from django.conf import settings
from django.core.exceptions import ValidationError
from django.db import models
from django.db.models import Q

from apps.users.models import ApiKey


def normalize_resolution(value: str | None) -> str:
    return "" if value is None else str(value).strip().upper()


class CallRecord(models.Model):
    class OperationType(models.TextChoices):
        TITLE = "title", "Generate title"
        IMAGE = "image", "Generate image"

    class Status(models.TextChoices):
        PENDING = "pending", "Pending"
        SUCCESS = "success", "Success"
        FAILED = "failed", "Failed"

    user = models.ForeignKey(
        settings.AUTH_USER_MODEL,
        on_delete=models.PROTECT,
        related_name="call_records",
    )
    api_key = models.ForeignKey(
        ApiKey,
        null=True,
        blank=True,
        on_delete=models.SET_NULL,
        related_name="call_records",
    )
    operation_type = models.CharField(max_length=32, choices=OperationType.choices)
    alias = models.CharField(max_length=64, blank=True)
    model_used = models.CharField(max_length=128, blank=True)
    resolution = models.CharField(max_length=32, blank=True)
    prompt = models.TextField(blank=True)
    points_cost = models.BigIntegerField(default=0)
    status = models.CharField(
        max_length=20,
        choices=Status.choices,
        default=Status.PENDING,
    )
    upstream_latency_ms = models.PositiveIntegerField(null=True, blank=True)
    error_message = models.TextField(blank=True)
    result_ref = models.TextField(blank=True)
    result_summary = models.TextField(blank=True)
    created_at = models.DateTimeField(auto_now_add=True)
    updated_at = models.DateTimeField(auto_now=True)

    class Meta:
        db_table = "call_record"
        ordering = ("-created_at", "-id")
        constraints = [
            models.CheckConstraint(
                condition=Q(points_cost__gte=0),
                name="call_record_points_cost_non_negative",
            ),
        ]
        indexes = [
            models.Index(fields=("user", "created_at")),
            models.Index(fields=("api_key", "created_at")),
            models.Index(fields=("operation_type", "status")),
            models.Index(fields=("alias",)),
        ]

    def __str__(self) -> str:
        return f"{self.operation_type}:{self.alias or '<default>'} {self.status}"


class PricingRule(models.Model):
    operation_type = models.CharField(max_length=32, choices=CallRecord.OperationType.choices)
    alias = models.CharField(max_length=64)
    resolution = models.CharField(
        max_length=32,
        blank=True,
        default="",
        help_text="Leave blank to apply to every resolution for this alias.",
    )
    points_cost = models.BigIntegerField()
    is_active = models.BooleanField(default=True)
    created_at = models.DateTimeField(auto_now_add=True)
    updated_at = models.DateTimeField(auto_now=True)

    class Meta:
        db_table = "pricing_rule"
        ordering = ("operation_type", "alias", "resolution")
        constraints = [
            models.UniqueConstraint(
                fields=("operation_type", "alias", "resolution"),
                name="unique_pricing_rule_per_alias_resolution",
            ),
            models.CheckConstraint(
                condition=Q(points_cost__gt=0),
                name="pricing_rule_points_cost_positive",
            ),
        ]
        indexes = [
            models.Index(fields=("operation_type", "alias", "is_active")),
            models.Index(fields=("operation_type", "alias", "resolution", "is_active")),
        ]

    def __str__(self) -> str:
        resolution = self.resolution or "*"
        return f"{self.operation_type}:{self.alias}:{resolution} = {self.points_cost}"

    def clean(self) -> None:
        super().clean()
        self.alias = str(self.alias or "").strip()
        self.resolution = normalize_resolution(self.resolution)
        if not self.alias:
            raise ValidationError({"alias": "Alias is required."})

    def save(self, *args, **kwargs) -> None:
        self.full_clean()
        super().save(*args, **kwargs)


class ExchangeRate(models.Model):
    currency = models.CharField(max_length=10, default="CNY")
    points_per_unit = models.DecimalField(max_digits=12, decimal_places=4)
    is_active = models.BooleanField(default=True)
    effective_from = models.DateTimeField()
    note = models.CharField(max_length=255, blank=True)
    created_at = models.DateTimeField(auto_now_add=True)
    updated_at = models.DateTimeField(auto_now=True)

    class Meta:
        db_table = "exchange_rate"
        ordering = ("-effective_from", "-id")
        constraints = [
            models.CheckConstraint(
                condition=Q(points_per_unit__gt=0),
                name="exchange_rate_points_per_unit_positive",
            ),
        ]
        indexes = [
            models.Index(fields=("currency", "is_active", "effective_from")),
        ]

    def __str__(self) -> str:
        return f"{self.currency} 1 = {self.points_per_unit} points"

    def clean(self) -> None:
        super().clean()
        self.currency = str(self.currency or "").strip().upper()
        if not self.currency:
            raise ValidationError({"currency": "Currency is required."})

    def save(self, *args, **kwargs) -> None:
        self.full_clean()
        super().save(*args, **kwargs)


class PointsLedger(models.Model):
    class ChangeType(models.TextChoices):
        RECHARGE = "recharge", "Recharge"
        CONSUME = "consume", "Consume"
        ADJUST = "adjust", "Adjust"
        REFUND = "refund", "Refund"

    user = models.ForeignKey(
        settings.AUTH_USER_MODEL,
        on_delete=models.PROTECT,
        related_name="points_ledger_entries",
    )
    change_type = models.CharField(max_length=20, choices=ChangeType.choices)
    points_delta = models.BigIntegerField()
    balance_after = models.BigIntegerField()
    ref_order_id = models.PositiveBigIntegerField(null=True, blank=True)
    ref_call = models.ForeignKey(
        CallRecord,
        null=True,
        blank=True,
        on_delete=models.PROTECT,
        related_name="ledger_entries",
    )
    reason = models.TextField(blank=True)
    created_at = models.DateTimeField(auto_now_add=True)

    class Meta:
        db_table = "points_ledger"
        ordering = ("-created_at", "-id")
        constraints = [
            models.CheckConstraint(
                condition=Q(balance_after__gte=0),
                name="points_ledger_balance_after_non_negative",
            ),
            models.CheckConstraint(
                condition=~Q(points_delta=0),
                name="points_ledger_points_delta_non_zero",
            ),
        ]
        indexes = [
            models.Index(fields=("user", "created_at")),
            models.Index(fields=("change_type", "created_at")),
            models.Index(fields=("ref_order_id",)),
            models.Index(fields=("ref_call",)),
        ]

    def __str__(self) -> str:
        return f"{self.user} {self.change_type} {self.points_delta}"

    def clean(self) -> None:
        super().clean()
        if self.change_type == self.ChangeType.ADJUST and not (self.reason or "").strip():
            raise ValidationError({"reason": "Adjust ledger entries require a reason."})