NOMe_filtering

#!/usr/bin/env perl
use warnings;
use strict;
$|++;
use Getopt::Long;
use Cwd;
use Carp;

## This program is Copyright (C) 2010-17, Felix Krueger (felix.krueger@babraham.ac.uk)

## This program is free software: you can redistribute it and/or modify
## it under the terms of the GNU General Public License as published by
## the Free Software Foundation, either version 3 of the License, or
## (at your option) any later version.

## This program is distributed in the hope that it will be useful,
## but WITHOUT ANY WARRANTY; without even the implied warranty of
## MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
## GNU General Public License for more details.

## You should have received a copy of the GNU General Public License
## along with this program. If not, see <http://www.gnu.org/licenses/>.

my %chromosomes; # storing sequence information of all chromosomes/scaffolds
my %processed;   # keeping a record of which chromosomes have been processed
my $nome_version = 'v0.19.0';

my ($output_dir,$genome_folder,$zero,$CpG_only,$CX_context,$split_by_chromosome,$parent_dir,$coverage_infile,$cytosine_out,$merge_CpGs,$gc_context,$gzip,$nome) = process_commandline();

warn "Methylation call infile:\t\t$coverage_infile\n";
warn "Genome directory:\t\t\t>$genome_folder<\n";

if($nome){
    warn "Sample specified as NOMe-Seq\t\tyes (only reporting ACG and TCG context)\n";
}

if($nome){
    warn "Optional GC context track:\t\tyes (NOMe-Seq; only reporting GCA, GCC and GCT context)\n";
}
read_genome_into_memory();
warn "Stored sequence information of ",scalar keys %chromosomes," chromosomes/scaffolds in total\n\n";

### 22 03 2017
per_read_filtering($coverage_infile);



sub per_read_filtering {
    
    warn  "="x78,"\n";
    warn "Methylation information will now be written into a genome-wide cytosine report\n";
    warn  "="x78,"\n\n";
    sleep (2);
    
    my $number_processed = 0;
    
    ### changing to the output directory again
    unless ($output_dir eq ''){ # default
	chdir $output_dir or die "Failed to change directory to $output_dir\n";
	# warn "Changed directory to $output_dir\n";
    }
    
    my $in = shift;
    
    # infiles handed over by the methylation extractor will be just the filename on their own. The directory should have been handed over with --dir
    if ($in =~ /gz$/){
	open (IN,"gunzip -c $in |") or die "Failed to read from gzipped file $in: $!\n"; # changed from gunzip -c to gunzip -c 08 04 16
    }
    else{
	open (IN,"$in") or die "Failed to read from file $in: $!\n";
    }
    
    ### note: we are still in the folder: $output_dir, so we do not have to include this into the open commands
    unless ($cytosine_out =~ /\.gz$/){
	$cytosine_out .= '.gz';
    }
    open (CYT,"| gzip -c - > $cytosine_out") or die "Failed to write to file $cytosine_out: $!\n";
    print CYT join ("\t","ReadID","Chr","Start","End","meth_CG","unmeth_CG","meth_GC","unmeth_GC"),"\n"; 
    warn ">>> Writing genome-wide cytosine report to: $cytosine_out <<<\n\n";
    
    my $last_read;
    my $last_start; # entire read length. Input format is Start End for 
    my $last_end;   # entire read length
    my $last_chr;

    my $read; # storing calls for one read at a time
   
    my $count = 0;
    while (<IN>){
	chomp;
	next if ($_ =~ /^Bismark/);
	++$count;
	my ($id,$state,$chr,$pos,$context,$start,$end,$strand) = (split /\t/);
	# print join (" ",$id,$state,$chr,$pos,$context,$start,$end,$strand),"\n"; sleep(1);
	
	# defining the first chromosome
	unless (defined $last_read){
	    $last_read = $id;
	    $last_start = $start;
	    $last_end = $end; 
	    $last_chr = $chr;
	    # warn "Storing all covered cytosine positions for read: $id\n";
	}
	
	if ($id eq $last_read){
	    # warn "$id (same read)\t$pos\t$context\n";
	    $read->{$pos}->{state} = $state;
	    $read->{$pos}->{context} = $context;
	}
	else{
	 
	    ### Reached new read
	    # warn "\n$id (new read)\n";sleep(1);
	    
	    ### Processing last stored read
	    my $length;
	    if ($last_end >= $last_start){ # forward read
		$length = $last_end - $last_start + 1;
	    }
	    else{ # reverse read
		$length = $last_start - $last_end + 1;
	    }
	 
    	    # exract genome sequence for the last read
	    # warn "Last Start: $last_start\nLast End: $last_end\nLength: $length\n";

	    my $seq;
	    my $ext_seq; # this sequence contains 2 additional bp at the start and end so that we can perform context calls in the cytosine lookup
	    
	    my $suitable = 0;
	    
	    if ($last_start - 2 > 1 and length($chromosomes{$last_chr}) >= ($last_start - 2 + $length + 4) ){ # making sure the extended sequence can be extracted
		if ($last_end >= $last_start){
		    $seq = substr($chromosomes{$last_chr},$last_start - 1,$length);
		    $ext_seq = substr($chromosomes{$last_chr},$last_start - 3,$length + 4); # we potentially need 2 extra bases on either side for a context lookup
		}
		else{
		    $seq = substr($chromosomes{$last_chr},$last_end - 1,$length);
		    $ext_seq = substr($chromosomes{$last_chr},$last_end - 3,$length + 4); # we potentially need 2 extra bases on either side for a context lookup
		}
		#  warn "$seq\n$ext_seq\n";
		$suitable = 1;
	    }
	    else{
		# read is not suitable for processing because it lacks the up- and downstream context
	    }
	    if ($suitable){
		++$number_processed;

		### Need to pass in the true start of the read, so the end for reverse reads
		if ($last_end >= $last_start){
		    cytosine_lookup ($last_read,$last_chr,$seq,$last_start,$last_end,$ext_seq,$read);
		}
		else{
		    cytosine_lookup ($last_read,$last_chr,$seq,$last_end,$last_start,$ext_seq,$read);
		}
	    }
	    
	    # Preparing for new read
	    $last_read = $id;
	    $last_start = $start;
	    $last_end = $end;
	    $last_chr = $chr;
	    
	    $read = (); # clearing positions
	    $read->{$pos}->{state} = $state;
	    $read->{$pos}->{context} = $context;
	}
    
    }
    
    # If there never was a last read then something must have gone wrong with reading the data in
    unless (defined $last_read){
	die "No last read was defined, something must have gone wrong while reading the data in (e.g. was the input file empty?). Please check your command!\n\n";
    }

    ### process last read
    my $length;
    if ($last_end >= $last_start){ # forward read
	$length = $last_end - $last_start + 1;
    }
    else{ # reverse read
	$length = $last_start - $last_end + 1;
    }
    
    # exract genome sequence for the last read
    # warn "Last Start: $last_start\nLast End: $last_end\nLength: $length\n";

    my $seq;
    my $ext_seq; # this sequence contains 2 additional bp at the start and end so that we can perform context calls in the cytosine lookup
    
    my $suitable = 0;
	    
    if ($last_start - 2 > 1 and length($chromosomes{$last_chr}) >= ($last_start - 2 + $length + 4) ){ # making sure the extended sequence can be extracted
	if ($last_end >= $last_start){
	    $seq = substr($chromosomes{$last_chr},$last_start - 1,$length);
	    $ext_seq = substr($chromosomes{$last_chr},$last_start - 3,$length + 4); # we potentially need 2 extra bases on either side for a context lookup
	}
	else{
	    $seq = substr($chromosomes{$last_chr},$last_end - 1,$length);
	    $ext_seq = substr($chromosomes{$last_chr},$last_end - 3,$length + 4); # we potentially need 2 extra bases on either side for a context lookup
	}
	#  warn "$seq\n$ext_seq\n";
	$suitable = 1;
    }
    else{
	# read is not suitable for processing because it lacks the up- and downstream context
    }
    
    if ($suitable){ 
	++$number_processed;
	### Need to pass in the true start of the read, so the end for reverse reads
	if ($last_end >= $last_start){
	    cytosine_lookup ($last_read,$last_chr,$seq,$last_start,$last_end,$ext_seq,$read);
	}
	else{
	    cytosine_lookup ($last_read,$last_chr,$seq,$last_end,$last_start,$ext_seq,$read);
	}
    }
    
    close IN or warn $!;

    if ($nome){
	warn "Finished writing out NOMe-Seq specific filtering report (only reporting CGs in ACG and TCG context; reporting GCs only when not in CG context).\n";
	warn "Processed $number_processed reads in total.\n\n";
    }
    
    close CYT or warn $!;
    
}







########################################################
#### SUBROUTINESSSSS
########################################################

sub cytosine_lookup{
    
    my ($id,$chr,$seq,$offset,$end,$ext_seq,$read) = @_; # start is the start of the sequence which we will use as the offset
    # warn "  $seq\n$ext_seq\nOffset: $offset\tchr: $chr\n";	

    my $strand;
    my $tri_nt;
    my $upstream_context; # for NOMe-Seq
    my $context;

    my ($meth_CG,$unmeth_CG,$meth_nonCG,$unmeth_nonCG) = (0,0,0,0); # keeping count for the entire read

    # warn "Stored the following methylation info: \n";
    foreach my $pos (keys %{$read}){
	# warn "$pos\t$read->{$pos}->{state}\t$read->{$pos}->{context}\n";
    }
    # warn "\n";

    while ($seq =~ /([CG])/g){ # C or G
 
	my $pos = pos$seq;
	
	if ($1 eq 'C'){    # C on forward strand
	    $tri_nt = substr ($ext_seq,$pos + 1,3);   # positions are 0-based!
	    if ($nome){
		$upstream_context = substr ($ext_seq,$pos,3);
		# warn "$1\t$pos\t",$pos + $offset - 1,"\t$tri_nt\t$upstream_context\n"; sleep(1);
	    }
	    $strand = '+';
	}
	elsif ($1 eq 'G'){ # C on reverse strand
	    
	    $tri_nt = substr ($ext_seq,$pos - 1,3);   # positions are 0-based!
	    $tri_nt = reverse $tri_nt;
	    $tri_nt =~ tr/ACTG/TGAC/;
	    
	    if ($nome){
		$upstream_context = substr ($ext_seq,$pos, 3);
		$upstream_context = reverse $upstream_context;
		$upstream_context =~ tr/ACTG/TGAC/;
		# warn "$1\t$pos\t",$pos + $offset - 1,"\t$tri_nt\t$upstream_context\n"; sleep(1);
	    }
	    $strand = '-';
	}
	
	next if (length$tri_nt < 3); # trinucleotide sequence could not be extracted
    

	### determining cytosine context	
	if ($tri_nt =~ /^CG/){
	    $context = 'CG';
	}
	elsif ($tri_nt =~ /^C.{1}G$/){
	    $context = 'CHG';
	}
	elsif ($tri_nt =~ /^C.{2}$/){
	    $context = 'CHH';
	}
	else{ # if the context can't be determined the positions will not be considered (it will equally not have been reported by Bismark)
	    warn "The sequence context could not be determined (found: '$tri_nt'). Skipping.\n";
	    next;
	}
	
	if (exists $read->{$pos + $offset - 1}){
	    # warn "Position was covered\nUpstream context: $upstream_context\ntrinuc context: $context\nreported context: ",$read->{$pos + $offset-1}->{context},"\n";
	    
	    # for NOMe-Seq (nucleosome occupancy and methylome sequencing) we limit the reporting of 
	    # 1. CpGs to A-C-G and T-C-G
	    # 2. GpC report files / cov files that only include G-C-A, G-C-C and G-C-T
	    
	    if ($context eq 'CG'){
		if ( ($read->{$pos + $offset-1}->{context}) eq 'z' or ($read->{$pos + $offset-1}->{context}) eq 'Z'){
		    # warn "Agreeing CG context calls. Fine!\n";
		    if ( ($upstream_context eq 'ACG') or ($upstream_context eq 'TCG') ){ # filtering out NOMe-biased CG positions
			# warn "Passed NOMe-filtering. Fine\n";
			if( ($read->{$pos + $offset-1}->{state}) eq '+'){
			    $meth_CG++;
			}
			elsif( ($read->{$pos + $offset-1}->{state}) eq '-' ){
			    $unmeth_CG++
			}
			else{
			    die "This should never happen\n";
			}
		    }
		    else{
			# warn "Potentially biased context, skipping\n";
			next; # skipping this base
		    }
		    
		}
		else{
		    # warn "Change in CG call context, disregarding...\n";
		}
	    }
	    elsif($context eq 'CHG'){
		if ( ($read->{$pos + $offset-1}->{context}) eq 'x' or ($read->{$pos + $offset-1}->{context}) eq 'X'){
		    # warn "Agreeing CHG context calls. Fine!\n";
		    if ( $upstream_context =~ /^GC/ ){ # this is a NOMe-relevant GC position
			# warn "This is a GC positions! Fine\n";  
                        if( ($read->{$pos + $offset-1}->{state}) eq '+'){
                            $meth_nonCG++; 
			} 
			elsif( ($read->{$pos + $offset-1}->{state}) eq '-' ){
   			    $unmeth_nonCG++                                                                                                                                               
			}  
			else{
			    die "This should never happen\n";
			}               
		    }
		}
		else{
		    # warn "Change in CHG call context, disregarding...\n";
		}	
	    }	    
	    elsif($context eq 'CHH'){
		if ( ($read->{$pos + $offset-1}->{context}) eq 'h' or ($read->{$pos + $offset-1}->{context}) eq 'H'){
		    # warn "Agreeing CHH context calls. Fine!\n";
		    if ( $upstream_context =~ /^GC/ ){ # this is a NOMe-relevant GC position
			# warn "This is a GC positions! Fine\n";
			if( ($read->{$pos + $offset-1}->{state}) eq '+'){
			    $meth_nonCG++;
			}
			elsif( ($read->{$pos + $offset-1}->{state}) eq '-' ){
			    $unmeth_nonCG++                                                                                                                                                
			}    
			else{
			    die "This should never happen\n";                                                                                    
                        }                                                                                               
                    }              
		}
		else{
		    # warn "Change in call context, disregarding...\n";
		}
	    }
	    else{
		die "Context was neither CG, CHG nor CHH, but: $tri_nt!\n\n";	
	    }
	    # warn "\n";
	}
	else{
	    # warn "Position was not covered\n";
	}
    
    }
   
    ### Printing out the NOMe-Seq filtered reads with their associated methylated/unmethylated counts
    print CYT join ("\t",$id,$chr,$offset,$end,$meth_CG,$unmeth_CG,$meth_nonCG,$unmeth_nonCG),"\n";

}


sub process_commandline{
    my $help;
    my $genome_folder;
    
    my $cytosine_out;
    my $parent_dir;
    my $version;
    my $merge_CpGs;
    my $gc_context;
    my $nome = 1; 

    my $command_line = GetOptions ('help|man'               => \$help,
				   'dir=s'                  => \$output_dir,
				   'g|genome_folder=s'      => \$genome_folder,
				   "zero_based"             => \$zero,	
				   "CX|CX_context"          => \$CX_context,
				   'parent_dir=s'           => \$parent_dir,
				   'version'                => \$version,
				   'merge_CpGs'             => \$merge_CpGs,
				   'GC|GC_context'          => \$gc_context,
				   'gzip'                   => \$gzip,
				   'nome-seq'               => \$nome,
	);

    ### EXIT ON ERROR if there were errors with any of the supplied options
    unless ($command_line){
	die "Please respecify command line options\n";
    }

    ### HELPFILE
    if ($help){
	print_helpfile();
	exit;
    }

    if ($version){
	print << "VERSION";


                Bismark NOMe_filtering, Version: $nome_version

          Copyright 2010-17 Felix Krueger, Babraham Bioinformatics
	    www.bioinformatics.babraham.ac.uk/projects/bismark/
                  https://github.com/FelixKrueger/Bismark


VERSION
	  exit;
    }

    ### no files provided
    unless (@ARGV){
	warn "You need to provide a Bismark coverage file (with counts methylated/unmethylated cytosines) to create an individual C methylation output. Please respecify!\n";
	sleep(2);

	print_helpfile();
	exit;
    }

    my $coverage_infile = shift @ARGV;
    unless (-e $coverage_infile){
	die "File did not exist in the current directory.\n";
    }

    unless ($parent_dir){
	$parent_dir = getcwd();
    }
    unless ($parent_dir =~ /\/$/){
	$parent_dir =~ s/$/\//;
    }
    
    # deriving output file
    $cytosine_out = $coverage_infile;
    $cytosine_out =~ s/\.gz$//;
    $cytosine_out =~ s/\.txt$//;
    $cytosine_out =~ s/$/.manOwar.txt/; # https://en.wikipedia.org/wiki/Man-of-war_fish
    
    ### OUTPUT DIR PATH
    if (defined $output_dir){
	unless ($output_dir eq ''){ # if the output dir has been passed on by the methylation extractor and is an empty string we don't want to change it
	    unless ($output_dir =~ /\/$/){
		$output_dir =~ s/$/\//;
	    }
	}
    }
    else{
	$output_dir = '';
    }

    unless ($CX_context){
	$CX_context = 0;
	$CpG_only = 1;
    }

    ### GENOME folder
    if ($genome_folder){
	unless ($genome_folder =~/\/$/){
	    $genome_folder =~ s/$/\//;
	}
    }
    else{
	die "Please specify a genome folder to proceed (full path only)\n";
    }

    if ($merge_CpGs){
	if ($CX_context){
	    die "Merging individual CpG calls into a single CpG dinucleotide entity is currently only supported if CpG-context is selected only (lose the option --CX)\n";
	}
	if ($split_by_chromosome){
	    die "Merging individual CpG calls into a single CpG dinucleotide entity is currently only supported if a single CpG report is written out (lose the option --split_by_chromosome)\n";
	}
    }
    
    if ($nome){
	unless ($gc_context){
	    warn "Sample specified as NOMe-Seq. Also setting `--gc` context\n\n";
	    $gc_context = 1;
	}
    }
    
    return ($output_dir,$genome_folder,$zero,$CpG_only,$CX_context,$split_by_chromosome,$parent_dir,$coverage_infile,$cytosine_out,$merge_CpGs,$gc_context,$gzip,$nome);
}

sub read_genome_into_memory{

    ## reading in and storing the specified genome in the %chromosomes hash
    chdir ($genome_folder) or die "Can't move to $genome_folder: $!";
    warn "Now reading in and storing sequence information of the genome specified in: $genome_folder\n\n";

    my @chromosome_filenames =  <*.fa>;

    ### if there aren't any genomic files with the extension .fa we will look for files with the extension .fasta
    unless (@chromosome_filenames){
	@chromosome_filenames =  <*.fasta>;
    }
    unless (@chromosome_filenames){
	die "The specified genome folder $genome_folder does not contain any sequence files in FastA format (with .fa or .fasta file extensions)\n";
    }

    foreach my $chromosome_filename (@chromosome_filenames){

	# skipping the tophat entire mouse genome fasta file
	next if ($chromosome_filename eq 'Mus_musculus.NCBIM37.fa');

	open (CHR_IN,$chromosome_filename) or die "Failed to read from sequence file $chromosome_filename $!\n";
	### first line needs to be a fastA header
	my $first_line = <CHR_IN>;
	chomp $first_line;
	$first_line =~ s/\r//; # removing /r carriage returns

	### Extracting chromosome name from the FastA header
	my $chromosome_name = extract_chromosome_name($first_line);
	
	my $sequence;
	while (<CHR_IN>){
	    chomp;
	    $_ =~ s/\r//; # removing /r carriage returns

	    if ($_ =~ /^>/){
		### storing the previous chromosome in the %chromosomes hash, only relevant for Multi-Fasta-Files (MFA)
		if (exists $chromosomes{$chromosome_name}){
		    warn "chr $chromosome_name (",length $sequence ," bp)\n";
		    die "Exiting because chromosome name already exists. Please make sure all chromosomes have a unique name!\n";
		}
		else {
		    if (length($sequence) == 0){
			warn "Chromosome $chromosome_name in the multi-fasta file $chromosome_filename did not contain any sequence information!\n";
		    }
		    warn "chr $chromosome_name (",length $sequence ," bp)\n";
		    $chromosomes{$chromosome_name} = $sequence;
		    $processed{$chromosome_name} = 0; # processed chromosomes will be set to 1 later to allow a record of which chromosome has been processed
		}
		### resetting the sequence variable
		$sequence = '';
		### setting new chromosome name
		$chromosome_name = extract_chromosome_name($_);
	    }
	    else{
		$sequence .= uc$_;
	    }
	}

	if (exists $chromosomes{$chromosome_name}){
	    warn "chr $chromosome_name (",length $sequence ," bp)\t";
	    die "Exiting because chromosome name already exists. Please make sure all chromosomes have a unique name.\n";
	}
	else{
	    if (length($sequence) == 0){
		warn "Chromosome $chromosome_name in the file $chromosome_filename did not contain any sequence information!\n";
	    }
	    warn "chr $chromosome_name (",length $sequence ," bp)\n";
	    $chromosomes{$chromosome_name} = $sequence;
	    $processed{$chromosome_name} = 0; # processed chromosomes will be set to 1 later to allow a record of which chromosome has been processed
	}
    }
    warn "\n";
    chdir $parent_dir or die "Failed to move to directory $parent_dir\n";
}

sub extract_chromosome_name {
    ## Bowtie extracts the first string after the inition > in the FASTA file, so we are doing this as well
    my $fasta_header = shift;
    if ($fasta_header =~ s/^>//){
	my ($chromosome_name) = split (/\s+/,$fasta_header);
	return $chromosome_name;
    }
    else{
	die "The specified chromosome ($fasta_header) file doesn't seem to be in FASTA format as required!\n";
    }
}


sub print_helpfile{

  warn <<EOF

  SYNOPSIS:

  This script reads in methylation call files from the Bismark methylation extract that contain additional information about the reads that 
  methylation calls belonged to. It processes entire (single-end) reads and then filters calls for NOMe-Seq positions (nucleosome occupancy
  and methylome sequencing) where accessible DNA gets methylated in a GpC context:
 
     (i) filters CpGs to only output cytosines in A-CG and T-CG context
    (ii) filters GC context to only report cytosines in GC-A, GC-C and GC-T context

  Both of these measures aim to reduce unwanted biases, i.e. the influence of G-CG (intended) and C-CG (off-target) on endogenous CpG
  methylation, and the influence of CpG methylation on (the NOMe-Seq specific) GC context methylation.

  The input file needs to have been generated with bismark_methylation_extractor with the option '--yacht' specified and be in the following format:
  
  <seq-ID>  <methylation state*>  <chromosome>  <start position (= end position)>  <methylation call>  <read start>  <read end>  <read orientation>

  *   Methylated cytosines receive a '+' orientation,
  * Unmethylated cytosines receive a '-' orientation.


  USAGE: NOMe_filtering --genome_folder <path> [input]


  The name of the output file is rerived from the input file, end will end in '.manOwar.txt.gz'

  --genome_folder <path>   Enter the genome folder you wish to use to extract sequences from (full path only!). Accepted
                           formats are FastA files ending with '.fa' or '.fasta'. Specifying a genome folder path is mandatory.


  --help                   Displays this help message and exits



OUTPUT FORMAT:

The NOMe-Seq filtering output reports cytosines in CpG context only if they are in A-CG or T-CG context,
and cytosines in GC context only when the C is not in CpG context. The output file is tab-delimited and in
the following format (1-based coords):
===========================================================================================================

<readID>  <chromosome>  <read start>  <read end>  <count methylated CpG>  <count non-methylated CpG>  <count methylated GC>  <count non-methylated GC>
HWI-D00436:298:C9KY4ANXX:1:1101:2035:2000_1:N:0:_ACAGTGGT 10 8517979 8518098 0 1 0 1 
HWI-D00436:298:C9KY4ANXX:1:1101:5072:1993_1:N:0:_ACAGTGGT 8 9476630 9476748 0 0 0 2 


                              Script last modified: 06 April 2017

EOF
    ;
  exit 1;
}