import uuid

from django.conf import settings
from django.db import models
from django.db.models import Q


class ContributionLedger(models.Model):
    class Activity(models.TextChoices):
        ATTENDANCE = "attendance", "Event attendance"
        POST = "post", "Published post"
        COMMENT = "comment", "Approved comment or reply"
        LIKE = "like", "Like given or received"
        SAVE = "save", "Save given or received"

    user = models.ForeignKey(
        settings.AUTH_USER_MODEL,
        on_delete=models.CASCADE,
        related_name="contribution_ledger_entries",
    )
    activity = models.CharField(max_length=20, choices=Activity.choices)
    source_type = models.CharField(max_length=32)
    source_id = models.CharField(max_length=80)
    effect_key = models.CharField(max_length=240, db_index=True)
    role = models.CharField(max_length=20)
    points = models.IntegerField()
    idempotency_key = models.UUIDField(default=uuid.uuid4, unique=True, editable=False)
    reversal_of = models.ForeignKey(
        "self",
        null=True,
        blank=True,
        on_delete=models.PROTECT,
        related_name="reversals",
    )
    reason = models.CharField(max_length=120, blank=True)
    created_at = models.DateTimeField(auto_now_add=True)

    class Meta:
        ordering = ["created_at", "id"]
        indexes = [
            models.Index(fields=["user", "activity"]),
            models.Index(fields=["source_type", "source_id"]),
        ]
        constraints = [
            models.CheckConstraint(condition=~Q(points=0), name="gamification_nonzero_ledger_points"),
        ]


class ScoringEpoch(models.Model):
    """The launch boundary for blog scoring; historical blog rows remain unscored."""

    id = models.PositiveSmallIntegerField(primary_key=True, default=1, editable=False)
    started_at = models.DateTimeField()