import configparser
import sys
from pathlib import Path
from jinja2 import Environment, FileSystemLoader
from .MsgData import MsgData


# \brief   Generates and maintains the message handling INI from loaded message data.
# \details One section per message keyed by hex msgId (e.g. [0x0100]), carrying:
#            msg_id - the MSG_ID_* reference name, regenerated from the conf on every run.
#            action - send_always | send_delta | drop; defaults to drop, preserved across runs.
#            topic  - MQTT topic; empty by default, preserved across runs.
#          Call loadConf() to load message definitions, then loadIni() to merge in existing
#          action/topic values, then write_ini() to write the result.
class MsgHandlingIni(MsgData):
    DEFAULT_ACTION = 'drop'
    VALID_ACTIONS   = ('send_always', 'send_delta', 'drop')

    # \brief        Initializer
    def __init__(self):
        super().__init__()


    # \brief        Load a .conf file and cache the data, enriching each entry with default INI fields.
    # \param[in]    filename    Filename of the .conf to load.
    # \param[in]    clear       If true, clear any previously loaded data before processing.
    # \return       none
    def loadConf(self, filename, clear=True):
        super().loadConf(filename, clear)
        for msg in self.data.values():
            msg['action'] = self.DEFAULT_ACTION
            msg['topic']    = ''


    # \brief        Merge action/topic values from an existing INI into the loaded message data.
    # \details      Only action and topic are read; msg_id is always regenerated from the conf.
    #               Sections in the INI that are no longer in the conf are ignored (and warned if
    #               they carried non-default values). Unknown action values are reset to drop.
    # \param[in]    filename    Path to the existing INI file; no-op if the file does not exist.
    # \return       none
    def loadIni(self, filename):
        path = Path(filename)
        if not path.is_file():
            return
        cfg = configparser.ConfigParser(inline_comment_prefixes=(';',))
        cfg.read(path, encoding='utf-8')

        # just use self.data.keys()
        conf_keys = set(MsgData.value_to_hex_string(v) for v in self.data.keys())

        for section in cfg.sections():
            try:
                msg_id_value = int(section, 16)
            except ValueError:
                print(f"WARNING: could not convert section message ID {section} to valid message ID, skipping")
                continue
            if msg_id_value not in self.data.keys():
                action = cfg.get(section, 'action', fallback=self.DEFAULT_ACTION).strip()
                topic  = cfg.get(section, 'topic',  fallback='').strip()
                if action != self.DEFAULT_ACTION or topic:
                    print(f"WARNING: {MsgData.value_to_hex_string(msg_id_value)} no longer in Unhandled.conf, "
                          f"dropping section with action={action} topic={topic or '<empty>'}")
                continue

            action = cfg.get(section, 'action', fallback=self.DEFAULT_ACTION).strip()
            if action not in self.VALID_ACTIONS:
                print(f"WARNING: {MsgData.value_to_hex_string(msg_id_value)} has invalid action \"{action}\", "
                      f"resetting to {self.DEFAULT_ACTION}")
                action = self.DEFAULT_ACTION

            self.data[msg_id_value]['action'] = action
            self.data[msg_id_value]['topic']    = cfg.get(section, 'topic', fallback='').strip()


    # \brief        Write the loaded message data to the INI file.
    # \param[in]    filename    Path to the INI file to create or update.
    # \return       none
    def write_ini(self, filename):
        env = Environment(loader=FileSystemLoader(f'{Path(__file__).parent.absolute()}/templates'),
                          keep_trailing_newline=True)
        template = env.get_template('MsgHandlingIni.jinja')
        render = template.render({'msg_ini': self})
        with open(filename, mode='w', encoding='utf-8', newline='\n') as out_file:
            out_file.write(render)
        print(f"Wrote message INI {filename} with {len(self.data)} messages")