#!/usr/bin/env python3
"""
S3 Restore Status Checker

This script checks the restore status of S3 objects that have been archived to
Glacier or Deep Archive storage classes. It reads a CSV file containing bucket
and object key pairs, then queries each object's restore status using the
S3 head_object API.

The script is useful for monitoring the progress of S3 batch restore operations
or checking the status of individual object restorations from Glacier storage.

Requirements:
    - boto3: AWS SDK for Python
    - AWS credentials configured (via ~/.aws/credentials, environment variables, or IAM role)
    - Proper IAM permissions to read object metadata (s3:GetObject, s3:ListBucket)

Usage:
    # Normal mode (debug output with filenames):
    python3 s3-restore-status.py
    
    # Optimized mode (status only, no filenames):
    python3 -O s3-restore-status.py

Input File Format:
    The script reads /tmp/objectlist.csv by default. Each line should contain:
    <bucket>,<object_key>
    
    Example:
        my-bucket,path/to/file1.log
        my-bucket,path/to/file2.log
        another-bucket,archive/data.json

Output:
    The script prints the restore status for each object:
    - "Not restoring" if the object has no active restore operation
    - Restore status string (e.g., 'ongoing-request="true"') if restoration is in progress
    - Restore status with expiry date (e.g., 'ongoing-request="false", expiry-date="..."') 
      if restoration is complete
    
    In normal mode (when Python is run without -O optimization flag), output includes 
    the filename: <filename>: <restore_status>
    
    In optimized mode (python3 -O), only the restore status is printed.

Example Output:
    Not-being-restored
    ongoing-request="true"
    ongoing-request="false", expiry-date="Mon, 25 Nov 2025 00:00:00 GMT"

"""

import boto3
import sys


def read_objectlist(path: str = "/tmp/objectlist.csv"):
    """Read object list CSV file and extract bucket and object keys.
    
    Parses a CSV file containing bucket and object key pairs. Each line should
    have the format: "<bucket>,<object_key>". The function collects all object
    keys and returns the last bucket name encountered (assuming all objects are
    in the same bucket).
    
    Args:
        path (str): Path to the CSV file containing bucket and object key pairs.
                   Defaults to "/tmp/objectlist.csv".
    
    Returns:
        tuple: A tuple containing:
            - list: List of object keys (strings)
            - str: The bucket name (last bucket encountered in the file)
    
    Raises:
        SystemExit: If the file is not found, the script exits with status code 1.
    
    Note:
        - Lines starting with '#' are treated as comments and ignored
        - Empty lines are ignored
        - Malformed lines (not containing exactly one comma) are silently skipped
        - The function assumes all objects are in the same bucket (returns last bucket)
    """
    bucket_to_keys = []
    try:
        with open(path, "r", encoding="utf-8") as f:
            for raw_line in f:
                line = raw_line.strip()
                # Split only on the first comma to allow commas in keys if ever present
                parts = line.split(",", 1)
                if len(parts) != 2:
                    continue
                bucket = parts[0].strip()
                key = parts[1].strip()
                bucket_to_keys.append(key)
    except FileNotFoundError:
        print(f"Error: object list file not found at {path}", file=sys.stderr)
        sys.exit(1)
    return bucket_to_keys, bucket


def main():
    """Main function to check restore status of S3 objects.
    
    Reads the object list from CSV file, connects to AWS S3 in ap-east-1 region,
    and queries the restore status for each object. Prints the restore status
    for each object to stdout.
    
    The restore status indicates:
    - "Not restoring": Object is not currently being restored (or restore completed and expired)
    - Restore status string: Contains restore progress and expiry information
    
    In debug mode (Python run without -O optimization flag), output includes
    the filename along with the status for easier identification.
    
    Region: ap-east-1 (Asia Pacific - Hong Kong)
    """
    session = boto3.Session(region_name="ap-east-1")
    s3_client = session.client('s3')
    keys, bucket = read_objectlist(path="/tmp/objectlist.csv")
    
    for object in keys:
        response = s3_client.head_object(
            Bucket=bucket,
            Key=object
        )
        # Split object path by / and get only the last element (filename)
        restore_status = response.get('Restore') or "Not-being-restored"
        if __debug__:
           filename = object.split('/')[-1]
           print(f"{filename}: {restore_status}")
        print(restore_status)


if __name__ == "__main__":
    main()