log: improve the most common use case (#19242)

vlib/log/common.v

@@ -0,0 +1,69 @@
+module log
+
+import term
+
+// Level defines the possible log levels, used by Log.set_level()
+pub enum Level {
+	disabled = 0 // lowest level, disables everything else
+	fatal // disables error, warn, info and debug
+	error // disables warn, info and debug
+	warn // disables info and debug
+	info // disables debug
+	debug
+}
+
+// LogTarget defines the possible log targets, that Log supports
+pub enum LogTarget {
+	console
+	file
+	both
+}
+
+// tag_to_cli returns the tag for log level `l` as a colored string.
+fn tag_to_cli(l Level) string {
+	return match l {
+		.disabled { '' }
+		.fatal { term.red('FATAL') }
+		.error { term.red('ERROR') }
+		.warn { term.yellow('WARN ') }
+		.info { term.white('INFO ') }
+		.debug { term.magenta('DEBUG') }
+	}
+}
+
+// tag_to_file returns the tag for log level `l` as a string.
+fn tag_to_file(l Level) string {
+	return match l {
+		.disabled { '     ' }
+		.fatal { 'FATAL' }
+		.error { 'ERROR' }
+		.warn { 'WARN ' }
+		.info { 'INFO ' }
+		.debug { 'DEBUG' }
+	}
+}
+
+// level_from_tag returns the log level from the given string.
+// It returns `none` when it does not find a match.
+pub fn level_from_tag(tag string) ?Level {
+	return match tag {
+		'DISABLED' { Level.disabled }
+		'FATAL' { Level.fatal }
+		'ERROR' { Level.error }
+		'WARN' { Level.warn }
+		'INFO' { Level.info }
+		'DEBUG' { Level.debug }
+		else { none }
+	}
+}
+
+// target_from_label returns the log target from the given string.
+// It returns `none` when it does not find a match.
+pub fn target_from_label(label string) ?LogTarget {
+	return match label {
+		'console' { LogTarget.console }
+		'file' { LogTarget.file }
+		'both' { LogTarget.both }
+		else { none }
+	}
+}