[biopieces.git] / code_ruby / lib / maasha / align / pair.rb

# Copyright (C) 2007-2012 Martin A. Hansen.

# 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 2
# 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, write to the Free Software
# Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.

# http://www.gnu.org/copyleft/gpl.html

# >>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>><<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<

# This software is part of the Biopieces framework (www.biopieces.org).

# >>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>><<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<

# Extending Math module with a couple of useful methods.
module Math
  # Method for calculating the distance between a point and a line.
  def self.dist_point2line(px, py, x1, y1, x2, y2)
    a = (y2.to_f - y1) / (x2.to_f - x1)

    b = y1 - a * x1

    (a * px + b - py ).abs / Math.sqrt(a ** 2 + 1 )
  end

  # Method for calculating the distance between two points.
  def self.dist_point2point(x1, y1, x2, y2)
    Math.sqrt((x2 - x1) ** 2 + (y2 - y1) ** 2)
  end
end

# Module with stuff to create a pairwise aligment.
module PairAlign
  # Class for creating a pairwise alignment.
  class AlignPair
    # Class method to create a pairwise alignment of two given Seq objects.
    def self.align(q_entry, s_entry)
      self.new(q_entry, s_entry)
    end

    # Method to inialize a pairwise alignment given two Seq objects.
    def initialize(q_entry, s_entry)
      @q_entry = q_entry
      @s_entry = s_entry
      @matches = []

      @q_entry.seq.downcase!
      @s_entry.seq.downcase!

      align_recurse(@q_entry.seq, @s_entry.seq, 0, 0, @q_entry.length - 1, @s_entry.length - 1, 16, [])
      matches_upcase
      gaps_insert
    end

    private

    # Method that creates an alignment by chaining matches, which are
    # subsequences shared between two sequences. This recursive method
    # functions by considering only matches within a given search space. If no
    # matches are given these will be located and matches will be included
    # depending on a calculated score. New search spaces spanning the spaces
    # between the best scoring matches and the search space boundaries will be
    # cast and recursed into.
    def align_recurse(q_seq, s_seq, q_min, s_min, q_max, s_max, kmer, matches)
      matches = matches_select_by_space(matches, q_min, s_min, q_max, s_max)

      while (matches.size == 0 and kmer > 0)
        matches = matches_find(q_seq, s_seq, q_min, s_min, q_max, s_max, kmer)
        kmer /= 2
      end

      matches = matches_select_by_score(matches, q_min, s_min, q_max, s_max)

      if best_match = matches.pop
        @matches << best_match

        l_q_min = q_min
        l_s_min = s_min
        l_q_max = best_match.q_beg - 1
        l_s_max = best_match.s_beg - 1

        r_q_min = best_match.q_end + 1
        r_s_min = best_match.s_end + 1
        r_q_max = q_max
        r_s_max = s_max

        if l_q_max - l_q_min > 0 and l_s_max - l_s_min > 0
          align_recurse(q_seq, s_seq, l_q_min, l_s_min, l_q_max, l_s_max, kmer, matches)
        end

        if r_q_max - r_q_min > 0 and r_s_max - r_s_min > 0
          align_recurse(q_seq, s_seq, r_q_min, r_s_min, r_q_max, r_s_max, kmer, matches)
        end
      end
    end

    # Method to select matches that lies within the search space.
    def matches_select_by_space(matches, q_min, s_min, q_max, s_max)
      new_matches = matches.select do |match|
        match.q_beg >= q_min and
        match.s_beg >= s_min and
        match.q_end <= q_max and
        match.s_end <= s_max
      end

      new_matches
    end

    # Method to select the best scoring matches and return these sorted
    # according to score.
    def matches_select_by_score(matches, q_min, s_min, q_max, s_max)
      new_matches = []

      matches.each do |match|
        score_length = match_score_by_length(match)
        score_diag   = match_score_by_diagonal_dist(match, q_min, s_min, q_max, s_max)

        match.score = score_length - score_diag

        new_matches << match if match.score > 0
      end

      new_matches.sort_by! { |match| match.score }

      new_matches
    end

    # Method to calculate score based on match length.
    def match_score_by_length(match)
      match.length.to_f
    end

    # Method to calculate score based on the distance to the closest
    # diagonal. The smaller the distance the better the score.
    def match_score_by_diagonal_dist(match, q_min, s_min, q_max, s_max)
      q_dim = q_max - q_min + 1
      s_dim = s_max - s_min + 1

      if q_dim >= s_dim   # s_dim is the narrow end
        beg_dist = Math.dist_point2line(match.q_beg, match.s_beg, q_min, s_min, q_min + s_dim, s_min + s_dim)
        end_dist = Math.dist_point2line(match.q_beg, match.s_beg, q_max - s_dim, s_max - s_dim, q_max, s_max)
      else
        beg_dist = Math.dist_point2line(match.q_beg, match.s_beg, q_min, s_min, q_min + q_dim, s_min + q_dim)
        end_dist = Math.dist_point2line(match.q_beg, match.s_beg, q_max - q_dim, s_max - q_dim, q_max, s_max)
      end

      min_dist = (beg_dist < end_dist) ? beg_dist : end_dist
      min_dist.to_f
    end

    # Method that finds all maximally expanded non-redundant matches shared
    # between two sequences inside a given search space.
    def matches_find(q_seq, s_seq, q_min, s_min, q_max, s_max, kmer)
      matches   = []
      redundant = Hash.new { |h, k| h[k] = [] }

      s_index = index_seq(s_seq, s_min, s_max, kmer)

      q_pos = q_min

      while q_pos <= q_max - kmer + 1
        q_oligo = q_seq[q_pos ... q_pos + kmer]

        s_index[q_oligo].each do |s_pos|
          match = Match.new(q_pos, s_pos, kmer)

          unless match_redundant?(redundant, match)
            match_expand(match, q_seq, s_seq, q_min, s_min, q_max, s_max)
            matches << match

            match_redundant_add(redundant, match)
          end
        end

        q_pos += 1
      end

      matches
    end

    # Method that indexes a seuquence within a given interval such that the
    # index contains all oligos of a given kmer size and the positions where
    # this oligo was located.
    def index_seq(seq, min, max, kmer)
      index_hash = Hash.new { |h, k| h[k] = [] }

      pos = min

      while pos <= max - kmer + 1
        oligo = seq[pos ... pos + kmer]
        index_hash[oligo] << pos

        pos += 1
      end

      index_hash
    end

    # Method to check if a match is redundant.
    def match_redundant?(redundant, match)
      redundant[match.q_beg].each do |s_interval|
        if s_interval.include? match.s_beg and s_interval.include? match.s_end
          return true
        end
      end

      false
    end

    # Method that adds a match to the redundancy index.
    def match_redundant_add(redundant, match)
      (match.q_beg .. match.q_end).each do |q|
        redundant[q] << (match.s_beg .. match.s_end)
      end
    end

    # Method that expands a match as far as possible to the left and right.
    def match_expand(match, q_seq, s_seq, q_min, s_min, q_max, s_max)
      match_expand_left(match, q_seq, s_seq, q_min, s_min)
      match_expand_right(match, q_seq, s_seq, q_max, s_max)

      match
    end

    # Method that expands a match as far as possible to the left.
    def match_expand_left(match, q_seq, s_seq, q_min, s_min)
      while match.q_beg > q_min and
            match.s_beg > s_min and 
            q_seq[match.q_beg - 1] == s_seq[match.s_beg - 1]
        match.q_beg  -= 1
        match.s_beg  -= 1
        match.length += 1
      end

      match
    end

    # Method that expands a match as far as possible to the right.
    def match_expand_right(match, q_seq, s_seq, q_max, s_max)
      while match.q_end < q_max and
            match.s_end < s_max and
            q_seq[match.q_end + 1] == s_seq[match.s_end + 1]
        match.length += 1
      end

      match
    end

    # Method for debugging purposes that upcase matching sequence while non-matches
    # sequence is kept in lower case.
    def matches_upcase
      @matches.each do |match|
        @q_entry.seq[match.q_beg .. match.q_end] = @q_entry.seq[match.q_beg .. match.q_end].upcase
        @s_entry.seq[match.s_beg .. match.s_end] = @s_entry.seq[match.s_beg .. match.s_end].upcase
      end
    end

    # Method that insert gaps in sequences based on a list of matches and thus
    # creating an alignment.
    # TODO check boundaries!
    def gaps_insert
      @matches.sort_by! { |m| m.q_beg }

      q_gaps = 0
      s_gaps = 0

      @matches.each do |match|
        diff = (q_gaps + match.q_beg) - (s_gaps + match.s_beg)

        #pp "q_gaps #{q_gaps}   s_gaps #{s_gaps}   diff #{diff}"

        if diff < 0
          @q_entry.seq.insert(match.q_beg + q_gaps, "-" * diff.abs)
          q_gaps += diff.abs
        elsif diff > 0
          @s_entry.seq.insert(match.s_beg + s_gaps, "-" * diff.abs)
          s_gaps += diff.abs
        end
      end

      diff = @q_entry.length - @s_entry.length

      if diff < 0
        @q_entry.seq << ("-" * diff.abs)
      else
        @s_entry.seq << ("-" * diff.abs)
      end
    end
  end

  # Class for containing a match between two sequences q and s.
  class Match
    attr_accessor :q_beg, :s_beg, :length, :score

    def initialize(q_beg, s_beg, length, score = 0.0)
      @q_beg  = q_beg
      @s_beg  = s_beg
      @length = length
      @score  = score
    end

    def q_end
      @q_beg + @length - 1
    end

    def s_end
      @s_beg + @length - 1
    end

    def to_s(seq = nil)
      s = "q: #{@q_beg} #{q_end} s: #{@s_beg} #{s_end} l: #{@length} s: #{@score}"
      s << " seq: #{seq[@q_beg .. q_end]}" if seq
      s
    end
  end
end