firehol/netdata

// 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/pkg/netdataapi"
    "github.com/netdata/netdata/go/plugins/pkg/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)
}