# standard imports
import uuid
import logging
import time
import signal
import json

# external imports
from chainlib.eth.block import (
        block_by_number,
        Block,
        )
from chainlib.eth.tx import (
        receipt,
        transaction,
        Tx,
        )
from chainlib.error import JSONRPCException

# local imports
from chainsyncer.filter import SyncFilter
from chainsyncer.error import (
        SyncDone,
        NoBlockForYou,
    )

logg = logging.getLogger().getChild(__name__)


def noop_callback(block, tx):
    logg.debug('noop callback ({},{})'.format(block, tx))


class Syncer:

    running_global = True
    yield_delay=0.005
    signal_request = [signal.SIGINT, signal.SIGTERM]
    signal_set = False

    def __init__(self, backend, pre_callback=None, block_callback=None, post_callback=None):
        self.cursor = None
        self.running = True
        self.backend = backend
        self.filter = SyncFilter(backend)
        self.block_callback = block_callback
        self.pre_callback = pre_callback
        self.post_callback = post_callback
        if not Syncer.signal_set:
            for sig in Syncer.signal_request:
                signal.signal(sig, Syncer.__sig_terminate)
            Syncer.signal_set = True


    @staticmethod
    def __sig_terminate(sig, frame):
        logg.warning('got signal {}'.format(sig))
        Syncer.terminate()


    @staticmethod
    def terminate():
        logg.info('termination requested!')
        Syncer.running_global = False


    def chain(self):
        """Returns the string representation of the chain spec for the chain the syncer is running on.

        :returns: Chain spec string
        :rtype: str
        """
        return self.bc_cache.chain()


    def add_filter(self, f):
        self.filter.add(f)
        self.backend.register_filter(str(f))


    def process_single(self, conn, block, tx):
        self.backend.set(block.number, tx.index)
        self.filter.apply(conn, block, tx)

    
class BlockPollSyncer(Syncer):

    def __init__(self, backend, pre_callback=None, block_callback=None, post_callback=None):
        super(BlockPollSyncer, self).__init__(backend, pre_callback, block_callback, post_callback)


    def loop(self, interval, conn):
        (pair, fltr) = self.backend.get()
        start_tx = pair[1]

        while self.running and Syncer.running_global:
            if self.pre_callback != None:
                self.pre_callback()
            while True and Syncer.running_global:
                if start_tx > 0:
                    start_tx -= 1
                    continue
                try:
                    block = self.get(conn)
                except SyncDone as e:
                    logg.info('sync done: {}'.format(e))
                    return self.backend.get()
                except NoBlockForYou as e:
                    break
# TODO: To properly handle this, ensure that previous request is rolled back
#                except sqlalchemy.exc.OperationalError as e:
#                    logg.error('database error: {}'.format(e))
#                    break

                if self.block_callback != None:
                    self.block_callback(block, None)

                last_block = block
                self.process(conn, block)
                start_tx = 0
                time.sleep(self.yield_delay)
            if self.post_callback != None:
                self.post_callback()
            time.sleep(interval)


class HeadSyncer(BlockPollSyncer):

    def process(self, conn, block):
        (pair, fltr) = self.backend.get()
        logg.debug('process block {} (backend {}:{})'.format(block, pair, fltr))
        i = pair[1] # set tx index from previous
        tx = None
        while True:
            try:
                tx = block.tx(i)
            except AttributeError:
                o = transaction(block.txs[i])
                r = conn.do(o)
                tx = Tx(Tx.src_normalize(r), block=block)
            except IndexError as e:
                logg.debug('index error syncer rcpt get {}'.format(e))
                self.backend.set(block.number + 1, 0)
                break

            # TODO: Move specifics to eth subpackage, receipts are not a global concept
            rcpt = conn.do(receipt(tx.hash))
            if rcpt != None:
                tx.apply_receipt(Tx.src_normalize(rcpt))
    
            self.process_single(conn, block, tx)
            self.backend.reset_filter()
                        
            i += 1
        

    def get(self, conn):
        (height, flags) = self.backend.get()
        block_number = height[0]
        block_hash = []
        o = block_by_number(block_number)
        r = conn.do(o)
        if r == None:
            raise NoBlockForYou()
        b = Block(r)
        b.txs = b.txs[height[1]:]

        return b


    def __str__(self):
        return '[headsyncer] {}'.format(str(self.backend))


class HistorySyncer(HeadSyncer):

    def __init__(self, backend, pre_callback=None, block_callback=None, post_callback=None):
        super(HeadSyncer, self).__init__(backend, pre_callback, block_callback, post_callback)
        self.block_target = None
        (block_number, flags) = self.backend.target()
        if block_number == None:
            raise AttributeError('backend has no future target. Use HeadSyner instead')
        self.block_target = block_number
        logg.debug('block target {}'.format(self.block_target))


    def get(self, conn):
        (height, flags) = self.backend.get()
        if self.block_target < height[0]:
            raise SyncDone(self.block_target)
        block_number = height[0]
        block_hash = []
        o = block_by_number(block_number)
        try:
            r = conn.do(o)
        # TODO: Disambiguate whether error is temporary or permanent, if permanent, SyncDone should be raised, because a historical sync is attempted into the future
        except JSONRPCException:
            r = None
        if r == None:
            raise SyncDone() #NoBlockForYou()
        b = Block(r)

        return b


    def __str__(self):
        return '[historysyncer] {}'.format(str(self.backend))