module Gitlab
  class GitAccess
    DOWNLOAD_COMMANDS = %w{ git-upload-pack git-upload-archive }
    PUSH_COMMANDS = %w{ git-receive-pack }

    attr_reader :params, :project, :git_cmd, :user

    def self.can_push_to_branch?(user, project, ref)
      if project.protected_branch?(ref)  &&
          !(project.developers_can_push_to_protected_branch?(ref) && project.team.developer?(user))
        user.can?(:push_code_to_protected_branches, project)
      else
        user.can?(:push_code, project)
      end
    end

    def check(actor, cmd, project, changes = nil)
      case cmd
      when *DOWNLOAD_COMMANDS
        download_access_check(actor, project)
      when *PUSH_COMMANDS
        if actor.is_a? User
          push_access_check(actor, project, changes)
        elsif actor.is_a? DeployKey
          return build_status_object(false, "Deploy key not allowed to push")
        elsif actor.is_a? Key
          push_access_check(actor.user, project, changes)
        else
          raise 'Wrong actor'
        end
      else
        return build_status_object(false, "Wrong command")
      end
    end

    def download_access_check(actor, project)
      if actor.is_a?(User)
        user_download_access_check(actor, project)
      elsif actor.is_a?(DeployKey)
        if actor.projects.include?(project)
          build_status_object(true)
        else
          build_status_object(false, "Deploy key not allowed to access this project")
        end
      elsif actor.is_a? Key
        user_download_access_check(actor.user, project)
      else
        raise 'Wrong actor'
      end
    end

    def user_download_access_check(user, project)
      if user && user_allowed?(user) && user.can?(:download_code, project)
        build_status_object(true)
      else
        build_status_object(false, "You don't have access")
      end
    end

    def push_access_check(user, project, changes)
      unless user && user_allowed?(user)
        return build_status_object(false, "You don't have access")
      end

      if changes.blank?
        return build_status_object(true)
      end

      unless project.repository.exists?
        return build_status_object(false, "Repository does not exist")
      end

      changes = changes.lines if changes.kind_of?(String)

      # Iterate over all changes to find if user allowed all of them to be applied
      changes.map(&:strip).reject(&:blank?).each do |change|
        status = change_access_check(user, project, change)
        unless status.allowed?
          # If user does not have access to make at least one change - cancel all push
          return status
        end
      end

      return build_status_object(true)
    end

    def change_access_check(user, project, change)
      oldrev, newrev, ref = change.split(' ')

      action = if project.protected_branch?(branch_name(ref))
                 protected_branch_action(project, oldrev, newrev, branch_name(ref))
               elsif protected_tag?(project, tag_name(ref))
                 # Prevent any changes to existing git tag unless user has permissions
                 :admin_project
               else
                 :push_code
               end

      if user.can?(action, project)
        build_status_object(true)
      else
        build_status_object(false, "You don't have permission")
      end
    end

    def forced_push?(project, oldrev, newrev)
      Gitlab::ForcePushCheck.force_push?(project, oldrev, newrev)
    end

    private

    def protected_branch_action(project, oldrev, newrev, branch_name)
      # we dont allow force push to protected branch
      if forced_push?(project, oldrev, newrev)
        :force_push_code_to_protected_branches
      elsif newrev == Gitlab::Git::BLANK_SHA
        # and we dont allow remove of protected branch
        :remove_protected_branches
      elsif project.developers_can_push_to_protected_branch?(branch_name)
        :push_code
      else
        :push_code_to_protected_branches
      end
    end

    def protected_tag?(project, tag_name)
      project.repository.tag_names.include?(tag_name)
    end

    def user_allowed?(user)
      Gitlab::UserAccess.allowed?(user)
    end

    def branch_name(ref)
      ref = ref.to_s
      if ref.start_with?('refs/heads')
        ref.sub(%r{\Arefs/heads/}, '')
      else
        nil
      end
    end

    def tag_name(ref)
      ref = ref.to_s
      if ref.start_with?('refs/tags')
        ref.sub(%r{\Arefs/tags/}, '')
      else
        nil
      end
    end

    protected

    def build_status_object(status, message = '')
      GitAccessStatus.new(status, message)
    end
  end
end