module Report
  class SurveyItem
    def self.create_report(school:, academic_year:, filename:)
      # first, determine headers by finding the school and grades
      # Q: Should a grade not be included if it has no sufficient responses?
      # A: Include all grades, except preschool

      # Convert they keys in this hash to a hash where the key is the grade
      # and the value is a set of sufficient survey IDs
      survey_ids_to_grades = Hash.new
      SurveyItemResponse.student_survey_items_with_responses_by_grade(
        school:,
        academic_year:
      ).each do |key, count|
        # key[1] is survey item ID
        # key[0] is grade
        survey_ids_to_grades[key[1]] ||= Set.new
        # we do not display the grade avg if there are < 10 responses
        survey_ids_to_grades[key[1]].add(key[0]) if count >= 10
      end
      headers = [
        "Survey Item",
        "Category",
        "Subcategory",
        "Survey Measure",
        "Survey Scale",
        "Survey Population"
      ]
      school.grades(academic_year:).sort.each do |value|
        next if value == -1
        if value == 0
          headers.append("Kindergarten")
        else
          headers.append("Grade #{value}")
        end
      end
      headers.append("#{school.name}")
      # Then, add the headers to data
      data = []
      data << headers
      # for each survey item id
      survey_ids_to_grades.each do |id, grades|
        row = []
        survey_item = ::SurveyItem.find_by_id(id)
        row.concat(survey_item_info(survey_item:)) # fills prompt + categories
        row.append("Students")
        school.grades(academic_year:).sort.each do |grade|
          next if grade == -1
          if grades.include?(grade)
            # we already know grade has sufficient responses
            row.append("#{survey_item.survey_item_responses.where(school:, academic_year:, grade:).average(:likert_score).to_f.round(2)}")
          else
            row.append("N/A")
          end
        end
        # filter out response rate at subcategory level <24.5% for school average
        scale = Scale.find_by_id(survey_item.scale_id)
        measure = ::Measure.find_by_id(scale.measure_id)
        subcategory = ::Subcategory.find_by_id(measure.subcategory_id)
        if ::StudentResponseRateCalculator.new(subcategory:, school:, academic_year:).meets_student_threshold?
          row.append("#{survey_item.survey_item_responses.where(
                     # We allow the nil (unknown) grades in the school survey item average
                     # also filter less than 10 responses in the whole school
                     "school_id = ? and academic_year_id = ? and (grade IS NULL or grade IN (?))", school.id, academic_year.id, school.grades(academic_year:)
                  ).group("survey_item_id").having("count(*) >= 10").average(:likert_score).values[0].to_f.round(2)}")
        else
          row.append("N/A")
        end
        data << row
      end
      # Next up is teacher data
      SurveyItemResponse.teacher_survey_items_with_sufficient_responses(school:, academic_year:).keys.each do |key| # each key is a survey item id
        row = []
        survey_item = ::SurveyItem.find_by_id(key)
        row.concat(survey_item_info(survey_item:))
        row.append("Teacher")
        # we need to add padding to skip the grades columns
        # we also need to remove another column if the school teaches preschool, which we skip entirely
        preschool_adjustment = school.grades(academic_year:).include?(-1) ? 1 : 0
        padding = Array.new(school.grades(academic_year:).length - preschool_adjustment) { '' }
        row.concat(padding)
        # we already know that the survey item we are looking at has sufficient responses
        row.append("#{survey_item.survey_item_responses.where(school:, academic_year:).average(:likert_score).to_f.round(2)}")
        data << row
      end
      FileUtils.mkdir_p Rails.root.join("tmp", "reports")
      filepath = Rails.root.join("tmp", "reports", filename)
      write_csv(data:, filepath:)
      data
    end

    def self.write_csv(data:, filepath:)
      csv = CSV.generate do |csv|
        data.each do |row|
          csv << row
        end
      end
      File.write(filepath, csv)
    end

    def self.survey_item_info(survey_item:)
      prompt = survey_item.prompt
      scale = Scale.find_by_id(survey_item.scale_id)
      measure = ::Measure.find_by_id(scale.measure_id)
      subcategory = ::Subcategory.find_by_id(measure.subcategory_id)
      category = Category.find_by_id(subcategory.category_id)
      return [prompt, category.name, subcategory.name, measure.name, scale.scale_id]
    end
  end
end