"""
Billing Models for Credit System
"""
from django.db import models
from django.core.validators import MinValueValidator
from django.conf import settings
from igny8_core.auth.models import AccountBaseModel


class CreditTransaction(AccountBaseModel):
    """Track all credit transactions (additions, deductions)"""
    TRANSACTION_TYPE_CHOICES = [
        ('purchase', 'Purchase'),
        ('subscription', 'Subscription Renewal'),
        ('refund', 'Refund'),
        ('deduction', 'Usage Deduction'),
        ('adjustment', 'Manual Adjustment'),
    ]
    
    transaction_type = models.CharField(max_length=20, choices=TRANSACTION_TYPE_CHOICES, db_index=True)
    amount = models.IntegerField(help_text="Positive for additions, negative for deductions")
    balance_after = models.IntegerField(help_text="Credit balance after this transaction")
    description = models.CharField(max_length=255)
    metadata = models.JSONField(default=dict, help_text="Additional context (AI call details, etc.)")
    created_at = models.DateTimeField(auto_now_add=True)
    
    class Meta:
        app_label = 'billing'
        db_table = 'igny8_credit_transactions'
        ordering = ['-created_at']
        indexes = [
            models.Index(fields=['account', 'transaction_type']),
            models.Index(fields=['account', 'created_at']),
        ]
    
    def __str__(self):
        account = getattr(self, 'account', None)
        return f"{self.get_transaction_type_display()} - {self.amount} credits - {account.name if account else 'No Account'}"


class CreditUsageLog(AccountBaseModel):
    """Detailed log of credit usage per AI operation"""
    OPERATION_TYPE_CHOICES = [
        ('clustering', 'Keyword Clustering'),
        ('idea_generation', 'Content Ideas Generation'),
        ('content_generation', 'Content Generation'),
        ('image_generation', 'Image Generation'),
        ('reparse', 'Content Reparse'),
        ('ideas', 'Content Ideas Generation'),  # Legacy
        ('content', 'Content Generation'),  # Legacy
        ('images', 'Image Generation'),  # Legacy
    ]
    
    operation_type = models.CharField(max_length=50, choices=OPERATION_TYPE_CHOICES, db_index=True)
    credits_used = models.IntegerField(validators=[MinValueValidator(0)])
    cost_usd = models.DecimalField(max_digits=10, decimal_places=4, null=True, blank=True)
    model_used = models.CharField(max_length=100, blank=True)
    tokens_input = models.IntegerField(null=True, blank=True, validators=[MinValueValidator(0)])
    tokens_output = models.IntegerField(null=True, blank=True, validators=[MinValueValidator(0)])
    related_object_type = models.CharField(max_length=50, blank=True)  # 'keyword', 'cluster', 'task'
    related_object_id = models.IntegerField(null=True, blank=True)
    metadata = models.JSONField(default=dict)
    created_at = models.DateTimeField(auto_now_add=True)
    
    class Meta:
        app_label = 'billing'
        db_table = 'igny8_credit_usage_logs'
        ordering = ['-created_at']
        indexes = [
            models.Index(fields=['account', 'operation_type']),
            models.Index(fields=['account', 'created_at']),
            models.Index(fields=['account', 'operation_type', 'created_at']),
        ]
    
    def __str__(self):
        account = getattr(self, 'account', None)
        return f"{self.get_operation_type_display()} - {self.credits_used} credits - {account.name if account else 'No Account'}"


class CreditCostConfig(models.Model):
    """
    Configurable credit costs per AI function
    Admin-editable alternative to hardcoded constants
    """
    # Operation identification
    operation_type = models.CharField(
        max_length=50,
        unique=True,
        choices=CreditUsageLog.OPERATION_TYPE_CHOICES,
        help_text="AI operation type"
    )
    
    # Cost configuration
    credits_cost = models.IntegerField(
        validators=[MinValueValidator(0)],
        help_text="Credits required for this operation"
    )
    
    # Unit of measurement
    UNIT_CHOICES = [
        ('per_request', 'Per Request'),
        ('per_100_words', 'Per 100 Words'),
        ('per_200_words', 'Per 200 Words'),
        ('per_item', 'Per Item'),
        ('per_image', 'Per Image'),
    ]
    
    unit = models.CharField(
        max_length=50,
        default='per_request',
        choices=UNIT_CHOICES,
        help_text="What the cost applies to"
    )
    
    # Metadata
    display_name = models.CharField(max_length=100, help_text="Human-readable name")
    description = models.TextField(blank=True, help_text="What this operation does")
    
    # Status
    is_active = models.BooleanField(default=True, help_text="Enable/disable this operation")
    
    # Audit fields
    created_at = models.DateTimeField(auto_now_add=True)
    updated_at = models.DateTimeField(auto_now=True)
    updated_by = models.ForeignKey(
        settings.AUTH_USER_MODEL,
        null=True,
        blank=True,
        on_delete=models.SET_NULL,
        related_name='credit_cost_updates',
        help_text="Admin who last updated"
    )
    
    # Change tracking
    previous_cost = models.IntegerField(
        null=True,
        blank=True,
        help_text="Cost before last update (for audit trail)"
    )
    
    class Meta:
        app_label = 'billing'
        db_table = 'igny8_credit_cost_config'
        verbose_name = 'Credit Cost Configuration'
        verbose_name_plural = 'Credit Cost Configurations'
        ordering = ['operation_type']
    
    def __str__(self):
        return f"{self.display_name} - {self.credits_cost} credits {self.unit}"
    
    def save(self, *args, **kwargs):
        # Track cost changes
        if self.pk:
            try:
                old = CreditCostConfig.objects.get(pk=self.pk)
                if old.credits_cost != self.credits_cost:
                    self.previous_cost = old.credits_cost
            except CreditCostConfig.DoesNotExist:
                pass
        super().save(*args, **kwargs)