from typing import Collection, Tuple, Optional, Union

import pandas as pd
import numpy as np
from numpy import linalg as la
from scipy.sparse import issparse
from anndata import AnnData

from .. import logging as logg
from .._utils import sanitize_anndata


def _design_matrix(
    model: pd.DataFrame, batch_key: str, batch_levels: Collection[str],
) -> pd.DataFrame:
    """\
    Computes a simple design matrix.
    Parameters
    --------
    model
        Contains the batch annotation
    batch_key
        Name of the batch column
    batch_levels
        Levels of the batch annotation
    Returns
    --------
    The design matrix for the regression problem
    """
    import patsy

    design = patsy.dmatrix(
        "~ 0 + C(Q('{}'), levels=batch_levels)".format(batch_key),
        model,
        return_type="dataframe",
    )
    model = model.drop([batch_key], axis=1)
    numerical_covariates = model.select_dtypes('number').columns.values

    logg.info(f"Found {design.shape[1]} batches\n")
    other_cols = [c for c in model.columns.values if c not in numerical_covariates]

    if other_cols:
        col_repr = " + ".join("Q('{}')".format(x) for x in other_cols)
        factor_matrix = patsy.dmatrix(
            "~ 0 + {}".format(col_repr), model[other_cols], return_type="dataframe"
        )

        design = pd.concat((design, factor_matrix), axis=1)
        logg.info(f"Found {len(other_cols)} categorical variables:")
        logg.info("\t" + ", ".join(other_cols) + '\n')

    if numerical_covariates is not None:
        logg.info(f"Found {len(numerical_covariates)} numerical variables:")
        logg.info("\t" + ", ".join(numerical_covariates) + '\n')

        for nC in numerical_covariates:
            design[nC] = model[nC]

    return design


def _standardize_data(
    model: pd.DataFrame, data: pd.DataFrame, batch_key: str,
) -> Tuple[pd.DataFrame, pd.DataFrame, np.ndarray, np.ndarray]:
    """\
    Standardizes the data per feature.
    The aim here is to make mean and variance be comparable across batches.
    Parameters
    --------
    model
        Contains the batch annotation
    data
        Contains the Data
    batch_key
        Name of the batch column in the model matrix
    Returns
    --------
    s_data
        Standardized Data
    design
        Batch assignment as one-hot encodings
    var_pooled
        Pooled variance per feature
    stand_mean
        Feature-wise mean
    """

    # compute the design matrix
    batch_items = model.groupby(batch_key).groups.items()
    batch_levels, batch_info = zip(*batch_items)
    n_batch = len(batch_info)
    n_batches = np.array([len(v) for v in batch_info])
    n_array = float(sum(n_batches))

    design = _design_matrix(model, batch_key, batch_levels)

    # compute pooled variance estimator
    B_hat = np.dot(np.dot(la.inv(np.dot(design.T, design)), design.T), data.T)
    grand_mean = np.dot((n_batches / n_array).T, B_hat[:n_batch, :])
    var_pooled = (data - np.dot(design, B_hat).T) ** 2
    var_pooled = np.dot(var_pooled, np.ones((int(n_array), 1)) / int(n_array))

    # Compute the means
    if np.sum(var_pooled == 0) > 0:
        print(f'Found {np.sum(var_pooled == 0)} features with zero variance.')
    stand_mean = np.dot(
        grand_mean.T.reshape((len(grand_mean), 1)), np.ones((1, int(n_array)))
    )
    tmp = np.array(design.copy())
    tmp[:, :n_batch] = 0
    stand_mean += np.dot(tmp, B_hat).T

    # need to be a bit careful with the zero variance features
    # just set the zero variance features to zero in the standardized data
    s_data = np.where(
        var_pooled == 0,
        0,
        ((data - stand_mean) / np.dot(np.sqrt(var_pooled), np.ones((1, int(n_array))))),
    )
    s_data = pd.DataFrame(s_data, index=data.index, columns=data.columns)

    return s_data, design, var_pooled, stand_mean


def combat(
    adata: AnnData,
    key: str = 'batch',
    covariates: Optional[Collection[str]] = None,
    inplace: bool = True,
) -> Union[AnnData, np.ndarray, None]:
    """\
    ComBat function for batch effect correction [Johnson07]_ [Leek12]_
    [Pedersen12]_.
    Corrects for batch effects by fitting linear models, gains statistical power
    via an EB framework where information is borrowed across features.
    This uses the implementation `combat.py`_ [Pedersen12]_.
    .. _combat.py: https://github.com/brentp/combat.py
    Parameters
    ----------
    adata
        Annotated data matrix
    key
        Key to a categorical annotation from :attr:`~anndata.AnnData.obs`
        that will be used for batch effect removal.
    covariates
        Additional covariates besides the batch variable such as adjustment
        variables or biological condition. This parameter refers to the design
        matrix `X` in Equation 2.1 in [Johnson07]_ and to the `mod` argument in
        the original combat function in the sva R package.
        Note that not including covariates may introduce bias or lead to the
        removal of biological signal in unbalanced designs.
    inplace
        Whether to replace adata.X or to return the corrected data
    Returns
    -------
    Depending on the value of `inplace`, either returns the corrected matrix or
    or modifies `adata.X`.
    """

    # check the input
    if key not in adata.obs_keys():
        raise ValueError('Could not find the key {!r} in adata.obs'.format(key))

    if covariates is not None:
        cov_exist = np.isin(covariates, adata.obs_keys())
        if np.any(~cov_exist):
            missing_cov = np.array(covariates)[~cov_exist].tolist()
            raise ValueError(
                'Could not find the covariate(s) {!r} in adata.obs'.format(missing_cov)
            )

        if key in covariates:
            raise ValueError('Batch key and covariates cannot overlap')

        if len(covariates) != len(set(covariates)):
            raise ValueError('Covariates must be unique')

    # only works on dense matrices so far
    if issparse(adata.X):
        X = adata.X.A.T
    else:
        X = adata.X.T
    data = pd.DataFrame(data=X, index=adata.var_names, columns=adata.obs_names,)

    sanitize_anndata(adata)

    # construct a pandas series of the batch annotation
    model = adata.obs[[key] + (covariates if covariates else [])]
    batch_info = model.groupby(key).indices.values()
    n_batch = len(batch_info)
    n_batches = np.array([len(v) for v in batch_info])
    n_array = float(sum(n_batches))

    # standardize across features using a pooled variance estimator
    logg.info("Standardizing Data across features.\n")
    s_data, design, var_pooled, stand_mean = _standardize_data(model, data, key)

    # fitting the parameters on the standardized data
    logg.info("Fitting L/S model and finding priors\n")
    batch_design = design[design.columns[:n_batch]]
    # first estimate of the additive batch effect
    gamma_hat = (
        la.inv(batch_design.T @ batch_design) @ batch_design.T @ s_data.T
    ).values
    delta_hat = []

    # first estimate for the multiplicative batch effect
    for i, batch_idxs in enumerate(batch_info):
        delta_hat.append(s_data.iloc[:, batch_idxs].var(axis=1))

    # empirically fix the prior hyperparameters
    gamma_bar = gamma_hat.mean(axis=1)
    t2 = gamma_hat.var(axis=1)
    # a_prior and b_prior are the priors on lambda and theta from Johnson and Li (2006)
    a_prior = list(map(_aprior, delta_hat))
    b_prior = list(map(_bprior, delta_hat))

    logg.info("Finding parametric adjustments\n")
    # gamma star and delta star will be our empirical bayes (EB) estimators
    # for the additive and multiplicative batch effect per batch and subject
    gamma_star, delta_star = [], []
    for i, batch_idxs in enumerate(batch_info):
        # temp stores our estimates for the batch effect parameters.
        # temp[0] is the additive batch effect
        # temp[1] is the multiplicative batch effect
        gamma, delta = _it_sol(
            s_data.iloc[:, batch_idxs].values,
            gamma_hat[i],
            delta_hat[i].values,
            gamma_bar[i],
            t2[i],
            a_prior[i],
            b_prior[i],
        )

        gamma_star.append(gamma)
        delta_star.append(delta)

    logg.info("Adjusting data\n")
    bayesdata = s_data
    gamma_star = np.array(gamma_star)
    delta_star = np.array(delta_star)

    # we now apply the parametric adjustment to the standardized data from above
    # loop over all batches in the data
    for j, batch_idxs in enumerate(batch_info):
        # we basically substract the additive batch effect, rescale by the ratio
        # of multiplicative batch effect to pooled variance and add the overall feature
        # wise mean
        dsq = np.sqrt(delta_star[j, :])
        dsq = dsq.reshape((len(dsq), 1))
        denom = np.dot(dsq, np.ones((1, n_batches[j])))
        numer = np.array(
            bayesdata.iloc[:, batch_idxs]
            - np.dot(batch_design.iloc[batch_idxs], gamma_star).T
        )
        bayesdata.iloc[:, batch_idxs] = numer / denom

    vpsq = np.sqrt(var_pooled).reshape((len(var_pooled), 1))
    bayesdata = bayesdata * np.dot(vpsq, np.ones((1, int(n_array)))) + stand_mean

    # put back into the adata object or return
    if inplace:
        adata.X = bayesdata.values.transpose()
    else:
        return bayesdata.values.transpose()


def _it_sol(
    s_data: np.ndarray,
    g_hat: np.ndarray,
    d_hat: np.ndarray,
    g_bar: float,
    t2: float,
    a: float,
    b: float,
    conv: float = 0.0001,
) -> Tuple[np.ndarray, np.ndarray]:
    """\
    Iteratively compute the conditional posterior means for gamma and delta.
    gamma is an estimator for the additive batch effect, deltat is an estimator
    for the multiplicative batch effect. We use an EB framework to estimate these
    two. Analytical expressions exist for both parameters, which however depend on each other.
    We therefore iteratively evalutate these two expressions until convergence is reached.
    Parameters
    --------
    s_data
        Contains the standardized Data
    g_hat
        Initial guess for gamma
    d_hat
        Initial guess for delta
    g_bar, t_2, a, b
        Hyperparameters
    conv: float, optional (default: `0.0001`)
        convergence criterium
    Returns:
    --------
    gamma
        estimated value for gamma
    delta
        estimated value for delta
    """

    n = (1 - np.isnan(s_data)).sum(axis=1)
    g_old = g_hat.copy()
    d_old = d_hat.copy()

    change = 1
    count = 0

    # They need to be initialized for numba to properly infer types
    g_new = g_old
    d_new = d_old
    # we place a normally distributed prior on gamma and and inverse gamma prior on delta
    # in the loop, gamma and delta are updated together. they depend on each other. we iterate until convergence.
    while change > conv:
        g_new = (t2 * n * g_hat + d_old * g_bar) / (t2 * n + d_old)
        sum2 = s_data - g_new.reshape((g_new.shape[0], 1)) @ np.ones(
            (1, s_data.shape[1])
        )
        sum2 = sum2 ** 2
        sum2 = sum2.sum(axis=1)
        d_new = (0.5 * sum2 + b) / (n / 2.0 + a - 1.0)

        change = max(
            (abs(g_new - g_old) / g_old).max(), (abs(d_new - d_old) / d_old).max()
        )
        g_old = g_new  # .copy()
        d_old = d_new  # .copy()
        count = count + 1

    return g_new, d_new


def _aprior(delta_hat):
    m = delta_hat.mean()
    s2 = delta_hat.var()
    return (2 * s2 + m ** 2) / s2


def _bprior(delta_hat):
    m = delta_hat.mean()
    s2 = delta_hat.var()
    return (m * s2 + m ** 3) / s2
