"""
Utilities for iterating constructing data sets and iterating over
DNA sequence data.
"""
import math
import pandas as pd
import numpy as np
import logging
import pysam
import pyBigWig
import pybigtools
from Bio import motifs
from pyfaidx import Fasta
from multiprocessing import Pool
from pybedtools import Interval, BedTool
from pybedtools.helpers import chromsizes

from seqchromloader import config

logger = logging.getLogger(__name__)

class BigWig():
    def __init__(self, bw_path, backend='pyBigWig'):
        if backend == 'pyBigWig':
            self.bw = pyBigWig.open(bw_path)
        else:
            self.bw = pybigtools.open(bw_path)
        self.backend = backend

    def intervals(self, chrom):
        if self.backend == 'pyBigWig':
            return self.bw.intervals(chrom)
        else:
            return self.bw.records(chrom)

    def stats(self, chrom, type='mean'):
        if self.backend == 'pyBigWig':
            return self.bw.stats(chrom, type=type, exact=True)[0]
        else:
            return self.bw.values(chrom, missing=np.nan, bins=1, exact=True, summary='mean')[0].item()

    def values(self, chrom, start, end, missing=0):
        if self.backend == 'pyBigWig':
            return np.nan_to_num(self.bw.values(chrom, start, end)).astype(np.float32)
        else:
            return self.bw.values(chrom, start, end, missing=0.).astype(np.float32)
    
    def chroms(self):
        return self.bw.chroms()

    def close(self):
        self.bw.close()

def get_genome_sizes(gs=None, genome=None, to_filter=None, to_keep=None):
    """
    Loads the genome sizes file, filter or keep chromosomes
    
    :param gs: genome size file path, only one of `gs` and `genome` is required
    :type gs: string
    :param genome: genome build name, only one of `gs` and `genome` is required
    :type genome: string
    :param to_filter: list of chrmosomes to filter, mutually exclusive with `to_keep`
    :type to_filter: list
    :param to_keep: list of chromosomes to keep, mutually exclusive with `to_filter`
    :type to_keep: list
    """
    
    if gs:
        genome_sizes = pd.read_table(gs, header=None, usecols=[0,1], names=['chrom', 'length'])
    elif genome:
        genome_sizes = (pd.DataFrame(chromsizes(genome))
                        .T
                        .reset_index()
                        .rename(columns={"index":"chrom", 0:"start", 1:"end"})
                        .assign(length=lambda x: x["end"] - x["start"]))[["chrom", "length"]]
    else:
        raise Exception("Either gs or genome should be provided!")

    genome_sizes_filt = filter_chromosomes(genome_sizes, to_filter=to_filter, to_keep=to_keep)

    return genome_sizes_filt

def filter_chromosomes(coords, to_filter=None, to_keep=None):
    """
    Filter or keep the specified chromosomes
    
    :param coords: input coordinate dataframe, first column should be `chrom`
    :type coords: pandas.DataFrame
    :param to_filter: list of chrmosomes to filter, mutually exclusive with `to_keep`
    :type to_filter: list
    :param to_keep: list of chromosomes to keep, mutually exclusive with `to_filter`
    :type to_keep: list
    :rtype: filtered coordinate dataframe
    """
    
    if to_filter and to_keep:
        logger.error("Both to_filter and to_keep are provided, only to_filter will work under this circumstance!")
    
    if to_filter:
        coords_out = coords.copy()
        # note: using the str.contains method to remove all
        # contigs; for example: chrUn_JH584304
        bool_filter = ~(coords_out['chrom'].isin(to_filter))
        coords_out = coords_out[bool_filter]
    elif to_keep:
        coords_out = coords.copy()
        # keep only the to_keep chromosomes:
        # note: this is slightly different from to_filter, because
        # at a time, if only one chromosome is retained, it can be used
        # sequentially.
        bool_keep = coords_out['chrom'].isin(to_keep)
        coords_out = coords_out[bool_keep]
    else:
        coords_out = coords
    return coords_out

def make_random_shift(coords, L, buffer=0, rng=None):
    """
    This function takes as input a set of bed coordinates dataframe 
    It finds the mid-point for each record or Interval in the bed file,
    shifts the mid-point, and generates a windows of length L.

    If training window length is L, then we must ensure that the
    peak center is still within the training window.
    Therefore: -L/2 < shift < L/2
    To add in a buffer: -L/2 + buffer <= shift <= L/2 - 25
    
    :param coords: input coordinate dataframe, first 3 columns are: [chrom, start, end]
    :type coords: pandas.DataFrame
    :param L: training/shifting window size, the shifted midpoint should fall into the range -L/2 + buffer ~ L/2 + buffer
    :type L: integer
    :param buffer: buffer size
    :type buffer: integer
    :param rng: random number generator from numpy, optional
    :type rng: np.random.Generator
    :rtype: shifted coordinate dataframe
    """
    low = int(-L/2 + buffer)
    high = int(L/2 - buffer + 1)

    if rng is None:
        rng = np.random.default_rng()

    return (coords.assign(midpoint=lambda x: (x["start"]+x["end"])/2)
            .astype({"midpoint": int})
            .assign(midpoint=lambda x: x["midpoint"] + rng.integers(low=low, high=high, size=len(coords)))
            .apply(lambda s: pd.Series([s["chrom"], int(s["midpoint"]-L/2), int(s["midpoint"]+L/2)],
                                        index=["chrom", "start", "end"]), axis=1))

def make_flank(coords, L, d):
    """
    Make flanking regions by:
    1. Shift midpoint by d
    2. Expand midpoint to upstream/downstream by L/2
    
    :param coords: input coordinate dataframe, first 3 columns are: [chrom, start, end]
    :type coords: pandas.DataFrame
    :param L: window size of output regions
    :type L: integer
    :param d: shifting distance
    :type d: integer
    :rtype: shifted coordinate dataframe
    """
    return (coords.assign(midpoint=lambda x: (x["start"]+x["end"])/2)
                .astype({"midpoint": int})
                .assign(midpoint=lambda x: x["midpoint"] + d)
                .apply(lambda s: pd.Series([s["chrom"], int(s["midpoint"]-L/2), int(s["midpoint"]+L/2)],
                                            index=["chrom", "start", "end"]), axis=1))

def make_gc_match(coords, genome_fa, n, l=500, seed=1, gc_diff_max=0.05, max_attempts=1000, incl=None, excl=None):
    """
    Make GC amtch regions by:
    1. Randomly shuffle genomic regions by bedtools
    2. Keep regions of GC content matching the global original coordinate dataframes

    :param coords: input coordinate dataframe, first 3 columns are: [chrom, start, end]
    :type coords: pandas.DataFrame
    :param genome_fa: genome fasta file
    :type genome_fa: str
    :param l: random interval size
    :type l: integer
    :param n: number of returned GC matched regions
    :type n: int
    :param seed: random seed
    :type seed: int
    :param gc_diff_max: allowed gc percentage difference between input and returned regions
    :type gc_diff_max: float
    :param max_attempts: maximum number of attempts to shuffle the input dataframe for extracting GC matched regions
    :type max_attempts: int
    :param excl: regions that chopped regions shouldn't overlap with
    :type excl: BedTool object
    :param incl: regions that chopped regions should overlap with
    :type incl: BedTool object
    :rtype: GC match region coordinate dataframe
    """
    genome_pyfaidx = Fasta(genome_fa)
    # compute global gc percentage in input coordinate dataframe
    nuc_total, gc_total = 0, 0
    for item in coords.itertuples():
        subseq = genome_pyfaidx[item.chrom][item.start:item.end]
        nuc_total += len(subseq)
        gc_total += len(subseq) * subseq.gc
    gc_percent_global = gc_total / nuc_total
    logger.info(f"Global GC content of input regions is {gc_percent_global}")

    return make_gc_match_given_ratio(gc_percent_global, n, genome_fa, l=l, seed=seed, gc_diff_max=gc_diff_max, max_attempts=max_attempts, incl=incl, excl=excl)


def make_gc_match_given_ratio(gc_ratio, n, genome_fa, l=500, seed=1, gc_diff_max=0.05, max_attempts=1000, incl=None, excl=None):
    """
    Make GC amtch regions by:
    1. Randomly shuffle genomic regions by bedtools
    2. Keep regions of GC content matching the global original coordinate dataframes

    :param gc_ratio: expected GC ratio
    :type gc_ratio: float
    :param l: random interval size
    :type l: integer
    :param n: number of returned GC matched regions
    :type n: int
    :param seed: random seed
    :type seed: int
    :param gc_diff_max: allowed gc percentage difference between input and returned regions
    :type gc_diff_max: float
    :param max_attempts: maximum number of attempts to shuffle the input dataframe for extracting GC matched regions
    :type max_attempts: int
    :param excl: regions that chopped regions shouldn't overlap with
    :type excl: BedTool object
    :param incl: regions that chopped regions should overlap with
    :type incl: BedTool object
    :rtype: GC match region coordinate dataframe
    """
    genome_pyfaidx = Fasta(genome_fa)
    # shuffle regions and keep those of similar gc percentage
    rng = np.random.RandomState(seed)    # create a random number generator by given seed to get different shuffled regions per loop
    return_regions = []
    for i in range(max_attempts):
        regions_shuffle = random_coords(gs=f'{genome_fa}.fai', incl=incl, excl=excl, l=l, n=n, seed=rng.randint(1e5))
        for item in regions_shuffle.itertuples():
            subseq = genome_pyfaidx[item.chrom][item.start:item.end]
            if abs(subseq.gc - gc_ratio) <= gc_diff_max:
                return_regions.append(item)
                if len(return_regions) >= n:
                    return pd.DataFrame(return_regions)[['chrom', 'start', 'end']]
    
    logger.warning("Reach max attemps, return currently found GC matched regions, increase max_attempts if you need more regions")
    return pd.DataFrame(return_regions)[['chrom', 'start', 'end']]

def make_motif_match(motif: motifs.Motif, genome_fa, l=500, n=1000, gc_content=0.4, threshold=1.0, seed=1, max_attempts=1000, incl=None, excl=None):
    """
    Make regions containing the sub-sequence that matches the given motfi above a threshold

    :param motif: biopython motif object
    :type motif: motifs.Motif
    :param genome_fa: genome fasta file
    :type genome_fa: str
    :param l: random interval size
    :type l: integer
    :param n: number of returned motif matched regions
    :type n: int
    :param seed: random seed
    :type seed: int
    :param gc_content: background gc content to compute pwm score
    :type gc_content: float
    :param threshold: threshold to filter regions containing sub-sequence match the given motif by pssm score
    :type threshold: float
    :param max_attempts: maximum number of attempts to shuffle the input dataframe for extracting GC matched regions
    :type max_attempts: int
    :param excl: regions that chopped regions should overlap with
    :type excl: BedTool object
    :param incl: regions that chopped regions shouldn't overlap with
    :type incl: BedTool object
    :rtype: motif match region coordinate dataframe
    """
    assert len(motif) <= l  # make sure the interval len is larger than motif len
    # convert motif instance to pssm
    pwm = motif.counts.normalize(pseudocounts={'A':1-gc_content, 'C': gc_content, 'G': gc_content, 'T': 1-gc_content})
    pssm = pwm.log_odds({'A':(1-gc_content)/2,'C':gc_content/2,'G':gc_content/2,'T':(1-gc_content)/2})
    rpssm = pssm.reverse_complement()

    genome_pyfaidx = Fasta(genome_fa)
    rng = np.random.RandomState(seed)    # create a random number generator by given seed to get different shuffled regions per loop
    return_regions = []
    for i in range(max_attempts):
        regions_shuffle = random_coords(gs=f'{genome_fa}.fai', incl=incl, excl=excl, l=l, n=n, seed=rng.randint(1e5))
        for item in regions_shuffle.itertuples():
            subseq = genome_pyfaidx[item.chrom][item.start:item.end]
            if len(subseq) < len(motif):
                logger.warning("Skip subsequence due to length < motif length")
                continue
            pssm_score = pssm.calculate(subseq.seq); rpssm_score = rpssm.calculate(subseq.seq)

            if len(subseq) == len(motif):
                max_pssm_score = np.nan_to_num(pssm_score, nan=-100)
                max_rpssm_score = np.nan_to_num(rpssm_score, nan=-100) # if subseq len == motif len, calculate returns a single value
            else:
                max_pssm_score = max(np.nan_to_num(pssm_score, nan=-100))
                max_rpssm_score = max(np.nan_to_num(rpssm_score, nan=-100))

            max_score = max(max_pssm_score, max_rpssm_score)    

            if max_score > threshold:
                return_regions.append(item)
                if len(return_regions) >= n:
                    return pd.DataFrame(return_regions)[['chrom', 'start', 'end']]
    
    logger.warning("Reach max attempts, return currently found motif matched regions, increase max_attempts if you need more regions")
    return pd.DataFrame(return_regions)[['chrom', 'start', 'end']]
    
def random_coords(gs:str=None, genome:str=None, incl:BedTool=None, excl:BedTool=None,
                  l=500, n=1000, seed=1):
    """
    Randomly sample n intervals of length l from the genome,
    shuffle to make all intervals inside the desired regions 
    and outside exclusion regions
    
    :param gs: genome size file path, only one of `gs` and `genome` is required
    :type gs: string
    :param genome: genome build name, only one of `gs` and `genome` is required
    :type genome: string
    :param excl: regions that chopped regions should overlap with
    :type excl: BedTool object
    :param incl: regions that chopped regions shouldn't overlap with
    :type incl: BedTool object
    :param l: random interval size
    :type l: integer
    :param n: number of random intervals generated
    :type n: integer
    :param seed: random seed
    :type seed: integer
    """
    random_kwargs = {}
    shuffle_kwargs = {}
    if genome:
        random_kwargs.update({"genome": genome}); shuffle_kwargs.update({"genome": genome})
    elif gs:
        random_kwargs.update({"g": gs}); shuffle_kwargs.update({"g": gs})
    else:
        raise Exception("Either gs or genome should be provided!")
    
    if incl: shuffle_kwargs.update({"incl": incl.fn})
    if excl: shuffle_kwargs.update({"excl": excl.fn})
    
    return (BedTool()
            .random(l=l, n=n, seed=seed, **random_kwargs)
            .shuffle(seed=seed, **shuffle_kwargs)
            .to_dataframe()[["chrom", "start", "end"]])

def motif_scan(motif):
    """Scan the genome for regions that gives a high precision against given motif

    :arg1: TODO
    :returns: TODO

    """
    pass

def chop_genome(chroms:list=None, incl:BedTool=None, excl:BedTool=None, gs=None, genome=None, stride=500, l=500):
    """
    Given a genome size file and chromosome list,
    chop these chromosomes into intervals of length l,
    with include/exclude regions specified
    
    :param chroms: list of chromosomes to be chopped
    :type chroms: list of strings
    :param excl: regions that chopped regions should overlap with
    :type incl: BedTool object
    :param incl: regions that chopped regions shouldn't overlap with
    :type excl: BedTool object
    :param gs: genome size file path, only one of `gs` and `genome` is required
    :type gs: string
    :param genome: genome build name, only one of `gs` and `genome` is required
    :type genome: string
    :param stride: step size that everytime chopped region start coordinate moving forward by
    :type stride: int
    :param l: interval window size
    :type l: int
    :rtype: chopped intervals coordinate dataframe
    """
    def intervals_loop(chrom, start, stride, l, size):
        intervals = []
        while True:
            if (start + l) < size:
                intervals.append((chrom, start, start+l))
            else:
                break
            start += stride
        return pd.DataFrame(intervals, columns=["chrom", "start", "end"])
    
    genome_sizes = get_genome_sizes(gs=gs, genome=genome, to_keep=chroms)
    
    genome_chops = pd.concat([intervals_loop(i.chrom, 0, stride, l, i.length) 
                                for i in genome_sizes.itertuples()])
    genome_chops_bdt = BedTool.from_dataframe(genome_chops)
    
    if incl: genome_chops_bdt = genome_chops_bdt.intersect(incl, wa=True)
    if excl: genome_chops_bdt = genome_chops_bdt.intersect(excl, v=True)

    return genome_chops_bdt.to_dataframe()[["chrom", "start", "end"]]

def compute_mean_std_bigwig(bigwig):
    """
    
    Compute the overall mean and standard deviation of a given bigwig file

    :param bigwig: bigwig file path
    :type bigwig: str
    :rtype: (mean, stddev)
    """
    bw = BigWig(bigwig)
    
    # get chrom length list
    chroms = bw.chroms()
    
    # iterate chrom list to get mean and std
    ns = []; means = []; stds = []
    for chrom, length in chroms.items():
        # iterate all intervals to get the covered length
        length = sum([i[1]-i[0] for i in bw.intervals(chrom)])
        ns.append(length)
        means.append(bw.stats(chrom, type="mean", exact=True)[0])
        try:
            stds.append(bw.stats(chrom, type="std", exact=True)[0])
        except RuntimeError:
            logger.error(chrom)
            logger.error(length)
            raise Exception
    
    # compute overall metrics
    std_all = 0
    ns_sum = sum(ns); mean_all = sum([n*means[i] for i, n in enumerate(ns)])/ns_sum
    for i, n in enumerate(ns):
        std_all += n* math.pow(means[i]- mean_all, 2)
        std_all += n* math.pow(stds[i], 2)
    std_all /= ns_sum
    std_all = math.sqrt(std_all)
    
    return mean_all, std_all

class DNA2OneHot(object):
    def __init__(self):
        self.DNA2Index = {
            "A": 0,
            "C": 1, 
            "G": 2,
            "T": 3,
        }
    
    def __call__(self, dnaSeq):
        seqLen = len(dnaSeq)
        # initialize the matrix as 4 x len(dnaSeq)
        seqMatrix = np.zeros((4, len(dnaSeq)), dtype=np.float32)
        # change the value to matrix
        dnaSeq = dnaSeq.upper()
        for j in range(0, seqLen):
            if dnaSeq[j] == "N": continue
            try:
                seqMatrix[self.DNA2Index[dnaSeq[j]], j] = 1
            except KeyError as e:
                logger.error(f"Keyerror happened at position {j}: {dnaSeq[j]}, legal keys are: [A, C, G, T, N]")
                continue
        return seqMatrix

DNA2Index = {
        "A": 0,
        "C": 1, 
        "G": 2,
        "T": 3,
    }
    
def dna2OneHot(dnaSeq):
    """
    One-hot code input DNA sequence into an array of shape (4, len)
    Mapping is in the order of ACGT
    
    :param dnaSeq: input DNA sequence
    :type dnaSeq: string
    :rtype: numpy array of shape (4, len)
    """
    seqLen = len(dnaSeq)
    # initialize the matrix as 4 x len(dnaSeq)
    seqMatrix = np.zeros((4, len(dnaSeq)), dtype=np.float32)
    # change the value to matrix
    dnaSeq = dnaSeq.upper()
    for j in range(0, seqLen):
        if dnaSeq[j] == "N": continue
        try:
            seqMatrix[DNA2Index[dnaSeq[j]], j] = 1
        except KeyError as e:
            logger.error(f"Keyerror happened at position {j}: {dnaSeq[j]}, legal keys are: [A, C, G, T, N]")
            continue
    return seqMatrix

def rev_comp(inp_str):
    """
    Return reverse complemented sequence
    
    :param input_str: input DNA sequence
    :type input_str: string
    :rtype: reverse complemented DNA sequence
    """
    rc_dict = {'A': 'T', 'G': 'C', 'T': 'A', 'C': 'G', 'c': 'g',
               'g': 'c', 't': 'a', 'a': 't', 'n': 'n', 'N': 'N'}
    outp_str = list()
    for nucl in inp_str:
        outp_str.append(rc_dict[nucl])
    return ''.join(outp_str)[::-1]  

class BigWigInaccessible(Exception):
    def __init__(self, chrom, start, end, *args):
        super().__init__(*args)
        self.chrom = chrom
        self.start = start
        self.end = end

    def __str__(self) -> str:
        return f'Chromatin Info Inaccessible in region {self.chrom}:{self.start}-{self.end}'
    
def extract_bw(chrom, start, end, strand, bigwigs):
    chroms_array = []
    try:
        for idx, bigwig in enumerate(bigwigs):
            c = bigwig.values(chrom, start, end)
            if strand=="-":
                c = c[::-1] 
            chroms_array.append(c)
    except RuntimeError as e:
        logger.warning(e)
        logger.warning(f"RuntimeError happened when accessing {chrom}:{start}-{end}, it's probably due to at least one chromatin track bigwig doesn't have information in this region")
        raise BigWigInaccessible(chrom, start, end)
    chroms_array = np.vstack(chroms_array)  # create the chromatin track array, shape (num_tracks, length)
    
    return chroms_array

def extract_dnaOneHot(chrom, start, end, strand, genome_pyfaidx):
    seq = genome_pyfaidx[chrom][int(start):int(end)].seq
    if strand=="-":
        seq = rev_comp(seq)
    seq_array = dna2OneHot(seq)
    
    return seq_array

def extract_single_target(chrom, start, end, strand, target):
    if isinstance(target, pysam.AlignmentFile):
        target_array = np.array(target.count(chrom, start, end), dtype=np.float32)[np.newaxis]
    elif isinstance(target, BigWig):
        try:
            target_array = target.values(chrom, start, end)
            if strand=="-":
                target_array = target_array[::-1]
        except RuntimeError as e:
            logger.warning(e)
            logger.warning(f"RuntimeError happened when accessing {chrom}:{start}-{end}, it's probably due to at least one chromatin track bigwig doesn't have information in this region")
            raise BigWigInaccessible(chrom, start, end)
    else:
        target_array = np.array([np.nan], dtype="float32")
    return target_array

def extract_target(chrom, start, end, strand, target):
    if isinstance(target, list):
        target_arrs = [extract_single_target(chrom, start, end, strand, t) for t in target]
        return np.stack(target_arrs)
    else:
        return extract_single_target(chrom, start, end, strand, target)

def extract_info(chrom, start, end, label, genome_pyfaidx, bigwigs, target, strand="+", transforms:dict=None, patch_left=0, patch_right=0):
    if patch_left > 0: patched_start = start - patch_left 
    else: patched_start = start
    if patch_right > 0: patched_end = end + patch_right 
    else: patched_end = end

    seq_array = extract_dnaOneHot(chrom, patched_start, patched_end, strand, genome_pyfaidx)
    assert seq_array.shape[1] == patched_end - patched_start, f"extracted DNA sequence length different from given region ({chrom}:{start}-{end}) length, does the coordinate hit the chromosome boundary?"

    #chromatin track
    if bigwigs is not None and len(bigwigs)>0:
        chroms_array = extract_bw(chrom, patched_start, patched_end, strand, bigwigs)
        assert chroms_array.shape[1] == patched_end - patched_start, f"extracted chrom track length different from given region ({chrom}:{start}-{end}) length, does the coordinate hit the chromosome boundary?"
    else:
        chroms_array = np.array([np.nan], dtype="float32")
    # label
    label_array = np.array(label, dtype=np.int32)[np.newaxis]
    # counts
    target_array = extract_target(chrom, start, end, strand, target)

    feature = {
        'seq': seq_array,
        'chrom': chroms_array,
        'target': target_array,
        'label': label_array
    }

    if transforms is not None:
        for k,t in transforms.items(): 
            feature[k] = t(feature[k])
    
    return feature

if __name__ == '__main__':
    from pyjaspar import jaspardb
    jdb_obj = jaspardb()
    jdb_obj.fetch_motif_by_id('MA0095.2')
    motif = jdb_obj.fetch_motif_by_id('MA0095.2')

    make_motif_match(motif, "../data/chr1.fa").to_csv("motif_match.txt", header=True, index=False, sep="\t")
