#!/usr/bin/perl

use v5.36;
use utf8;
use open qw(:std :encoding(UTF-8));
use autodie;
use Feature::Compat::Try;
use Feature::Compat::Class 0.07;

use FindBin qw($Bin);

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;
use Text::Xslate;

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, $SKELDIR, $OUTPUT_FILE );
$BASE_URI     = $ENV{CAL_DAV_URL_BASE};
$CALENDAR_URI = $ENV{CAL_DAV_URL_CALENDAR};
$SKELDIR      = $ENV{SKELDIR} || "$Bin/../templates";
$BASE_URI ||= shift @ARGV
	if @ARGV;
$CALENDAR_URI ||= shift @ARGV
	if @ARGV;
$OUTPUT_FILE = shift @ARGV
	if @ARGV;

class Calendar {
	field $log = Log::Any->get_logger;

	# borrow from Data::ICal::new() signature
	field $data : param     = undef;
	field $filename : param = undef;

	ADJUST {
		if ($data) {
			if ( $data isa Data::ICal ) { }
			else { $data = Data::ICal->new( data => $data ) }
		}
		elsif ($filename) { $data = Data::ICal->new( filename => $filename ) }

		if ( $log->is_trace ) {
			use DDP;
			p $data;
		}
	}

	# mimick Data::ICal::DateTime::events() signature
	method events ( $set = undef, $period = undef )
	{
		$log->infof(
			'will pick events between %s and %s',
			$set->start, $set->end
		) if $set;

		my @events = sort {
				   DateTime->compare( $a->begin, $b->begin )
				|| DateTime->compare( $a->end,   $b->end )
				|| $a->summary cmp $b->summary
		} map { Event->new( entry => $_ ) }
			$data->events( $set || (), $period || () );

		return @events;
	}
}

class Event {
	use Encode qw(decode_utf8);    # TODO: modernize CalDAV access instead

	field $log = Log::Any->get_logger;

	field $entry : param;

	field $begin : reader      = $entry->start;
	field $date_begin : reader = $begin->strftime('%A %e. %B');
	field $time_begin : reader = $begin->strftime('%k.%M');
	field $end : reader        = $entry->end;
	field $date_end : reader;
	field $time_end : reader;
	field $datespan : reader;
	field $timespan : reader;
	field $time_brief : reader;
	field $summary : reader
		= $entry->property('summary')
		? decode_utf8 $entry->property('summary')->[0]->value
		: '';
	field $description : reader
		= $entry->property('description')
		? decode_utf8 $entry->property('description')->[0]->value
		: '';
	field $location : reader
		= $entry->property('location')
		? decode_utf8 $entry->property('location')->[0]->value
		: '';
	field $price : reader;
	field @attendees;
	field @attachments;

	ADJUST {
		if ( defined $end ) {
			$date_end = $end->strftime('%A %e. %B');
			$time_end = $end->strftime('%k.%M');
		}
		$datespan
			= ( defined $end and $date_end ne $date_begin )
			? ucfirst("$date_begin - $date_end")
			: ucfirst("$date_begin");
		$timespan
			= ( defined $end and not $entry->all_day )
			? ucfirst("$date_begin kl. $time_begin-$time_end")
			: undef;
		$time_brief
			= $entry->all_day
			? $datespan
			: ucfirst("$date_begin kl. $time_begin");
		$description =~ s/\n\n[Pp]ris:\s*((?!\n).+)\s*\z//m;
		$price = $1;

		if ( $entry->property('attendee') ) {
			for ( @{ $entry->property('attendee') } ) {
				push @attendees, decode_utf8 $_->parameters->{'CN'}
					|| $_->value =~ s/^mailto://r;
			}
		}
		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;
			}
		}

		if ( $log->is_trace ) {
			use DDP;
			p $entry;
			p $begin;
			p $end;
		}
	}

	method attendees   { !!@attendees   ? [@attendees]   : undef }
	method attachments { !!@attachments ? [@attachments] : undef }
}

# 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...');
	my $session = Cal::DAV->new(
		user => $user,
		pass => $pass,
		url  => $base_uri,
	);
	$session->get($calendar_uri)
		if $calendar_uri;
	$calendar = Calendar->new( data => $session->cal );
}
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 ) {
		$calendar = Calendar->new( filename => "$path" );
	}
	else {
		my $data;
		$path->visit( sub { $data .= $_->slurp_raw if $_->is_file } );
		$calendar = Calendar->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>

# select subset of 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 );
my $span   = DateTime::Span->from_datetimes( start => $start, end => $end );
my @events = $calendar->events($span);

# serialize calendar view
my $output_path;
if ($OUTPUT_FILE) {
	$output_path = path($OUTPUT_FILE);
	$output_path->parent->mkpath;
	$output_path->remove;
}

my %vars;
for (@events) {
	next unless $_->summary;
	push @{ $vars{events} }, $_;
}

my %tmpl;
$tmpl{list} = path($SKELDIR)->child('list.md')->slurp_utf8;

my $template = Text::Xslate->new(
	path   => \%tmpl,
	syntax => 'TTerse',
	type   => 'text',
);

my $content = $template->render( 'list', \%vars );

if ($output_path) {
	$output_path->append_utf8($content);
}
else {
	print $content;
}

1;