using System;
using NewLife.Data;

namespace NewLife.Algorithms
{
    /// <summary>
    /// 平均值采样算法
    /// </summary>
    public class AverageSampling : ISampling
    {
        /// <summary>
        /// 对齐模式。每个桶X轴对齐方式
        /// </summary>
        public AlignModes AlignMode { get; set; }

        /// <summary>
        /// 插值填充算法
        /// </summary>
        public IInterpolation Interpolation { get; set; } = new LinearInterpolation();

        /// <summary>
        /// 降采样处理。保留边界两个点
        /// </summary>
        /// <param name="data">原始数据</param>
        /// <param name="threshold">阈值，采样数</param>
        /// <returns></returns>
        public TimePoint[] Down(TimePoint[] data, Int32 threshold)
        {
            if (data == null || data.Length < 2) return data;
            if (threshold < 2 || threshold >= data.Length) return data;

            var buckets = SamplingHelper.SplitByAverage(data.Length, threshold, true);

            // 每个桶选择一个点作为代表
            var sampled = new TimePoint[buckets.Length];
            for (var i = 0; i < buckets.Length; i++)
            {
                var item = buckets[i];
                TimePoint point = default;
                var vs = 0.0;
                for (var j = item.Start; j < item.End; j++)
                {
                    vs += data[j].Value;
                }
                point.Value = vs / (item.End - item.Start);

                // 对齐
                point.Time = AlignMode switch
                {
                    AlignModes.Right => data[item.End - 1].Time,
                    AlignModes.Center => data[(Int32)Math.Round((item.Start + item.End - 1) / 2.0)].Time,
                    _ => data[item.Start].Time,
                };
                sampled[i] = point;
            }

            return sampled;
        }

        /// <summary>
        /// 混合处理，降采样和插值，不保留边界节点
        /// </summary>
        /// <param name="data">原始数据</param>
        /// <param name="size">桶大小。如60/3600/86400</param>
        /// <param name="offset">偏移量。时间不是对齐零点时使用</param>
        /// <returns></returns>
        public TimePoint[] Process(TimePoint[] data, Int32 size, Int32 offset = 0)
        {
            if (data == null || data.Length < 2) return data;
            if (size <= 1) return data;

            var xs = new Int64[data.Length];
            for (var i = 0; i < data.Length; i++) xs[i] = data[i].Time;

            var buckets = SamplingHelper.SplitByFixedSize(xs, size, offset);

            // 每个桶选择一个点作为代表
            var sampled = new TimePoint[buckets.Length];
            var last = 0;
            for (var i = 0; i < buckets.Length; i++)
            {
                // 断层，插值
                var item = buckets[i];
                if (item.Start < 0)
                {
                    // 取last用于插值起点，如果不存在，可以取0点
                    // 此时End指向下一个有效点，即使下一个桶也是断层
                    sampled[i].Time = i * size;
                    sampled[i].Value = Interpolation.Process(data, last, item.End, i);
                    continue;
                }

                TimePoint point = default;
                var vs = 0.0;
                for (var j = item.Start; j < item.End; j++)
                {
                    vs += data[j].Value;
                }
                last = item.End - 1;
                point.Value = vs / (item.End - item.Start);

                // 对齐
                point.Time = AlignMode switch
                {
                    AlignModes.Right => (i + 1) * size - 1,
                    AlignModes.Center => data[(Int32)Math.Round((i + 0.5) * size)].Time,
                    _ => i * size,
                };
                sampled[i] = point;
            }

            return sampled;
        }
    }
}