#
# Copyright:: Chef Software Inc.
# License:: Apache License, Version 2.0
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
#     http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
#

require_relative "base"
require_relative "../ui"
require_relative "../pager"
require_relative "../policyfile/differ"
require_relative "../policyfile/comparison_base"
require_relative "../policyfile/storage_config"
require_relative "../configurable"
require_relative "../dist"
require "chef/server_api"

module ChefCLI
  module Command

    class Diff < Base

      include Configurable
      include Policyfile::StorageConfigDelegation

      banner(<<~BANNER)
        Usage: #{ChefCLI::Dist::EXEC} diff [POLICYFILE] [--head | --git GIT_REF | POLICY_GROUP | POLICY_GROUP...POLICY_GROUP ]

        `#{ChefCLI::Dist::EXEC} diff` displays an itemized diff comparing two revisions of a
        Policyfile lock.

        When the `--git` option is given, `#{ChefCLI::Dist::EXEC} diff` either compares a given
        git reference against the current lockfile revision on disk or compares
        between two git references. Examples:

        * `#{ChefCLI::Dist::EXEC} diff --git HEAD`: compares the current lock with the latest
          commit on the current branch.
        * `#{ChefCLI::Dist::EXEC} diff --git master`: compares the current lock with the latest
          commit to master.
        * `#{ChefCLI::Dist::EXEC} diff --git v1.0.0`: compares the current lock with the revision
          as of the `v1.0.0` tag.
        * `#{ChefCLI::Dist::EXEC} diff --git master...dev-branch`: compares the Policyfile lock on
          master with the revision on the `dev-branch` branch.
        * `#{ChefCLI::Dist::EXEC} diff --git v1.0.0...master`: compares the Policyfile lock at the
          `v1.0.0` tag with the lastest revision on the master branch.

        `#{ChefCLI::Dist::EXEC} diff --head` is a shortcut for `#{ChefCLI::Dist::EXEC} diff --git HEAD`.

        When no git-specific flag is given, `#{ChefCLI::Dist::EXEC} diff` either compares the
        current lockfile revision on disk to one on the #{ChefCLI::Dist::SERVER_PRODUCT} or compares
        two lockfiles on the #{ChefCLI::Dist::SERVER_PRODUCT}. Lockfiles on the #{ChefCLI::Dist::SERVER_PRODUCT}
        are specified by Policy Group. Examples:

        * `#{ChefCLI::Dist::EXEC} diff staging`: compares the current lock with the one currently
          assigned to the `staging` Policy Group.
        * `#{ChefCLI::Dist::EXEC} diff production...staging`: compares the lock currently assigned
          to the `production` Policy Group to the lock currently assigned to the
          `staging` Policy Group.

        Options:
      BANNER

      option :git,
        short:       "-g GIT_REF",
        long:        "--git GIT_REF",
        description: "Compare local lock against GIT_REF, or between two git commits."

      option :head,
        long:        "--head",
        description: "Compare local lock against last git commit.",
        boolean:     true

      option :pager,
        long:        "--[no-]pager",
        description: "Enable/disable paged diff ouput (default: enabled).",
        default:     true,
        boolean:     true

      option :config_file,
        short:       "-c CONFIG_FILE",
        long:        "--config CONFIG_FILE",
        description: "Path to configuration file."

      option :debug,
        short:       "-D",
        long:        "--debug",
        description: "Enable stacktraces and other debug output.",
        default:     false

      attr_accessor :ui

      attr_reader :old_base
      attr_reader :new_base

      attr_reader :storage_config

      def initialize(*args)
        super

        @ui = UI.new

        @old_base = nil
        @new_base = nil
        @policyfile_relative_path = nil
        @storage_config = nil
        @http_client = nil

        @old_lock = nil
        @new_lock = nil
      end

      def debug?
        !!config[:debug]
      end

      def run(params = [])
        return 1 unless apply_params!(params)

        print_diff
        0
      rescue PolicyfileServiceError => e
        handle_error(e)
        1
      end

      def handle_error(error)
        ui.err("Error: #{error.message}")
        if error.respond_to?(:reason)
          ui.err("Reason: #{error.reason}")
          ui.err("")
          ui.err(error.extended_error_info) if debug?
          ui.err(error.cause.backtrace.join("\n")) if debug?
        end
      end

      def print_diff
        # eagerly evaluate locks so we hit any errors before we've entered
        # pagerland. Also, git commands behave weirdly when run while the pager
        # is active, doing this eagerly also avoids that issue
        materialize_locks
        Pager.new(enable_pager: config[:pager]).with_pager do |pager|
          differ = differ(pager.ui)
          differ.run_report
        end
      end

      def differ(ui = self.ui)
        Policyfile::Differ.new(old_name: old_base.name,
                               old_lock: old_lock,
                               new_name: new_base.name,
                               new_lock: new_lock,
                               ui: ui)
      end

      def http_client
        @http_client ||= Chef::ServerAPI.new(chef_config.chef_server_url,
          signing_key_filename: chef_config.client_key,
          client_name: chef_config.node_name)
      end

      def old_lock
        materialize_locks unless @old_lock
        @old_lock
      end

      def new_lock
        materialize_locks unless @new_lock
        @new_lock
      end

      def policy_name
        local_lock["name"]
      end

      def local_lock
        @local_lock ||= local_lock_comparison_base.lock
      end

      # ComparisonBase for the local lockfile. This is used to get the
      # policy_name which is needed to query the server for the lockfile of a
      # particular policy_group.
      def local_lock_comparison_base
        Policyfile::ComparisonBase::Local.new(policyfile_lock_relpath)
      end

      def policyfile_lock_relpath
        storage_config.policyfile_lock_filename
      end

      def apply_params!(params)
        remaining_args = parse_options(params)

        if no_comparison_specified?(remaining_args)
          ui.err("No comparison specified")
          ui.err("")
          ui.err(opt_parser)
          false
        elsif conflicting_args_and_opts_given?(remaining_args)
          ui.err("Conflicting arguments and options: git and Policy Group comparisons cannot be mixed")
          ui.err("")
          ui.err(opt_parser)
          false
        elsif conflicting_git_options_given?
          ui.err("Conflicting git options: --head and --git are exclusive")
          ui.err("")
          ui.err(opt_parser)

          false
        elsif config[:head]
          set_policyfile_path_from_args(remaining_args)
          @old_base = Policyfile::ComparisonBase::Git.new("HEAD", policyfile_lock_relpath)
          @new_base = Policyfile::ComparisonBase::Local.new(policyfile_lock_relpath)
          true
        elsif config[:git]
          set_policyfile_path_from_args(remaining_args)
          parse_git_comparison(config[:git])
        else
          set_policyfile_path_from_args(remaining_args)
          parse_server_comparison(remaining_args)
        end
      end

      def parse_server_comparison(args)
        comparison_string = args.last
        if comparison_string.include?("...")
          old_pgroup, new_pgroup, *extra = comparison_string.split("...")
          @old_base, @new_base = [old_pgroup, new_pgroup].map do |g|
            Policyfile::ComparisonBase::PolicyGroup.new(g, policy_name, http_client)
          end

          unless extra.empty?
            ui.err("Unable to parse policy group comparison `#{comparison_string}`. Only 2 references can be specified.")
            return false
          end
        else
          @old_base = Policyfile::ComparisonBase::PolicyGroup.new(comparison_string, policy_name, http_client)
          @new_base = Policyfile::ComparisonBase::Local.new(policyfile_lock_relpath)
        end
        true
      end

      def parse_git_comparison(git_ref)
        if git_ref.include?("...")
          old_ref, new_ref, *extra = git_ref.split("...")
          @old_base, @new_base = [old_ref, new_ref].map do |r|
            Policyfile::ComparisonBase::Git.new(r, policyfile_lock_relpath)
          end

          unless extra.empty?
            ui.err("Unable to parse git comparison `#{git_ref}`. Only 2 references can be specified.")
            return false
          end
        else
          @old_base = Policyfile::ComparisonBase::Git.new(git_ref, policyfile_lock_relpath)
          @new_base = Policyfile::ComparisonBase::Local.new(policyfile_lock_relpath)
        end
        true
      end

      def no_comparison_specified?(args)
        !policy_group_comparison?(args) && !config[:head] && !config[:git]
      end

      def conflicting_args_and_opts_given?(args)
        (config[:git] || config[:head]) && policy_group_comparison?(args)
      end

      def conflicting_git_options_given?
        config[:git] && config[:head]
      end

      def comparing_policy_groups?
        !(config[:git] || config[:head])
      end

      # Try to detect if the only argument given is a policyfile path. This is
      # necessary because we support an optional argument with the path to the
      # ruby policyfile. It would be easier if we used an option like `-f`, but
      # that would be inconsistent with other commands (`chef install`, `chef
      # push`, etc.).
      def policy_group_comparison?(args)
        return false if args.empty?
        return true if args.size > 1

        !(args.first =~ /\.rb\Z/)
      end

      def set_policyfile_path_from_args(args)
        policyfile_relative_path =
          if !comparing_policy_groups?
            args.first || "Policyfile.rb"
          elsif args.size == 1
            "Policyfile.rb"
          else
            args.first
          end
        @storage_config = Policyfile::StorageConfig.new.use_policyfile(policyfile_relative_path)
      end

      def materialize_locks
        @old_lock = old_base.lock
        @new_lock = new_base.lock
      end

    end

  end
end