# Copyright (c) 2017–2018 crocoite contributors
# 
# Permission is hereby granted, free of charge, to any person obtaining a copy
# of this software and associated documentation files (the "Software"), to deal
# in the Software without restriction, including without limitation the rights
# to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
# copies of the Software, and to permit persons to whom the Software is
# furnished to do so, subject to the following conditions:
# 
# The above copyright notice and this permission notice shall be included in
# all copies or substantial portions of the Software.
# 
# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
# IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
# FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
# AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
# LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
# OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
# THE SOFTWARE.

"""
Simple logger inspired by structlog.

It is usually used like this: Classes are passed a logger instance. They bind
context to their name, so identifying the source of messages is easier. Every
log message carries a unique id (uuid) for automated identification as well as
a short human-readable message (msg) and arbitrary payload.
"""

import sys, json
from datetime import datetime
from functools import partial
from enum import IntEnum

from pytz import utc

class Level(IntEnum):
    DEBUG = 0
    INFO = 1
    WARNING = 2
    ERROR = 3

class Logger:
    def __init__ (self, consumer=[], bindings={}):
        self.bindings = bindings
        self.consumer = consumer

    def __call__ (self, level, *args, **kwargs):
        if not isinstance (level, Level):
            level = Level[level.upper ()]
        kwargs['level'] = level
        if args:
            if len (args) == 1:
                args, = args
            kwargs['msg'] = args
        # do not overwrite arguments
        for k, v in self.bindings.items ():
            if k not in kwargs:
                kwargs[k] = v
        for c in self.consumer:
            kwargs = c (**kwargs)
        return kwargs

    def __getattr__ (self, k):
        """ Bind all method names to level, so Logger.info, Logger.warning, … work """
        return partial (self.__call__, k)

    def bind (self, **kwargs):
        d = self.bindings.copy ()
        d.update (kwargs)
        # consumer is not a copy intentionally, so attaching to the parent
        # logger will attach to all children as well
        return self.__class__ (consumer=self.consumer, bindings=d)

    def unbind (self, **kwargs):
        d = self.bindings.copy ()
        for k in kwargs.keys ():
            del d[k]
        return self.__class__ (consumer=self.consumer, bindings=d)

    def connect (self, consumer):
        self.consumer.append (consumer)

    def disconnect (self, consumer):
        self.consumer.remove (consumer)

class Consumer:
    def __call__ (self, **kwargs): # pragma: no cover
        raise NotImplementedError ()

class NullConsumer (Consumer):
    def __call__ (self, **kwargs):
        return kwargs

class PrintConsumer (Consumer):
    """
    Simple printing consumer
    """
    def __call__ (self, **kwargs):
        sys.stderr.write (str (kwargs))
        sys.stderr.write ('\n')
        sys.stderr.flush ()
        return kwargs

class JsonEncoder (json.JSONEncoder):
    def default (self, obj):
        if isinstance (obj, datetime):
            return obj.isoformat ()

        # make sure serialization always succeeds
        try:
            return json.JSONEncoder.default(self, obj)
        except TypeError:
            return str (obj)

class JsonPrintConsumer (Consumer):
    def __init__ (self, minLevel=Level.INFO):
        self.minLevel = minLevel

    def __call__ (self, **kwargs):
        if kwargs['level'] >= self.minLevel:
            json.dump (kwargs, sys.stdout, cls=JsonEncoder)
            sys.stdout.write ('\n')
            sys.stdout.flush ()
        return kwargs

class DatetimeConsumer (Consumer):
    def __call__ (self, **kwargs):
        kwargs['date'] = datetime.utcnow ().replace (tzinfo=utc)
        return kwargs

class WarcHandlerConsumer (Consumer):
    def __init__ (self, warc, minLevel=Level.INFO):
        self.warc = warc
        self.minLevel = minLevel

    def __call__ (self, **kwargs):
        if kwargs['level'] >= self.minLevel:
            self.warc._writeLog (json.dumps (kwargs, cls=JsonEncoder))
        return kwargs