converter

#!/usr/bin/env ruby

src_file_path, dst_file_path = *ARGV
dst_file_path ||= src_file_path
lines = File.readlines(src_file_path)

indent_size_calc = lambda do |line|
  size = 0

  line.each_char do |char|
    char =~ /\s/ ? size += 1 : break
  end

  size
end

swap_variable_prefix = lambda do |line, _|
  line.gsub(/\@[[:alnum:]]+/) do |var|
    if %w(@media @import).include?(var)
      var
    else
      var.sub('@', '$')
    end
  end
end

turn_percentages_into_percentiles = lambda do |line, _|
  line.gsub(/([\d\.]+)%/) do
    ($1.to_f / 100.0).to_s.sub(/^0/, '')
  end
end

convert_mixin_declarations = lambda do |line, _|
  line.sub(/^\.([^\(\s]+)\(/) do
    "@mixin #{$1}("
  end
end

convert_namespace_include_syntax = lambda do |line, _|
  line.sub(/#(\S+)\s+>\s+\.([[:alnum:]]+)/) do
    "@include #{$1}-#{$2}"
  end
end

convert_include_syntax = lambda do |line, _|
  line.sub(/^(\s+)\.([^\(\s]+)\(/) do
    "#{$1}@include #{$2}("
  end
end

escape_box_shadow_arguments = lambda do |line, _|
  box_shadow     = /@include\s+box-shadow/
  without_comma  = /@include\s+box-shadow\([^,]+$/
  without_dollar = /@include\s+box-shadow\([^\$]+$/

  with_dollar_and_comma =
    (line !~ without_comma) && (line !~ without_dollar)

  if line =~ box_shadow && with_dollar_and_comma
    line.sub(/\((.+)\);/) { "(\#{#{$1}});" }
  else
    line
  end
end

swap_spin_adjust_hue = lambda do |line, _|
  line.gsub(/(\W)spin\(/) do
    "#{$1}adjust-hue("
  end
end

resolve_ampersand_dash = lambda do |line, index|
  line.sub(/^(\s*)&-(\S+)/) do
    indent, suffix, prefix = $1, $2, ''

    while index > 0
      index -= 1
      parent = lines[index]
      next if parent.strip == ''

      parent_indent_size = indent_size_calc.call(parent)
      if parent_indent_size < indent.size
        prefix = parent[/^\s*(\S+)/, 1].to_s.strip
        break
      end
    end

    if prefix == ''
      raise "Could not find parent for &- substitution on line #{index}\n" +
        line
    else
      "#{indent}#{prefix}-#{suffix}"
    end
  end
end

clear_out_escapes = lambda do |line, _|
  line.gsub(/~"([^"]+)"/) { $1 }
end

rewrite_image_paths = lambda do |line, _|
  if line =~ /^\s*\$/ && line.include?(':') && line.include?('.png"')
    line.sub(/"([^"]+)"/) do
      "image-path(\"#{File.basename($1)}\")"
    end
  else
    line
  end
end

remove_icon_font_path = lambda do |line, _|
  if line =~ /^\s*\$icon-font-path/
    ""
  else 
    line
  end  
end

mark_variables_default = lambda do |line, _|
  if line =~ /^\s*\$/ && line.include?(':')
    line.sub(';', ' !default;')
  else
    line
  end
end

line_processors = [
  swap_variable_prefix,

  # This converter doesn't seem to be actually needed
  # turn_percentages_into_percentiles,

  convert_mixin_declarations,
  convert_namespace_include_syntax,
  convert_include_syntax,
  escape_box_shadow_arguments,
  swap_spin_adjust_hue,
  resolve_ampersand_dash,
  clear_out_escapes
]

if File.basename(src_file_path) =~ /variables/
  line_processors += [
    rewrite_image_paths,
    remove_icon_font_path,
    mark_variables_default
  ]
end

comment_line = /^\s*\/\//

processed_lines = lines.map.with_index do |line, index|
  if line =~ comment_line
    line
  else
    line_processors.each do |processor|
      line = processor.call(line, index)
    end

    line
  end
end

File.open(dst_file_path, 'w') do |file|
  file.write(processed_lines.join)
end