import os
from django.db import models
from django.utils.text import slugify
from mptt.models import MPTTModel, TreeForeignKey


def thing_picture_upload_path(instance, filename):
    """Generate a custom path for thing pictures in format: <id>-<name>.<extension>"""
    extension = os.path.splitext(filename)[1]
    safe_name = slugify(instance.name)
    if instance.pk:
        return f'things/{instance.pk}-{safe_name}{extension}'
    else:
        return f'things/temp-{safe_name}{extension}'


class BoxType(models.Model):
    """A type of storage box with specific dimensions."""

    name = models.CharField(max_length=255)
    width = models.PositiveIntegerField(help_text='Width in millimeters')
    height = models.PositiveIntegerField(help_text='Height in millimeters')
    length = models.PositiveIntegerField(help_text='Length in millimeters')

    class Meta:
        ordering = ['name']

    def __str__(self):
        return self.name


class Box(models.Model):
    """A storage box in the lab."""

    id = models.CharField(
        max_length=10,
        primary_key=True,
        help_text='Alphanumeric identifier (max 10 characters)'
    )
    box_type = models.ForeignKey(
        BoxType,
        on_delete=models.PROTECT,
        related_name='boxes'
    )

    class Meta:
        verbose_name_plural = 'boxes'

    def __str__(self):
        return self.id


class ThingType(MPTTModel):
    """A hierarchical type/category for things stored in boxes."""

    name = models.CharField(max_length=255)
    parent = TreeForeignKey(
        'self',
        on_delete=models.CASCADE,
        null=True,
        blank=True,
        related_name='children'
    )

    class MPTTMeta:
        order_insertion_by = ['name']

    def __str__(self):
        return self.name


class Thing(models.Model):
    """An item stored in a box."""

    name = models.CharField(max_length=255)
    thing_type = models.ForeignKey(
        ThingType,
        on_delete=models.PROTECT,
        related_name='things'
    )
    box = models.ForeignKey(
        Box,
        on_delete=models.PROTECT,
        related_name='things'
    )
    description = models.TextField(blank=True)
    picture = models.ImageField(upload_to=thing_picture_upload_path, blank=True)

    class Meta:
        ordering = ['name']

    def save(self, *args, **kwargs):
        """Override save to rename picture file after instance gets a pk."""
        if self.picture and not self.pk:
            picture = self.picture
            super().save(*args, **kwargs)
            new_path = thing_picture_upload_path(self, picture.name)
            if picture.name != new_path:
                try:
                    old_path = self.picture.path
                    if os.path.exists(old_path):
                        new_full_path = os.path.join(os.path.dirname(old_path), os.path.basename(new_path))
                        os.rename(old_path, new_full_path)
                        self.picture.name = new_path
                        super().save(update_fields=['picture'])
                except (AttributeError, FileNotFoundError):
                    pass
        else:
            super().save(*args, **kwargs)

    def __str__(self):
        return self.name


def thing_file_upload_path(instance, filename):
    """Generate a custom path for thing files in format: things/files/<thing_id>/<filename>"""
    return f'things/files/{instance.thing.id}/{filename}'


class ThingFile(models.Model):
    """A file attachment for a Thing."""

    thing = models.ForeignKey(
        Thing,
        on_delete=models.CASCADE,
        related_name='files'
    )
    file = models.FileField(upload_to=thing_file_upload_path)
    title = models.CharField(max_length=255, help_text='Descriptive name for the file')
    uploaded_at = models.DateTimeField(auto_now_add=True)

    class Meta:
        ordering = ['-uploaded_at']

    def __str__(self):
        return f'{self.thing.name} - {self.title}'

    def filename(self):
        """Return the original filename."""
        return os.path.basename(self.file.name)


class ThingLink(models.Model):
    """A hyperlink for a Thing."""

    thing = models.ForeignKey(
        Thing,
        on_delete=models.CASCADE,
        related_name='links'
    )
    url = models.URLField(max_length=2048)
    title = models.CharField(max_length=255, help_text='Descriptive title for the link')
    uploaded_at = models.DateTimeField(auto_now_add=True)

    class Meta:
        ordering = ['-uploaded_at']

    def __str__(self):
        return f'{self.thing.name} - {self.title}'