from datetime import datetime, timedelta
from typing import Tuple


def get_date_range(days: int) -> Tuple[datetime, datetime]:
    """Get date range for the last N days."""
    end_date = datetime.now()
    start_date = end_date - timedelta(days=days)
    return start_date, end_date


def parse_timestamp(timestamp_str: str) -> datetime:
    """Parse a timestamp string to datetime."""
    formats = [
        "%Y-%m-%d %H:%M:%S",
        "%Y-%m-%dT%H:%M:%S",
        "%Y-%m-%d %H:%M:%S%z",
        "%Y-%m-%dT%H:%M:%SZ",
    ]

    for fmt in formats:
        try:
            return datetime.strptime(timestamp_str, fmt)
        except ValueError:
            continue

    raise ValueError(f"Cannot parse timestamp: {timestamp_str}")


def format_duration(seconds: float) -> str:
    """Format duration in human-readable format."""
    if seconds < 60:
        return f"{seconds:.1f}s"
    elif seconds < 3600:
        minutes = seconds / 60
        return f"{minutes:.1f}m"
    elif seconds < 86400:
        hours = seconds / 3600
        return f"{hours:.1f}h"
    else:
        days = seconds / 86400
        return f"{days:.1f}d"


def group_by_period(
    commits: list,
    period: str = "day",
) -> dict:
    """Group commits by time period."""
    result = {}
    for commit in commits:
        if period == "hour":
            key = commit.timestamp.strftime("%Y-%m-%d %H:00")
        elif period == "day":
            key = commit.timestamp.strftime("%Y-%m-%d")
        elif period == "week":
            key = commit.timestamp.strftime("%Y-%W")
        elif period == "month":
            key = commit.timestamp.strftime("%Y-%m")
        else:
            key = commit.timestamp.strftime("%Y-%m-%d")

        result[key] = result.get(key, 0) + 1

    return result