require 'openssl'

module SchemaAutoForeignKeys
  module AutoCreate
    # defined below
  end

  module Middleware
    module Migration
      module Column
        module PostgreSQL ; include AutoCreate ; end
        module SQLite3 ; include AutoCreate ; end
        module MySQL
          include AutoCreate
          def auto_index?(env, config) ; false end
          def remove_auto_index?(env) ; false end
        end
      end

      module RenameTable
        def after(env)
          newname = env.new_name
          oldname = env.table_name
          indexes = env.connection.indexes(newname)
          env.connection.foreign_keys(newname).each do |fk|
            index = indexes.find { |it| it.name == AutoCreate.auto_index_name(oldname, fk.column) }
            env.connection.rename_index(newname, index.name, AutoCreate.auto_index_name(newname, index.columns)) if index
          end
        end
      end
    end
  end

  module AutoCreate
    def before(env)
      config ||= env.caller.try(:schema_plus_foreign_keys_config) || SchemaPlus::ForeignKeys.config
      set_foreign_key(env) if auto_fk?(env, config)
      set_auto_index(env) if auto_index?(env, config)
    end

    def after(env)
      remove_auto_index(env) if env.operation == :change and remove_auto_index?(env)
    end

    def auto_fk?(env, config)
      return false if env.options.include? :foreign_key
      return false unless config.auto_create?
      return true if env.type == :reference
      return false if env.implements_reference
      return true if env.column_name.to_s =~ /_id$/ # later on add a config option for this
    end

    def auto_index?(env, config)
      return false if env.options.include? :index
      return false unless env.options[:foreign_key]
      return true if config.auto_index?
    end

    def remove_auto_index?(env)
      env.options.include? :foreign_key and not env.options[:foreign_key]
    end

    def set_foreign_key(env)
      env.options[:foreign_key] = true
    end

    def set_auto_index(env)
      env.options[:index] = { name: auto_index_name(env) }
    end

    def remove_auto_index(env)
      env.caller.remove_index(env.table_name, name: auto_index_name(env), column: env.column_name, if_exists: true)
    end

    def auto_index_name(env)
      AutoCreate.auto_index_name(env.table_name, env.column_name)
    end

    def self.auto_index_name(from_table, column_name)
      name = "fk__#{fixup_schema_name(from_table)}_#{Array.wrap(column_name).join('_and_')}"
      name = name.slice(0, 27) + "_" + OpenSSL::Digest::MD5.new.hexdigest(name) if name.length > 60
      name
    end

    def self.fixup_schema_name(table_name)
      # replace . with _
      table_name.to_s.gsub(/[.]/, '_')
    end
  end
end