require 'digest/sha1'

module CouchTomato
  class JsViewSource
    # todo: provide a 'dirty?' method that can be called in an initializer and warn the developer that view are out of sync
    # todo: provide more granular information about which views are being modified
    # todo: limitation (bug?) where if you remove a database's views entirely from the file system, view's will not be removed from the database as may be expected
    def self.push(silent=false)
      fs_database_names.each do |database_name|
        db = database!(database_name)

        fs_docs = fs_design_docs(database_name)
        db_docs = db_design_docs(db)

        fs_docs.each do |design_name, fs_doc|
          db_doc = db_docs[design_name]

          if db_doc
            fs_doc['_id'] = db_doc['_id']
            fs_doc['_rev'] = db_doc['_rev']
          end

          if fs_doc['views'].empty?
            next unless fs_doc['_rev']
            puts "DELETE #{fs_doc['_id']}" unless silent
            db.delete_doc(fs_doc)
          else
            if changed_views?(fs_doc, db_doc)
              puts "UPDATE #{fs_doc['_id']}" unless silent
              db.save_doc(fs_doc)
            end
          end
        end
      end
    end

    def self.changed_views?(fs_doc, db_doc)
      return true if db_doc.nil?

      fs_doc['views'].each do |name, fs_view|
        db_view = db_doc['views'][name]
        %w(map reduce).each do |method|
          return true if db_view.nil? || db_view["sha1-#{method}"] != fs_view["sha1-#{method}"]
        end
      end

      return fs_doc['views'].length != db_doc['views'].length
    end

    def self.diff
      fs_database_names.each do |database_name|
        db = database!(database_name)

        fs_docs = fs_design_docs(database_name)
        db_docs = db_design_docs(db)

        # design docs on fs but not in db
        (fs_docs.keys - db_docs.keys).each do |design_name|
          unless fs_docs[design_name]['views'].empty?
            puts "    NEW: #{database_name}/_#{design_name}: #{fs_docs[design_name]['views'].keys.join(', ')}"
          end
        end

        # design docs in db but not on fs
        (db_docs.keys - fs_docs.keys).each do |design_name|
          puts "REMOVED: #{database_name}/_#{design_name}"
        end

        # design docs in both db and fs
        (fs_docs.keys & db_docs.keys).each do |design_name|
          common_view_keys = (fs_docs[design_name]['views'].keys & db_docs[design_name]['views'].keys)
          fs_only_view_keys = fs_docs[design_name]['views'].keys - common_view_keys
          db_only_view_keys = db_docs[design_name]['views'].keys - common_view_keys

          unless fs_only_view_keys.empty?
            methods = fs_only_view_keys.map do |key|
              %w(map reduce).map {|method| fs_docs[design_name]['views'][key][method].nil? ? nil : "#{key}.#{method}()"}.compact
            end.flatten
            puts "  ADDED: #{database_name}/_#{design_name}: #{methods.join(', ')}"
          end

          unless db_only_view_keys.empty?
            methods = db_only_view_keys.map do |key|
              %w(map reduce).map {|method| db_docs[design_name]['views'][key][method] ? "#{key}.#{method}()" : nil}.compact
            end
            puts "REMOVED: #{database_name}/_#{design_name}: #{methods.join(', ')}"
          end

          common_view_keys.each do |common_key|
            # are the sha's the same?
            # map reduce sha1
            fs_view = fs_docs[design_name]['views'][common_key]
            db_view = db_docs[design_name]['views'][common_key]

            # has either the map or reduce been added or removed
            %w(map reduce).each do |method|
              if db_view[method] && !fs_view[method]
                puts "REMOVED: #{database_name}/_#{design_name}:#{method}()" and next
              end

              if fs_view[method] && !db_view[method]
                puts "  ADDED: #{database_name}/_#{design_name}:#{method}()" and next
              end

              if fs_view["sha1-#{method}"] != db_view["sha1-#{method}"]
                puts "OUTDATED: #{database_name}/_#{design_name}:#{method}()" and next
              end
            end
          end

        end

      end
    end

    private

    def self.path(db_name="")
      "#{Rails.root}/couchdb/views/#{db_name}" if Rails
    end

    def self.fs_database_names
      Dir[path + "/**"].map {|path| path.split('/').last}
    end

    def self.db_design_docs(db)
      design_docs = db.get("_all_docs", {:startkey => "_design/", :endkey => "_design0", :include_docs => true})['rows']
      design_docs.inject({}) do |res, row|
        doc = row['doc']
        design_name = doc['_id'].split('/').last
        res[design_name.to_sym] = doc#['views']
        res
      end
    end

    # :clicks => {'by_date' => {'map' => ..., 'reduce' => ..., sha1-map => ..., sha1-reduce => ...} }
    def self.fs_design_docs(db_name)
      design_docs = {}

      path = "#{RAILS_ROOT}/couchdb/views/#{db_name}"
      Dir[path + "/**"].each do |file|
        throw "Invalid filename '#{File.basename(file)}': expecting '-map.js' or '-reduce.js' suffix" unless file.match(/-((map)|(reduce))\.js$/)

        design_name = db_name.to_sym
        design_docs[design_name] ||= {'_id' => "_design/#{db_name}", 'views' => {}}
        fs_view(design_docs[design_name], file)
      end

      design_docs.each do |db, design|
        design["views"].each do |view, functions|
          if !functions["reduce"].nil?
            raise "#{view}-reduce was found without a corresponding map function." if functions["map"].nil?
          end
        end
      end

      design_docs
    end

    def self.fs_view(design_doc, view_path)
      filename = view_path.split('/').last.split('.').first
      name, type = filename.split('-')

      file = open(view_path)
      content = file.read
      file.close

      sha1 = Digest::SHA1.hexdigest(content)

      design_doc['views'][name] ||= {}
      design_doc['views'][name][type] = content
      design_doc['views'][name]["sha1-#{type}"] = sha1
      design_doc
    end

    # todo: don't depend on "proprietary" APP_CONFIG
    def self.database!(database_name)
      CouchRest.database!("http://" + APP_CONFIG["couchdb_address"] + ":" + APP_CONFIG["couchdb_port"].to_s \
       + "/" + APP_CONFIG["couchdb_basename"] + "_" + database_name + "_" + RAILS_ENV)
    end

  end
end