package radarfetch

import (
	"fmt"
	"math"
)

func BuildCMAURL(base string, date int, hour int, minute int, z int, y int, x int) string {
	yyyy := date / 10000
	mm := (date / 100) % 100
	dd := date % 100
	return fmt.Sprintf("%s/tiles/China/RADAR_L3_MST_CREF_GISJPG_Tiles_CR/%04d%02d%02d/%02d/%02d/%d/%d/%d.bin",
		trimSlash(base), yyyy, mm, dd, hour, minute, z, y, x)
}

func Bounds4326(z, y, x int) (west, south, east, north, resDeg float64) {
	step := 360.0 / math.Ldexp(1.0, z)
	west = -180.0 + float64(x)*step
	east = west + step
	south = -90.0 + float64(y)*step
	north = south + step
	resDeg = step / 256.0
	return
}

func trimSlash(s string) string {
	n := len(s)
	for n > 0 && s[n-1] == '/' {
		s = s[:n-1]
		n--
	}
	return s
}