require_relative 'stoppable'
require 'rugged'

module NdrDevSupport
  module Daemon
    # Wrapper around Rake based CI testing loop
    class CIServer
      include Stoppable

      GIT_SVN_REMOTE_BRANCH_NAME = 'git-svn'.freeze
      MASTER_BRANCH_NAME = 'master'.freeze
      ORIGIN_MASTER_BRANCH_NAME = 'origin/master'.freeze

      attr_reader :repo

      def self.from_args(env)
        name = env['WORKER_NAME'].to_s

        new(name: name)
      end

      def initialize(name:)
        super

        # Worker name can be used for clear logging:
        @name = name
        raise ArgumentError, 'No WORKER_NAME specified!' if name.blank?

        @repo = Rugged::Repository.new('.')
      end

      def self.friendly_revision_name(commit)
        if (matchdata = commit.message.match(/\bgit-svn-id: [^@]+@(\d+)\s/))
          matchdata[1]
        else
          commit.oid[0, 7]
        end
      end

      private

      def run_once
        git_fetch
        git_checkout(MASTER_BRANCH_NAME)

        objectids_between_master_and_remote.each do |oid|
          `git rebase #{oid}`

          Rake::Task['ci:all'].invoke
        end
      end

      def git_fetch
        svn_remote? ? `git svn fetch` : `git fetch`
      end

      def git_checkout(oid)
        `git checkout #{oid}`
      end

      def svn_remote?
        GIT_SVN_REMOTE_BRANCH_NAME == remote_branch
      end

      def remote_branch
        return @remote_branch if @remote_branch

        remote_branches = repo.branches.each_name(:remote)
        if remote_branches.count == 1
          @remote_branch = remote_branches.first
        elsif remote_branches.include?(ORIGIN_MASTER_BRANCH_NAME)
          @remote_branch = ORIGIN_MASTER_BRANCH_NAME
        else
          raise "One remote branch expected (#{remote_branches.to_a.inspect})"
        end
      end

      def objectids_between_master_and_remote
        walker = Rugged::Walker.new(@repo)
        walker.push(repo.branches[remote_branch].target_id)
        current_target_id = repo.branches[MASTER_BRANCH_NAME].target_id

        revisions = []
        # walk backwards from the most recent commit, breaking at the current one
        walker.each do |commit|
          break if commit.oid == current_target_id
          revisions << commit.oid
        end

        revisions.reverse
      end
    end
  end
end