use v6;
unit module JK::Logging;

role Handler is export {
    method handle(Str:D $entry) { ... }
}

class StdoutHandler does Handler is export {
    method handle(Str:D $entry) {
        say $entry;
    }
}

enum Severity <debug info warn error>;

role LogEntry is export {
    has Str $.message;
}

role Formatter[::LogEntryType] is export {
    method format(Severity $severity, LogEntryType:D $entry) returns Str { ... }
}

class DefaultFormatter does Formatter[LogEntry] is export {
    method format(Severity $severity, LogEntry:D $entry) returns Str {
        return "$severity.uc(): $entry";
    }
}

role Logger[::LogEntryType] is export {
    method debug(LogEntryType:D $entry) { ... }
    method info(LogEntryType:D $entry) { ... }
    method warn(LogEntryType:D $entry) { ... }
    method err(LogEntryType:D $entry) { ... }
}


role DefaultLogger[LogEntry:U ::LogEntryType] does Logger[LogEntryType] is export {
    has Formatter[LogEntryType] $.formatter is rw;
    has Handler @handlers = StdoutHandler.new();

    submethod do-log(Severity $severity, LogEntryType:D $entry) {
        say $!formatter;
        my Str $formatted-entry = $!formatter.format($severity, $entry);
        for @handlers {
            $_.handle($formatted-entry);
        }
    }

    method debug(LogEntryType:D $entry) {
        self.do-log(Severity::debug, $entry);
    }

    method info(LogEntryType:D $entry) {
        self.do-log(Severity::info, $entry);
    }

    method warn(LogEntryType:D $entry) {
        self.do-log(Severity::warn, $entry);
    }

    method err(LogEntryType:D $entry) {
        self.do-log(Severity::error, $entry);
    }
}

my Logger %logger-registry{LogEntry};
%logger-registry{LogEntry} = DefaultLogger[LogEntry].new(:formatter(DefaultFormatter.new()));

sub registerLogger(LogEntry:U ::LogEntryType $logEntryType, Logger[LogEntryType] $logger) is export {
    unless %logger-registry{$logEntryType}:exists {
        %logger-registry{$logEntryType} = $logger;
    }
}

sub getLogger(Str $name, LogEntry:U $logEntryType=LogEntry) returns Logger[$logEntryType] is export {
    given %logger-registry{$logEntryType} {
        when $_ { $_.new(); }
        default { die "Cannot get logger for unknown LogEntry type $logEntryType" }
    }
}

my $logger = getLogger('anything');
my $entry = LogEntry.new(message => 'hello, logger');
$logger.info($entry);