from datetime import datetime, timedelta
from dataclasses import dataclass, field
from typing import List, Tuple

@dataclass
class Incident:
    start: datetime
    end: datetime
    description: str

    @property
    def duration_minutes(self) -> float:
        return (self.end - self.start).total_seconds() / 60


@dataclass
class ErrorBudget:
    service: str
    slo_pct: float  # e.g., 99.9
    window_days: int  # e.g., 28
    incidents: List[Incident] = field(default_factory=list)

    @property
    def total_budget_minutes(self) -> float:
        """Total allowed downtime in minutes"""
        return self.window_days * 24 * 60 * (1 - self.slo_pct / 100)

    @property
    def spent_minutes(self) -> float:
        """Total incident minutes in the window"""
        return sum(i.duration_minutes for i in self.incidents)

    @property
    def remaining_minutes(self) -> float:
        return max(0, self.total_budget_minutes - self.spent_minutes)

    @property
    def remaining_pct(self) -> float:
        if self.total_budget_minutes == 0:
            return 0
        return (self.remaining_minutes / self.total_budget_minutes) * 100

    @property
    def is_exhausted(self) -> bool:
        return self.spent_minutes >= self.total_budget_minutes


# Usage
budget = ErrorBudget(
    service="checkout-api",
    slo_pct=99.9,
    window_days=28,
    incidents=[
        Incident(
            start=datetime(2024, 3, 5, 14, 30),
            end=datetime(2024, 3, 5, 14, 47),
            description="DB connection pool exhausted after deploy v3.1.4"
        ),
        Incident(
            start=datetime(2024, 3, 18, 9, 0),
            end=datetime(2024, 3, 18, 9, 23),
            description="Redis failover — cache miss storm"
        )
    ]
)

print(f"Total budget: {budget.total_budget_minutes:.1f}m")
print(f"Spent: {budget.spent_minutes:.1f}m")
print(f"Remaining: {budget.remaining_minutes:.1f}m ({budget.remaining_pct:.1f}%)")
# → Total budget: 40.3m
# → Spent: 40.0m (17+23 minutes)
# → Remaining: 0.3m (0.7%)
# → WARNING: Budget nearly exhausted
Error Budgets — תקציב שגיאות

Error Budgets — תקציב שגיאות

Error Budgets — תקציב שגיאות
