seriow/decoder.py

"""
This module
"""

from typing import Optional
from dataclasses import dataclass, asdict


@dataclass
class Message:
    orig_line: str

    def asdict(self):
        return asdict(self)


@dataclass
class LogMessage(Message):
    level: int
    message: str


@dataclass
class DumpMessage(Message):
    variables: dict[str, int]


class Decoder:
    """
    >>> d = Decoder()
    >>> sorted(d.decode(b'DMP V=1 G=200 FREQ=1234567').variables.items())
    [('FREQ', 1234567), ('G', 200), ('V', 1)]
    >>> d.decode(b'LOG D ciao').level
    1
    >>> d.decode(b'LOG D ciao').message
    'ciao'
    """

    log_levels = {
        "D": 1,
        "I": 2,
        "W": 3,
        "E": 4,
        "C": 5,
    }

    def __init__(self):
        pass

    def decode_level(self, description: str) -> int:
        return self.log_levels[description]

    def decode_value(self, key: str, value: str) -> Optional[dict]:
        return int(value, base=10)

    def decode_log(self, line: str) -> LogMessage:
        level, message = line.split(" ", 1)
        level = self.decode_level(level)
        return LogMessage(level=level, message=message, orig_line=line)

    def decode_dump(self, line: str) -> DumpMessage:
        variables = {}
        variables_settings = line.split()
        for varset in variables_settings:
            key, val = varset.split("=", 1)
            val = self.decode_value(key, val)
            variables[key] = val
        return DumpMessage(variables=variables, orig_line=line)

    def decode(self, line: bytes) -> Optional[Message]:
        """
        Returns None if the line is not meant to be handled by this decoder.

        Raise if meant for us but invalid.
        """
        line = line.decode("ascii")

        if line.startswith("LOG "):
            return self.decode_log(line.removeprefix("LOG "))
        if line.startswith("DMP "):
            return self.decode_dump(line.removeprefix("DMP "))
        return None