module Danger

  # Lint files of a gradle based Android project.
  # This is done using the Android's [Lint](https://developer.android.com/studio/write/lint.html) tool.
  # Results are passed out as tables in markdown.
  #
  # @example Running AndroidLint with its basic configuration
  #
  #          android_lint.lint
  #
  # @example Running AndroidLint with a specific gradle task
  #
  #          android_lint.gradle_task = "lintMyFlavorDebug"
  #          android_lint.lint
  #
  # @example Running AndroidLint for a specific severity level and up
  #
  #          # options are ["Warning", "Error", "Fatal"]
  #          android_lint.severity = "Error"
  #          android_lint.lint
  #
  # @see loadsmart/danger-android_lint
  # @tags android, lint
  #
  class DangerAndroidLint < Plugin

    SEVERITY_LEVELS = ["Warning", "Error", "Fatal"]

    # Location of lint report file
    # If your Android lint task outputs to a different location, you can specify it here.
    # Defaults to "app/build/reports/lint/lint-result.xml".
    # @return [String]
    attr_accessor :report_file
    # A getter for `report_file`.
    # @return [String]
    def report_file
      return @report_file || 'app/build/reports/lint/lint-result.xml'
    end

    # Custom gradle task to run.
    # This is useful when your project has different flavors.
    # Defaults to "lint".
    # @return [String]
    attr_accessor :gradle_task

    # Defines the severity level of the execution.
    # Selected levels are the chosen one and up.
    # Possible values are "Warning", "Error" or "Fatal".
    # Defaults to "Warning".
    # @return [String]
    attr_writer :severity

    # Calls lint task of your gradle project.
    # It fails if `gradlew` cannot be found inside current directory.
    # It fails if `severity` level is not a valid option.
    # It fails if `xmlReport` configuration is not set to `true` in your `build.gradle` file.
    # @return [void]
    #
    def lint
      unless gradlew_exists?
        fail("Could not find `gradlew` inside current directory")
        return
      end

      unless SEVERITY_LEVELS.include?(severity)
        fail("'#{severity}' is not a valid value for `severity` parameter.")
        return
      end

      system "./gradlew #{gradle_task || 'lint'}"

      unless File.exists?(report_file)
        fail("Lint report not found at `#{report_file}`. "\
          "Have you forgot to add `xmlReport true` to your `build.gradle` file?")
      end

      issues = read_issues_from_report
      filtered_issues = filter_issues_by_severity(issues)

      message = message_for_issues(filtered_issues)
      markdown(message) unless filtered_issues.empty?
    end

    # A getter for `severity`, returning "Warning" if value is nil.
    # @return [String]
    def severity
      @severity || SEVERITY_LEVELS.first
    end

    private

    def read_issues_from_report
      file = File.open(report_file)

      require 'oga'
      report = Oga.parse_xml(file)

      report.xpath('//issue')
    end

    def filter_issues_by_severity(issues)
      issues.select do |issue|
        severity_index(issue.get("severity")) >= severity_index(severity)
      end
    end

    def severity_index(severity)
      SEVERITY_LEVELS.index(severity) || 0
    end

    def message_for_issues(issues)
      message = "### AndroidLint found issues\n\n"

      SEVERITY_LEVELS.reverse.each do |level|
        filtered = issues.select{|issue| issue.get("severity") == level}
        message << parse_results(filtered, level) unless filtered.empty?
      end

      message
    end

    def parse_results(results, heading)
      message = "#### #{heading} (#{results.count})\n\n"

      message << "| File | Line | Reason |\n"
      message << "| ---- | ---- | ------ |\n"

      results.each do |r|
        location = r.xpath('location').first
        filename = location.get('file').split('/').last
        line = location.get('line') || 'N/A'
        reason = r.get('message')

        message << "`#{filename}` | #{line} | #{reason} \n"
      end

      message
    end

    def gradlew_exists?
      `ls gradlew`.strip.empty? == false
    end
  end
end