#!/usr/bin/env python3
import nbdkit
import json
import os

backup_dir = "/mnt2/backed-up-drive/backupstore/volumes/2c/df/pvc-5c1f48e3-346f-4c35-8e6a-8fc0c4c3a842"
blocks_dir = f"{backup_dir}/blocks"
backup_cfg = f"{backup_dir}/backups/backup_backup-eac0221d1cab4a9c.cfg"

with open(backup_cfg) as f:
    data = json.load(f)

size = int(data['Size'])
block_map = {b['Offset']: b['BlockChecksum'] for b in data['Blocks']}
block_size = 2097152

def thread_model():
    return nbdkit.THREAD_MODEL_SERIALIZE_ALL_REQUESTS

def get_size():
    return size

def pread(h, count, offset, flags):
    result = bytearray()
    remaining = count
    current_offset = offset
    
    while remaining > 0:
        block_start = (current_offset // block_size) * block_size
        block_offset = current_offset - block_start
        read_size = min(remaining, block_size - block_offset)
        
        if block_start in block_map:
            checksum = block_map[block_start]
            block_path = f"{blocks_dir}/{checksum[:2]}/{checksum[2:4]}/{checksum}.blk"
            
            if os.path.exists(block_path):
                with open(block_path, 'rb') as f:
                    f.seek(block_offset)
                    result.extend(f.read(read_size))
            else:
                result.extend(b'\x00' * read_size)
        else:
            result.extend(b'\x00' * read_size)
        
        current_offset += read_size
        remaining -= read_size
    
    return bytes(result)