namespace Encoder;

public static class Utils {
    static Tuple<int, int>[] QPTable = new Tuple<int, int>[] {
        new(1280*720,  64),
        new(1920*1080, 96),
        new(3840*2160, 128),
        new(5760*2880, 96), //VR6K
        new(8128*4096, 120) //VR8K
    }.OrderBy(t => t.Item1).ToArray();
    
    static float lerp(float v0, float v1, float t) {
        return v0 + t * (v1 - v0);
    }

    static float remap(float value, float from1, float to1, float from2, float to2) {
        return from2 + (value - from1) * (to2 - from2) / (to1 - from1);
    }
    
    public static int ToQPValue(int W, int H) {
        int pixels = W * H;
        for (var i = 0; i < QPTable.Length; i++) {
            var t = QPTable[i];
            if (pixels <= t.Item1) {
                var minQP = QPTable[i - 1].Item2;
                var maxQP = QPTable[i].Item2;
                
                var minPixels = QPTable[i - 1].Item1;
                var maxPixels = QPTable[i].Item1;
                var tPixels = remap(pixels, minPixels, maxPixels, 0, 1);

                return (int)lerp(minQP, maxQP, tPixels);
            }
        }
        // Return the highest QP for anything higher than 8K VR
        return QPTable.Last().Item2;
    }
}