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import hashlib
import os

from time import time

from .storage import StorageClient


def pithos_hash(block, blockhash):
    h = hashlib.new(blockhash)
    h.update(block.rstrip('\x00'))
    return h.hexdigest()


class PithosClient(StorageClient):
    """GRNet Pithos API client"""

    def purge_container(self, container):
        self.assert_account()

        path = '/%s/%s' % (self.account, container)
        params = {'until': int(time())}
        self.delete(path, params=params, success=204)

    def put_block(self, data, hash):
        path = '/%s/%s' % (self.account, self.container)
        params = {'update': ''}
        headers = {'Content-Type': 'application/octet-stream',
                   'Content-Length': str(len(data))}
        r = self.post(path, params=params, data=data, headers=headers,
                      success=202)
        assert r.text.strip() == hash, 'Local hash does not match server'
    
    def create_object(self, object, f, size=None, hash_cb=None,
                      upload_cb=None):
        """Create an object by uploading only the missing blocks
        
        hash_cb is a generator function taking the total number of blocks to
        be hashed as an argument. Its next() will be called every time a block
        is hashed.
        
        upload_cb is a generator function with the same properties that is
        called every time a block is uploaded.
        """
        self.assert_container()
        
        meta = self.get_container_meta(self.container)
        blocksize = int(meta['block-size'])
        blockhash = meta['block-hash']

        size = size if size is not None else os.fstat(f.fileno()).st_size
        nblocks = 1 + (file_size - 1) // blocksize
        hashes = []
        map = {}

        offset = 0

        if hash_cb:
            hash_gen = hash_cb(nblocks)
            hash_gen.next()

        for i in range(nblocks):
            block = f.read(min(blocksize, size - offset))
            bytes = len(block)
            hash = pithos_hash(block, blockhash)
            hashes.append(hash)
            map[hash] = (offset, bytes)
            offset += bytes
            if hash_cb:
                hash_gen.next()

        assert offset == size

        path = '/%s/%s/%s' % (self.account, self.container, object)
        params = dict(format='json', hashmap='')
        hashmap = dict(bytes=size, hashes=hashes)
        headers = {'Content-Type': 'application/octet-stream'}
        r = self.put(path, params=params, headers=headers, json=hashmap,
                     success=(201, 409))

        if r.status_code == 201:
            return
        
        missing = r.json
        
        if upload_cb:
            upload_gen = upload_cb(len(missing))
            upload_gen.next()

        for hash in missing:
            offset, bytes = map[hash]
            f.seek(offset)
            data = f.read(bytes)
            self.put_block(data, hash)
            if upload_cb:
                upload_gen.next()

        self.put(path, params=params, headers=headers, json=hashmap,
                 success=201)