1 files changed, 127 insertions, 0 deletions
diff --git a/src/go/plugin/go.d/agent/functions/manager.go b/src/go/plugin/go.d/agent/functions/manager.go
new file mode 100644
index 000000000..b7cdecd6a
--- /dev/null
+++ b/src/go/plugin/go.d/agent/functions/manager.go
@@ -0,0 +1,127 @@
+// SPDX-License-Identifier: GPL-3.0-or-later
+
+package functions
+
+import (
+	"context"
+	"encoding/json"
+	"fmt"
+	"log/slog"
+	"strconv"
+	"strings"
+	"sync"
+	"time"
+
+	"github.com/netdata/netdata/go/plugins/logger"
+	"github.com/netdata/netdata/go/plugins/plugin/go.d/agent/netdataapi"
+	"github.com/netdata/netdata/go/plugins/plugin/go.d/agent/safewriter"
+)
+
+func NewManager() *Manager {
+	return &Manager{
+		Logger: logger.New().With(
+			slog.String("component", "functions manager"),
+		),
+		api:              netdataapi.New(safewriter.Stdout),
+		input:            stdinInput,
+		mux:              &sync.Mutex{},
+		FunctionRegistry: make(map[string]func(Function)),
+	}
+}
+
+type Manager struct {
+	*logger.Logger
+
+	api *netdataapi.API
+
+	input input
+
+	mux              *sync.Mutex
+	FunctionRegistry map[string]func(Function)
+}
+
+func (m *Manager) Run(ctx context.Context) {
+	m.Info("instance is started")
+	defer func() { m.Info("instance is stopped") }()
+
+	var wg sync.WaitGroup
+
+	wg.Add(1)
+	go func() { defer wg.Done(); m.run(ctx) }()
+
+	wg.Wait()
+
+	<-ctx.Done()
+}
+
+func (m *Manager) run(ctx context.Context) {
+	for {
+		select {
+		case <-ctx.Done():
+			return
+		case line, ok := <-m.input.lines():
+			if !ok {
+				return
+			}
+
+			var fn *Function
+			var err error
+
+			// FIXME:  if we are waiting for FUNCTION_PAYLOAD_END and a new FUNCTION* appears,
+			// we need to discard the current one and switch to the new one
+			switch {
+			case strings.HasPrefix(line, "FUNCTION "):
+				fn, err = parseFunction(line)
+			case strings.HasPrefix(line, "FUNCTION_PAYLOAD "):
+				fn, err = parseFunctionWithPayload(ctx, line, m.input)
+			case line == "":
+				continue
+			default:
+				m.Warningf("unexpected line: '%s'", line)
+				continue
+			}
+
+			if err != nil {
+				m.Warningf("parse function: %v ('%s')", err, line)
+				continue
+			}
+			if fn == nil {
+				continue
+			}
+
+			function, ok := m.lookupFunction(fn.Name)
+			if !ok {
+				m.Infof("skipping execution of '%s': unregistered function", fn.Name)
+				m.respf(fn, 501, "unregistered function: %s", fn.Name)
+				continue
+			}
+			if function == nil {
+				m.Warningf("skipping execution of '%s': nil function registered", fn.Name)
+				m.respf(fn, 501, "nil function: %s", fn.Name)
+				continue
+			}
+
+			function(*fn)
+		}
+	}
+}
+
+func (m *Manager) lookupFunction(name string) (func(Function), bool) {
+	m.mux.Lock()
+	defer m.mux.Unlock()
+
+	f, ok := m.FunctionRegistry[name]
+	return f, ok
+}
+
+func (m *Manager) respf(fn *Function, code int, msgf string, a ...any) {
+	bs, _ := json.Marshal(struct {
+		Status  int    `json:"status"`
+		Message string `json:"message"`
+	}{
+		Status:  code,
+		Message: fmt.Sprintf(msgf, a...),
+	})
+	ts := strconv.FormatInt(time.Now().Unix(), 10)
+	m.api.FUNCRESULT(fn.UID, "application/json", string(bs), strconv.Itoa(code), ts)
+}