package apple2

import (
	"image"
	"image/color"
)

const (
	loResPixelWidth  = charWidth * 2
	loResPixelHeight = charHeight / 2
)

func getColorPatterns(light color.Color) [16][16]color.Color {
	/*
		For each lores pixel we have to fill 14 half mono pixels with
		the 4 bits of the color repeated. We will need to shift by 2 bits
		on the odd columns. Lets prepare 14+2 values for each color.
	*/

	var data [16][16]color.Color

	for ci := 0; ci < 16; ci++ {
		for cb := uint8(0); cb < 4; cb++ {
			bit := (ci >> cb) & 1
			var colour color.Color
			if bit == 0 {
				colour = color.Black
			} else {
				colour = light
			}
			for i := uint8(0); i < 4; i++ {
				data[ci][cb+4*i] = colour
			}
		}
	}
	return data

}

func snapshotLoResModeMono(a *Apple2, isSecondPage bool, isMixMode bool, light color.Color) *image.RGBA {
	text, columns, lines := getActiveText(a, false, isSecondPage, false)
	if isMixMode {
		lines -= textLinesMix
	}
	grLines := lines * 2

	size := image.Rect(0, 0, columns*loResPixelWidth, grLines*loResPixelHeight)
	img := image.NewRGBA(size)

	patterns := getColorPatterns(light)
	for l := 0; l < grLines; l++ {
		for c := 0; c < columns; c++ {
			char := text[(l/2)*columns+c]
			grPixel := char >> 4
			if l%2 == 0 {
				grPixel = char & 0xf
			}
			offset := (c % 2) * 2 // 2 pixel offset for odd lores pixels, 0 for even pixels

			// Insert the 14 half pixels required
			for i := 0; i < loResPixelWidth; i++ {
				v := patterns[grPixel][i+offset]
				// Repeat the same color for 4 lines
				for r := 0; r < loResPixelHeight; r++ {
					img.Set(c*loResPixelWidth+i, l*4+r, v)
				}
			}

		}
	}

	return img
}