Touhou/client/Assets/Game/Scripts/Util/Common/Random.cs

using System.Collections.Generic;
using UnityEngine;

namespace Game
{
    public static class GameRandom
    {
        private static System.Random _random;

        static GameRandom()
        {
            _random = new System.Random();
        }

        public static int Randint(int min, int max)
        {
            return _random.Next(min, max + 1);
        }

        public static float Random()
        {
            return Mathf.Abs((float)(_random.NextDouble())) % 1;
        }

        public static float Random(float min, float max)
        {
            return Random() * (max - min) + min;
        }

        public static float RandomRot(float rot, float angle)
        {
            var ret = rot - angle / 2 + GameRandom.Random(0, angle);
            return ret;
        }

        public static Vector3 RandomDir(Vector3 dir, float rot, float forbidRot)
        {
            var rotHalf = rot * 0.5f;
            var forbidRotHalf = forbidRot * 0.5f;
            var vNew = dir;
            if (rotHalf == 0) return vNew;
            if (rotHalf <= forbidRotHalf)
                forbidRotHalf = 0;

            var rotAdd = Random(forbidRotHalf, rotHalf) * RollSymbol(0.5f);
            vNew = Quaternion.AngleAxis(rotAdd, Vector3.up) * vNew;
            return vNew;
        }

        public static Vector3 RandomVector3(float min, float max)
        {
            return new Vector3(Random(min, max), 0, Random(min, max));
        }

        public static Vector3 RandomVector3(Vector3 vec, float range)
        {
            return vec + RandomVector3(-range, range);
        }

        public static T Pick<T>(List<T> list)
        {
            return (list.Count > 0 ? list[Randint(0, list.Count - 1)] : default(T));
        }

        public static List<T> Sample<T>(List<T> list, int pickNum)
        {
            var listCount = list.Count;
            if (listCount <= pickNum)
            {
                return list;
            }

            var ret = list.GetRange(0, pickNum);
            for (int i = pickNum; i < listCount; i++)
            {
                if (i / listCount > Random())
                {
                    ret[Randint(0, pickNum)] = list[i];
                }
            }

            return ret;
        }

        public static void Shuffle<T>(List<T> list)
        {
            var listCount = list.Count;
            for (int i = 0; i < listCount; i++)
            {
                var targetIndex = Randint(0, listCount - 1);
                (list[i], list[targetIndex]) = (list[targetIndex], list[i]);
            }
        }

        public static T Pick<T>(HashSet<T> set)
        {
            return Pick<T>(new List<T>(set));
        }

        public static bool Roll(float chance)
        {
            return Random() < chance;
        }

        public static float RollSymbol(float chance)
        {
            return Random() < chance ? 1 : -1;
        }
    }
}