# coding: utf-8
# Based on convert script from vwall/compass-twitter-bootstrap gem.
# https://github.com/vwall/compass-twitter-bootstrap/blob/master/build/convert.rb
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this work except in compliance with the License.
# You may obtain a copy of the License in the LICENSE file, or at:
#
#    http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.

require 'open-uri'
require 'json'
require 'strscan'

class Converter
  def initialize(branch)
    @repo   = 'twbs/bootstrap'
    @branch = branch || 'master'
    @mixins = get_mixins_name
  end

  def process
    process_stylesheet_assets
    process_javascript_assets
  end

  def process_stylesheet_assets
    puts "\nProcessing stylesheets..."
    read_files('less', bootstrap_less_files).each do |name, file|
      case name
      when 'bootstrap.less'
        file = replace_file_imports(file)
      when 'mixins.less'
        file = replace_vars(file)
        file = replace_escaping(file)
        file = replace_mixin_file(file)
        file = replace_mixins(file)
        file = flatten_mixins(file, '#gradient', 'gradient')
        file = parameterize_mixin_parent_selector(file, 'responsive-(in)?visibility')
        file = file.gsub(
            /filter: e\(%\("progid:DXImageTransform.Microsoft.gradient\(startColorstr='%d', endColorstr='%d', GradientType=(\d)\)",argb\(([\-$\w]+)\),argb\(([\-$\w]+)\)\)\);/,
            %Q(filter: progid:DXImageTransform.Microsoft.gradient(startColorstr='\#{ie-hex-str(\\2)}', endColorstr='\#{ie-hex-str(\\3)}', GradientType=\\1);)
        )


      when 'responsive-utilities.less'
        file = convert_to_scss(file)
        file = apply_mixin_parent_selector(file, '\.(visible|hidden)')
      when 'utilities.less'
        file = replace_mixin_file(file)
        file = convert_to_scss(file)
      when 'variables.less'
        file = convert_to_scss(file)
        file = insert_default_vars(file)
      when 'close.less'
        file = convert_to_scss(file)
        # extract .close { button& {...} } rule
        file = extract_nested_rule(file, '\s*button&', 'button.close')
      when 'forms.less'
        file = convert_to_scss(file)
        file = extract_nested_rule(file, '\s*textarea&', 'textarea.form-control')
      else
        file = convert_to_scss(file)
      end

      name = name.gsub(/\.less$/, '.scss')
      if name == 'bootstrap.scss'
        path = "vendor/assets/stylesheets/bootstrap/bootstrap.scss"
      else
        path = "vendor/assets/stylesheets/bootstrap/_#{name}"
      end
      save_file(path, file)
    end
  end

  def process_javascript_assets
    puts "\nProcessing javascripts..."
    read_files('js', bootstrap_js_files).each do |name, file|
      save_file("vendor/assets/javascripts/bootstrap/#{name}", file)
    end

    # Update javascript manifest
    content = ''
    bootstrap_js_files.each do |name|
      name = name.gsub(/\.js$/, '')
      content << "//= require bootstrap/#{name}\n"
    end
    path = "vendor/assets/javascripts/bootstrap.js"
    save_file(path, content)
  end

  private

  def read_files(path, files)
    contents = {}
    full_path = "https://raw.github.com/#@repo/#@branch/#{path}"
    puts "downloading from #{full_path}..."
    files.map do |name|
      Thread.start {
        content = open("#{full_path}/#{name}").read
        Thread.exclusive {
          puts "  ↓ #{name}"
          contents[name] = content
        }
      }
    end.each(&:join)
    contents
  end

  # Get the sha of a dir
  def get_tree_sha(dir)
    trees = open("https://api.github.com/repos/#@repo/git/trees/#@branch").read
    trees = JSON.parse trees
    trees['tree'].find{|t| t['path'] == dir}['sha']
  end

  def bootstrap_less_files
    @bootstrap_less_files ||= begin
      files = open("https://api.github.com/repos/#@repo/git/trees/#{get_tree_sha('less')}").read
      files = JSON.parse files
      files['tree'].select{|f| f['type'] == 'blob' && f['path'] =~ /.less$/ }.map{|f| f['path'] }
    end
  end

  def bootstrap_js_files
    @bootstrap_js_files ||= begin
      files = open("https://api.github.com/repos/#@repo/git/trees/#{get_tree_sha('js')}").read
      files = JSON.parse files
      files = files['tree'].select { |f| f['type'] == 'blob' && f['path'] =~ /.js$/ }.map { |f| f['path'] }
      files.sort_by { |f|
        case f
          # tooltip depends on popover and must be loaded earlier
          when /tooltip/ then
            1
          when /popover/ then
            2
          else
            0
        end
      }
    end
  end

  def get_mixins_name
    mixins      = []
    less_mixins = open("https://raw.github.com/#@repo/#@branch/less/mixins.less").read

    less_mixins.scan(/\.([\w-]+)\(.*\)\s?{?/) do |mixin|
      mixins << mixin.first
    end

    mixins
  end

  def convert_to_scss(file)
    file = replace_vars(file)
    file = replace_mixins(file)
    file = replace_less_extend(file)
    file = replace_spin(file)
    file = replace_image_urls(file)
    file = replace_image_paths(file)
    file = replace_escaping(file)
    file = convert_less_ampersand(file)
    file
  end

  def save_file(path, content, mode='w')
    File.open(path, mode) { |file| file.write(content) }
    puts "Saved #{path}\n"
  end

  def replace_file_imports(less)
    less.gsub(/@import ["|']([\w-]+).less["|'];/, '@import "bootstrap/\1";');
  end

  # @mixin a() { tr& { color:white } }
  # to:
  # @mixin a($parent) { tr#{$parent} { color: white } }
  def parameterize_mixin_parent_selector(file, rule_sel)
    param = '$parent'
    replace_rules(file, '^[ \t]*@mixin\s*' + rule_sel) do |mxn_css|
      mxn_css.sub! /(?=@mixin)/, "// [converter] $parent hack\n"
      # insert param into mixin def
      mxn_css.sub! /(@mixin [\w-]+\()/, "\\1#{param}"
      # wrap properties in #{$parent} { ... }
      replace_properties(mxn_css) { |props| "  \#{#{param}} { #{props.strip} }\n  " }
      # change nested& rules to nested#{$parent}
      replace_rules(mxn_css, /.*[^\s ]&/) { |rule| replace_in_selector rule, /&/, "\#{#{param}}" }
    end
  end

  # extracts rule immediately after it's parent and optionally changes selector to new_selector
  def extract_nested_rule(css, selector, new_selector = selector)
    matches = []
    # first find the rules, and remove them
    css     = replace_rules(css, selector, comments: true) { |rule, pos|
      matches << [rule, pos]
      indent "// [converter] extracted #{get_selector(rule)} to #{new_selector}", indent_width(rule)
    }
    # replace rule selector with new_selector
    matches.each do |m|
      m[0].sub! /(#{COMMENT_RE}*)^(\s*).*?(\s*){/m, "\\1\\2#{new_selector}\\3{"
    end
    replace_substrings_at css,
                          matches.map { |_, pos| pos.begin + css[pos.begin..-1].index('}') + 1 },
                          matches.map { |rule, _| "\n\n" + unindent(rule) }
  end

  # .visible-sm { @include responsive-visibility() }
  # to:
  # @include responsive-visibility('.visible-sm')
  def apply_mixin_parent_selector(file, rule_sel)
    replace_rules file, "(\s*)#{rule_sel}" do |rule|
      next rule unless rule =~ /@include/
      rule =~ /\A\s+/ # keep indentation
      $~.to_s + rule.sub(/(#{COMMENT_RE}*)(#{SELECTOR_RE})\{(.*)\}/m, '\3').sub(/(@include [\w-]+\()/, "#{$1}\\1'#{$2.strip}'").strip
    end
  end

  # #gradient > { @mixin horizontal ... }
  # to:
  # @mixin gradient-horizontal
  def flatten_mixins(file, container, prefix)
    replace_rules file, Regexp.escape(container) do |mixins_css|
      unindent unwrap_rule_block(mixins_css).gsub(/@mixin\s*([\w-]+)/, "@mixin #{prefix}-\\1")
    end
  end

  # Replaces the following:
  #  .mixin()          -> @include mixin()
  #  #scope > .mixin() -> @include scope-mixin()
  def replace_mixins(less)
    mixin_pattern = /(\s+)(([#|\.][\w-]+\s*>\s*)*)\.([\w-]+\(.*\))/
    less.gsub(mixin_pattern) do |match|
      matches = match.scan(mixin_pattern).flatten
      scope = matches[1] || ''
      if scope != ''
        scope = scope.scan(/[\w-]+/).join('-') + '-'
      end
      mixin_name = match.scan(/\.([\w-]+)\(.*\)\s?\{?/).first

      if mixin_name && @mixins.include?(mixin_name.first)
        "#{matches.first}@include #{scope}#{matches.last}".gsub(/; \$/, ", $")
      else
        "#{matches.first}@extend .#{scope}#{matches.last.gsub(/\(\)/, '')}"
      end
    end
  end

  # unwraps topmost rule block
  # #sel { a: b; }
  # to:
  # a: b;
  def unwrap_rule_block(css)
    replace_in_selector(css, /.*/, '').sub(/}\s*\z/m, '')
  end

  def replace_mixin_file(less)
    less.gsub(/^(\s*)\.([\w-]+\(.*\))(\s*\{)/) { |match|
      "#{$1}@mixin #{$2.tr(';', ',')}#{$3}"
    }
  end

  def replace_vars(less)
    less = less.gsub(/(?!@media|@page|@keyframes|@font-face|@-\w)@/, '$')
    # variables that would be ignored by gsub above: e.g. @page-header-border-color
    less.gsub! /@(page[\w-]+)/, '$\1'
    less
  end

  # #gradient > .horizontal()
  # to:
  # @include .horizontal-gradient()
  def replace_less_extend(less)
    less.gsub(/\#(\w+) \> \.([\w-]*)(\(.*\));?/, '@include \1-\2\3;')
  end

  def replace_spin(less)
    less.gsub(/(?![\-$@.])spin(?!-)/, 'adjust-hue')
  end

  def replace_image_urls(less)
    less.gsub(/background-image: url\("?(.*?)"?\);/) {|s| "background-image: image-url(\"#{$1}\");" }
  end

  def replace_image_paths(less)
    less.gsub('../img/', '')
  end

  def replace_escaping(less)
    less = less.gsub(/\~"([^"]+)"/, '#{\1}') # Get rid of ~"" escape
    less.gsub!(/\${([^}]+)}/, '$\1') # Get rid of @{} escape
    less.gsub(/(\W)e\(%\("?([^"]*)"?\)\)/, '\1\2') # Get rid of e(%("")) escape
  end

  def insert_default_vars(scss)
    scss.gsub(/^(\$.+);/, '\1 !default;')
  end

  # Converts &-
  def convert_less_ampersand(less)
    regx = /^\.badge\s*\{[\s\/\w\(\)]+(&{1}-{1})\w.*?^}$/m

    tmp = ''
    less.scan(/^(\s*&)(-[\w\[\]]+\s*{.+})$/) do |ampersand, css|
      tmp << ".badge#{css}\n"
    end

    less.gsub(regx, tmp)
  end

  # unindent by n spaces
  def unindent(txt, n = 2)
    txt.gsub /^[ ]{#{n}}/, ''
  end

  # indent by n spaces
  def indent(txt, n = 2)
    "#{' ' * n}#{txt}"
  end

  # get indent length from the first line of txt
  def indent_width(txt)
    txt.match(/\A\s*/).to_s.length
  end

  # get full selector for rule_block
  def get_selector(rule_block)
    /^\s*(#{SELECTOR_RE}?)\s*\{/.match(rule_block) && $1 && $1.strip
  end

  # replace CSS rule blocks matching rule_prefix with yield(rule_block, rule_pos)
  # will also include immediately preceding comments in rule_block
  #
  # option :comments -- include immediately preceding comments in rule_block
  #
  # replace_rules(".a{ \n .b{} }", '.b') { |rule| ">#{rule}<"  } #=> ".a{ \n >.b{}< }"
  def replace_rules(less, rule_prefix = SELECTOR_RE, options = {})
    options = {comments: true}.merge(options || {})
    less    = less.dup
    s       = StringScanner.new(less)
    rule_re = "#{rule_prefix}[^{]*#{RULE_OPEN_BRACE_RE}"
    if options[:comments]
      rule_start_re = /#{COMMENT_RE}*^#{rule_re}/
    else
      rule_start_re = /^#{rule_re}/
    end

    while (rule_start = scan_next(s, rule_start_re))
      rule_pos       = (s.pos - rule_start.length..next_brace_pos(less, s.pos - 1))
      less[rule_pos] = yield(less[rule_pos], rule_pos)
    end
    less
  end

  # replace in the top-level selector
  # replace_in_selector('a {a: {a: a} } a {}', /a/, 'b') => 'b {a: {a: a} } b {}'
  def replace_in_selector(css, pattern, sub)
    # scan for selector positions in css
    s        = StringScanner.new(css)
    prev_pos = 0
    sel_pos  = []
    while (brace = scan_next(s, /#{RULE_OPEN_BRACE_RE}/))
      sel_pos << (prev_pos .. s.pos - 1)
      s.pos    = next_brace_pos(css, s.pos - 1) + 1
      prev_pos = s.pos
    end
    replace_substrings_at(css, sel_pos) { |s| s.gsub(pattern, sub) }
  end


  sel_chars = '\[\]$\w\-{}#,.:&>@'
  SELECTOR_RE = /[#{sel_chars}]+[#{sel_chars}\s]*/
  COMMENT_RE = %r((?:^[ \t]*//[^\n]*\n))
  RULE_OPEN_BRACE_RE = /(?<!#)\{/
  RULE_CLOSE_BRACE_RE = /(?<!\w)\}/
  BRACE_RE    = /#{RULE_OPEN_BRACE_RE}|#{RULE_CLOSE_BRACE_RE}/m

  # replace first level properties in the css with yields
  # replace_properties("a { color: white }") { |props| props.gsub 'white', 'red' }
  def replace_properties(css, &block)
    s = StringScanner.new(css)
    s.skip_until /#{RULE_OPEN_BRACE_RE}\n?/
    prev_pos = s.pos
    depth = 0
    pos = []
    while (b = scan_next(s, /#{SELECTOR_RE}#{RULE_OPEN_BRACE_RE}|#{RULE_CLOSE_BRACE_RE}/m))
      depth += (b == '}' ? -1 : +1)
      if depth == 1
        if b == '}'
          prev_pos = s.pos
        else
          pos << (prev_pos .. s.pos - b.length - 1)
        end
      end
    end
    replace_substrings_at css, pos, &block
  end


  # next matching brace for brace at brace_pos in css
  def next_brace_pos(css, brace_pos)
    depth = 0
    s     = StringScanner.new(css[brace_pos..-1])
    while (b = scan_next(s, BRACE_RE))
      depth += (b == '}' ? -1 : +1)
      break if depth.zero?
    end
    raise "match not found for {" unless depth.zero?
    brace_pos + s.pos - 1
  end

  # advance scanner to pos after the next match of pattern and return the match
  def scan_next(scanner, pattern)
    return unless scanner.skip_until(pattern)
    scanner.pos -= scanner.matched_size
    scanner.scan pattern
  end

  # insert substitutions into text at positions (Range or Fixnum)
  # substitutions can be passed as array or as yields from the &block called with |substring, position, text|
  # position is a range (begin..end)
  def replace_substrings_at(text, positions, replacements = nil, &block)
    offset = 0
    positions.each_with_index do |p, i|
      p = (p...p) if p.is_a?(Fixnum)
      p       = p.exclude_end? ? (p.begin + offset ... p.end + offset) : (p.begin + offset .. p.end + offset)
      # block returns the substitution, e.g.: { |text, pos| text[pos].upcase }
      r       = replacements ? replacements[i] : block.call(text[p], p, text)
      offset  += r.size - (p.end - p.begin + 1)
      text[p] = r
    end
    text
  end
end