module Bugspots

# File lib/bugspots/scanner.rb, line 7
def self.scan(repo, branch = "master", depth = 500, regex = nil)
  regex ||= /\b(fix(es|ed)?|close(s|d)?)\b/i
  fixes = []

  repo = Rugged::Repository.new(repo)
  unless repo.branches.each_name(:local).sort.find { |b| b == branch }
    raise ArgumentError, "no such branch in the repo: #{branch}"
  end

  walker = Rugged::Walker.new(repo)
  walker.sorting(Rugged::SORT_TOPO | Rugged::SORT_REVERSE)
  walker.push(repo.branches[branch].target)
  walker.each do |commit|
    if commit.message =~ regex
      files = commit.diff(commit.parents.first).deltas.collect do |d|
        d.old_file[:path]
      end
      fixes << Fix.new(commit.message.split("\n").first, commit.time, files)
    end
  end

  hotspots = Hash.new(0)
  fixes.each do |fix|
    fix.files.each do |file|
      # The timestamp used in the equation is normalized from 0 to 1, where
      # 0 is the earliest point in the code base, and 1 is now (where now is
      # when the algorithm was run). Note that the score changes over time
      # with this algorithm due to the moving normalization; it's not meant
      # to provide some objective score, only provide a means of comparison
      # between one file and another at any one point in time
      t = 1 - ((Time.now - fix.date).to_f / (Time.now - fixes.first.date))
      hotspots[file] += 1/(1+Math.exp((-12*t)+12))
    end
  end

  spots = hotspots.sort_by {|k,v| v}.reverse.collect do |spot|
    Spot.new(spot.first, sprintf('%.4f', spot.last))
  end

  return fixes, spots
end