refactor(pkg): refactor Plugin to make it easier to test

Writing the plugin's output string and exiting the program will no
longer take place in the plugin status itself. It will only be done in
the main program.

cmd/sslcert/main.go

@@ -215,9 +215,9 @@ func NewProgram() program.Program {
 	return program
 }
 
-// Terminate the monitoring check program.
-func (program *checkProgram) Done() {
-	program.plugin.Done()
+// Return the program's output value.
+func (program *checkProgram) Output() *plugin.Plugin {
+	return program.plugin
 }
 
 // Check the values that were specified from the command line. Returns true

cmd/zoneserial/main.go

@@ -85,13 +85,9 @@ func NewProgram() program.Program {
 	return program
 }
 
-// Terminate the monitoring check program.
-func (program *checkProgram) Done() {
-	if r := recover(); r != nil {
-		program.plugin.SetState(plugin.StatusUnknown, "Internal error")
-		program.plugin.AddLinef("Error info: %v", r)
-	}
-	program.plugin.Done()
+// Return the program's output value.
+func (program *checkProgram) Output() *plugin.Plugin {
+	return program.plugin
 }
 
 // Check the values that were specified from the command line. Returns true if the arguments made sense.

main.go

@@ -7,6 +7,7 @@ import (
 
 	"nocternity.net/gomonop/cmd/sslcert"
 	"nocternity.net/gomonop/cmd/zoneserial"
+	"nocternity.net/gomonop/pkg/plugin"
 	"nocternity.net/gomonop/pkg/program"
 	"nocternity.net/gomonop/pkg/version"
 )
@@ -55,7 +56,17 @@ func getProgram() program.Program {
 
 func main() {
 	program := getProgram()
-	defer program.Done()
+
+	output := program.Output()
+	defer func() {
+		if r := recover(); r != nil {
+			output.SetState(plugin.StatusUnknown, "Internal error")
+			output.AddLinef("Error info: %v", r)
+		}
+		fmt.Println(output.String())
+		os.Exit(output.ExitCode())
+	}()
+
 	if program.CheckArguments() {
 		program.RunCheck()
 	}

pkg/plugin/plugin.go

@@ -5,7 +5,6 @@ package plugin // import nocternity.net/gomonop/pkg/perfdata
 import (
 	"container/list"
 	"fmt"
-	"os"
 	"strings"
 
 	"nocternity.net/gomonop/pkg/perfdata"
@@ -70,10 +69,9 @@ 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() {
+// String generates the plugin's text output from its name, status, text data
+// and performance data.
+func (p *Plugin) String() string {
 	var strBuilder strings.Builder
 	strBuilder.WriteString(p.name)
 	strBuilder.WriteString(" ")
@@ -99,6 +97,10 @@ func (p *Plugin) Done() {
 			strBuilder.WriteString(em.Value.(string))
 		}
 	}
-	fmt.Println(strBuilder.String())
-	os.Exit(int(p.status))
+	return strBuilder.String()
+}
+
+// ExitCode returns the plugin's exit code.
+func (p *Plugin) ExitCode() int {
+	return int(p.status)
 }

pkg/program/program.go

@@ -1,9 +1,11 @@
 package program // import nocternity.net/gomonop/pkg/program
 
+import "nocternity.net/gomonop/pkg/plugin"
+
 type Program interface {
+	Output() *plugin.Plugin
 	CheckArguments() bool
 	RunCheck()
-	Done()
 }
 
 type Builder func() Program