require 'rubypython/python'
require 'rubypython/macros'


module RubyPython
  
  #Raised when an error occurs in the Python interpreter.
  class PythonError < Exception
    
    #@param [String] typeName the class name of the Python error
    #@param [String] msg the message attached to the Python error
    def initialize(typeName, msg)
      @type = typeName
      super([typeName, msg].join(': '))
    end

    #This method should be called when an error has occured in the
    #Python interpreter. This acts as factory function for PythonError
    #objects. The function fetchs calls {fetch} to get the error
    #information from the Python interpreter and uses this to build
    #a PythonError object. It then calls {clear} to clear the error
    #flag of the python interpreter
    #@return [PythonError] an error enscapsulating the Python error
    def self.handle_error
      rbType, rbValue, rbTraceback = fetch()

      if not rbValue.null?
        msg = rbValue.getAttr("__str__").callObject PyObject.buildArgTuple
        msg = msg.rubify
      else
        msg = nil
      end
      
      #Decrease the reference count. This will happen anyway when they go
      #out of scope but might as well.
      rbValue.xDecref
      rbTraceback.xDecref
      pyName = rbType.getAttr("__name__")

      rbType.xDecref
      rbName = pyName.rubify
      pyName.xDecref

      PythonError.clear

      PythonError.new(rbName, msg)
    end

    #A wrapper to the Python C API PyErr_Fetch function.
    #@return [Array<PyObject>] an array containing three {PyObject} instances.
    #   representing the Type, Value, and stacktrace of the python
    #   error respectively.
    def self.fetch
      typePointer = FFI::MemoryPointer.new :pointer
      valuePointer = FFI::MemoryPointer.new :pointer
      tracebackPointer = FFI::MemoryPointer.new :pointer

      Python.PyErr_Fetch typePointer, valuePointer, tracebackPointer

      rbType = PyObject.new typePointer.read_pointer
      rbValue = PyObject.new valuePointer.read_pointer
      rbTraceback = PyObject.new tracebackPointer.read_pointer
      [rbType, rbValue, rbTraceback]
    end

    #Determines whether an error has occured in the python interpreter.
    def self.error?
      !Python.PyErr_Occurred.null?
    end

    #Resets the Python interpreter error flag
    #@return [void]
    def self.clear
      Python.PyErr_Clear
    end

  end
end