#!/usr/bin/perl

use v5.14;
use utf8;
use open qw(:std :encoding(UTF-8));
use strictures;
use autodie;
use Feature::Compat::Try;

use POSIX qw(locale_h);
use locale;
use Encode qw(decode_utf8);    # TODO: modernize CalDAV access instead
use Net::Netrc;
use List::Util qw(first);

use IO::Interactive::Tiny;
use Log::Any qw($log);
use Log::Any::Adapter;

use URI;
use IO::Prompter;
use Cal::DAV;
use Data::ICal::DateTime;
use DateTime;
use Path::Tiny;

if ( IO::Interactive::Tiny::is_interactive() ) {
	Log::Any::Adapter->set( 'Screen', default_level => 'info' );
}

# set defaults and parse command-line options
my ( $BASE_URI, $CALENDAR_URI, $OUTPUT_FILE );
$BASE_URI     = $ENV{CAL_DAV_URL_BASE};
$CALENDAR_URI = $ENV{CAL_DAV_URL_CALENDAR};
$BASE_URI ||= shift @ARGV
	if @ARGV;
$CALENDAR_URI ||= shift @ARGV
	if @ARGV;
$OUTPUT_FILE = shift @ARGV
	if @ARGV;

# use system locale to format DateTime objects parsed from iCal data
DateTime->DefaultLocale( setlocale(LC_TIME) );

# resolve calendar URIs
my ( $base_uri, $calendar_uri, $calendar );
$base_uri = URI->new($BASE_URI)
	if ($BASE_URI);
$base_uri
	or $log->fatal('required base URI not provided') && exit 2;
$base_uri->scheme
	or $base_uri->scheme('file');

if ( $base_uri->scheme eq 'http' or $base_uri->scheme eq 'https' ) {
	$log->infof( 'will use base URI %s', $base_uri );
	$calendar_uri = URI->new( $CALENDAR_URI || $base_uri );
	$calendar_uri and $calendar_uri->authority
		or $log->fatal('bad calendar URI: must be an internet URI') && exit 2;
	$base_uri->eq($calendar_uri) and $calendar_uri = undef
		or $log->infof( 'will use calendar URI %s', $calendar_uri );

	# resolve credentials
	$log->debug('resolve credentials...');
	my ( $mach, $user, $pass );
	( $user, $pass ) = split ':', $base_uri->userinfo
		if $base_uri->userinfo;
	$user ||= $ENV{CAL_DAV_USER};
	$pass ||= $ENV{CAL_DAV_PASS};
	$mach = Net::Netrc->lookup( $base_uri->host, $user )
		if !$user or !$pass;
	if ($mach) {
		$user ||= $mach->login;
		$pass ||= $mach->password;
		$log->infof(
			'will use .netrc provided credentials for user %s',
			$user
		);
	}
	elsif ( IO::Interactive::Tiny::is_interactive() ) {
		$log->warn(
			'will ask for missing info - this will fail in headless mode');
		$user ||= prompt 'Enter your username';
		$pass ||= prompt 'Enter your password', -echo => '*';
	}
	$log->debugf( 'resolved credentials for user %s', $user );

	# fetch and parse CalDAV calendar data
	$log->debug('fetch and parse CalDAV calendar data...');
	$calendar = Cal::DAV->new(
		user => $user,
		pass => $pass,
		url  => $base_uri,
	);
	$calendar->get($calendar_uri)
		if $calendar_uri;
}
elsif ( $base_uri->scheme eq 'file' ) {
	defined $base_uri->file
		or $log->fatal('bad base URI: cannot open file') && exit 2;
	$log->infof( 'will use base URI %s', $base_uri );

	# parse local calendar data
	$log->debug('parse local calendar data...');
	my $path = path( $base_uri->file );
	if ( $path->is_file ) {
		$calendar = Data::ICal->new( data => $path->slurp_raw );
	}
	else {
		my $data;
		$path->visit( sub { $data .= $_->slurp_raw if $_->is_file } );
		$calendar = Data::ICal->new( data => $data );
	}
}
if ( $log->is_trace ) {
	use DDP;
	p $calendar;
}

# TODO: if list is empty and no calendar uri was explicitly supplied,
# warn on stdout with list of abailable collections using this sequence:
#  1. PROPFIND on base-URL for {DAV:}current-user-principal
#  2. PROPFIND for calendar-home-set property in caldav namespace
#  3. PROPFIND with depth: 1
# as documented at <https://stackoverflow.com/a/11673483>

# serialize calendar events
$log->debug('serialize calendar events...');
my $start;
if ( $ENV{CAL_DAV_NOW} ) {
	try { require DateTimeX::Easy }
	catch ($e) {
		$log->fatalf( 'failed parsing CAL_DAV_NOW: %s', $e ) && exit 2
	}
	$start = DateTimeX::Easy->new( $ENV{CAL_DAV_NOW} );
	$log->fatalf(
		'failed parsing CAL_DAV_NOW: unknown start time "%s"',
		$ENV{CAL_DAV_NOW}
		)
		&& exit 2
		unless defined $start;
}
$start ||= DateTime->now;
my $end = $start->clone->add( months => 6 );
$log->infof( 'will pick events between %s and %s', $start, $end );
my $span   = DateTime::Span->from_datetimes( start => $start, end => $end );
my @events = sort {
		   DateTime->compare( $a->start, $b->start )
		|| DateTime->compare( $a->end,   $b->end )
		|| get_property_string( $a, 'summary' )
		cmp get_property_string( $b, 'summary' )
} $calendar->events($span);
if ( $log->is_trace ) {
	use DDP;
	p @events;
}
my $output_path;
if ($OUTPUT_FILE) {
	$output_path = path($OUTPUT_FILE);
	$output_path->parent->mkpath;
	$output_path->remove;
}

for (@events) {
	next unless $_->summary;
	print_event( $_, $_->start, $_->end, $output_path, );
}

sub print_event
{
	my ( $entry, $start, $end, $path ) = @_;

	if ( $log->is_trace ) {
		use DDP;
		p $entry;
		p $start;
		p $end;
		p $path;
	}
	my $summary     = get_property_string( $entry, 'summary' );
	my $description = get_property_string( $entry, 'description' );
	$description =~ s/\n\n[Pp]ris:\s*((?!\n).+)\s*\z//m;
	my $price = $1;
	my @attendees;
	if ( $entry->property('attendee') ) {
		for ( @{ $entry->property('attendee') } ) {
			push @attendees, decode_utf8 $_->parameters->{'CN'}
				|| $_->value =~ s/^mailto://r;
		}
	}
	my $location   = get_property_string( $entry, 'location' );
	my $date_begin = $start->strftime('%A %e. %B');
	my $time_begin = $start->strftime('%k.%M');
	my $time_end   = $end->strftime('%k.%M');
	my $time_brief = ucfirst("$date_begin kl. $time_begin");
	my $timespan
		= $time_end
		? ucfirst("$date_begin kl. $time_begin-$time_end")
		: undef;
	my %attachments;

	if ( $entry->property('attach') ) {
		for ( @{ $entry->property('attach') } ) {
			my $uri;
			try { $uri = URI->new( $_->value ) }
			catch ($e) {
				$log->errorf( 'failed to parse URI %s: %s', $uri, $e );
				next;
			}
			$uri->authority and $uri->host
				or next;
			push @{ $attachments{ $uri->host } }, $uri;
		}
	}

	$_ = "### $time_brief.";
	$_ .= " $summary"
		if $summary;
	$_ .= "\n$description";
	$_ .= "  \nMed " . join( ' og ', @attendees ) . '.'
		if @attendees;
	$_ .= "  \n**Mødested:** $location"
		if $location;
	$_ .= "  \n**Tid:** $timespan."
		if $timespan;
	$_ .= "  \n**Pris:** $price"
		if $price;
	$_ .= "  \n[Køb billet på Billetto]($attachments{'billetto.dk'}[0])"
		if $attachments{'billetto.dk'};
	$_ .= "  \n[Læs mere her]($attachments{'byvandring.nu'}[0])"
		if $attachments{'byvandring.nu'};
	$_ .= "\n\n---\n\n";

	if ($path) {
		$path->append_utf8($_);
	}
	else {
		print $_;
	}
}

sub get_property_string
{
	my ( $entry, $key ) = @_;

	return ''
		unless $entry->property($key);

	return decode_utf8 $entry->property($key)->[0]->value;
}

1;