Creates an SVG-File with a calender for a whole year

calender.kt

import java.awt.*
import java.awt.SystemColor.*
import java.io.*
import java.nio.charset.*
import java.nio.file.*
import java.time.*
import java.time.DayOfWeek.*
import java.time.Month.*
import java.time.temporal.*

val year = 2021
val marginLeft = 4
val marginRight = 6
val marginTop = 4
val marginBottom = 4
val availableWidth = 297.0 - marginLeft - marginRight
val availableHeight = 210.0 - marginTop - marginBottom

val monthFields = generateSequence(LocalDate.of(year, 1, 1)!!) { date ->
	date.plusDays(1).takeIf { it.year == year }
}
		.groupBy { it.get(ChronoField.MONTH_OF_YEAR) }
		.map { (month, days) ->
			val dayOfWeekOnFirst = days.first().dayOfWeek!!
			month to (1.rangeTo(dayOfWeekOnFirst.value).map { index ->
				Cell(right = CellText("%02d".format(month), "rgb(0%,0%,100%"))
						.takeIf { index == dayOfWeekOnFirst.value }
			} +
					days.map { day ->
						val week = day.get(WeekFields.ISO.weekOfWeekBasedYear())
						val dayOfWeek = day.dayOfWeek!!
						val weekYear = day.get(WeekFields.ISO.weekBasedYear())
						val leftCellText = when {
							(day.dayOfMonth == 1) && (month == 1) -> CellText("%02d".format(week), "rgb(60%,60%,60%)")
							dayOfWeek == WeekFields.ISO.firstDayOfWeek -> CellText("%02d".format(week), "rgb(60%,60%,60%)")
							(weekYear != year) && ((day.dayOfMonth == 2) && (day.month == JANUARY)) -> CellText("%02d".format(weekYear % 100), "rgb(40%,40%,40%)")
							(weekYear != year) && (dayOfWeek == WeekFields.ISO.firstDayOfWeek.plus(1)) -> CellText("%02d".format(weekYear % 100), "rgb(40%,40%,40%)")
							else -> null
						}
						val rightCellText = CellText("%02d".format(day.dayOfMonth), when (dayOfWeek) {
							SATURDAY -> "rgb(85%,0%,0%)"
							SUNDAY -> "rgb(100%,0%,0%)"
							else -> null
						})
						Cell(leftCellText, rightCellText)
					})
		}

val maxFields = monthFields.maxBy { it.second.size }!!.second.size

val svg = svg { svg ->
	monthFields
			.forEach { (month, days) ->
				days.forEachIndexed { index, field ->
					field?.run {
						left?.run {
							svg.text(marginLeft + availableWidth / 12 * (month - 1), marginTop + availableHeight / (maxFields + 1) * (index + 1), text, color)
						}
						svg.text(marginLeft + availableWidth / 12 * (month - 1) + 4, marginTop + availableHeight / (maxFields + 1) * (index + 1), right.text, right.color)
					}
				}
			}
}
File("calender-$year.svg").writeText(svg.toString(), Charsets.UTF_8)

data class Cell(val left: CellText? = null, val right: CellText)
data class CellText(val text: String, val color: String? = null)

fun svg(body: (Svg) -> Unit) =
		Svg().apply {
			body(this)
		}

class Svg {

	private val texts: MutableList<Text> = mutableListOf()

	fun text(x: Double, y: Double, text: String, color: String? = null) {
		texts += Text(x, y, text, color)
	}

	override fun toString(): String {
		return "<?xml version=\"1.0\" encoding=\"UTF-8\"?>" +
				"<svg xmlns=\"http://www.w3.org/2000/svg\" xmlns:xlink=\"http://www.w3.org/1999/xlink\" version=\"1.1\" baseProfile=\"full\" width=\"297mm\" height=\"210mm\" viewBox=\"0 0 297 210\">" +
				texts.joinToString(separator = "", transform = Any::toString) +
				"</svg>"
	}

}

class Text(private val x: Double, private val y: Double, private val text: String, private val color: String? = null) {
	private val font = "MonoSpatial"

	override fun toString() = "<text x=\"$x\" y=\"$y\" font-family=\"$font\" font-size=\"3.75\"${color?.let { " fill=\"$it\"" }
			?: ""}>$text</text>"

}