_[0] =~ m/(\d\d\d\d)-(\d\d)-(\d\d)T(\d\d):(\d\d):(\d\d)/);
    return timegm($s, $min, $h, $d, $m-1, $y-1900);
}
sub epoch2ccsds {
    my @t = gmtime($_[0]);
    return sprintf("%04d-%02d-%02dT%02d:%02d:%02d", $t[5]+1900,
        $t[4]+1, $t[3], $t[2], $t[1], $t[0]);
}
sub usage() {
    die "esip_fedsearch.pl [options]\
  --osdd=url                     URL of dataset-level OpenSearch 
                                 Description Document (Required)\
  --bbox=lon,lat,lon,lat         Bounding box of search area\
  --start=yyyy-mm-ddThh:mm:ssZ   Start time of search (Default=yesterday)\
  --end=yyyy-mm-ddThh:mm:ssZ     End time of search (Default = start+1day)\
  --keywords=word+word+word...   Keywords, separated by '+' (Required)
";
}