import xml.parsers.expat
import os
from .hydro_message_type import HydroMessageType
from .hydro_field import HydroField
from .hydro_enum import HydroEnum, HydroEnumEntry


class HydroXml:
    def __init__(self, filename):
        self.filename = filename
        self.basename = os.path.basename(filename)
        self.basenamer_upper = self.basename.upper()
        self.messages: list[HydroMessageType] = []
        self.enums: list[HydroEnum] = []
        self.in_element_list = []
        with open(filename, "rb") as f:
            self.parser = xml.parsers.expat.ParserCreate()
            self.parser.StartElementHandler = self._start_element
            self.parser.EndElementHandler = self._end_element
            self.parser.CharacterDataHandler = self._element_text
            self.parser.ParseFile(f)
        self.message_lengths = {}
        self.message_names = {}
        self.largest_payload = 0

        msg: HydroMessageType
        for msg in self.messages:
            print(msg.name)
            msg.update_all_field_properties()
            key = msg.id
            self.message_lengths[key] = msg.wire_length
            self.message_names[key] = msg.name
            if msg.wire_length > self.largest_payload:
                self.largest_payload = msg.wire_length

    def _check_attributes(self, attributes, check, where):
        for c in check:
            if c not in attributes:
                raise Exception(
                    f"Expected missing {where} '{c}' attribute at {self.filename}:{self.parser.CurrentLineNumber}"
                )

    def _start_element(self, name, attributes):
        self.in_element_list.append(name)
        in_element = ".".join(self.in_element_list)
        if in_element == "hydrolink.messages.message":
            # make sure at least the attributes 'name' and 'id' are defined
            self._check_attributes(attributes, ["name", "id"], "message")
            self.messages.append(
                HydroMessageType(
                    attributes["name"], attributes["id"], self.parser.CurrentLineNumber
                )
            )
        elif in_element == "hydrolink.messages.message.field":
            # makre sure at least the 'name' and 'type' attribute are set for a field
            self._check_attributes(attributes, ["name", "type"], "field")
            units = attributes.get("units", "")
            if units:
                units = f"[{units}]"
            print_format = attributes.get("print_format", None)
            new_field = HydroField(
                name=attributes["name"],
                type=attributes["type"],
                print_format=print_format,
                xml=self,
                units=units,
            )
            self.messages[-1].add_field(new_field)
        elif in_element == "hydrolink.enums.enum":
            # make sure that the name of the enum is defined
            self._check_attributes(attributes, ['name'], 'enum') 
            bitmask = 'bitmask' in attributes and attributes['bitmask'] == 'true'
            self.enums.append(HydroEnum(attributes['name'], self.parser.CurrentLineNumber, bitmask=bitmask))
        elif in_element == "hydrolink.enums.enum.entry":
            if 'value' in attributes:
                value = eval(attributes["value"])
                autovalue = False
            else:
                value = self.enums[-1].highest_value + 1
                autovalue = True
            if (self.enums[-1].start_value is None or value < self.enums[-1].start_value):
                self.enums[-1].start_value = value
            if (value > self.enums[-1].highest_value):
                self.enums[-1].highest_value = value
            self.enums[-1].entries.append(HydroEnumEntry(attributes['name'], value, auto=autovalue))

    def _end_element(self, name):
        self.in_element_list.pop()

    def _element_text(self, text):
        in_element = ".".join(self.in_element_list)
        if in_element == "hydrolink.messages.message.description":
            self.messages[-1].description += text
        elif in_element == "hydrolink.messages.message.field":
            self.messages[-1].fields[-1].description += text
        elif in_element == "hydrolink.enums.enum.description":
            self.enums[-1].description += text
        elif in_element == "hydrolink.enums.enum.entry.description":
            self.enums[-1].entries[-1].description += text