module Gitlab
  module GithubImport
    class Importer
      include Gitlab::ShellAdapter

      attr_reader :client, :project, :repo, :repo_url

      def initialize(project)
        @project  = project
        @repo     = project.import_source
        @repo_url = project.import_url

        if credentials
          @client = Client.new(credentials[:user])
          @formatter = Gitlab::ImportFormatter.new
        else
          raise Projects::ImportService::Error, "Unable to find project import data credentials for project ID: #{@project.id}"
        end
      end

      def execute
        import_labels && import_milestones && import_issues &&
          import_pull_requests && import_wiki
      end

      private

      def credentials
        @credentials ||= project.import_data.credentials if project.import_data
      end

      def import_labels
        client.labels(repo).each do |raw_data|
          Label.create!(LabelFormatter.new(project, raw_data).attributes)
        end

        true
      rescue ActiveRecord::RecordInvalid => e
        raise Projects::ImportService::Error, e.message
      end

      def import_milestones
        client.list_milestones(repo, state: :all).each do |raw_data|
          Milestone.create!(MilestoneFormatter.new(project, raw_data).attributes)
        end

        true
      rescue ActiveRecord::RecordInvalid => e
        raise Projects::ImportService::Error, e.message
      end

      def import_issues
        client.list_issues(repo, state: :all, sort: :created, direction: :asc).each do |raw_data|
          gh_issue = IssueFormatter.new(project, raw_data)

          if gh_issue.valid?
            issue = Issue.create!(gh_issue.attributes)
            apply_labels(gh_issue.number, issue)

            if gh_issue.has_comments?
              import_comments(gh_issue.number, issue)
            end
          end
        end

        true
      rescue ActiveRecord::RecordInvalid => e
        raise Projects::ImportService::Error, e.message
      end

      def import_pull_requests
        pull_requests = client.pull_requests(repo, state: :all, sort: :created, direction: :asc)
                              .map { |raw| PullRequestFormatter.new(project, raw) }
                              .select(&:valid?)

        source_branches_removed = pull_requests.reject(&:source_branch_exists?).map { |pr| [pr.source_branch_name, pr.source_branch_sha] }
        target_branches_removed = pull_requests.reject(&:target_branch_exists?).map { |pr| [pr.target_branch_name, pr.target_branch_sha] }
        branches_removed = source_branches_removed | target_branches_removed

        create_refs(branches_removed)

        project.repository.fetch_ref(repo_url, '+refs/heads/*', 'refs/heads/*')

        pull_requests.each do |pull_request|
          merge_request = MergeRequest.new(pull_request.attributes)

          if merge_request.save
            apply_labels(pull_request.number, merge_request)
            import_comments(pull_request.number, merge_request)
            import_comments_on_diff(pull_request.number, merge_request)
          end
        end

        delete_refs(branches_removed)

        true
      rescue ActiveRecord::RecordInvalid => e
        raise Projects::ImportService::Error, e.message
      end

      def create_refs(branches)
        branches.each do |name, sha|
          client.create_ref(repo, "refs/heads/#{name}", sha)
        end
      end

      def delete_refs(branches)
        branches.each do |name, _|
          client.delete_ref(repo, "heads/#{name}")
        end
      end

      def apply_labels(number, issuable)
        issue = client.issue(repo, number)

        if issue.labels.count > 0
          label_ids = issue.labels.map do |raw|
            Label.find_by(LabelFormatter.new(project, raw).attributes).try(:id)
          end

          issuable.update_attribute(:label_ids, label_ids)
        end
      end

      def import_comments(issue_number, noteable)
        comments = client.issue_comments(repo, issue_number)
        create_comments(comments, noteable)
      end

      def import_comments_on_diff(pull_request_number, merge_request)
        comments = client.pull_request_comments(repo, pull_request_number)
        create_comments(comments, merge_request)
      end

      def create_comments(comments, noteable)
        comments.each do |raw_data|
          comment = CommentFormatter.new(project, raw_data)
          noteable.notes.create!(comment.attributes)
        end
      end

      def import_wiki
        unless project.wiki_enabled?
          wiki = WikiFormatter.new(project)
          gitlab_shell.import_repository(wiki.path_with_namespace, wiki.import_url)
          project.update_attribute(:wiki_enabled, true)
        end

        true
      rescue Gitlab::Shell::Error => e
        # GitHub error message when the wiki repo has not been created,
        # this means that repo has wiki enabled, but have no pages. So,
        # we can skip the import.
        if e.message !~ /repository not exported/
          raise Projects::ImportService::Error, e.message
        else
          true
        end
      end
    end
  end
end