"""
Numba 1D min/max kernels that can be shared by
* Dataframe / Series
* groupby
* rolling / expanding

Mirrors pandas/_libs/window/aggregation.pyx
"""
from __future__ import annotations

import numba
import numpy as np


@numba.jit(nopython=True, nogil=True, parallel=False)
def sliding_min_max(
    values: np.ndarray,
    start: np.ndarray,
    end: np.ndarray,
    min_periods: int,
    is_max: bool,
) -> np.ndarray:
    N = len(start)
    nobs = 0
    output = np.empty(N, dtype=np.float64)
    # Use deque once numba supports it
    # https://github.com/numba/numba/issues/7417
    Q: list = []
    W: list = []
    for i in range(N):
        curr_win_size = end[i] - start[i]
        if i == 0:
            st = start[i]
        else:
            st = end[i - 1]

        for k in range(st, end[i]):
            ai = values[k]
            if not np.isnan(ai):
                nobs += 1
            elif is_max:
                ai = -np.inf
            else:
                ai = np.inf
            # Discard previous entries if we find new min or max
            if is_max:
                while Q and ((ai >= values[Q[-1]]) or values[Q[-1]] != values[Q[-1]]):
                    Q.pop()
            else:
                while Q and ((ai <= values[Q[-1]]) or values[Q[-1]] != values[Q[-1]]):
                    Q.pop()
            Q.append(k)
            W.append(k)

        # Discard entries outside and left of current window
        while Q and Q[0] <= start[i] - 1:
            Q.pop(0)
        while W and W[0] <= start[i] - 1:
            if not np.isnan(values[W[0]]):
                nobs -= 1
            W.pop(0)

        # Save output based on index in input value array
        if Q and curr_win_size > 0 and nobs >= min_periods:
            output[i] = values[Q[0]]
        else:
            output[i] = np.nan

    return output