// Package mifare holds MIFARE Classic 1K layout helpers with no brand-specific memory map.
package mifare

import "fmt"

const (
	Sectors    = 16
	Blocks     = 64
	BlockSize  = 16
	SectorSize = 64
	Size1K     = 1024
)

// SectorOf returns the sector index for a block number (0–63).
func SectorOf(block int) int {
	return block / 4
}

// BlockRange returns the half-open block range [first, last) for a sector.
func BlockRange(sector int) (first, last int) {
	first = sector * 4
	last = first + 4
	return first, last
}

// SectorBytes returns the 64-byte slice for sector (0–15) from a 1K image.
func SectorBytes(image []byte, sector int) ([]byte, error) {
	if len(image) != Size1K {
		return nil, fmt.Errorf("image size: want %d got %d", Size1K, len(image))
	}
	if sector < 0 || sector >= Sectors {
		return nil, fmt.Errorf("sector %d out of range", sector)
	}
	off := sector * SectorSize
	return image[off : off+SectorSize], nil
}