refactor: reorganize project in order to include automation (#1)

Reviewed-on: #1
Co-authored-by: Emmanuel BENOÎT <tseeker@nocternity.net>
Co-committed-by: Emmanuel BENOÎT <tseeker@nocternity.net>

pkg/plugin/plugin.go

@@ -0,0 +1,122 @@
+// Package plugin implements a helper that can be used to implement a Nagios,
+// Centreon, Icinga... service monitoring plugin.
+package plugin // import nocternity.net/gomonop/pkg/perfdata
+
+import (
+	"container/list"
+	"fmt"
+	"os"
+	"strings"
+
+	"nocternity.net/gomonop/pkg/perfdata"
+)
+
+// Status represents the 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
+
+// Plugin exit statuses.
+const (
+	OK Status = iota
+	WARNING
+	CRITICAL
+	UNKNOWN
+)
+
+// String representations of the plugin statuses.
+func (s Status) String() string {
+	return [...]string{"OK", "WARNING", "ERROR", "UNKNOWN"}[s]
+}
+
+// Plugin represents the monitoring plugin's state, including its 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
+	message   string
+	extraText *list.List
+	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
+	p.status = UNKNOWN
+	p.message = "no status set"
+	p.perfData = make(map[string]*perfdata.PerfData)
+	return p
+}
+
+// SetState sets the plugin's output code to `status` and its message to
+// the specified `message`.
+func (p *Plugin) SetState(status Status, message string) {
+	p.status = status
+	p.message = message
+}
+
+// AddLine adds the specified string to the extra output text buffer.
+func (p *Plugin) AddLine(line string) {
+	if p.extraText == nil {
+		p.extraText = list.New()
+	}
+	p.extraText.PushBack(line)
+}
+
+// AddLinef formats the input and adds it to the text buffer.
+func (p *Plugin) AddLinef(format string, data ...interface{}) {
+	p.AddLine(fmt.Sprintf(format, data...))
+}
+
+// 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 the "pd" argument 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 {
+		panic("duplicate performance data " + pd.Label)
+	}
+	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 strBuilder strings.Builder
+	strBuilder.WriteString(p.name)
+	strBuilder.WriteString(" ")
+	strBuilder.WriteString(p.status.String())
+	strBuilder.WriteString(": ")
+	strBuilder.WriteString(p.message)
+	if len(p.perfData) > 0 {
+		strBuilder.WriteString(" | ")
+		needSep := false
+		for _, data := range p.perfData {
+			if needSep {
+				strBuilder.WriteString(", ")
+			} else {
+				needSep = true
+			}
+			strBuilder.WriteString(data.String())
+		}
+	}
+	if p.extraText != nil {
+		for em := p.extraText.Front(); em != nil; em = em.Next() {
+			strBuilder.WriteString("\n")
+			//nolint:forcetypeassert // we want to panic if this isn't a string
+			strBuilder.WriteString(em.Value.(string))
+		}
+	}
+	fmt.Println(strBuilder.String())
+	os.Exit(int(p.status))
+}