# Copyright 2020 Google Inc. All rights reserved.
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
#     http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
"""Python benchmarking utilities.

Example usage:
  import google_benchmark as benchmark

  @benchmark.register
  def my_benchmark(state):
      ...  # Code executed outside `while` loop is not timed.

      while state:
        ...  # Code executed within `while` loop is timed.

  if __name__ == '__main__':
    benchmark.main()
"""
import atexit

from absl import app

from google_benchmark import _benchmark
from google_benchmark._benchmark import (
    Counter as Counter,
    State as State,
    kMicrosecond as kMicrosecond,
    kMillisecond as kMillisecond,
    kNanosecond as kNanosecond,
    kSecond as kSecond,
    o1 as o1,
    oAuto as oAuto,
    oLambda as oLambda,
    oLogN as oLogN,
    oN as oN,
    oNCubed as oNCubed,
    oNLogN as oNLogN,
    oNone as oNone,
    oNSquared as oNSquared,
)
from google_benchmark.version import __version__ as __version__


class __OptionMaker:
    """A stateless class to collect benchmark options.

    Collect all decorator calls like @option.range(start=0, limit=1<<5).
    """

    class Options:
        """Pure data class to store options calls, along with the benchmarked function."""

        def __init__(self, func):
            self.func = func
            self.builder_calls = []

    @classmethod
    def make(cls, func_or_options):
        """Make Options from Options or the benchmarked function."""
        if isinstance(func_or_options, cls.Options):
            return func_or_options
        return cls.Options(func_or_options)

    def __getattr__(self, builder_name):
        """Append option call in the Options."""

        # The function that get returned on @option.range(start=0, limit=1<<5).
        def __builder_method(*args, **kwargs):
            # The decorator that get called, either with the benchmared function
            # or the previous Options
            def __decorator(func_or_options):
                options = self.make(func_or_options)
                options.builder_calls.append((builder_name, args, kwargs))
                # The decorator returns Options so it is not technically a decorator
                # and needs a final call to @register
                return options

            return __decorator

        return __builder_method


# Alias for nicer API.
# We have to instantiate an object, even if stateless, to be able to use __getattr__
# on option.range
option = __OptionMaker()


def register(undefined=None, *, name=None):
    """Register function for benchmarking."""
    if undefined is None:
        # Decorator is called without parenthesis so we return a decorator
        return lambda f: register(f, name=name)

    # We have either the function to benchmark (simple case) or an instance of Options
    # (@option._ case).
    options = __OptionMaker.make(undefined)

    if name is None:
        name = options.func.__name__

    # We register the benchmark and reproduce all the @option._ calls onto the
    # benchmark builder pattern
    benchmark = _benchmark.RegisterBenchmark(name, options.func)
    for name, args, kwargs in options.builder_calls[::-1]:
        getattr(benchmark, name)(*args, **kwargs)

    # return the benchmarked function because the decorator does not modify it
    return options.func


def _flags_parser(argv):
    argv = _benchmark.Initialize(argv)
    return app.parse_flags_with_usage(argv)


def _run_benchmarks(argv):
    if len(argv) > 1:
        raise app.UsageError("Too many command-line arguments.")
    return _benchmark.RunSpecifiedBenchmarks()


def main(argv=None):
    return app.run(_run_benchmarks, argv=argv, flags_parser=_flags_parser)


# Methods for use with custom main function.
initialize = _benchmark.Initialize
run_benchmarks = _benchmark.RunSpecifiedBenchmarks
atexit.register(_benchmark.ClearRegisteredBenchmarks)
