scalacache.memoization.MethodCallToStringConverter.scala Maven / Gradle / Ivy

package scalacache.memoization

/**
 * Converts information about a method call to a String for use in a cache key
 */
trait MethodCallToStringConverter {

  /**
   * Convert the given method call information to a String for use in a cache key
   *
   * @param fullClassName the name of the class whose method was called, including fully-qualified package name
   * @param constructorParamss
   *                the values of the constructor parameters of the method's enclosing class, where applicable.
   *                This is a `[IndexedSeq[IndexedSeq[Any]]` because there may be multiple parameter lists.
   *                If the method is inside an `object`, a `trait` or a class with no constructor params, this will be empty.
   * @param methodName the name of the called method
   * @param paramss
   *                the values of the parameters that were passed to the method.
   *                This is a `[IndexedSeq[IndexedSeq[Any]]` because there may be multiple parameter lists
   * @return
   */
  def toString(fullClassName: String, constructorParamss: IndexedSeq[IndexedSeq[Any]], methodName: String, paramss: IndexedSeq[IndexedSeq[Any]]): String

}

object MethodCallToStringConverter {
  import java.lang.{ StringBuilder => JStringBuilder }

  private def appendClassNamePart(sb: JStringBuilder)(className: String): Unit = {
    if (className.nonEmpty) {
      sb.append(className)
      sb.append('.')
    }
  }

  private def appendClassNameAndParamsPart(sb: JStringBuilder)(className: String, constructorParamss: IndexedSeq[IndexedSeq[Any]]): Unit = {
    if (className.nonEmpty) {
      sb.append(className)
      appendParamssPart(sb)(constructorParamss)
      sb.append('.')
    }
  }

  private def appendParamssPart(sb: JStringBuilder)(paramss: IndexedSeq[IndexedSeq[Any]]): Unit = {
    var i = 0
    while (i < paramss.size) {
      val params = paramss(i)
      appendParamsPart(sb)(params)
      i += 1
    }
  }

  private def appendParamsPart(sb: JStringBuilder)(params: IndexedSeq[Any]): Unit = {
    sb.append('(')
    var i = 0
    // Add all params except the last one, with the separator after each one
    while (i < params.size - 1) {
      sb.append(params(i))
      sb.append(", ")
      i += 1
    }
    // Add the final param
    if (i < params.size) {
      sb.append(params(i))
    }
    sb.append(')')
    sb.toString
  }

  /**
   * A converter that builds keys of the form: "package.class.method(arg, ...)(arg, ...)..."
   * e.g. "com.foo.MyClass.doSomething(123, abc)(foo)"
   *
   * Note that this converter ignores the class's constructor params and does NOT include them in the cache key.
   */
  val excludeClassConstructorParams: MethodCallToStringConverter = new MethodCallToStringConverter {
    def toString(fullClassName: String, constructorParamss: IndexedSeq[IndexedSeq[Any]], methodName: String, paramss: IndexedSeq[IndexedSeq[Any]]): String = {
      val sb = new JStringBuilder(128)
      appendClassNamePart(sb)(fullClassName)
      sb.append(methodName)
      appendParamssPart(sb)(paramss)
      sb.toString
    }
  }

  /**
   * A converter that builds keys of the form: "package.class(arg, ...)(arg, ...).method(arg, ...)(arg, ...)..."
   * e.g. "com.foo.MyClass(42, wow).doSomething(123, abc)(foo)"
   *
   * Note that this converter includes the class's constructor params in the cache key, where applicable.
   */
  val includeClassConstructorParams = new MethodCallToStringConverter {
    def toString(fullClassName: String, constructorParamss: IndexedSeq[IndexedSeq[Any]], methodName: String, paramss: IndexedSeq[IndexedSeq[Any]]): String = {
      val sb = new JStringBuilder(128)
      appendClassNameAndParamsPart(sb)(fullClassName, constructorParamss)
      sb.append(methodName)
      appendParamssPart(sb)(paramss)
      sb.toString
    }
  }

  /**
   * A converter that includes only the method arguments in the cache key.
   * It builds keys of the form: "(arg, ...)(arg, ...)..."
   * e.g. a call to `com.foo.MyClass(42, wow).doSomething(123, abc)(foo)` would be cached as "(123, abc)(foo)".
   *
   * Warning: Do not use this key if you have multiple methods that you want to memoize, because cache keys can collide.
   * e.g. the results of `Foo.bar(123)` and `Baz.wow(123)` would be cached with the same key `123`.
   */
  val onlyMethodParams = new MethodCallToStringConverter {
    def toString(fullClassName: String, constructorParamss: IndexedSeq[IndexedSeq[Any]], methodName: String, paramss: IndexedSeq[IndexedSeq[Any]]): String = {
      val sb = new JStringBuilder(128)
      appendParamssPart(sb)(paramss)
      sb.toString
    }
  }

}