import logging
import os

import django.contrib.auth.models as amodels
import rrdtool
from django.conf import settings
from django.db import models

log = logging.getLogger(__name__)


class ModelWithPerms(models.Model):
    users_read = models.ManyToManyField(
        amodels.User,
        related_name="%(class)s_read"
    )
    users_write = models.ManyToManyField(
        amodels.User,
        related_name="%(class)s_write"
    )
    groups_read = models.ManyToManyField(
        amodels.Group,
        related_name="%(class)s_read"
    )
    groups_write = models.ManyToManyField(
        amodels.Group,
        related_name="%(class)s_write"
    )

    class Meta:
        abstract = True


class DataSource(ModelWithPerms):
    # an mqtt topic can be as long as 65,535 bytes when UTF-8 encoded,
    # which is probably too much for a sensible db
    topic = models.CharField(max_length=512)
    path = models.FilePathField(
        path=settings.RRD_DB_PATH.as_posix(),
        recursive=True,
        max_length=512,
    )
    rrd_config = models.TextField(
        default=settings.RRD_DS_CONFIG
    )
    active = models.BooleanField(
        default=True,
    )

    def __str__(self):
        return self.topic

    @property
    def lastupdate(self):
        try:
            last = rrdtool.lastupdate(os.path.join(
                settings.RRD_DB_PATH, self.path
            ))
        except rrdtool.OperationalError as e:
            log.warning("Failure reading from ds: %s", e)
            return (None, None)
        else:
            return last["date"], last["ds"][self.topic.split("/")[-1]]

    def update(self, ts, value):
        rrd_path = os.path.join(settings.RRD_DB_PATH, self.path)
        if not os.path.isfile(rrd_path):
            rrdtool.create(
                os.path.join(settings.RRD_DB_PATH, self.path),
                "--no-overwrite",
                self.rrd_config.format(
                    ds_name=self.topic.split("/")[-1]
                ).strip().split('\n'),
            )
        try:
            rrdtool.update(
                os.path.join(settings.RRD_DB_PATH, self.path),
                str(ts) + ":" + str(value)
            )
        except ValueError as e:
            log.warning("Could not update ds: %s", e)


class Graph(ModelWithPerms):
    title = models.CharField(max_length=64)
    data_sources = models.ManyToManyField(DataSource)
    path = models.FilePathField(
        path=settings.RRD_GRAPH_PATH.as_posix(),
        recursive=True,
        max_length=512,
    )
    rrd_config = models.TextField()

    def __str__(self):
        return self.title


class Dashboard(ModelWithPerms):
    title = models.CharField(max_length=64)
    graphs = models.ManyToManyField(Graph)
    data_sources = models.ManyToManyField(DataSource)
    template = models.TextField()

    def __str__(self):
        return self.title