require "nokogiri"
require "svg_optimizer"
require "bridgetown-core/liquid_extensions"

PLUGINS_BLOCKLIST = [
  SvgOptimizer::Plugins::CleanupId
]

PLUGINS = SvgOptimizer::DEFAULT_PLUGINS.delete_if { |plugin|
  PLUGINS_BLOCKLIST.include? plugin
}

module BridgetownInlineSvg
  class SvgTag < Liquid::Tag
    # import lookup_variable function
    # https://github.com/bridgetownrb/bridgetown/blob/main/bridgetown-core/lib/bridgetown-core/liquid_extensions.rb
    include Bridgetown::LiquidExtensions

    # For interpoaltion, look for liquid variables
    VARIABLE = /\{\{\s*([\w.\-]+)\s*\}\}/i

    # Separate file path from other attributes
    PATH_SYNTAX = %r{
      ^(?<path>[^\s"']+|"[^"]+"|'[^']+')
      (?<params>.*)
    }x

    # parse the first parameter in a string, giving :
    #  [full_match, param_name, double_quoted_val, single_quoted_val, unquoted_val]
    # The Regex works like :
    # - first group
    #    - match a group of characters that is alphanumeric, _ or -.
    # - second group (non-capturing OR)
    #    - match a double-quoted string
    #    - match a single-quoted string
    #    - match an unquoted string matching the set : [\w\.\-#]
    PARAM_SYNTAX = %r{
      ([\w-]+)\s*=\s*
      (?:"([^"\\]*(?:\\.[^"\\]*)*)"|'([^'\\]*(?:\\.[^'\\]*)*)'|([\w.\-#]+))
    }x

    def initialize(tag_name, markup, tokens)
      super
      @svg, @params = BridgetownInlineSvg::SvgTag.parse_params(markup)
    end

    # lookup Liquid variables from markup in context
    def interpolate(markup, context)
      markup.scan VARIABLE do |variable|
        markup = markup.sub(VARIABLE, lookup_variable(context, variable.first))
      end
      markup
    end

    def split_params(markup, context)
      params = {}
      while (match = PARAM_SYNTAX.match(markup))
        markup = markup[match.end(0)..-1]
        value = if match[2]
          interpolate(match[2].gsub(%r{\\"}, '"'), context)
        elsif match[3]
          interpolate(match[3].gsub(%r{\\'}, "'"), context)
        elsif match[4]
          lookup_variable(context, match[4])
        end
        params[match[1]] = value
      end
      params
    end

    # Parse parameters. Returns : [svg_path, parameters]
    # Does not interpret variables as it's done at render time
    def self.parse_params(markup)
      matched = markup.strip.match(PATH_SYNTAX)
      unless matched
        raise SyntaxError, <<~END
          Syntax Error in tag 'highlight' while parsing the following markup:
          #{markup}
          Valid syntax: svg <path> [property=value]
        END
      end
      path = matched["path"].sub(%r{^["']}, "").sub(%r{["']$}, "").strip
      params = matched["params"].strip
      [path, params]
    end

    def fmt(params)
      r = params.to_a.select { |v| v[1] != "" }.map { |v| %(#{v[0]}="#{v[1]}") }
      r.join(" ")
    end

    def create_plugin(params)
      mod = Class.new(SvgOptimizer::Plugins::Base) {
        def self.set(p)
          @@params = p
        end

        def process
          @@params.each { |key, val| xml.root.set_attribute(key, val) }
          xml
        end
      }
      mod.set(params)
      mod
    end

    def add_file_to_dependency(site, path, context)
      if context.registers[:page]&.key?("path")
        site.regenerator.add_dependency(
          site.in_source_dir(context.registers[:page]["path"]),
          path
        )
      end
    end

    def render(context)
      # global site variable
      site = context.registers[:site]
      # check if given name is a variable. Otherwise use it as a file name
      svg_file = Bridgetown.sanitized_path(site.source, interpolate(@svg, context))
      return unless svg_file
      add_file_to_dependency(site, svg_file, context)
      # replace variables with their current value
      params = split_params(@params, context)
      # because ie11 require to have a height AND a width
      if params.key?("width") && !params.key?("height")
        params["height"] = params["width"]
      end
      # params = @params
      file = File.open(svg_file, "rb").read
      conf = lookup_variable(context, "site.svg")
      if conf["optimize"] == true
        xml = SvgOptimizer.optimize(file, [create_plugin(params)] + PLUGINS)
      else
        xml = Nokogiri::XML(file)
        params.each { |key, val| xml.root.set_attribute(key, val) }
        xml = xml.root.to_xml
      end
      xml
    end
  end
end