# frozen_string_literal: true

module Boltless
  module Extensions
    # A top-level gem-module extension for neo4j operations.
    #
    # rubocop:disable Metrics/BlockLength because this is how
    #   an +ActiveSupport::Concern+ looks like
    module Operations
      extend ActiveSupport::Concern

      class_methods do
        # Clear everything from the neo4j database, including indexes,
        # constraints, all nodes and all relationships. Afterwards the
        # database is completely empty and "unconfigured". (dist clean)
        #
        # @param database [String, Symbol] the neo4j database to use
        #
        # rubocop:disable Metrics/MethodLength because of
        #   multiple transactions
        # rubocop:disable Metrics/AbcSize because of the extra transaction
        #   handlings (we cannot do multiple structural changes in a single
        #   transaction)
        def clear_database!(database: Boltless.configuration.default_db)
          logger.warn('Clear neo4j database ..')

          # Clear all constraints, this is a schema
          # modification so we have to run it in a separate transaction
          transaction!(database: database) do |tx|
            constraint_names.each do |name|
              logger.info(" > Drop neo4j constraint #{name} ..")
              tx.run!("DROP CONSTRAINT #{name}")
            end
          end

          # Clear all indexes, this is a schema
          # modification so we have to run it in a separate transaction
          transaction!(database: database) do |tx|
            index_names.each do |name|
              logger.info(" > Drop neo4j index #{name} ..")
              tx.run!("DROP INDEX #{name}")
            end
          end

          # Afterwards clear all nodes and relationships
          stats = write!('MATCH (n) DETACH DELETE n',
                         database: database,
                         with_stats: true).stats

          logger.info(" > Nodes deleted: #{stats[:nodes_deleted]}")
          logger.info(
            " > Relationships deleted: #{stats[:relationship_deleted]}"
          )
        end
        # rubocop:enable Metrics/MethodLength
        # rubocop:enable Metrics/AbcSize

        # Check whenever the given name is already taken on the neo4j
        # database for a component (index or constraint).
        #
        # @param database [String, Symbol] the neo4j database to use
        # @param name [String, Symbol] the name to check
        # @return [Boolean] whenever the name is taken/present or not
        def component_name_present?(name,
                                    database: Boltless.configuration.default_db)
          pool = index_names(database: database) +
                 constraint_names(database: database)
          pool.include? name.to_s
        end

        # List all currently available indexes by their names.
        #
        # @param database [String, Symbol] the neo4j database to use
        # @return [Array<String>] the index names
        def index_names(database: Boltless.configuration.default_db)
          res = query!('SHOW INDEXES YIELD name',
                       database: database).pluck(:name)
          res - constraint_names
        end

        # List all currently available constraints by their names.
        #
        # @param database [String, Symbol] the neo4j database to use
        # @return [Array<String>] the constraint names
        def constraint_names(database: Boltless.configuration.default_db)
          query!('SHOW CONSTRAINTS YIELD name',
                 database: database).pluck(:name)
        end

        # Create a new index at the neo4j database.
        #
        # @see https://bit.ly/3GawzVP
        # @param name [String, Symbol] the name of the index, we do not
        #   allow autogenerated names
        # @param type [String, Symbol] the index type (+:btree+, +:lookup+,
        #   +:text+, +:range+, +:point+, +:fulltext+)
        # @param options [Hash{Symbol => Mixed}] additional index options
        #   for neo4j
        # @param for [String] the node/property query for matching
        # @param on [String] the collection of nodes/properties to index
        # @param database [String, Symbol] the neo4j database to use
        #
        # rubocop:disable Metrics/ParameterLists because of the various
        #   configuration options of a neo4j index
        def add_index(name:, for:, on:, type: :btree, options: nil,
                      database: Boltless.configuration.default_db)
          # CREATE TEXT INDEX [index_name] IF NOT EXISTS
          # FOR ()-[r:TYPE_NAME]-()
          # ON (r.propertyName)
          # OPTIONS {option: value[, ...]}

          # Assemble and perform the neo4j query
          type = type == :btree ? '' : type.to_s.upcase
          options = options.blank? ? '' : "OPTIONS #{to_options(options)}"
          write <<~CYPHER, database: database
            CREATE #{type} INDEX #{name} IF NOT EXISTS
            FOR #{binding.local_variable_get(:for)}
            ON #{on}
            #{options}
          CYPHER
        end
        # rubocop:enable Metrics/ParameterLists

        # Drop an index from the neo4j database.
        #
        # @param name [String, Symbol] the name of the index
        # @param database [String, Symbol] the neo4j database to use
        def drop_index(name, database: Boltless.configuration.default_db)
          write!("DROP INDEX #{name} IF EXISTS", database: database)
        end

        # Create a new constraint at the neo4j database.
        #
        # Adding constraints is an atomic operation that can take a while.
        # All existing data has to be scanned before neo4j can turn the
        # constraint 'on'.
        #
        # @see https://bit.ly/3GawzVP
        #
        # @param name [String, Symbol] the name of the index, we do not
        #   allow autogenerated names
        # @param options [Hash{Symbol => Mixed}] additional index options
        #   for neo4j
        # @param for [String] the node/property query for matching
        # @param require [String] the constraint to apply
        # @param database [String, Symbol] the neo4j database to use
        def add_constraint(name:, for:, require:, options: nil,
                           database: Boltless.configuration.default_db)
          # CREATE CONSTRAINT [constraint_name] IF NOT EXISTS
          # FOR (n:LabelName)
          # REQUIRE n.propertyName IS UNIQUE
          # OPTIONS { option: value[, ...] }

          # Assemble and perform the neo4j query
          options = options.blank? ? '' : "OPTIONS #{to_options(options)}"
          write! <<~CYPHER, database: database
            CREATE CONSTRAINT #{name} IF NOT EXISTS
            FOR #{binding.local_variable_get(:for)}
            REQUIRE #{binding.local_variable_get(:require)}
            #{options}
          CYPHER
        end

        # Drop a constraint from the neo4j database.
        #
        # @param name [String, Symbol] the name of the constraint
        # @param database [String, Symbol] the neo4j database to use
        def drop_constraint(name, database: Boltless.configuration.default_db)
          write!("DROP CONSTRAINT #{name} IF EXISTS", database: database)
        end
      end
    end
    # rubocop:enable Metrics/BlockLength
  end
end