# frozen_string_literal: true

require "slim_lint/ruby_extractor"
require "slim_lint/ruby_extract_engine"
require "rubocop"

module SlimLint
  class Linter
    # Runs RuboCop on Ruby code extracted from Slim templates.
    class RuboCop < Linter
      include LinterRegistry

      on_start do |_sexp|
        processed_sexp = SlimLint::RubyExtractEngine.new.call(document.source)

        extractor = SlimLint::RubyExtractor.new
        extracted_source = extractor.extract(processed_sexp)

        next if extracted_source.source.empty?

        find_lints(extracted_source.source, extracted_source.source_map)
      end

      private

      # Executes RuboCop against the given Ruby code and records the offenses as
      # lints.
      #
      # @param ruby [String] Ruby code
      # @param source_map [Hash] map of Ruby code line numbers to original line
      #   numbers in the template
      def find_lints(ruby, source_map)
        rubocop = ::RuboCop::CLI.new

        filename = document.file ? "#{document.file}.rb" : "ruby_script.rb"

        with_ruby_from_stdin(ruby) do
          extract_lints_from_offenses(lint_file(rubocop, filename), source_map)
        end
      end

      # Defined so we can stub the results in tests
      #
      # @param rubocop [RuboCop::CLI]
      # @param file [String]
      # @return [Array<RuboCop::Cop::Offense>]
      def lint_file(rubocop, file)
        rubocop.run(rubocop_flags << file)
        OffenseCollector.offenses
      end

      # Aggregates RuboCop offenses and converts them to {SlimLint::Lint}s
      # suitable for reporting.
      #
      # @param offenses [Array<RuboCop::Cop::Offense>]
      # @param source_map [Hash]
      def extract_lints_from_offenses(offenses, source_map)
        offenses.reject! { |offense| config["ignored_cops"].include?(offense.cop_name) }
        offenses.each do |offense|
          @lints << Lint.new(
            [self, offense.cop_name],
            document.file,
            location_for_line(source_map, offense),
            offense.message.gsub(/ at \d+, \d+/, "")
          )
        end
      end

      # Returns flags that will be passed to RuboCop CLI.
      #
      # @return [Array<String>]
      def rubocop_flags
        flags = %w[--format SlimLint::Linter::RuboCop::OffenseCollector]
        flags += ["--no-display-cop-names"]
        flags += ["--config", ENV["SLIM_LINT_RUBOCOP_CONF"]] if ENV["SLIM_LINT_RUBOCOP_CONF"]
        flags += ["--stdin"]
        flags
      end

      # Overrides the global stdin to allow RuboCop to read Ruby code from it.
      #
      # @param ruby [String] the Ruby code to write to the overridden stdin
      # @param _block [Block] the block to perform with the overridden stdin
      # @return [void]
      def with_ruby_from_stdin(ruby, &_block)
        original_stdin = $stdin
        stdin = StringIO.new
        stdin.puts(ruby.chomp)
        stdin.rewind
        $stdin = stdin
        yield
      ensure
        $stdin = original_stdin
      end

      def location_for_line(source_map, offense)
        if source_map.key?(offense.line)
          start = source_map[offense.line].adjust(column: offense.column)
          finish = source_map[offense.last_line].adjust(column: offense.last_column)
          SourceLocation.merge(start, finish, length: offense.column_length)
        else
          SourceLocation.new(start_line: document.source_lines.size, start_column: 0)
        end
      end

      # Collects offenses detected by RuboCop.
      class OffenseCollector < ::RuboCop::Formatter::BaseFormatter
        class << self
          # List of offenses reported by RuboCop.
          attr_accessor :offenses
        end

        # Executed when RuboCop begins linting.
        #
        # @param _target_files [Array<String>]
        def started(_target_files)
          self.class.offenses = []
        end

        # Executed when a file has been scanned by RuboCop, adding the reported
        # offenses to our collection.
        #
        # @param _file [String]
        # @param offenses [Array<RuboCop::Cop::Offense>]
        def file_finished(_file, offenses)
          self.class.offenses += offenses
        end
      end
    end
  end
end