import scipy.stats
import numpy as np
from scipy.linalg import qr, inv, pinv
import scipy.stats
from progress.bar import Bar
from matplotlib import pyplot as plt
class SPA:
    def _projections_qr(self, X, k, M):
        X_projected = X.copy()
        norms = np.sum((X ** 2), axis=0)
        norm_max = np.amax(norms)
        X_projected.iloc[:, k] = X_projected.iloc[:, k] * 2 * norm_max / norms[k]
        _, __, order = qr(X_projected.to_numpy(), 0, pivoting=True)
        return order[:M].T

    def _validation(self, Xcal, ycal, var_sel, Xval=None, yval=None):
        N = Xcal.shape[0]
        NV = Xval.shape[0] if Xval is not None else 0

        yhat, e = None, None
        if NV > 0:
            Xcal_ones = np.hstack([np.ones((N, 1)), Xcal.iloc[:, var_sel].to_numpy()])
            b = np.linalg.lstsq(Xcal_ones, ycal, rcond=None)[0]
            Xval_ones = np.hstack([np.ones((NV, 1)), Xval.iloc[:, var_sel].to_numpy()])
            yhat = Xval_ones.dot(b)
            e = yval - yhat
        else:
            yhat = np.zeros((N, 1))
            for i in range(N):
                cal = np.hstack([np.arange(i), np.arange(i + 1, N)])
                X = Xcal.iloc[cal, var_sel]
                y = ycal.iloc[cal]
                X_ones = np.hstack([np.ones((N - 1, 1)), X.to_numpy()])
                b = np.linalg.lstsq(X_ones, y, rcond=None)[0]
                xtest = Xcal.iloc[i, var_sel].to_numpy()
                yhat[i] = np.hstack([1, xtest]).dot(b)
            e = ycal.to_numpy() - yhat
        return yhat, e

    def spa(self, Xcal, ycal, m_min=1, m_max=None, Xval=None, yval=None, autoscaling=1, save_path=None):
        N, K = Xcal.shape
        m_max = min(N - 1, K) if m_max is None else m_max

        normalization_factor = Xcal.std(ddof=1, axis=0) if autoscaling else np.ones(K)
        Xcaln = (Xcal - Xcal.mean()) / normalization_factor

        SEL = np.zeros((m_max, K))
        with Bar('Projections :', max=K) as bar:
            for k in range(K):
                SEL[:, k] = self._projections_qr(Xcaln, k, m_max)
                bar.next()

        PRESS = np.full((m_max + 1, K), np.inf)
        with Bar('Evaluating subsets:', max=K * (m_max - m_min + 1)) as bar:
            for k in range(K):
                for m in range(m_min, m_max + 1):
                    var_sel = SEL[:m, k].astype(int)
                    _, e = self._validation(Xcal, ycal, var_sel, Xval, yval)
                    PRESS[m, k] = e.T @ e
                    bar.next()

        m_sel = np.argmin(PRESS, axis=0)
        k_sel = np.argmin(np.min(PRESS, axis=0))
        var_sel_phase2 = SEL[:m_sel[k_sel], k_sel].astype(int)

        Xcal2 = np.hstack([np.ones((N, 1)), Xcal.iloc[:, var_sel_phase2].to_numpy()])
        b = np.linalg.lstsq(Xcal2, ycal, rcond=None)[0]
        std_deviation = Xcal2.std(ddof=1, axis=0)
        relev = np.abs(b * std_deviation)[1:]

        index_decreasing_relev = np.argsort(-relev)
        PRESS_scree = np.empty(len(var_sel_phase2))
        for i in range(len(var_sel_phase2)):
            var_sel = var_sel_phase2[index_decreasing_relev[:i + 1]]
            _, e = self._validation(Xcal, ycal, var_sel, Xval, yval)
            PRESS_scree[i] = np.conj(e).T @ e

        RMSEP_scree = np.sqrt(PRESS_scree / len(e))
        alpha = 0.25
        dof = len(e)
        fcrit = scipy.stats.f.ppf(1 - alpha, dof, dof)
        PRESS_crit = np.min(PRESS_scree) * fcrit
        i_crit = np.min(np.nonzero(PRESS_scree < PRESS_crit))
        i_crit = max(m_min, i_crit)
        var_sel = var_sel_phase2[index_decreasing_relev[:i_crit]]

        # 绘图
        plt.figure()

        # 设置字体为 Times New Roman
        plt.rcParams['font.sans-serif'] = ['Times New Roman']
        plt.rcParams['axes.unicode_minus'] = False  # 确保负号显示正常

        # 设置标题、标签和网格
        plt.xlabel('Number of variables included in the model', fontsize=14)
        plt.ylabel('RMSE', fontsize=14)
        plt.title(f'Final number of selected variables: {len(var_sel)} (RMSE={RMSEP_scree[i_crit]:.4f})', fontsize=16)

        # 绘制 RMSEP 曲线
        plt.plot(RMSEP_scree, label='RMSEP Scree Plot')
        plt.scatter(i_crit, RMSEP_scree[i_crit], color='r', marker='s', label='Selected Point')

        # 添加网格和图例
        plt.grid(True)
        plt.legend()

        # 显示或保存图像
        if save_path:
            plt.savefig(save_path, bbox_inches='tight', dpi=300)
            print(f"图像已保存至: {save_path}")
        else:
            plt.show()
        return var_sel, var_sel_phase2

    def __repr__(self):
        return "SPA()"