class TaxCode

# File lib/tax_code.rb, line 19
def initialize(path = '.')
  dir = path
  file = '.'
  unless File.directory? path
    dir = File.dirname path
    file = File.basename path
  end
  Dir.chdir(dir) do
    log = `git log --numstat -M #{file}`.encode('UTF-8', 'UTF-8', :invalid => :replace)
    raise 'Path has to be inside your git repository' if log == ""
    compute_history(log)
  end  
end

# File lib/tax_code.rb, line 14
def taxed_only(path = '.')
  TaxCode.new(path).taxed_only
end

# File lib/tax_code.rb, line 6
def taxes(path = '.')
  TaxCode.new(path).taxes    
end

# File lib/tax_code.rb, line 10
def worst(path = '.', num = 25)
  TaxCode.new(path).worst(num)
end

# File lib/tax_code.rb, line 44
def taxed_only
  taxes.select{ |_, t| t > 0 }
end

# File lib/tax_code.rb, line 33
def taxes
  @hist.inject({}) do |res, (f, changes)|
    size, tax = changes[0][1], 0
    changes[1..-1].each do |c|
      tax += score(size, *c)
      size += c[1] - c[2]
    end
    size > 0 ? res.merge(f => [tax.to_i, 0].max) : res
  end
end

# File lib/tax_code.rb, line 48
def worst(num = 25)
  taxed_only.sort_by(&:last).last(num).reverse 
end

# File lib/tax_code.rb, line 59
def commits(log)
  log.split(/^Date:\s+(.*)$/)[1..-1].each_slice(2).map do |(d,all)| 
    age = (Date.today - Date.parse(d)).to_i 
    all.split(/\n/).grep(/^\d/).inject({}) do |h, s| 
      a, d, f = s.split(/\t/)
      h.merge f => [age, a.to_i, d.to_i]
    end
  end
end

# File lib/tax_code.rb, line 69
def compute_history(log)
  @hist = Hash.new{|h,k| h[k] = []}
  commits(log).reverse.each do |cmt|
    cmt.each do |f, ar|
      fn = f
      if p = moved(f)
        fo, fn = p
        @hist[fn] = @hist[fo]
        @hist.delete(fo)
      end
      @hist[fn] << ar
    end
  end
end

# File lib/tax_code.rb, line 84
def moved(f)
  if f =~ /^(.*){([^\s]*) => ([^\s}]*)}(.*)$/
    [$1 + $2 + $4, $1 + $3 + $4].map{|fn| fn.sub('//','/')}
  end
end

# File lib/tax_code.rb, line 54
def score(s, age, a, d)
  hpr = 2 ** ( - age / 180.0)
  (s/40.0 + a * 2 - d ) * hpr 
end