require "asana"
require "tempfile"
require_relative "./shared/git_config"
require_relative "./shared/git_staged"

ASANA_URL_PATTERN = %r{https?://app.asana.com/\d+/(?<project_id>\d+)/(?<task_id>\d+)}.freeze


module Aid
  module Scripts
    class Begin < Aid::Script
      include Aid::GitConfig
      include Aid::GitStaged

      def self.description
        "Starts a new Asana story"
      end

      def self.help
        <<~HELP
          Fill me in.
          aid begin:
            Starts a story on Asana, moves it into the Work In Progress column,
            and opens a pull request on GitHub for you.
          Usage:
            aid begin "https://app.asana.com/0/1135298954694367/1135903276459289/f"
        HELP
      end

      def run
        check_for_hub!
        check_for_hub_credentials!

        prompt_for_config!(
          "asana.personal-access-token",
          "Enter your personal access token",
          <<~EOF
            1. Visit https://app.asana.com/0/developer-console
            2. Click "+ New access token" under "Personal access tokens"
            3. Give the token a name
            4. Copy the token and paste it back here.
          EOF
        )

        prompt_for_config!(
          "github.user",
          "Enter your GitHub username",
          <<~EOF
            1. Visit https://github.com and sign in
            2. Find the GitHub username you use and paste it in here
          EOF
        )

        set_asana_project_id_if_needed!
        check_for_existing_branch!
        ensure_base_branch_is_ok!

        step "Starting '#{asana_task.name}' on Asana" do
          start_task
        end

        step "Creating local branch off '#{base_branch}'" do
          check_for_staged_files!
          reset_hard_to_base_branch!
          create_git_branch!
          make_empty_commit!
        end

        step "Pushing to Github" do
          push_branch_to_github!
        end

        step "Opening pull request on Github" do
          open_pull_request_on_github!
        end
      end

      private

      def open_pull_request_on_github!
        tempfile = Tempfile.new("begin_pull_request")

        begin
          tempfile.write(pull_request_description)
          tempfile.close

          labels = "WIP"

          url = `hub pr list -h #{current_branch_name} -f '%U'`.strip
          if url.empty?
            url = `hub pull-request -F #{tempfile.path} -l "#{labels}" -d -a #{github_user}`.strip
          end
          puts colorize(:blue, url)

          # Copy it to your clipboard
          pbcopy_exist = system("command -v pbcopy >/dev/null 2>&1")
          system("echo #{url.inspect} | pbcopy") if pbcopy_exist

          # Update metadata in .git/config
          result = url.match(%r{pull/(\d+)})
          pull_request_id = result && result[1]

          git_config("tasks.#{asana_task_id}.url", asana_url)
          git_config("tasks.#{asana_task_id}.name", asana_task.name)
          git_config("tasks.#{asana_task_id}.pull-request-id", pull_request_id)
        ensure
          tempfile.unlink
        end
      end

      def github_user
        git_config("github.user")
      end

      def push_branch_to_github!
        silent "git push --force-with-lease -u origin '#{current_branch_name}'"
      end

      def make_empty_commit!
        msg = "Initial commit for task ##{asana_task_id} [ci skip]"

        silent("git commit --allow-empty -m #{msg.inspect}")
      end

      def current_branch_name
        `git rev-parse --abbrev-ref HEAD`.strip
      end

      def ensure_base_branch_is_ok!
        base_branch
      end

      def base_branch
        @base_branch ||= prompt_for_base_branch
      end

      def prompt_for_base_branch
        current_branch = current_branch_name

        if current_branch != "master"
          print colorize(
            :yellow,
            "Current branch is #{colorize(:blue, current_branch)} - do you want "\
              "to create a branch off that? (y/n) > "
          )

          answer = STDIN.gets.strip

          exit if answer[0] != "y"
        end

        current_branch
      end

      def story_branch_name
        name = asana_task
          .name
          .gsub(%r{[/.]}, "-")
          .gsub(/\s+/, "-")
          .gsub(/[^\w-]/, "")
          .downcase
          .slice(0, 50)

        "#{name}-#{asana_task_id}"
      end

      def start_task
        # Assign task to runner of this script
        user = asana.users.me
        asana_task.update(assignee: user.gid)

        # Move it to the WIP column
        asana_task.add_project(
          project: asana_project.gid,
          section: asana_wip_section.gid
        )
      end

      def asana_project
        @asana_project ||= asana.projects.find_by_id(asana_project_id)
      end

      def asana_task
        @asana_task ||= asana.tasks.find_by_id(asana_task_id)
      end

      def asana_sections
        asana.sections.find_by_project(project: asana_project.gid)
      end

      def asana_wip_section
        asana_sections.detect do |task|
          task.name =~ /(Work In Progress|WIP)/i
        end
      end

      def asana_project_id
        git_config("asana.project-id")&.to_i
      end

      def set_asana_project_id_if_needed!
        return if asana_project_id

        result = asana_url
          .match(ASANA_URL_PATTERN)

        abort help unless result

        id = result[:project_id].to_i

        puts "Setting asana.project-id to #{id}"

        git_config("asana.project-id", id)
      end

      def asana_task_id
        @asana_task_id ||=
          begin
            result = asana_url
              .match(ASANA_URL_PATTERN)

            abort help unless result

            result[:task_id].to_i
          end
      end

      def asana_url
        argv.first.to_s
      end

      def asana
        @asana ||=
          Asana::Client.new do |client|
            client.default_headers "asana-enable" => "string_ids,new_sections"
            client.authentication :access_token,
                                  git_config("asana.personal-access-token")
          end
      end

      def pull_request_description
        <<~EOF
          #{asana_task.name}

          #{asana_url}
        EOF
      end

      def reset_hard_to_base_branch!
        silent "git checkout #{base_branch}",
              "git fetch origin",
              "git reset --hard origin/#{base_branch}"
      end

      def check_for_existing_branch!
        return unless system "git ls-remote --exit-code --heads origin #{story_branch_name}"

        print colorize(
          :yellow,
          "The branch for this task (#{story_branch_name}) already exists on origin, \n"\
            "if you continue, it will be reset to master. \n"\
            "Do you want to continue? ? (y/n) > "
        )

        answer = STDIN.gets.strip.downcase

        exit if answer[0] != "y"
      end

      def create_git_branch!
        system! "git checkout -b '#{story_branch_name}'"
      end

      def check_for_hub_credentials!
        config_file = "#{ENV['HOME']}/.config/hub"
        credentials_exist = File.exist?(config_file) &&
                            File.read(config_file).match(/oauth_token/i)

        unless credentials_exist
          abort <<~EOF
            Your GitHub credentials are not set. Run this command:

              $ hub pull-request

            and when prompted for login details, enter them. It will give you
            an error at the end, but you can safely ignore it.
          EOF
        end
      end

      def command?(name)
        system("which #{name} 2>&1 >/dev/null")
      end

      def check_for_hub!
        unless command?("hub")
          abort <<~EOF
            You need to install `hub` before you can use this program.
            To fix:
              $ brew install hub
          EOF
        end
      end

      def silent(*cmds)
        cmds.each { |cmd| system("#{cmd} >/dev/null") }
      end
    end
  end
end