#!/usr/bin/env python
from __future__ import print_function

import pandas as pd


class BestHits(object):

    def __init__(self, comparison_cols=['E'], query_name_col='q_name', 
                 subject_name_col='s_name', query_length_col='q_len',
                 subject_length_col='s_len'):
        '''Build a BestHits object to manage finding best or reciprocal best
        hits.

        Args:
            comparison_cols (list): Columns to compare when determining which
                hit is "best."
            query_name_col (str): The column with the query sequence names.
            subject_name_col (str): The column with the subject suquence names.
            query_length_col (str): The column with the query length.
            subject_length_col (str): The column with the subject length.
        '''

        self.comparison_cols = comparison_cols
        self.query_name_col = query_name_col
        self.subject_name_col = subject_name_col
        self.query_length_col = query_length_col
        self.subject_length_col = subject_length_col

    def best_hits(self, aln_df, inplace=True):
        '''Get the best hit for each query in the alignment DataFrame.

        Operates in-place. Sorts the hits by query name and then comparison_cols,
        then uses the drop_duplicates() function to remove all but the
        first hit for each query.

        Args:
            aln_df (DataFrame): The MAF alignment DataFrame.
            inplace (bool): If True, perform the operation in-place and
                return the same DataFrame. If False, return a copy.
        Returns:
            DataFrame with the best hits.
        '''

        if inplace:
            aln_df.sort_values(by=[self.query_name_col] + self.comparison_cols,
                               inplace=True)
            aln_df.drop_duplicates(subset=self.query_name_col, inplace=True)
            return aln_df
        else:
            return aln_df.sort_values(
                       by=[self.query_name_col] + self.comparison_cols
                   ).drop_duplicates(subset=self.query_name_col)

    def reciprocal_best_hits(self, aln_df_A, aln_df_B, inplace=False, drop=True):
        '''Given to DataFrames with reciprocal MAF alignments, get the
        reciprocal best hits.

        Uses the best_hits function to get best hits for each DataFrame,
        and then does an inner join to find the reciprocals.

        Args:
            aln_df_A (DataFrame): The query hits.
            aln_df_B (DataFrame): The subject hits.
            inplace (bool): Passed to the best_hits calls.
            drop (bool): Drop extraneous columns and rename.
        Returns:
            DataFrame with the reciprocal best hits.
        '''

        aln_df_A = self.best_hits(aln_df_A, inplace=inplace)
        aln_df_B = self.best_hits(aln_df_B, inplace=inplace)

        # Join between subject A and query B
        rbh_df = pd.merge(aln_df_A, aln_df_B, how='inner', 
                          left_on=self.subject_name_col, 
                          right_on=self.query_name_col,
                          suffixes=('_A', '_B'))

        # Select those where query A is the same as subject B
        rbh_df = rbh_df[(rbh_df[self.query_name_col+'_A'] == rbh_df[self.subject_name_col+'_B'])]

        # Renamed columns after join
        if drop:
            rename_d = {}
            for rbh_col in rbh_df.columns:
                trimmed_col, _, _ = rbh_col.rpartition('_')
                if rbh_col.endswith('_A'):
                    rename_d[rbh_col] = trimmed_col

            rbh_df.rename(columns=rename_d, inplace=True)

            return rbh_df[list(rename_d.values()) + ['q_frame']]
        else:
            return rbh_df


