package printer

import (
	"errors"
	"image"
	"math"
)

// PrinterDriver is the interface all label printer implementations must satisfy.
// The PRT Qutie driver, mock driver, and any future printer use this interface.
type PrinterDriver interface {
	// Connect opens the connection to the printer. Must be called before Print.
	Connect() error
	// Print sends a rendered label bitmap to the printer.
	// bitmap is raw 1-bit packed row-major data from ImageToRawBitmap.
	Print(bitmap []byte, width, height int) error
	// Disconnect closes the connection.
	Disconnect() error
}

var (
	// ErrNoDevice is returned when no printer matching the VID/PID is found.
	ErrNoDevice = errors.New("printer: no device found matching VID/PID")
	// ErrNotConnected is returned when Print is called before Connect.
	ErrNotConnected = errors.New("printer: not connected")
	// ErrEmptyBitmap is returned when an empty or nil bitmap is passed to Print.
	ErrEmptyBitmap = errors.New("printer: bitmap is empty")
)

// ImageToRawBitmap converts an image.Image to 1-bit packed row-major bitmap.
// White pixels → 0, dark pixels → 1. Returns bytes, width, and height.
func ImageToRawBitmap(img image.Image) ([]byte, int, int) {
	b := img.Bounds()
	w, h := b.Max.X-b.Min.X, b.Max.Y-b.Min.Y
	rowBytes := int(math.Ceil(float64(w) / 8.0))
	out := make([]byte, rowBytes*h)
	for y := 0; y < h; y++ {
		for x := 0; x < w; x++ {
			r, g, bv, _ := img.At(b.Min.X+x, b.Min.Y+y).RGBA()
			// Luminance: pixel is dark if average < 50% of max (0xffff).
			lum := (r + g + bv) / 3
			if lum < 0x7fff {
				byteIdx := y*rowBytes + x/8
				out[byteIdx] |= 1 << (7 - uint(x%8))
			}
		}
	}
	return out, w, h
}