"""
Build database model definitions
"""

# -*- coding: utf-8 -*-
from __future__ import unicode_literals

from django.utils.translation import ugettext as _

from django.urls import reverse
from django.db import models
from django.core.validators import MinValueValidator


class Build(models.Model):
    """ A Build object organises the creation of new parts from the component parts.

    Attributes:
        part: The part to be built (from component BOM items)
        title: Brief title describing the build (required)
        quantity: Number of units to be built
        status: Build status code
        batch: Batch code transferred to build parts (optional)
        creation_date: Date the build was created (auto)
        completion_date: Date the build was completed
        URL: External URL for extra information
        notes: Text notes
    """

    def get_absolute_url(self):
        return reverse('build-detail', kwargs={'pk': self.id})

    part = models.ForeignKey('part.Part', on_delete=models.CASCADE,
                             related_name='builds',
                             limit_choices_to={'buildable': True},
                             )
    
    title = models.CharField(max_length=100, help_text='Brief description of the build')
    
    quantity = models.PositiveIntegerField(
        default=1,
        validators=[MinValueValidator(1)],
        help_text='Number of parts to build'
    )
    
    # Build status codes
    PENDING = 10  # Build is pending / active
    HOLDING = 20  # Build is currently being held
    CANCELLED = 30  # Build was cancelled
    COMPLETE = 40  # Build is complete

    #: Build status codes
    BUILD_STATUS_CODES = {PENDING: _("Pending"),
                          HOLDING: _("Holding"),
                          CANCELLED: _("Cancelled"),
                          COMPLETE: _("Complete"),
                          }

    status = models.PositiveIntegerField(default=PENDING,
                                         choices=BUILD_STATUS_CODES.items(),
                                         validators=[MinValueValidator(0)])
    
    batch = models.CharField(max_length=100, blank=True, null=True,
                             help_text='Batch code for this build output')
    
    creation_date = models.DateField(auto_now=True, editable=False)
    
    completion_date = models.DateField(null=True, blank=True)
    
    URL = models.URLField(blank=True, help_text='Link to external URL')

    notes = models.TextField(blank=True)
    """ Notes attached to each build output """

    @property
    def required_parts(self):
        """ Returns a dict of parts required to build this part (BOM) """
        parts = []

        for item in self.part.bom_items.all():
            part = {'part': item.sub_part,
                    'per_build': item.quantity,
                    'quantity': item.quantity * self.quantity
                    }

            parts.append(part)

        return parts

    @property
    def can_build(self):
        """ Return true if there are enough parts to supply build """

        for item in self.required_parts:
            if item['part'].total_stock < item['quantity']:
                return False

        return True

    @property
    def is_active(self):
        """ Is this build active? An active build is either:

        - PENDING
        - HOLDING
        """

        return self.status in [
            self.PENDING,
            self.HOLDING
        ]

    @property
    def is_complete(self):
        """ Returns True if the build status is COMPLETE """
        return self.status == self.COMPLETE


class BuildItemAllocation(models.Model):
    """ A BuildItemAllocation links multiple StockItem objects to a Build.
    These are used to allocate part stock to a build.
    Once the Build is completed, the parts are removed from stock and the
    BuildItemAllocation objects are removed.

    Attributes:
        build: Link to a Build object
        stock: Link to a StockItem object
        quantity: Number of units allocated
    """

    build = models.ForeignKey(
        Build,
        on_delete=models.CASCADE,
        related_name='allocated_stock',
    )

    stock = models.ForeignKey(
        'stock.StockItem',
        on_delete=models.CASCADE,
        related_name='allocations',
        help_text='Stock Item to allocate to build',
    )

    quantity = models.PositiveIntegerField(
        default=1,
        validators=[MinValueValidator(1)],
        help_text='Stock quantity to allocate to build'
    )