"""
Copyright (c) Microsoft Corporation. All rights reserved.
Licensed under the MIT License.
"""

import asyncio
import logging
import random
from typing import Awaitable, Callable, Literal, Optional, TypeVar

T = TypeVar("T")

logger = logging.getLogger(__name__)

# Type alias for jitter types using string literals
JitterType = Literal["none", "full", "equal", "decorrelated"]


class RetryOptions:
    def __init__(
        self,
        max_attempts: int = 5,
        delay: float = 0.5,  # in seconds
        max_delay: float = 30.0,  # maximum delay cap
        jitter_type: JitterType = "full",
        previous_delay: Optional[float] = None,  # Internal use for decorrelated jitter
        attempt_number: int = 1,  # Internal use to track current attempt number
    ):
        self.max_attempts = max_attempts
        self.delay = delay
        self.max_delay = max_delay
        self.jitter_type: JitterType = jitter_type
        self.previous_delay = previous_delay
        self.attempt_number = attempt_number


def _apply_jitter(delay: float, jitter_type: JitterType, previous_delay: Optional[float] = None) -> float:
    """Apply jitter to the delay to prevent thundering herd problems."""
    if jitter_type == "none":
        return delay
    elif jitter_type == "full":
        # Random delay between 0 and the computed delay
        return random.uniform(0, delay)
    elif jitter_type == "equal":
        # Random delay between half the computed delay and the full computed delay
        return random.uniform(delay / 2, delay)
    elif jitter_type == "decorrelated":
        # Decorrelated jitter: random delay between base delay and 3 * previous delay
        base_delay = delay / 4  # Start with a smaller base
        if previous_delay is None:
            previous_delay = base_delay
        return random.uniform(base_delay, min(delay, 3 * previous_delay))
    else:
        return delay


async def retry(factory: Callable[[], Awaitable[T]], options: Optional[RetryOptions] = None) -> T:
    options = options or RetryOptions()
    max_attempts = options.max_attempts
    base_delay = options.delay
    max_delay = options.max_delay
    jitter_type: JitterType = options.jitter_type
    previous_delay = options.previous_delay
    attempt_number = options.attempt_number

    try:
        return await factory()
    except (asyncio.CancelledError, KeyboardInterrupt):
        # Don't retry cancellation or keyboard interrupts
        logger.debug("Operation cancelled or interrupted, not retrying")
        raise
    except Exception as err:
        if max_attempts > 1:
            # Calculate exponential backoff delay using the attempt number
            exponential_delay = base_delay * (2 ** (attempt_number - 1))

            # Cap the delay at max_delay
            capped_delay = min(exponential_delay, max_delay)

            # Apply jitter
            jittered_delay = _apply_jitter(capped_delay, jitter_type, previous_delay)

            logger.debug(f"Delaying {jittered_delay:.2f}s before retry (attempt {attempt_number})...")
            await asyncio.sleep(jittered_delay)
            logger.debug("Retrying...")

            return await retry(
                factory,
                RetryOptions(
                    max_attempts=max_attempts - 1,
                    delay=base_delay,
                    max_delay=max_delay,
                    jitter_type=jitter_type,
                    previous_delay=jittered_delay,  # Pass current delay for decorrelated jitter
                    attempt_number=attempt_number + 1,  # Increment attempt number
                ),
            )
        logger.error("Final attempt failed.", exc_info=err)
        raise
