from django.db import models
from django.utils.translation import gettext_lazy as _
import django.contrib.auth.models as auth
from django.conf import settings
from django.dispatch import dispatcher
from django.db.models import signals
from signals import update_render

class Symbol(models.Model):
    name = models.CharField(_("Name"), max_length=256)
    latex = models.TextField(_("Raw LaTeX"), unique=True)
    unicode = models.TextField(_("Unicode Representation"), blank=True)
    renderdir = "symbolrenders/"
    render = models.ImageField(_("Rendered Image"), 
        upload_to=renderdir, editable=False)

    class Meta:
        get_latest_by = 'name'
    class Admin:
        ordering = ['name']

    def __str__(self):
        return self.name
    def get_absolute_url(self):
        return "/symbol/%s/" % self.id
    def get_admin_url(self):
        return "/admin/symbols/%s/" % self.id
    #def save(self):
    #    super(Symbol, self)
    #    self.update_generic_variable()
    def save(self):
        super(Symbol, self).save()
        self.render = self.renderdir + "%s.png" % self.id
        super(Symbol, self).save()

dispatcher.connect(update_render, signal=signals.pre_save, sender=Symbol)

def update_generic_variable(sender, instance, signal, *args, **kwargs):
    """Checks if there is a generic variable associated with this
        symbol; create one if there isn't"""
    for v in Variable.objects.filter(isgeneric=True):
        if v.latex == instance.latex:
            return
    genericv = Variable(name="Generic %s" % instance.name,
                        latex=instance.latex,
                        unicode=instance.unicode,
                        symbol=instance,
                        isgeneric=True)
    genericv.save()

signals.pre_save.connect(update_render, sender=Symbol)
signals.post_save.connect(update_generic_variable, sender=Symbol)
#dispatcher.connect(update_render, signal=signals.pre_save, sender=Symbol)
#dispatcher.connect(update_generic_variable, signal=signals.post_save, 
#    sender=Symbol)

class Variable(models.Model):
    name = models.CharField(_("Name"), max_length=256)
    latex = models.TextField(_("Raw LaTeX"), unique=True)
    unicode = models.TextField(_("Unicode Representation"), blank=True)
    description = models.TextField(_("Description"), blank=True)
    renderdir = "variablerenders/"
    render = models.ImageField(_("Rendered Image"), 
        upload_to=renderdir, editable=False)
    reference = models.URLField(_("Reference URL"), blank=True)
    symbol = models.ForeignKey(Symbol, verbose_name=_("Symbol"))
    isgeneric = models.BooleanField(_("Is Generic?"), default=False)

    class Meta:
        get_latest_by = 'name'
    class Admin:
        ordering = ['name']

    def __str__(self):
        return self.name
    def get_absolute_url(self):
        return "/variable/%s/" % self.id
    def get_admin_url(self):
        return "/admin/variables/%s/" % self.id
    def save(self):
        super(Variable, self).save()
        self.render = self.renderdir + "%s.png" % self.id
        super(Variable, self).save()

signals.pre_save.connect(update_render, sender=Variable)
#dispatcher.connect(update_render, signal=signals.pre_save, sender=Variable)

class Equation(models.Model):
    name = models.CharField(_("Name"), max_length=256)
    latex = models.TextField(_("Raw LaTeX"), unique=True)
    unicode = models.TextField(_("Unicode Representation"), blank=True)
    description = models.TextField(_("Description"), blank=True)
    created = models.DateField(_("Created"), auto_now_add=True)
    updated = models.DateField(_("Last Updated"), auto_now_add=True)
    owner = models.ForeignKey(auth.User, verbose_name=_("Owner"))
    variables = models.ManyToManyField(Variable, verbose_name="Variables",
        editable=True)
    renderdir = "equationrenders/"
    render = models.ImageField(_("Rendered Image"), 
        upload_to=renderdir, editable=False)
    reference = models.URLField(_("Reference URL"), blank=True)

    class Meta:
        get_latest_by = 'created'
    class Admin:
        ordering = ['created']

    def __str__(self):
        return self.name
    def get_absolute_url(self):
        return "/equation/%s/" % self.id
    def get_admin_url(self):
        return "/admin/equations/%s/" % self.id
    def update_variables(self):
        """Updates the variables field with all Variable objects found
           in the LaTeX representation."""
        pass # TODO: write
    def save(self):
        self.update_variables()
        super(Equation, self).save()
        self.render = self.renderdir + "%s.png" % self.id
        super(Equation, self).save()

signals.post_save.connect(update_render, sender=Equation)
#dispatcher.connect(update_render, signal=signals.post_save, sender=Equation)

from django.contrib import admin

admin.site.register(Symbol)
admin.site.register(Variable)
admin.site.register(Equation)