# -*- coding: utf-8 -*-
from scipy import interpolate

from .basetest import BaseTest
from ..calculators import AsymptoticCalculator
from ..parameters import POI
from ..exceptions import POIRangeError


class UpperLimit(BaseTest):
    """Class for upper limit calculation.

        Args:
            * **calculator** (`sktats.hypotests.BaseCalculator`): calculator to use for computing the pvalues
            * **poinull** (List[`hypotests.POI`]): parameters of interest for the null hypothesis
            * **poialt** (List[`hypotests.POI`]): parameters of interest for the alternative hypothesis
            * **qtilde** (bool, optional): if `True` use the :math:`\widetilde{q}` test statistics else (default) use the :math:`q` test statistic

        Example with `zfit`:
            >>> import numpy as np
            >>> import zfit
            >>> from zfit.loss import ExtendedUnbinnedNLL
            >>> from zfit.minimize import Minuit

            >>> bounds = (0.1, 3.0)
            >>> zfit.Space('x', limits=bounds)

            >>> bkg = np.random.exponential(0.5, 300)
            >>> peak = np.random.normal(1.2, 0.1, 10)
            >>> data = np.concatenate((bkg, peak))
            >>> data = data[(data > bounds[0]) & (data < bounds[1])]
            >>> N = data.size
            >>> data = zfit.data.Data.from_numpy(obs=obs, array=data)

            >>> lambda_ = zfit.Parameter("lambda", -2.0, -4.0, -1.0)
            >>> Nsig = zfit.Parameter("Ns", 20., -20., N)
            >>> Nbkg = zfit.Parameter("Nbkg", N, 0., N*1.1)
            >>> signal = Nsig * zfit.pdf.Gauss(obs=obs, mu=1.2, sigma=0.1)
            >>> background = Nbkg * zfit.pdf.Exponential(obs=obs, lambda_=lambda_)
            >>> loss = ExtendedUnbinnedNLL(model=signal + background, data=data)

            >>> from hepstats.hypotests.calculators import AsymptoticCalculator
            >>> from hepstats.hypotests import UpperLimit
            >>> from hepstats.hypotests.parameters import POI, POIarray

            >>> calculator = AsymptoticCalculator(loss, Minuit())
            >>> poinull = POIarray(Nsig, np.linspace(0.0, 25, 20))
            >>> poialt = POI(Nsig, 0)
            >>> ul = UpperLimit(calculator, poinull, poialt)
            >>> ul.upperlimit(alpha=0.05, CLs=True)
            Observed upper limit: Nsig = 15.725784747406346
            Expected upper limit: Nsig = 11.927442041887158
            Expected upper limit +1 sigma: Nsig = 16.596396280677116
            Expected upper limit -1 sigma: Nsig = 8.592750403611896
            Expected upper limit +2 sigma: Nsig = 22.24864429383046
            Expected upper limit -2 sigma: Nsig = 6.400549971360598
    """

    def __init__(self, calculator, poinull, poialt, qtilde=False):

        super(UpperLimit, self).__init__(calculator, poinull, poialt)

        self._qtilde = qtilde

    @property
    def qtilde(self):
        """
        Returns True if qtilde test statistic is used, else False.
        """
        return self._qtilde

    def pvalues(self, CLs=True):
        """
        Returns p-values scanned for the values of the parameters of interest
        in the null hypothesis.

        Args:
            * **CLs** (bool, optional): if `True` uses pvalues as :math:`p_{cls}=p_{null}/p_{alt}=p_{clsb}/p_{clb}` else as :math:`p_{clsb} = p_{null}`

        Returns:
            pvalues (Dict): CLsb, CLs, expected (+/- sigma bands) p-values
        """
        pvalue_func = self.calculator.pvalue

        pnull, palt = pvalue_func(
            poinull=self.poinull, poialt=self.poialt, qtilde=self.qtilde, onesided=True
        )

        pvalues = {"clsb": pnull, "clb": palt}

        sigmas = [0.0, 1.0, 2.0, -1.0, -2.0]

        exppvalue_func = self.calculator.expected_pvalue

        result = exppvalue_func(
            poinull=self.poinull,
            poialt=self.poialt,
            nsigma=sigmas,
            CLs=CLs,
            qtilde=self.qtilde,
            onesided=True,
        )

        pvalues["expected"] = result[0]
        pvalues["expected_p1"] = result[1]
        pvalues["expected_p2"] = result[2]
        pvalues["expected_m1"] = result[3]
        pvalues["expected_m2"] = result[4]

        pvalues["cls"] = pnull / palt

        return pvalues

    def upperlimit(self, alpha=0.05, CLs=True, printlevel=1):
        """
        Returns the upper limit of the parameter of interest.

        Args:
            * **alpha** (float, default=0.05): significance level
            * **CLs** (bool, optional): if `True` uses pvalues as :math:`p_{cls}=p_{null}/p_{alt}=p_{clsb}/p_{clb}` else as :math:`p_{clsb} = p_{null}`
            * **printlevel** (int, default=1): if > 0 print the result

        Returns:
            limits (Dict): observed, expected (+/- sigma bands) upper limits

        """

        poinull = self.poinull

        # create a filter for -1 and -2 sigma expected limits
        bestfit = self.calculator.bestfit.params[poinull.parameter]["value"]
        filter = poinull.values >= bestfit

        if CLs:
            observed_key = "cls"
        else:
            observed_key = "clsb"

        to_interpolate = [observed_key] + [
            f"expected{i}" for i in ["", "_p1", "_m1", "_p2", "_m2"]
        ]

        limits = {}
        for k in to_interpolate:

            pvalues = self.pvalues(CLs)[k]
            values = poinull.values

            if k == observed_key:
                k = "observed"
                pvalues = pvalues[filter]
                values = values[filter]

            if min(pvalues) > alpha:
                if k in ["expected", "observed"]:
                    msg = f"The minimum of the scanned p-values is {min(pvalues)} which is larger than the"
                    msg += f" confidence level alpha = {alpha}. Try to increase the maximum POI value."
                    raise POIRangeError(msg)
                else:
                    limits[k] = None
                    continue

            tck = interpolate.splrep(values, pvalues - alpha, s=0)
            root = interpolate.sproot(tck)

            if len(root) > 1:
                root = root[0]

            try:
                limits[k] = float(root)
            except TypeError:
                limits[k] = None

        if printlevel > 0:
            print(f"\nObserved upper limit: {poinull.name} = {limits['observed']}")
            print(f"Expected upper limit: {poinull.name} = {limits['expected']}")
            for sigma in ["+1", "-1", "+2", "-2"]:
                key = sigma.replace("+", "p").replace("-", "m")
                print(
                    f"Expected upper limit {sigma} sigma: {poinull.name} = {limits[f'expected_{key}']}"
                )

        return limits
