export interface TileRange {
    xstart: number
    ystart: number
    xend: number
    yend: number
    total: number
    zoomlevel: number
}

export class Tiles {
    public static MapRange<T>(tileRange: TileRange, f: (x: number, y: number) => T): T[] {
        const result: T[] = []
        const total = tileRange.total
        if (total > 100000) {
            throw `Tilerange too big (z is ${tileRange.zoomlevel}, total tiles needed: ${tileRange.total})`
        }
        for (let x = tileRange.xstart; x <= tileRange.xend; x++) {
            for (let y = tileRange.ystart; y <= tileRange.yend; y++) {
                const t = f(x, y)
                result.push(t)
            }
        }
        return result
    }

    /**
     * Calculates the tile bounds of the
     * @param z
     * @param x
     * @param y
     * @returns [[maxlat, minlon], [minlat, maxlon]]
     */
    static tile_bounds(z: number, x: number, y: number): [[number, number], [number, number]] {
        return [
            [Tiles.tile2lat(y, z), Tiles.tile2long(x, z)],
            [Tiles.tile2lat(y + 1, z), Tiles.tile2long(x + 1, z)],
        ]
    }

    static tile_bounds_lon_lat(
        z: number,
        x: number,
        y: number
    ): [[number, number], [number, number]] {
        return [
            [Tiles.tile2long(x, z), Tiles.tile2lat(y, z)],
            [Tiles.tile2long(x + 1, z), Tiles.tile2lat(y + 1, z)],
        ]
    }

    /**
     * Returns the centerpoint [lon, lat] of the specified tile
     * @param z
     * @param x
     * @param y
     */
    static centerPointOf(z: number, x: number, y: number): [number, number] {
        return [
            (Tiles.tile2long(x, z) + Tiles.tile2long(x + 1, z)) / 2,
            (Tiles.tile2lat(y, z) + Tiles.tile2lat(y + 1, z)) / 2,
        ]
    }

    static tile_index(z: number, x: number, y: number): number {
        return (x * (2 << z) + y) * 100 + z
    }

    /**
     * Given a tile index number, returns [z, x, y]
     * @param index
     * @returns 'zxy'
     */
    static tile_from_index(index: number): [number, number, number] {
        const z = index % 100
        const factor = 2 << z
        index = Math.floor(index / 100)
        const x = Math.floor(index / factor)
        return [z, x, index % factor]
    }

    /**
     * Return x, y of the tile containing (lat, lon) on the given zoom level
     */
    static embedded_tile(lat: number, lon: number, z: number): { x: number; y: number; z: number } {
        return { x: Tiles.lon2tile(lon, z), y: Tiles.lat2tile(lat, z), z: z }
    }

    static TileRangeBetween(
        zoomlevel: number,
        lat0: number,
        lon0: number,
        lat1: number,
        lon1: number
    ): TileRange {
        const t0 = Tiles.embedded_tile(lat0, lon0, zoomlevel)
        const t1 = Tiles.embedded_tile(lat1, lon1, zoomlevel)

        const xstart = Math.min(t0.x, t1.x)
        const xend = Math.max(t0.x, t1.x)
        const ystart = Math.min(t0.y, t1.y)
        const yend = Math.max(t0.y, t1.y)
        const total = (1 + xend - xstart) * (1 + yend - ystart)

        return {
            xstart: xstart,
            xend: xend,
            ystart: ystart,
            yend: yend,
            total: total,
            zoomlevel: zoomlevel,
        }
    }

    private static tile2long(x, z) {
        return (x / Math.pow(2, z)) * 360 - 180
    }

    private static tile2lat(y, z) {
        const n = Math.PI - (2 * Math.PI * y) / Math.pow(2, z)
        return (180 / Math.PI) * Math.atan(0.5 * (Math.exp(n) - Math.exp(-n)))
    }

    private static lon2tile(lon, zoom) {
        return Math.floor(((lon + 180) / 360) * Math.pow(2, zoom))
    }

    private static lat2tile(lat, zoom) {
        return Math.floor(
            ((1 -
                Math.log(Math.tan((lat * Math.PI) / 180) + 1 / Math.cos((lat * Math.PI) / 180)) /
                    Math.PI) /
                2) *
                Math.pow(2, zoom)
        )
    }
}