# Handler for runtime classes generation
#
# We need 3 kinds of runtime structures:
# * `RTClass` to represent a global class
# * `RTMethod` to represent a method definition
# * `RTVal` to represent runtime variables
class JavaRuntimeModel

	# Compile JavaRuntimeModel structures
	fun compile_rtmodel(compiler: JavaCompiler) do
		compile_rtclass(compiler)
		compile_rtmethod(compiler)
		compile_rtval(compiler)
	end

	# Compile the abstract runtime class structure
	#
	# Runtime classes have 3 attributes:
	# * `class_name`: the class name as a String
	# * `vft`: the virtual function table for the class (flattened)
	# * `supers`: the super type table (used for type tests)
	fun compile_rtclass(compiler: JavaCompiler) do
		var v = compiler.new_visitor("RTClass.java")
		v.add("import java.util.HashMap;")
		v.add("public abstract class RTClass \{")
		v.add("  public String class_name;")
		v.add("  public HashMap<String, RTMethod> vft = new HashMap<>();")
		v.add("  public HashMap<String, RTClass> supers = new HashMap<>();")
		v.add("  protected RTClass() \{\}")
		v.add("\}")
	end

	# Compile the abstract runtime method structure
	#
	# Method body is executed through the `exec` method:
	# * `exec` always take an array of RTVal as arg, the first one must be the receiver
	# * `exec` always returns a RTVal (or null if the Nit return type is void)
	fun compile_rtmethod(compiler: JavaCompiler) do
		var v = compiler.new_visitor("RTMethod.java")
		v.add("public abstract class RTMethod \{")
		v.add("  protected RTMethod() \{\}")
		v.add("  public abstract RTVal exec(RTVal[] args);")
		v.add("\}")
	end

	# Compile the runtime value structure
	#
	# RTVal both represents object instances and primitives values:
	# * object instances:
	#   * `rtclass` the class of the RTVal is instance of
	#   * `attrs` contains the attributes of the instance
	# * primitive values:
	#   * `rtclass` represents the class of the primitive value Nit type
	#   * `value` contains the primitive value of the instance
	# * null values:
	#   * they must have both `rtclass` and `value` as null
	fun compile_rtval(compiler: JavaCompiler) do
		var v = compiler.new_visitor("RTVal.java")
		v.add("import java.util.HashMap;")
		v.add("public class RTVal \{")
		v.add("  public RTClass rtclass;")
		v.add("  public HashMap<String, RTVal> attrs = new HashMap<>();")
		v.add("  Object value;")
		v.add("  public RTVal(RTClass rtclass) \{")
		v.add("    this.rtclass = rtclass;")
		v.add("  \}")
		v.add("  public RTVal(RTClass rtclass, Object value) \{")
		v.add("    this.rtclass = rtclass;")
		v.add("    this.value = value;")
		v.add("  \}")
		v.add("  public boolean is_null() \{ return rtclass == null && value == null; \}")
		v.add("\}")
	end
end