from django.db import models
from django.contrib.auth import get_user_model
from django.utils.translation import gettext_lazy as _
from core.models import Patient

User = get_user_model()


class DocumentTemplate(models.Model):
    """
    Reusable document templates for clinical notes and other documents.
    """
    CATEGORY_CHOICES = [
        ('medical', _('Medical')),
        ('nursing', _('Nursing')),
        ('aba', _('ABA')),
        ('ot', _('Occupational Therapy')),
        ('slp', _('Speech-Language Pathology')),
        ('assessment', _('Assessment')),
        ('progress', _('Progress Report')),
        ('discharge', _('Discharge Summary')),
        ('other', _('Other')),
    ]

    name = models.CharField(_('Template Name'), max_length=200)
    category = models.CharField(_('Category'), max_length=50, choices=CATEGORY_CHOICES)
    description = models.TextField(_('Description'), blank=True)
    content = models.TextField(_('Template Content'), help_text=_('Use {{variable_name}} for dynamic fields'))
    is_active = models.BooleanField(_('Active'), default=True)
    created_by = models.ForeignKey(User, on_delete=models.SET_NULL, null=True, related_name='created_templates')
    created_at = models.DateTimeField(_('Created At'), auto_now_add=True)
    updated_at = models.DateTimeField(_('Updated At'), auto_now=True)

    class Meta:
        verbose_name = _('Document Template')
        verbose_name_plural = _('Document Templates')
        ordering = ['category', 'name']

    def __str__(self):
        return f"{self.name} ({self.get_category_display()})"


class ClinicalNote(models.Model):
    """
    Clinical notes and documentation for patient care.
    """
    STATUS_CHOICES = [
        ('draft', _('Draft')),
        ('final', _('Final')),
        ('amended', _('Amended')),
        ('deleted', _('Deleted')),
    ]

    patient = models.ForeignKey(Patient, on_delete=models.CASCADE, related_name='clinical_notes')
    template = models.ForeignKey(DocumentTemplate, on_delete=models.SET_NULL, null=True, blank=True, related_name='notes')
    title = models.CharField(_('Title'), max_length=200)
    content = models.TextField(_('Content'))
    status = models.CharField(_('Status'), max_length=20, choices=STATUS_CHOICES, default='draft')
    
    # Metadata
    author = models.ForeignKey(User, on_delete=models.SET_NULL, null=True, related_name='authored_notes')
    created_at = models.DateTimeField(_('Created At'), auto_now_add=True)
    updated_at = models.DateTimeField(_('Updated At'), auto_now=True)
    finalized_at = models.DateTimeField(_('Finalized At'), null=True, blank=True)
    finalized_by = models.ForeignKey(User, on_delete=models.SET_NULL, null=True, blank=True, related_name='finalized_notes')
    
    # Versioning
    version = models.IntegerField(_('Version'), default=1)
    parent_note = models.ForeignKey('self', on_delete=models.SET_NULL, null=True, blank=True, related_name='amendments')

    class Meta:
        verbose_name = _('Clinical Note')
        verbose_name_plural = _('Clinical Notes')
        ordering = ['-created_at']
        permissions = [
            ('can_finalize_note', 'Can finalize clinical notes'),
            ('can_amend_note', 'Can amend finalized notes'),
        ]

    def __str__(self):
        return f"{self.title} - {self.patient.get_full_name()} ({self.created_at.strftime('%Y-%m-%d')})"


class NoteAddendum(models.Model):
    """
    Addendums to clinical notes for corrections or additional information.
    """
    note = models.ForeignKey(ClinicalNote, on_delete=models.CASCADE, related_name='addendums')
    content = models.TextField(_('Addendum Content'))
    reason = models.CharField(_('Reason'), max_length=200)
    author = models.ForeignKey(User, on_delete=models.SET_NULL, null=True)
    created_at = models.DateTimeField(_('Created At'), auto_now_add=True)

    class Meta:
        verbose_name = _('Note Addendum')
        verbose_name_plural = _('Note Addendums')
        ordering = ['-created_at']

    def __str__(self):
        return f"Addendum to {self.note.title} - {self.created_at.strftime('%Y-%m-%d %H:%M')}"


class NoteAuditLog(models.Model):
    """
    Audit trail for clinical note changes.
    """
    ACTION_CHOICES = [
        ('created', _('Created')),
        ('updated', _('Updated')),
        ('finalized', _('Finalized')),
        ('amended', _('Amended')),
        ('deleted', _('Deleted')),
        ('viewed', _('Viewed')),
    ]

    note = models.ForeignKey(ClinicalNote, on_delete=models.CASCADE, related_name='audit_logs')
    action = models.CharField(_('Action'), max_length=20, choices=ACTION_CHOICES)
    user = models.ForeignKey(User, on_delete=models.SET_NULL, null=True)
    timestamp = models.DateTimeField(_('Timestamp'), auto_now_add=True)
    ip_address = models.GenericIPAddressField(_('IP Address'), null=True, blank=True)
    changes = models.JSONField(_('Changes'), null=True, blank=True)

    class Meta:
        verbose_name = _('Note Audit Log')
        verbose_name_plural = _('Note Audit Logs')
        ordering = ['-timestamp']

    def __str__(self):
        return f"{self.get_action_display()} - {self.note.title} by {self.user} at {self.timestamp}"