#!/usr/bin/perl

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

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

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

use URI;
use IO::Prompter;
use Cal::DAV;
use iCal::Parser;
use List::Util qw(first);
use List::MoreUtils qw(nsort_by sort_by);
use DateTime;
use Try::Tiny;
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 );
$base_uri = URI->new($BASE_URI)
	if ($BASE_URI);
if ( !$base_uri or !$base_uri->authority ) {
	$log->fatal('bad base URI: must be an internet URI');
	exit 2;
}
$log->infof( 'will use base URI %s', $base_uri );
$calendar_uri = URI->new( $CALENDAR_URI || $base_uri );
if ( !$calendar_uri or !$calendar_uri->authority ) {
	$log->fatal('bad calendar URI: must be an internet URI');
	exit 2;
}
elsif ( $base_uri->eq($calendar_uri) ) {
	$calendar_uri = undef;
}
else {
	$log->infof( 'will use calendar URI %s', $calendar_uri );
}

# resolve credentials
$log->debug('resolve credentials...');
my ( $mach, $user, $pass );
if ( $base_uri->userinfo ) {
	( $user, $pass ) = split ':', $base_uri->userinfo;
}
$user ||= $ENV{CAL_DAV_USER};
$pass ||= $ENV{CAL_DAV_PASS};
if ( !$user or !$pass ) {
	$mach = Net::Netrc->lookup( $base_uri->host, $user );
}
if ($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 calendar data
$log->debug('fetch and parse calendar data...');
my $start    = DateTime->now;
my $end      = $start->clone->add( months => 1 );
my $calendar = Cal::DAV->new(
	user => $user,
	pass => $pass,
	url  => $base_uri,
);
$calendar->get($calendar_uri)
	if $calendar_uri;
if ( $log->is_trace ) {
	use DDP;
	p $calendar;
}

# index calendar entries
$log->debug('index calendar entries...');
my %calendar_entries;
for ( @{ $calendar->entries } ) {
	if ( 'VEVENT' eq $_->ical_entry_type ) {
		my $uid = try { $_->property('uid')->[0]->value };
		$uid ||= Data::ICal::Entry::Event->new()->property('uid')->[0]->value;
		$calendar_entries{VEVENT}{$uid} = $_;
	}
	else {
		# TODO
		next;
	}
}
if ( $log->is_trace ) {
	use DDP;
	p %calendar_entries;
}

# 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 $parser = iCal::Parser->new( start => $start, end => $end );
my $events = $parser->parse_strings( decode_utf8 $calendar->as_string );
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 my $year ( map { $_->value }
	nsort_by { $_->key } pairs %{ $events->{events} } )
{
	for my $month ( map { $_->value } nsort_by { $_->key } pairs %$year ) {
		for my $day ( map { $_->value } nsort_by { $_->key } pairs %$month ) {
			for (
				sort_by {
					$_->value->{DTSTART}
						. $_->value->{DTEND}
						. $_->value->{SUMMARY}
				}
				pairs %$day
				)
			{
				print_event(
					$calendar_entries{VEVENT}{ $_->key },
					$_->value,
					$output_path,
				);
			}
		}
	}
}

sub print_event
{
	my ( $calendar_event, $event, $path ) = @_;

	if ( $log->is_trace ) {
		use DDP;
		p $calendar_event;
		p $event;
	}
	my $summary     = unescape( $event->{SUMMARY} );
	my $description = unescape( $event->{DESCRIPTION} );
	$description =~ s/\n\n[Pp]ris:\s*((?!\n).+)\s*\z//m;
	my $price = $1;
	if ( $event->{ATTENDEE} ) {
		$description .= "\nMed ";
		$description .= join ' og ',
			map { $_->{CN} || $_->{value} =~ s/^mailto://r }
			@{ $event->{ATTENDEE} };
		$description .= '.';
	}
	my $location   = unescape( $event->{LOCATION} );
	my $time_begin = ucfirst( $event->{DTSTART}->strftime('%A') );
	$time_begin .= $event->{DTSTART}->strftime(' %e. %B kl. %k.%M');
	my $time_end = $event->{DTEND}->strftime('%k.%M');
	my %attachments;
	if ( $calendar_event->property('attach') ) {
		for ( @{ $calendar_event->property('attach') } ) {
			my $uri = try { URI->new( $_->value ) }
				or next;
			$uri->authority and $uri->host
				or next;
			push @{ $attachments{ $uri->host } }, $uri;
		}
	}

	$_ = <<"STRING";
### $time_begin. $summary
$description
STRING
	$_ .= "**Mødested:** $location  \n"
		if $location;
	$_ .= "**Tid:** ${time_begin}-${time_end}.  \n"
		if $time_begin and $time_end;
	$_ .= "**Pris:** $price  \n"
		if $price;
	$_ .= "[Køb billet på Billetto]($attachments{'billetto.dk'}[0])  \n"
		if $attachments{'billetto.dk'};
	$_ .= "\n---\n\n";

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

# unescape characters in iCalendar TEXT content strings
# should fully cover iCalendar 2.0 (rfc5545 and rfc6868)
sub unescape
{
	($_) = @_;

	s/\^n|\\[Nn]/\n/g;
	s/\^\'/\"/g;
	s/\^\^/^/g;
	s/\\([\\;,])/$1/g;

	return $_;
}

1;