############################################################################
#
# Copyright (c) 2004 Zope Foundation and Contributors.
# All Rights Reserved.
#
# This software is subject to the provisions of the Zope Public License,
# Version 2.1 (ZPL).  A copy of the ZPL should accompany this distribution.
# THIS SOFTWARE IS PROVIDED "AS IS" AND ANY AND ALL EXPRESS OR IMPLIED
# WARRANTIES ARE DISCLAIMED, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
# WARRANTIES OF TITLE, MERCHANTABILITY, AGAINST INFRINGEMENT, AND FITNESS
# FOR A PARTICULAR PURPOSE.
#
############################################################################
"""A TransactionManager controls transaction boundaries.

It coordinates application code and resource managers, so that they
are associated with the right transaction.
"""
import sys
import threading

from zope.interface import implementer

from transaction.interfaces import AlreadyInTransaction
from transaction.interfaces import ITransactionManager
from transaction.interfaces import NoTransaction
from transaction.interfaces import TransientError
from transaction.weakset import WeakSet
from transaction._compat import reraise
from transaction._compat import text_type
from transaction._transaction import Transaction


# We have to remember sets of synch objects, especially Connections.
# But we don't want mere registration with a transaction manager to
# keep a synch object alive forever; in particular, it's common
# practice not to explicitly close Connection objects, and keeping
# a Connection alive keeps a potentially huge number of other objects
# alive (e.g., the cache, and everything reachable from it too).
# Therefore we use "weak sets" internally.

# Call the ISynchronizer newTransaction() method on every element of
# WeakSet synchs.
# A transaction manager needs to do this whenever begin() is called.
# Since it would be good if tm.get() returned the new transaction while
# newTransaction() is running, calling this has to be delayed until after
# the transaction manager has done whatever it needs to do to make its
# get() return the new txn.
def _new_transaction(txn, synchs):
    if synchs:
        synchs.map(lambda s: s.newTransaction(txn))

# Important:  we must always pass a WeakSet (even if empty) to the Transaction
# constructor:  synchronizers are registered with the TM, but the
# ISynchronizer xyzCompletion() methods are called by Transactions without
# consulting the TM, so we need to pass a mutable collection of synchronizers
# so that Transactions "see" synchronizers that get registered after the
# Transaction object is constructed.


@implementer(ITransactionManager)
class TransactionManager(object):

    def __init__(self, explicit=False):
        self.explicit = explicit
        self._txn = None
        self._synchs = WeakSet()

    def begin(self):
        """ See ITransactionManager.
        """
        if self._txn is not None:
            if self.explicit:
                raise AlreadyInTransaction()
            self._txn.abort()
        txn = self._txn = Transaction(self._synchs, self)
        _new_transaction(txn, self._synchs)
        return txn

    __enter__ = lambda self: self.begin()

    def get(self):
        """ See ITransactionManager.
        """
        if self._txn is None:
            if self.explicit:
                raise NoTransaction()
            self._txn = Transaction(self._synchs, self)
        return self._txn

    def free(self, txn):
        if txn is not self._txn:
            raise ValueError("Foreign transaction")
        self._txn = None

    def registerSynch(self, synch):
        """ See ITransactionManager.
        """
        self._synchs.add(synch)
        if self._txn is not None:
            synch.newTransaction(self._txn)

    def unregisterSynch(self, synch):
        """ See ITransactionManager.
        """
        self._synchs.remove(synch)

    def clearSynchs(self):
        """ See ITransactionManager.
        """
        self._synchs.clear()

    def registeredSynchs(self):
        """ See ITransactionManager.
        """
        return bool(self._synchs)

    def isDoomed(self):
        """ See ITransactionManager.
        """
        return self.get().isDoomed()

    def doom(self):
        """ See ITransactionManager.
        """
        return self.get().doom()

    def commit(self):
        """ See ITransactionManager.
        """
        return self.get().commit()

    def abort(self):
        """ See ITransactionManager.
        """
        return self.get().abort()

    def __exit__(self, t, v, tb):
        if v is None:
            self.commit()
        else:
            self.abort()

    def savepoint(self, optimistic=False):
        """ See ITransactionManager.
        """
        return self.get().savepoint(optimistic)

    def attempts(self, number=3):
        if number <= 0:
            raise ValueError("number must be positive")
        while number:
            number -= 1
            if number:
                attempt = Attempt(self)
                yield attempt
                if attempt.success:
                    break
            else:
                yield self

    def _retryable(self, error_type, error):
        if issubclass(error_type, TransientError):
            return True

        for dm in self.get()._resources:
            should_retry = getattr(dm, 'should_retry', None)
            if (should_retry is not None) and should_retry(error):
                return True
        return False

    run_no_func_types = int, type(None)
    def run(self, func=None, tries=3):
        if isinstance(func, self.run_no_func_types):
            if func is not None:
                tries = func
            return lambda func: self.run(func, tries)

        if tries <= 0:
            raise ValueError("tries must be positive")

        name = func.__name__
        doc = func.__doc__
        if name != '_':
            if doc:
                doc = name + '\n\n' + doc
            else:
                doc = name

        if doc and not isinstance(doc, text_type):
            doc = doc.decode('utf-8')

        for i in range(1, tries + 1):  # pragma: no branch
            txn = self.begin()
            if doc:
                txn.note(doc)

            try:
                result = func()
                txn.commit()
            except Exception as v:
                if i == tries:
                    raise # that was our last chance
                retry = self._retryable(v.__class__, v)
                txn.abort()
                if not retry:
                    raise
            else:
                return result


class ThreadTransactionManager(TransactionManager, threading.local):
    """Thread-aware transaction manager.

    Each thread is associated with a unique transaction.
    """


class Attempt(object):

    success = False

    def __init__(self, manager):
        self.manager = manager

    def _retry_or_raise(self, t, v, tb):
        retry = self.manager._retryable(t, v)
        self.manager.abort()
        if retry:
            return retry # suppress the exception if necessary
        reraise(t, v, tb) # otherwise reraise the exception

    def __enter__(self):
        return self.manager.__enter__()

    def __exit__(self, t, v, tb):
        if v is None:
            try:
                self.manager.commit()
            except:
                return self._retry_or_raise(*sys.exc_info())
            else:
                self.success = True
        else:
            return self._retry_or_raise(t, v, tb)
