from enum import IntEnum

from aiokafka.metrics.compound_stat import AbstractCompoundStat, NamedMeasurable
from aiokafka.metrics.measurable import AnonMeasurable

from .histogram import Histogram
from .sampled_stat import AbstractSampledStat


class BucketSizing(IntEnum):
    CONSTANT = 0
    LINEAR = 1


class Percentiles(AbstractSampledStat, AbstractCompoundStat):
    """A compound stat that reports one or more percentiles"""

    def __init__(
        self, size_in_bytes, bucketing, max_val, min_val=0.0, percentiles=None
    ):
        super().__init__(0.0)
        self._percentiles = percentiles or []
        self._buckets = int(size_in_bytes / 4)
        if bucketing == BucketSizing.CONSTANT:
            self._bin_scheme = Histogram.ConstantBinScheme(
                self._buckets, min_val, max_val
            )
        elif bucketing == BucketSizing.LINEAR:
            if min_val != 0.0:
                raise ValueError("Linear bucket sizing requires min_val to be 0.0.")
            self.bin_scheme = Histogram.LinearBinScheme(self._buckets, max_val)
        else:
            raise ValueError(f"Unknown bucket type: {bucketing}")

    def stats(self):
        measurables = []

        def make_measure_fn(pct):
            return lambda config, now: self.value(config, now, pct / 100.0)

        for percentile in self._percentiles:
            measure_fn = make_measure_fn(percentile.percentile)
            stat = NamedMeasurable(percentile.name, AnonMeasurable(measure_fn))
            measurables.append(stat)
        return measurables

    def value(self, config, now, quantile):
        self.purge_obsolete_samples(config, now)
        count = sum(sample.event_count for sample in self._samples)
        if count == 0.0:
            return float("NaN")
        sum_val = 0.0
        quant = float(quantile)
        for b in range(self._buckets):
            for sample in self._samples:
                assert type(sample) is self.HistogramSample
                hist = sample.histogram.counts
                sum_val += hist[b]
                if sum_val / count > quant:
                    return self._bin_scheme.from_bin(b)
        return float("inf")

    def combine(self, samples, config, now):
        return self.value(config, now, 0.5)

    def new_sample(self, time_ms):
        return Percentiles.HistogramSample(self._bin_scheme, time_ms)

    def update(self, sample, config, value, time_ms):
        assert type(sample) is self.HistogramSample
        sample.histogram.record(value)

    class HistogramSample(AbstractSampledStat.Sample):
        def __init__(self, scheme, now):
            super(Percentiles.HistogramSample, self).__init__(0.0, now)
            self.histogram = Histogram(scheme)
