# frozen_string_literal: true

require 'uri'

class Groupie
  # Tokenizer helps turn a String into an Array of Strings that are the
  # individual tokens (mostly words) from the input.
  #
  # Please consider this entire class to be a private API,
  # and use Groupie.tokenize to tokenize things.
  class Tokenizer
    def initialize(input)
      # Ensure our input is converted to a String and duplicated so we can modify it in-place
      @raw = input.to_s.dup
    end

    def to_tokens
      return @tokens if @tokens

      # In-place modifications to our @raw String
      downcase!
      normalize_whitespace!
      strip_html_tags!
      tokenize_urls!
      strip_non_word_characters!

      # Split the resulting string on whitespace and clean up the token candidates
      @tokens = @raw.split.map { |str| remove_interpunction!(str) }

      @tokens
    end

    private

    # Ignore case by downcasing everything
    def downcase!
      @raw.downcase!
    end

    # Convert all types of whitespace (space, tab, newline) into regular spaces
    def normalize_whitespace!
      @raw.gsub!(/\s+/, ' ')
    end

    # Strip HTML tags entirely
    def strip_html_tags!
      @raw.gsub!(/<[^>]+?>/, ' ')
    end

    # Intelligently split URLs into their component parts
    def tokenize_urls!
      @raw.gsub!(%r{http[\w\-\#:/_.?&=]+}) do |url|
        maybe_parse_url(url) do |uri|
          path = uri.path.tap { |str| str.tr!('/_\-', ' ') }
          query = uri.query.tap { |str| str&.tr!('?=&#_\-', ' ') }
          fragment = uri.fragment.tap { |str| str&.tr!('#_/\-', ' ') }

          "#{uri.scheme} #{uri.host} #{path} #{query} #{fragment}"
        end
      end
    end

    # Strip characters not likely to be part of a word or number
    def strip_non_word_characters!
      @raw.gsub!(/[^\w\ \-.,]/, ' ')
    end

    # Remove wrapping quotes and interpunction from individual token candidates
    def remove_interpunction!(str)
      str.gsub!(/\A['"]+|[!,."']+\Z/, '')
      str
    end

    # Sometimes a String looks like a URL, but it's not.
    # This method attempts to parse the input string into a URI.
    # If it's successful, yield it to the block and return its response.
    # In case of failure, return the original string.
    def maybe_parse_url(input)
      uri = URI.parse(input)
      yield uri
    rescue URI::InvalidURIError
      input
    end
  end
end