Initial commit

.gitignore

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+*.db
+.envrc
+build

Makefile

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+# Makefile
+
+# Project name / binary name
+BINARY_NAME := furnacecheck
+
+# Default target
+all: build
+
+# Run go app from CLI
+run:
+	go run .
+
+install-linux:
+	sudo apt install libopencv-dev
+
+install-macos:
+	brew install opencv
+
+# Build for the host system
+build:
+	export CGO_CPPFLAGS="$(pkg-config --cflags opencv4)"
+	export CGO_LDFLAGS="$(pkg-config --libs opencv4 | sed 's/-lopencv_hdf//g' | sed 's/-lopencv_viz//g')"
+	go build -tags customenv -o build/$(BINARY_NAME) .
+
+# Cross-compile for macOS ARM64
+build-macos-arm64:
+	GOOS=darwin GOARCH=arm64 go build -o build/$(BINARY_NAME)-macos-arm64 .
+
+# Cross-compile for Linux AMD64
+build-linux-amd64:
+	GOOS=linux GOARCH=amd64 go build -o build/$(BINARY_NAME)-linux-amd64 .
+
+# Build all targets
+build-all: build-macos-arm64 build-linux-amd64
+
+# Clean build artifacts
+clean:
+	rm -rf build
+
+.PHONY: all build build-macos-arm64 build-linux-amd64 build-all clean

PROJECT.org

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+#+title: FurnaceCheck
+
+* Expectations
+* Usage
+* Backlog
+** DONE Ask ChatGPT to write the start of a furnacecheck app :project:personal:furnacecheck:chatgpt:feature:
+:PROPERTIES:
+:ID:       578e0c5b-7a6b-de9b-c9b6-b2edbe45ae82
+:END:
+
+** STRT Deploy basic check app to mundilfari :project:personal:furnacecheck:deploy:build:
+:PROPERTIES:
+:ID:       6fa2f545-470e-257d-50fd-97a6ee59a859
+:END:

README.md

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+FurnaceCheck
+============
+
+A simple microservice which reads in a webcam snapshot (preferrably from ustreamer) and outputs whether the furnace is on and which zones are being heated.

go.mod

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+module furnacecheck
+
+go 1.24.4

go.sum

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+gocv.io/x/gocv v0.42.0 h1:AAsrFJH2aIsQHukkCovWqj0MCGZleQpVyf5gNVRXjQI=
+gocv.io/x/gocv v0.42.0/go.mod h1:zYdWMj29WAEznM3Y8NsU3A0TRq/wR/cy75jeUypThqU=

main.go

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+package main
+
+import (
+	"bufio"
+	"bytes"
+	"fmt"
+	"image"
+	"image/jpeg"
+	"log"
+	"net/http"
+	"strings"
+	"time"
+)
+
+const (
+	streamURL = "http://furnace.service:8082/stream"
+
+	// 🔧 TUNE THESE ONCE
+	roiX = 1050
+	roiY = 760
+	roiW = 60
+	roiH = 10
+
+	// Thresholds
+	minAvgRed     = 90 // below this → light OFF
+	checkInterval = 2 * time.Second
+)
+
+func main() {
+	fmt.Println("Starting furnace light monitor")
+
+	var prevState bool // false = Off, true = On
+
+	for {
+		on, err := checkOnce()
+		if err != nil {
+			log.Println("Error:", err)
+			time.Sleep(time.Second)
+			continue
+		}
+
+		// Check for state change
+		if on != prevState {
+			if on {
+				fmt.Println("RED LIGHT: ON")
+			} else {
+				fmt.Println("RED LIGHT: OFF")
+			}
+
+			// Send notification
+			sendNtfyNotification(on)
+
+			prevState = on
+		}
+
+		time.Sleep(checkInterval)
+	}
+}
+
+func checkOnce() (bool, error) {
+	resp, err := http.Get(streamURL)
+	if err != nil {
+		return false, err
+	}
+	defer resp.Body.Close()
+
+	reader := bufio.NewReader(resp.Body)
+
+	for {
+		frame, err := readJPEGFrame(reader)
+		if err != nil {
+			return false, err
+		}
+
+		img, err := jpeg.Decode(bytes.NewReader(frame))
+		return isRedLightOn(img), nil
+	}
+
+}
+
+func readJPEGFrame(r *bufio.Reader) ([]byte, error) {
+	var buf bytes.Buffer
+
+	for {
+		line, err := r.ReadString('\n')
+		if err != nil {
+			return nil, err
+		}
+		if strings.HasPrefix(line, "--") {
+			break
+		}
+	}
+
+	for {
+		line, err := r.ReadString('\n')
+		if err != nil {
+			return nil, err
+		}
+		if line == "\r\n" {
+			break
+		}
+	}
+
+	for {
+		b, err := r.ReadByte()
+		if err != nil {
+			return nil, err
+		}
+		buf.WriteByte(b)
+
+		if buf.Len() > 2 {
+			data := buf.Bytes()
+			if data[len(data)-2] == 0xFF && data[len(data)-1] == 0xD9 {
+				return buf.Bytes(), nil
+			}
+		}
+	}
+}
+
+func isRedLightOn(img image.Image) bool {
+	bounds := img.Bounds()
+
+	x0 := clamp(roiX, bounds.Min.X, bounds.Max.X)
+	y0 := clamp(roiY, bounds.Min.Y, bounds.Max.Y)
+	x1 := clamp(roiX+roiW, bounds.Min.X, bounds.Max.X)
+	y1 := clamp(roiY+roiH, bounds.Min.Y, bounds.Max.Y)
+
+	var redSum int
+	var count int
+
+	for y := y0; y < y1; y++ {
+		for x := x0; x < x1; x++ {
+			r, g, b, _ := img.At(x, y).RGBA()
+			red := int(r >> 8)
+			green := int(g >> 8)
+			blue := int(b >> 8)
+
+			// ensure it's "red", not white glare
+			if red > 100 && red > green+30 && red > blue+30 {
+				redSum += red
+				count++
+			}
+		}
+	}
+
+	if count == 0 {
+		return false
+	}
+
+	avgRed := redSum / count
+	return avgRed > minAvgRed
+}
+
+func clamp(v, min, max int) int {
+	if v < min {
+		return min
+	}
+	if v > max {
+		return max
+	}
+	return v
+}
+
+func sendNtfyNotification(on bool) {
+	state := "OFF"
+	if on {
+		state = "ON"
+	}
+
+	url := "https://ntfy.unbl.ink/furnace"
+	body := bytes.NewBufferString(state)
+	req, err := http.NewRequest("POST", url, body)
+	if err != nil {
+		log.Println("Failed to create request:", err)
+		return
+	}
+	req.Header.Set("Title", "Furnace Power")
+	req.Header.Set("Priority", "high")
+
+	client := &http.Client{Timeout: 5 * time.Second}
+	resp, err := client.Do(req)
+	if err != nil {
+		log.Println("Failed to send notification:", err)
+		return
+	}
+	resp.Body.Close()
+}