# frozen_string_literal: true

################################################################################
# For more details on Composer version constraints, see:                       #
# https://getcomposer.org/doc/articles/versions.md#writing-version-constraints #
################################################################################

require "dependabot/composer/update_checker"
require "dependabot/composer/version"
require "dependabot/composer/requirement"

module Dependabot
  module Composer
    class UpdateChecker
      class RequirementsUpdater
        ALIAS_REGEX = /[a-z0-9\-_\.]*\sas\s+/.freeze
        VERSION_REGEX =
          /(?:#{ALIAS_REGEX})?[0-9]+(?:\.[a-zA-Z0-9*\-]+)*/.freeze
        AND_SEPARATOR =
          /(?<=[a-zA-Z0-9*])(?<!\sas)[\s,]+(?![\s,]*[|-]|as)/.freeze
        OR_SEPARATOR = /(?<=[a-zA-Z0-9*])[\s,]*\|\|?\s*/.freeze
        SEPARATOR = /(?:#{AND_SEPARATOR})|(?:#{OR_SEPARATOR})/.freeze
        ALLOWED_UPDATE_STRATEGIES =
          %i(widen_ranges bump_versions bump_versions_if_necessary).freeze

        def initialize(requirements:, update_strategy:,
                       latest_resolvable_version:)
          @requirements = requirements
          @update_strategy = update_strategy

          check_update_strategy

          return unless latest_resolvable_version

          @latest_resolvable_version =
            version_class.new(latest_resolvable_version)
        end

        def updated_requirements
          return requirements unless latest_resolvable_version

          requirements.map { |req| updated_requirement(req) }
        end

        private

        attr_reader :requirements, :update_strategy,
                    :latest_resolvable_version

        def check_update_strategy
          return if ALLOWED_UPDATE_STRATEGIES.include?(update_strategy)

          raise "Unknown update strategy: #{update_strategy}"
        end

        # rubocop:disable Metrics/PerceivedComplexity
        def updated_requirement(req)
          req_string = req[:requirement].strip
          or_string_reqs = req_string.split(OR_SEPARATOR)
          or_separator = req_string.match(OR_SEPARATOR)&.to_s || " || "
          numeric_or_string_reqs = or_string_reqs.
                                   reject { |r| r.strip.start_with?("dev-") }
          branch_or_string_reqs = or_string_reqs.
                                  select { |r| r.strip.start_with?("dev-") }

          return req unless req_string.match?(/\d/)
          return req if numeric_or_string_reqs.none?
          return updated_alias(req) if req_string.match?(ALIAS_REGEX)
          return req if req_satisfied_by_latest_resolvable?(req_string) &&
                        update_strategy != :bump_versions

          new_req =
            case update_strategy
            when :widen_ranges
              widen_requirement(req, or_separator)
            when :bump_versions, :bump_versions_if_necessary
              update_requirement_version(req, or_separator)
            end

          new_req_string =
            [new_req[:requirement], *branch_or_string_reqs].join(or_separator)
          new_req.merge(requirement: new_req_string)
        end
        # rubocop:enable Metrics/PerceivedComplexity

        def updated_alias(req)
          req_string = req[:requirement]
          real_version = req_string.split(/\sas\s/).first.strip

          # If the version we're aliasing isn't a version then we don't know
          # how to update it, so we just return the existing requirement.
          return req unless version_class.correct?(real_version)

          new_version_string = latest_resolvable_version.to_s
          new_req = req_string.sub(real_version, new_version_string)
          req.merge(requirement: new_req)
        end

        def widen_requirement(req, or_separator)
          current_requirement = req[:requirement]
          reqs = current_requirement.strip.split(SEPARATOR).map(&:strip)

          updated_requirement =
            if reqs.any? { |r| r.strip.start_with?("^") }
              update_caret_requirement(current_requirement, or_separator)
            elsif reqs.any? { |r| r.strip.start_with?("~") }
              update_tilda_requirement(current_requirement, or_separator)
            elsif reqs.any? { |r| r.include?("*") }
              update_wildcard_requirement(current_requirement, or_separator)
            elsif reqs.any? { |r| r.match?(/<|(\s+-\s+)/) }
              update_range_requirement(current_requirement, or_separator)
            else
              update_version_string(current_requirement)
            end

          req.merge(requirement: updated_requirement)
        end

        def update_requirement_version(req, or_separator)
          current_requirement = req[:requirement]
          reqs = current_requirement.strip.split(SEPARATOR).map(&:strip)

          updated_requirement =
            if reqs.count > 1
              "^#{latest_resolvable_version}"
            elsif reqs.any? { |r| r.match?(/<|(\s+-\s+)/) }
              update_range_requirement(current_requirement, or_separator)
            elsif reqs.any? { |r| r.match?(/>[^=]/) }
              current_requirement
            else
              update_version_string(current_requirement)
            end

          req.merge(requirement: updated_requirement)
        end

        def req_satisfied_by_latest_resolvable?(requirement_string)
          ruby_requirements(requirement_string).
            any? { |r| r.satisfied_by?(latest_resolvable_version) }
        end

        def update_version_string(req_string)
          req_string.
            sub(VERSION_REGEX) do |old_version|
              unless req_string.match?(/[~*\^]/)
                next latest_resolvable_version.to_s
              end

              old_parts = old_version.split(".")
              new_parts = latest_resolvable_version.to_s.split(".").
                          first(old_parts.count)
              new_parts.map.with_index do |part, i|
                old_parts[i] == "*" ? "*" : part
              end.join(".")
            end
        end

        def ruby_requirements(requirement_string)
          Composer::Requirement.requirements_array(requirement_string)
        end

        def update_caret_requirement(req_string, or_separator)
          caret_requirements =
            req_string.split(SEPARATOR).select { |r| r.strip.start_with?("^") }
          version_parts = latest_resolvable_version.segments

          min_existing_precision =
            caret_requirements.map { |r| r.split(".").count }.min
          first_non_zero_index =
            version_parts.count.times.find { |i| version_parts[i] != 0 }

          precision = [min_existing_precision, first_non_zero_index + 1].max
          version = version_parts.first(precision).map.with_index do |part, i|
            i <= first_non_zero_index ? part : 0
          end.join(".")

          req_string + "#{or_separator}^#{version}"
        end

        def update_tilda_requirement(req_string, or_separator)
          tilda_requirements =
            req_string.split(SEPARATOR).select { |r| r.strip.start_with?("~") }
          precision = tilda_requirements.map { |r| r.split(".").count }.min

          version_parts = latest_resolvable_version.segments.first(precision)
          version_parts[-1] = 0
          version = version_parts.join(".")

          req_string + "#{or_separator}~#{version}"
        end

        def update_wildcard_requirement(req_string, or_separator)
          wildcard_requirements =
            req_string.split(SEPARATOR).select { |r| r.include?("*") }
          precision = wildcard_requirements.map do |r|
            r.split(".").reject { |s| s == "*" }.count
          end.min
          wildcard_count = wildcard_requirements.map do |r|
            r.split(".").select { |s| s == "*" }.count
          end.min

          version_parts = latest_resolvable_version.segments.first(precision)
          version = version_parts.join(".")

          req_string + "#{or_separator}#{version}#{'.*' * wildcard_count}"
        end

        def update_range_requirement(req_string, or_separator)
          range_requirements =
            req_string.split(SEPARATOR).select { |r| r.match?(/<|(\s+-\s+)/) }

          if range_requirements.count == 1
            range_requirement = range_requirements.first
            versions = range_requirement.scan(VERSION_REGEX)
            upper_bound = versions.map { |v| version_class.new(v) }.max
            new_upper_bound = update_greatest_version(
              upper_bound,
              latest_resolvable_version
            )

            req_string.sub(upper_bound.to_s, new_upper_bound.to_s)
          else
            req_string + "#{or_separator}^#{latest_resolvable_version}"
          end
        end

        def update_greatest_version(old_version, version_to_be_permitted)
          version = version_class.new(old_version)
          version = version.release if version.prerelease?

          index_to_update =
            version.segments.map.with_index { |seg, i| seg.zero? ? 0 : i }.max

          version.segments.map.with_index do |_, index|
            if index < index_to_update
              version_to_be_permitted.segments[index]
            elsif index == index_to_update
              version_to_be_permitted.segments[index] + 1
            else 0
            end
          end.join(".")
        end

        def version_class
          Composer::Version
        end
      end
    end
  end
end