from lxml import etree
class Xml_reader:
    """ reader for the XML configuration """

    def __init__(self, xml_path: str, xsd_path: str):
        """inits the reader

        Args:
            xml_path (str): the path to the XML file
            xsd_path (str): the path to the XSD file

        Raises:
            SyntaxError: validity of XML file is checked with the XSD file
        """
        #check the XML for validity using the XSD file
        if not self.validate(xml_path,xsd_path):
            raise SyntaxError('the XML config file has an invalid syntax')
        self.set_root(xml_path)

    def set_root(self, xml_path: str):
        self.root = etree.parse(xml_path).getroot()

    def validate(self, xml_path: str, xsd_path: str) -> bool:
        """validates a XML by using a XSD file

        Args:
            xml_path (str): the path to the XML file
            xsd_path (str): the path to the XSD file

        Returns:
            bool: result of the validation
        """
        xml_schema = etree.XMLSchema(etree.parse(xsd_path))
        return xml_schema.validate(etree.parse(xml_path))

    def get_device_names(self) -> list:
        """lists all the device names from the config XML

        Returns:
            list: all device names as strings
        """
        return [device.get("name") for device in self.root.findall('Device')]

    def get_value_info(self,device_name: str) -> dict:
        """returns the value information for a given device

        Args:
            device_name (str): the name of a device

        Returns:
            dict: {'type','unit','offset','factor'}

        Raises:
            NameError: device_name will be checked against the config XML
        """
        #check if a device exists in the config XML
        if self.root.find("Device[@name='%s']" % device_name) is None:
            raise NameError("unknown device %s" % device_name)
        value_info = self.root.find(
            "Device[@name='%s']/ValueInfo" % device_name)
        #format the output
        return {
            'type': value_info.get('type'),
            'unit': value_info.get('unit'),
            'offset': None if value_info.find("Offset") is None
                else value_info.find("Offset").text,
            'factor': None if value_info.find("Factor") is None 
                else value_info.find("Factor").text,
        } 
    
    def get_port(self,device_name:str) -> dict:
        """returns the information about a port of a given device

        Args:
            device_name (str): the name of a device

        Returns:
            dict: {'protocol', [list: pins]}

        Raises:
            NameError: device_name will be checked against the config XML
        """
        if self.root.find("Device[@name='%s']" % device_name) is None:
            raise NameError("unknown device %s" % device_name)
        port = self.root.find(
            "Device[@name='%s']/Port" % device_name)
        return {
            'protocol': port.get('protocol'),
            'pins': [
                pin.text for pin in self.root.findall(
                    "Device[@name='%s']/Port/Pin" % device_name
                    )
                ]
        }

# ##test
# xml_reader = Xml_reader('XML/Test.xml','XML/config.xsd')
# print(xml_reader.get_device_names)
# print(xml_reader.get_value_info("example"))
# print(xml_reader.get_port("example"))
# print(xml_reader.get_value_info("sensorarray"))
# print(xml_reader.get_port("sensorarray"))