From b86fdf53b97988a969296c31642333daf1ee9019 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Emmanuel=20Beno=C3=AEt?= <tseeker@nocternity.net>
Date: Sun, 3 Jan 2021 11:59:05 +0100
Subject: [PATCH] Short documentation for the plugin state code

---
 cmd/check_ssl_certificate/main.go |  6 +++---
 plugin/plugin.go                  | 20 +++++++++++++++++++-
 2 files changed, 22 insertions(+), 4 deletions(-)

diff --git a/cmd/check_ssl_certificate/main.go b/cmd/check_ssl_certificate/main.go
index 0c7f92a..29a23e8 100644
--- a/cmd/check_ssl_certificate/main.go
+++ b/cmd/check_ssl_certificate/main.go
@@ -93,17 +93,17 @@ func main() {
 		}
 		dn := strings.ToLower(certificate.Subject.String())
 		if !strings.HasPrefix(dn, fmt.Sprintf("cn=%s,", flags.hostname)) {
-			p.SetState(plugin.ERROR, "incorrect certificate CN")
+			p.SetState(plugin.CRITICAL, "incorrect certificate CN")
 			return
 		}
 	} else if !findHostname(certificate, flags.hostname) {
-		p.SetState(plugin.ERROR, "host name not found in SAN domain names")
+		p.SetState(plugin.CRITICAL, "host name not found in SAN domain names")
 		return
 	}
 	timeLeft := certificate.NotAfter.Sub(time.Now())
 	tlDays := int((timeLeft + 86399*time.Second) / (24 * time.Hour))
 	if flags.crit > 0 && tlDays <= flags.crit {
-		p.SetState(plugin.ERROR, fmt.Sprintf("certificate will expire in %d days (<= %d)", tlDays, flags.crit))
+		p.SetState(plugin.CRITICAL, fmt.Sprintf("certificate will expire in %d days (<= %d)", tlDays, flags.crit))
 	} else if flags.warn > 0 && tlDays <= flags.warn {
 		p.SetState(plugin.WARNING, fmt.Sprintf("certificate will expire in %d days (<= %d)", tlDays, flags.warn))
 	} else {
diff --git a/plugin/plugin.go b/plugin/plugin.go
index 68b1df7..b9ccfcd 100644
--- a/plugin/plugin.go
+++ b/plugin/plugin.go
@@ -1,3 +1,4 @@
+// Package that represents a monitoring plugin.
 package plugin
 
 import (
@@ -8,12 +9,15 @@ import (
 	"strings"
 )
 
+// Return status of the monitoring plugin. The corresponding integer
+// value will be used as the program's exit code, to be interpreted
+// by the monitoring system.
 type Status int
 
 const (
 	OK Status = iota
 	WARNING
-	ERROR
+	CRITICAL
 	UNKNOWN
 )
 
@@ -21,6 +25,9 @@ func (s Status) String() string {
 	return [...]string{"OK", "WARNING", "ERROR", "UNKNOWN"}[s]
 }
 
+// Monitoring plugin state, including a name, return status and message,
+// additional lines of text, and performance data to be encoded in the
+// output.
 type Plugin struct {
 	name      string
 	status    Status
@@ -29,6 +36,7 @@ type Plugin struct {
 	perfData  map[string]perfdata.PerfData
 }
 
+// `New` creates the plugin with `name` as its name and an unknown status.
 func New(name string) *Plugin {
 	p := new(Plugin)
 	p.name = name
@@ -38,12 +46,15 @@ func New(name string) *Plugin {
 	return p
 }
 
+// `SetState` sets the plugin's output code to `status` and its message to
+// the specified `message`. Any extra text is cleared.
 func (p *Plugin) SetState(status Status, message string) {
 	p.status = status
 	p.message = message
 	p.extraText = nil
 }
 
+// `AddLine` adds `line` to the extra output text.
 func (p *Plugin) AddLine(line string) {
 	if p.extraText == nil {
 		p.extraText = list.New()
@@ -51,12 +62,16 @@ func (p *Plugin) AddLine(line string) {
 	p.extraText.PushBack(line)
 }
 
+// `AddLines` add the specified `lines` to the output text.
 func (p *Plugin) AddLines(lines []string) {
 	for _, line := range lines {
 		p.AddLine(line)
 	}
 }
 
+// `AddPerfData` adds performance data described by `pd` to the output's
+// performance data. If two performance data records are added for the same
+// label, the program panics.
 func (p *Plugin) AddPerfData(pd perfdata.PerfData) {
 	_, exists := p.perfData[pd.Label]
 	if exists {
@@ -65,6 +80,9 @@ func (p *Plugin) AddPerfData(pd perfdata.PerfData) {
 	p.perfData[pd.Label] = pd
 }
 
+// `Done` generates the plugin's text output from its name, status, text data
+// and performance data, before exiting with the code corresponding to the
+// status.
 func (p *Plugin) Done() {
 	var sb strings.Builder
 	sb.WriteString(p.name)