package main

import (
	"fmt"
	"image"
	"strings"
	"time"

	"github.com/otiai10/gosseract/v2"
	"gocv.io/x/gocv"
)

// Global reusable OCR client
var timestampOCRClient *gosseract.Client

// InitTimestampOCR initializes the reusable OCR client
func InitTimestampOCR() {
	timestampOCRClient = gosseract.NewClient()
	timestampOCRClient.SetPageSegMode(gosseract.PSM_SINGLE_LINE)
	timestampOCRClient.SetWhitelist("0123456789-: ")
}

// CloseTimestampOCR closes the OCR client
func CloseTimestampOCR() {
	if timestampOCRClient != nil {
		timestampOCRClient.Close()
	}
}

// extractTimestamp extracts and OCRs the timestamp from the top of the frame
// Returns: (secondsDifference, ocrDurationMs, error)
func extractTimestamp(frame gocv.Mat) (int, int64, error) {
	startTime := time.Now()
	
	// Extract 1024x68 region
	timestampRegion := frame.Region(image.Rect(0, 0, 1024, 68))
	defer timestampRegion.Close()
	
	// Downscale 50% (reduces OCR processing time)
	downscaled := gocv.NewMat()
	defer downscaled.Close()
	gocv.Resize(timestampRegion, &downscaled, image.Point{512, 34}, 0, 0, gocv.InterpolationArea)
	
	// Grayscale
	gray := gocv.NewMat()
	defer gray.Close()
	gocv.CvtColor(downscaled, &gray, gocv.ColorBGRToGray)
	
	// Binary threshold (Otsu automatically finds best threshold)
	binary := gocv.NewMat()
	defer binary.Close()
	gocv.Threshold(gray, &binary, 0, 255, gocv.ThresholdBinary|gocv.ThresholdOtsu)
	
	// Invert (white text on black → black text on white for better OCR)
	inverted := gocv.NewMat()
	defer inverted.Close()
	gocv.BitwiseNot(binary, &inverted)
	
	// Encode as PNG (lossless, better for text)
	buf, err := gocv.IMEncode(".png", inverted)
	if err != nil {
		return 0, time.Since(startTime).Milliseconds(), fmt.Errorf("failed to encode: %w", err)
	}
	defer buf.Close()
	
	// OCR with REUSED client (major speed boost)
	err = timestampOCRClient.SetImageFromBytes(buf.GetBytes())
	if err != nil {
		return 0, time.Since(startTime).Milliseconds(), fmt.Errorf("failed to set image: %w", err)
	}
	
	text, err := timestampOCRClient.Text()
	if err != nil {
		return 0, time.Since(startTime).Milliseconds(), fmt.Errorf("OCR failed: %w", err)
	}
	
	// Parse timestamp
	text = strings.TrimSpace(strings.ReplaceAll(text, "\n", ""))
	cameraTime, err := time.ParseInLocation("2006-01-02 15:04:05", text, time.Local)
	if err != nil {
		return 0, time.Since(startTime).Milliseconds(), fmt.Errorf("could not parse timestamp from: '%s'", text)
	}
	
	return int(time.Since(cameraTime).Seconds()), time.Since(startTime).Milliseconds(), nil
}