From 77eca93c9dc74e7aa89739cbc129fd041ec962ae Mon Sep 17 00:00:00 2001
From: Michael Quigley <michael@quigley.com>
Date: Wed, 13 Nov 2024 16:15:10 -0500
Subject: [PATCH] first iteration of work on the subordinate process framework
 (#789)

---
 cmd/zrok/subordinate/tail.go | 85 ++++++++++++++++++++++++++++++++++++
 1 file changed, 85 insertions(+)
 create mode 100644 cmd/zrok/subordinate/tail.go

diff --git a/cmd/zrok/subordinate/tail.go b/cmd/zrok/subordinate/tail.go
new file mode 100644
index 00000000..a9f2a56a
--- /dev/null
+++ b/cmd/zrok/subordinate/tail.go
@@ -0,0 +1,85 @@
+package subordinate
+
+import (
+	"bytes"
+	"encoding/json"
+	"github.com/sirupsen/logrus"
+	"strings"
+)
+
+const (
+	MessageKey  = "msg"
+	RawMessage  = "raw"
+	BootMessage = "boot"
+)
+
+type Message map[string]interface{}
+
+type MessageHandler struct {
+	BootHandler      func(Message)
+	MessageHandler   func(Message)
+	MalformedHandler func(Message)
+	readBuffer       bytes.Buffer
+	booted           bool
+	bootComplete     chan struct{}
+	bootErr          error
+}
+
+func NewMessageHandler() *MessageHandler {
+	return &MessageHandler{
+		bootComplete: make(chan struct{}),
+	}
+}
+
+func (h *MessageHandler) Tail(data []byte) {
+	defer func() {
+		if r := recover(); r != nil {
+			logrus.Errorf("recovered: %v", r)
+		}
+	}()
+
+	h.readBuffer.Write(data)
+	if line, err := h.readBuffer.ReadString('\n'); err == nil {
+		line = strings.Trim(line, "\n \t")
+		msg := make(map[string]interface{})
+		if !h.booted {
+			if line[0] == '{' {
+				if err := json.Unmarshal([]byte(line), &msg); err == nil {
+					if v, found := msg[MessageKey]; found {
+						if vStr, ok := v.(string); ok {
+							if vStr == BootMessage {
+								h.BootHandler(msg)
+								h.booted = true
+								close(h.bootComplete)
+							} else {
+								h.MessageHandler(msg)
+							}
+						} else {
+							h.MalformedHandler(msg)
+						}
+					} else {
+						h.MalformedHandler(msg)
+					}
+				} else {
+					msg[MessageKey] = RawMessage
+					msg[RawMessage] = line
+					h.MessageHandler(msg)
+				}
+			} else {
+				msg[MessageKey] = RawMessage
+				msg[RawMessage] = line
+				h.MessageHandler(msg)
+			}
+		} else {
+			if line[0] == '{' {
+				if err := json.Unmarshal([]byte(line), &msg); err != nil {
+					logrus.Error(line)
+				}
+			} else {
+				msg[MessageKey] = RawMessage
+				msg[RawMessage] = line
+			}
+			h.MessageHandler(msg)
+		}
+	}
+}