fix: use plain color theme (#153)

* fix: use plain color theme

Show logs with INFO in plain white.
Show logs with WARN in dark yellow.
Show logs with ERROR in dark red.
Show logs with SUCCESS in dark green.

* feat: add loglevel option to colored-output flag

Adds a new 'loglevel' option to the existing -k/--colored-output flag
that provides log level-based coloring while preserving backward compatibility.

- Extends -k flag to support pod|line|loglevel|false options
- loglevel mode colors pod names (for pod differentiation) + log content based on log levels
- Preserves existing pod/line/false behavior unchanged
- Adds validation for colored-output option values
- Updates help text to document the new option

This addresses upstream feedback to provide log level coloring behind a flag
instead of breaking backward compatibility.

Author: sangshuduo

kubetail

@@ -86,8 +86,8 @@ where:
     -e, --regex             The type of name matching to use (regex|substring). Defaults to ${regex}.
     -j, --jq                If your output is json - use this jq-selector to parse it. Defaults to \"${default_jq_selector}\".
                             example: --jq \".logger + \\\" \\\" + .message\"
-    -k, --colored-output    Use colored output (pod|line|false).
-                            pod = only color pod name, line = color entire line, false = don't use any colors.
+    -k, --colored-output    Use colored output (pod|line|loglevel|false).
+                            pod = only color pod name, line = color entire line, loglevel = color pod name + log content based on log levels, false = don't use any colors.
                             Defaults to ${default_colored_output}.
     -z, --skip-colors       Comma-separated list of colors to not use in output.
                             If you have green foreground on black, this will skip dark grey and some greens: -z 2,8,10
@@ -248,6 +248,12 @@ else
 	exit 1
 fi
 
+# Validate colored_output option
+if [ "$colored_output" != "pod" ] && [ "$colored_output" != "line" ] && [ "$colored_output" != "loglevel" ] && [ "$colored_output" != "false" ]; then
+	echo "Invalid colored output option: $colored_output. Valid options are: pod, line, loglevel, false"
+	exit 1
+fi
+
 # Join function that supports a multi-character separator (copied from http://stackoverflow.com/a/23673883/398441)
 function join() {
 	# $1 is sep
@@ -381,7 +387,38 @@ for pod in ${matching_pods[@]}; do
 		fi
 
 		kubectl_cmd="${KUBECTL_BIN} ${context:+--context=${context}} logs ${pod} ${container} -f=${follow} --previous=${previous} --since=${since} --tail=${tail} ${namespace_arg} ${cluster}"
-		colorify_lines_cmd="while read -r; do echo \"$colored_line\" | tail -n +1; done"
+
+		if [ ${colored_output} == "loglevel" ]; then
+			# Log level based coloring with colored pod names
+			colorify_lines_cmd="while read -r; do
+				# Create colored prefix similar to pod mode
+				colored_prefix=\"${color_start}[${color_end}${color_index_prefix}${color_start}${display_name}]${color_end} \"
+
+				# Apply log level colorization to log content only, keeping pod name colored
+				if echo \"\$REPLY\" | grep -qE '\\b(INFO|info)\\b'; then
+					# INFO: plain white (default terminal color) for log content
+					colored_line=\"\$colored_prefix\$REPLY\"
+				elif echo \"\$REPLY\" | grep -qE '\\b(WARN|warn|WARNING|warning)\\b'; then
+					# WARN: dark yellow for log content
+					colored_line=\"\$colored_prefix\$(tput setaf 3)\$REPLY\$(tput sgr0)\"
+				elif echo \"\$REPLY\" | grep -qE '\\b(ERROR|error|ERR|err)\\b'; then
+					# ERROR: dark red for log content
+					colored_line=\"\$colored_prefix\$(tput setaf 1)\$REPLY\$(tput sgr0)\"
+				elif echo \"\$REPLY\" | grep -qE '\\b(SUCCESS|success)\\b'; then
+					# SUCCESS: dark green for log content
+					colored_line=\"\$colored_prefix\$(tput setaf 2)\$REPLY\$(tput sgr0)\"
+				else
+					# Default: plain log content with colored pod name
+					colored_line=\"\$colored_prefix\$REPLY\"
+				fi
+				echo \"\$colored_line\" | tail -n +1
+			done"
+		else
+			# Original coloring logic for pod/line/false modes
+			colorify_lines_cmd="while read -r; do
+				echo \"$colored_line\" | tail -n +1
+			done"
+		fi
 		if [ "z" == "z$jq_selector" ]; then
 			logs_commands+=("${kubectl_cmd} ${timestamps} | ${colorify_lines_cmd}");
 		else