package main

import (
	"fmt"
	"image"
	"image/color"
	"log"
	"os"
	"time"

	"gocv.io/x/gocv"
)

const (
	minimumMotionArea       = 3000 // Motion detection minimum area needed to move
	recordLengthAfterMotion = 30   // Number of seconds to keep recording going after motion was last detected
	motionDetectInterval    = 1    //number of seconds between motion detection attempts // TBD: Implement this, currently does nothing
)

var (
	lastMotionDetectedTime   time.Time
	currentRecording         *gocv.VideoWriter
	img, imgDelta, imgThresh gocv.Mat
	mog2                     gocv.BackgroundSubtractorMOG2
	osdColor                 color.RGBA
)

func init() {
	if len(os.Args) < 2 {
		fmt.Println("How to run:\n\tstorage-security [camera ID]")
		return
	}

	img = gocv.NewMat()
	imgDelta = gocv.NewMat()
	imgThresh = gocv.NewMat()
	mog2 = gocv.NewBackgroundSubtractorMOG2()
	osdColor = color.RGBA{0, 0, 255, 0}
}

func main() {
	defer img.Close()
	defer imgDelta.Close()
	defer imgThresh.Close()
	defer mog2.Close()

	// parse args
	deviceID := os.Args[1]

	webcam, err := gocv.OpenVideoCapture(deviceID)
	if err != nil {
		fmt.Printf("Error opening video capture device: %v\n", deviceID)
		return
	}
	defer webcam.Close()

	fmt.Printf("Start reading device: %v\n", deviceID)

	// This is a warm up ladies and gentlemen.  
	for i := 0; i < 20; i++ {
		if ok := webcam.Read(&img); !ok {
			fmt.Printf("Device closed: %v\n", deviceID)
			return
		}
	}

	// main loop
	for {
		if ok := webcam.Read(&img); !ok {
			fmt.Printf("Device closed: %v\n", deviceID)
			return
		}
		if img.Empty() {
			continue
		}

		if detectMotion(img) {
			// Determine if a new recording needs to start
			if time.Now().After(lastMotionDetectedTime.Add(time.Second * recordLengthAfterMotion)) {
				fileName := fmt.Sprintf("storage-%s.avi", time.Now().Format(time.RFC3339))
				log.Printf("motion detected, started recording to file named %s", fileName)
				currentRecording, err = gocv.VideoWriterFile(fileName, "MJPG", 25, img.Cols(), img.Rows(), true)
				if err != nil {
					fmt.Printf("error opening video writer device: %v\n", err)
					return
				}
			}
			// And always update the timestamp
			lastMotionDetectedTime = time.Now()
		}

		// Determine if we are currently recording and if so, then save the frame to the video
		if currentRecording != nil {
			// OSD / timestamp
			gocv.PutText(&img, time.Now().Format(time.RFC3339), image.Pt(10, 20), gocv.FontHersheyPlain, 1.2, osdColor, 2)

			currentRecording.Write(img)
			// Determine if we should stop recording
			if lastMotionDetectedTime.Add(time.Second * recordLengthAfterMotion).Before(time.Now()) {
				log.Printf("motion has not been detected for the last %d seconds stopping recording to file", recordLengthAfterMotion)
				err = currentRecording.Close()
				if err != nil {
					log.Printf("failed to close openCV file recording handle: %v", err)
				}
				currentRecording = nil
			}
		}
	}
}

// Returns true if motion detected in current frame
func detectMotion(frame gocv.Mat) bool {
	// first phase of cleaning up image, obtain foreground only
	mog2.Apply(frame, &imgDelta)

	// remaining cleanup of the image to use for finding contours.
	// first use threshold
	gocv.Threshold(imgDelta, &imgThresh, 25, 255, gocv.ThresholdBinary)

	// then dilate
	kernel := gocv.GetStructuringElement(gocv.MorphRect, image.Pt(3, 3))
	defer kernel.Close()
	gocv.Dilate(imgThresh, &imgThresh, kernel)

	// now find contours
	contours := gocv.FindContours(imgThresh, gocv.RetrievalExternal, gocv.ChainApproxSimple)
	for _, c := range contours {
		area := gocv.ContourArea(c)
		if area < minimumMotionArea {
			continue
		}
		return true
	}
	return false
}