from typing import List, Optional, Sequence

from .math_round_div import round_div
from .monitor_series_window import MetricSample, series_window
from .monitor_rollup_types import Bucket

_MAX_BUCKETS = 10000


def rollup(samples: Sequence[MetricSample], from_: int, to: int, bucket_seconds: int) -> List[Bucket]:
    """One row per bucket from `from` to `to`, empty buckets included so a chart
    shows gaps as gaps. Buckets are aligned to `from`; the last is clipped to `to`."""
    if not isinstance(bucket_seconds, int) or isinstance(bucket_seconds, bool):
        raise ValueError("bucketSeconds must be a whole number of seconds")
    if bucket_seconds < 1:
        raise ValueError("bucketSeconds must be at least 1, received %d" % bucket_seconds)
    inside = series_window(samples, from_, to)
    n = -((from_ - to) // bucket_seconds)
    if n > _MAX_BUCKETS:
        raise ValueError("too many buckets: %d, at most %d" % (n, _MAX_BUCKETS))
    out: List[Bucket] = []
    j = 0
    for i in range(n):
        start = from_ + i * bucket_seconds
        end = min(start + bucket_seconds, to)
        count = 0
        total = 0
        lo: Optional[int] = None
        hi: Optional[int] = None
        last: Optional[int] = None
        while j < len(inside) and inside[j].at < end:
            v = inside[j].value
            count += 1
            total += v
            lo = v if lo is None or v < lo else lo
            hi = v if hi is None or v > hi else hi
            last = v
            j += 1
        avg = None if count == 0 else round_div(total, count, "half-up")
        out.append(Bucket(start=start, end=end, count=count, min=lo, max=hi, avg=avg, sum=total, last=last))
    return out