require 'coverage'
require 'find'
require 'json'

module OneshotCoverage
  class SimplecovReporter
    module DefaultFilter
      module_function def call(path)
        return false unless File.extname(path) == '.rb'
        return false if path.include?('/spec/')
        return false if path.include?('/test/')
        return false if path.include?('/script/')
        return false if path.include?('/config/')

        true
      end
    end

    # @option log_path [String] oneshot coverage log generated by FileLogger or same scheme json file acceptable
    # @option project_path [String] target project path.
    # @option file_filter [Object] Object respond to #call with return true | false. this filter used for coverage target. file_filter.call(path) return false, then path will not be included to report
    def initialize(
      log_path:,
      project_path: Dir.pwd,
      file_filter: DefaultFilter
    )
      @project_path = project_path.end_with?('/') ? project_path : "#{project_path}/"
      @log_path = log_path
      @file_filter = file_filter
    end

    def run
      raise "Please install & require 'simplecov' if you want to use this" unless defined? SimpleCov

      coverages = coverage_stubs
      fill_lines(coverages)
      gen_html(coverages)
    end

    private

    def coverage_candidates
      @coverage_candidates ||=
        Find.find(@project_path).
          select { |fp| @file_filter.call(fp) }
          # map { |fp| fp.sub(@project_path, '') }
    end

    def coverage_stubs
      {}.tap do |stubs|
        coverage_candidates.each do |filepath|
          stub = Coverage.line_stub(filepath)
          stubs[filepath] = stub
        end
      end
    end

    def oneshot_coverage_logs
      @oneshot_coverage_logs ||= begin
        raise "#{@log_path} isn't exist!" unless File.exist?(@log_path)

        JSON.parse(File.read(@log_path)).transform_keys do |filepath_with_md5_hash|
          *path_tokens, _md5_hash = filepath_with_md5_hash.split('-')
          "#{@project_path}#{path_tokens.join('-')}"
        end
      end
    end

    def fill_lines(coverages)
      oneshot_coverage_logs.each do |filepath, linenums|
        linenums.each do |linenum|
          coverages[filepath][linenum - 1] = 1
        end
      end
    end

    def format_data(coverages)
      coverages.transform_values do |lines|
        { "lines" => lines }
      end
    end

    def gen_html(coverages)
      coverages_for_simcov = format_data(coverages)
      SimpleCov.root(@project_path)
      result = SimpleCov::Result.from_hash({
        'oneshot' => {
          'coverage' => coverages_for_simcov,
          'timestamp' => Time.now.to_i
        }
      }).first
      SimpleCov::Formatter::HTMLFormatter.new.format(result)
    end
  end
end