#
# Author:: John Keiser (<jkeiser@opscode.com>)
# Copyright:: Copyright (c) 2012 Opscode, 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 'chef_fs/file_system'

module ChefFS
  module CommandLine
    def self.diff(pattern, a_root, b_root, recurse_depth, output_mode)
      found_result = false
      ChefFS::FileSystem.list_pairs(pattern, a_root, b_root) do |a, b|
        existed = diff_entries(a, b, recurse_depth, output_mode) do |diff|
          yield diff
        end
        found_result = true if existed
      end
      if !found_result && pattern.exact_path
        yield "#{pattern}: No such file or directory on remote or local"
      end
    end

    # Diff two known entries (could be files or dirs)
    def self.diff_entries(old_entry, new_entry, recurse_depth, output_mode)
      # If both are directories
      if old_entry.dir?
        if new_entry.dir?
          if recurse_depth == 0
            if output_mode != :name_only && output_mode != :name_status
              yield "Common subdirectories: #{old_entry.path}\n"
            end
          else
            ChefFS::FileSystem.child_pairs(old_entry, new_entry).each do |old_child,new_child|
              diff_entries(old_child, new_child,
                           recurse_depth ? recurse_depth - 1 : nil, output_mode) do |diff|
                yield diff
              end
            end
          end

      # If old is a directory and new is a file
        elsif new_entry.exists?
          if output_mode == :name_only
            yield "#{new_entry.path_for_printing}\n"
          elsif output_mode == :name_status
            yield "T\t#{new_entry.path_for_printing}\n"
          else
            yield "File #{new_entry.path_for_printing} is a directory while file #{new_entry.path_for_printing} is a regular file\n"
          end

      # If old is a directory and new does not exist
        elsif new_entry.parent.can_have_child?(old_entry.name, old_entry.dir?)
          if output_mode == :name_only
            yield "#{new_entry.path_for_printing}\n"
          elsif output_mode == :name_status
            yield "D\t#{new_entry.path_for_printing}\n"
          else
            yield "Only in #{old_entry.parent.path_for_printing}: #{old_entry.name}\n"
          end
        end

      # If new is a directory and old is a file
      elsif new_entry.dir?
        if old_entry.exists?
          if output_mode == :name_only
            yield "#{new_entry.path_for_printing}\n"
          elsif output_mode == :name_status
            yield "T\t#{new_entry.path_for_printing}\n"
          else
            yield "File #{old_entry.path_for_printing} is a regular file while file #{old_entry.path_for_printing} is a directory\n"
          end

      # If new is a directory and old does not exist
        elsif old_entry.parent.can_have_child?(new_entry.name, new_entry.dir?)
          if output_mode == :name_only
            yield "#{new_entry.path_for_printing}\n"
          elsif output_mode == :name_status
            yield "A\t#{new_entry.path_for_printing}\n"
          else
            yield "Only in #{new_entry.parent.path_for_printing}: #{new_entry.name}\n"
          end
        end

      # Neither is a directory, so they are diffable with file diff
      else
        are_same, old_value, new_value = ChefFS::FileSystem.compare(old_entry, new_entry)
        if are_same
          return old_value != :none
        else
          if old_value == :none
            old_exists = false
          elsif old_value.nil?
            old_exists = old_entry.exists?
          else
            old_exists = true
          end
          if new_value == :none
            new_exists = false
          elsif new_value.nil?
            new_exists = new_entry.exists?
          else
            new_exists = true
          end

          # If one of the files doesn't exist, we only want to print the diff if the
          # other file *could be uploaded/downloaded*.
          if !old_exists && !old_entry.parent.can_have_child?(new_entry.name, new_entry.dir?)
            return true
          end
          if !new_exists && !new_entry.parent.can_have_child?(old_entry.name, old_entry.dir?)
            return true
          end

          if output_mode == :name_only
            yield "#{new_entry.path_for_printing}\n"
          elsif output_mode == :name_status
            if old_value == :none || (old_value == nil && !old_entry.exists?)
              yield "A\t#{new_entry.path_for_printing}\n"
            elsif new_value == :none
              yield "D\t#{new_entry.path_for_printing}\n"
            else
              yield "M\t#{new_entry.path_for_printing}\n"
            end
          else
            # If we haven't read the values yet, get them now.
            begin
              old_value = old_entry.read if old_value.nil?
            rescue ChefFS::FileSystem::NotFoundError
              old_value = :none
            end
            begin
              new_value = new_entry.read if new_value.nil?
            rescue ChefFS::FileSystem::NotFoundError
              new_value = :none
            end

            old_path = old_entry.path_for_printing
            new_path = new_entry.path_for_printing
            result = ''
            result << "diff --knife #{old_path} #{new_path}\n"
            if old_value == :none
              result << "new file\n"
              old_path = "/dev/null"
              old_value = ''
            end
            if new_value == :none
              result << "deleted file\n"
              new_path = "/dev/null"
              new_value = ''
            end
            result << diff_text(old_path, new_path, old_value, new_value)
            yield result
          end
        end
      end
      return true
    end

    private

    def self.sort_keys(json_object)
      if json_object.is_a?(Array)
        json_object.map { |o| sort_keys(o) }
      elsif json_object.is_a?(Hash)
        new_hash = {}
        json_object.keys.sort.each { |key| new_hash[key] = sort_keys(json_object[key]) }
        new_hash
      else
        json_object
      end
    end

    def self.canonicalize_json(json_text)
      parsed_json = JSON.parse(json_text, :create_additions => false)
      sorted_json = sort_keys(parsed_json)
      JSON.pretty_generate(sorted_json)
    end

    def self.diff_text(old_path, new_path, old_value, new_value)
      # Reformat JSON for a nicer diff.
      if old_path =~ /\.json$/
        begin
          reformatted_old_value = canonicalize_json(old_value)
          reformatted_new_value = canonicalize_json(new_value)
          old_value = reformatted_old_value
          new_value = reformatted_new_value
        rescue
          # If JSON parsing fails, we just won't change any values and fall back
          # to normal diff.
        end
      end

      # Copy to tempfiles before diffing
      # TODO don't copy things that are already in files!  Or find an in-memory diff algorithm
      begin
        new_tempfile = Tempfile.new("new")
        new_tempfile.write(new_value)
        new_tempfile.close

        begin
          old_tempfile = Tempfile.new("old")
          old_tempfile.write(old_value)
          old_tempfile.close

          result = `diff -u #{old_tempfile.path} #{new_tempfile.path}`
          result = result.gsub(/^--- #{old_tempfile.path}/, "--- #{old_path}")
          result = result.gsub(/^\+\+\+ #{new_tempfile.path}/, "+++ #{new_path}")
          result
        ensure
          old_tempfile.close!
        end
      ensure
        new_tempfile.close!
      end
    end
  end
end