# frozen-string-literal: true

# Copyright (C) 2020 Thomas Baron
#
# This file is part of term_utils.
#
# term_utils is free software: you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation, version 3 of the License.
#
# term_utils is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with term_utils.  If not, see <https://www.gnu.org/licenses/>.

module TermUtils
  module AP
    # Represents the argument list parser.
    class Parser
      # Constructs a new Parser.
      def initialize
      end

      # Parses a given list of arguments.
      # @param syntax [Syntax]
      # @param arguments [Array<String>]
      # @param opts [Hash]
      # @return [Result]
      # @raise [ParseError]
      # @raise [SyntaxError]
      def parse_arguments(syntax, arguments, opts = {}, &block)
        syntax = syntax.dup
        syntax.finalize!
        arguments = arguments.dup
        res = TermUtils::AP::Result.new(syntax)
        catch :done do
          parse0(res, syntax, arguments, opts)
        end
        res.remaining_arguments = arguments
        res.walk(&block) if block
        res
      end

      # Tests whether a given sample matches a shortcut flag.
      # @param shortcut_flags [Hash<String, Flag>]
      # @param arg [String]
      # @return [Array<String>, nil] Replacements on success, nil otherwise.
      def self.match_shortcut_flag(shortcut_flags, arg)
        shortcut_flags.each do |label, flag|
          next unless arg.start_with? label

          return [flag.label, arg[label.length..-1]]
        end

        nil
      end

      # Evaluates the added number of min occurs of a given array of articles.
      # @param articles [Array<TermUtils::AP::Article>]
      # @return [Integer]
      def self.eval_article_min_occurs(articles)
        articles.inject(0) { |acc, a| acc + a.min_occurs }
      end

      private

      # Parses a given argument list.
      # @param result [Result]
      # @param syntax [Syntax]
      # @param arguments [Array<String>]
      # @raise [ParseError]
      def parse0(result, syntax, arguments, opts = {})
        unflagged_params, flagged_params, shortcut_flags = syntax.fetch_parameters
        fp_occ = {}
        syntax.parameters.each { |p| fp_occ[p.id] = 0 if p.flagged? }
        up_occ = 0
        loop do
          break if arguments.empty?

          if arguments.first.start_with?('-') && !%w[- --].include?(arguments.first)
            # Flagged
            unless flagged_params.key? arguments.first
              # Unknown flag
              # Try shortcut flag
              flag, arg = self.class.match_shortcut_flag(shortcut_flags, arguments.first)
              if flag && arg
                # Shortcut match
                arguments.shift
                arguments.unshift arg
                arguments.unshift flag
              end
            end
            unless flagged_params.key? arguments.first
              # Unknown flag
              # End of parsing
              raise TermUtils::AP::ParseError, 'flagged parameter unexpected' if opts.fetch(:strict, false)

              break
            end

            param = flagged_params[arguments.first]
            if param.occur_bounded? && (fp_occ[param.id] >= param.max_occurs)
              # Max occurs reached
              raise TermUtils::AP::ParseError, "occur limit reached (#{param.id})" if opts.fetch(:strict, false)

              break
            end

            fp_occ[param.id] += 1
            arguments.shift
            param_res = TermUtils::AP::ParameterResult.new(result, param)
            parse0_param(param_res, param, arguments)
          else
            # Unflagged
            if unflagged_params.empty?
              # End of parsing
              raise TermUtils::AP::ParseError, 'unflagged parameter unexpected' if opts.fetch(:strict, false)

              break
            end

            param = unflagged_params.first
            if arguments.first == '--'
              # End of parameter
              raise TermUtils::AP::ParseError, "parameter not consumed (#{param.id})" if up_occ < param.min_occurs

              arguments.shift
              unflagged_params.shift
              up_occ = 0
              next
            end

            up_occ += 1
            param_res = TermUtils::AP::ParameterResult.new(result, param)
            case parse0_param(param_res, param, arguments)
            when :esc_param
              raise TermUtils::AP::ParseError, "parameter not consumed (#{param.id})" if up_occ < param.min_occurs

              unflagged_params.shift
              up_occ = 0
            else
              if !param.multiple_occurs? || (param.occur_bounded? && (up_occ >= param.max_occurs))
                unflagged_params.shift
                up_occ = 0
              end
            end
          end
        end # loop
        # Check min occurs
        syntax.parameters.each do |p|
          next if result.find_parameters(p.id).length >= p.min_occurs

          raise TermUtils::AP::ParseError, "parameter not consumed (#{p.id})"
        end
      end

      # Parses with a given Parameter.
      # @param result [ParameterResult]
      # @param param [Parameter]
      # @param arguments [Array<String>]
      # @return [Symbol, nil] `:esc_param`, or nil.
      def parse0_param(result, param, arguments)
        arts = param.fetch_articles
        occ = 0
        loop do
          break if arts.empty?

          if arguments.empty?
            # End of arguments
            raise TermUtils::AP::ParseError, 'article not consumed' if occ < arts.first.min_occurs
            raise TermUtils::AP::ParseError, 'article not consumed' if self.class.eval_article_min_occurs(arts[1..-1]) > 0

            break
          end

          if arguments.first == '-'
            # End of article
            raise TermUtils::AP::ParseError, 'article not consumed' if occ < arts.first.min_occurs

            arguments.shift
            arts.shift
            occ = 0
            next
          elsif arguments.first.start_with? '-'
            # End of parameter
            raise TermUtils::AP::ParseError, 'article not consumed' if occ < arts.first.min_occurs
            raise TermUtils::AP::ParseError, 'article not consumed' if self.class.eval_article_min_occurs(arts[1..-1]) > 0

            if arguments.first == '--'
              arguments.shift
              return :esc_param
            end

            break
          end
          art = arts.first
          TermUtils::AP::ArticleResult.new(result, art, arguments.shift)
          occ += 1
          if !art.multiple_occurs? || (art.occur_bounded? && (occ >= art.max_occurs))
            arts.shift
            occ = 0
          end
        end # loop
        nil
      end
    end
  end
end