#!/usr/bin/env python3
'''
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Copyright:

   This program is free software: you can redistribute it
   and/or modify it under the terms of the GNU General
   Public License as published by the Free Software
   Foundation, either version 3 of the License, or (at your
   option) any later version.

   This program is distributed in the hope that it will be
   useful, but WITHOUT ANY WARRANTY; without even the implied
   warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR
   PURPOSE. See the GNU General Public License for more details.

   You should have received a copy of the GNU General Public
   License along with this program. If not, see
   <https://www.gnu.org/licenses/>.


Commentary:

   Aergia is a sampling based profiler based off of SCALENE
   by Emery Berger (https://github.com/plasma-umass/scalene).

   It is not particularly informative, but unlike SCALENE
   or other sampling-based profilers I could find, reports
   the wall-time each asyncio await call spends idling.

   The goal behind Aergia is to eventually have these features,
   or similar, merged into SCALENE.


Code:
'''

from collections import defaultdict
from types import FrameType
from typing import cast, List, Tuple
import argparse
import asyncio
import atexit
import selectors
import signal
import sys
import time
import traceback


class ReplacementEpollSelector(selectors.EpollSelector):
    '''
    Provides a replacement for selectors.PollSelector that
    periodically wakes up to accept signals.
    '''

    def select(
        self, timeout=None
    ) -> List[Tuple[selectors.SelectorKey, int]]:
        start_time = time.perf_counter()
        if not timeout or timeout < 0:
            interval = sys.getswitchinterval()
        else:
            interval = min(timeout, sys.getswitchinterval())
        while True:
            selected = super().select(interval)
            if selected or timeout == 0 or not timeout:
                return selected
            end_time = time.perf_counter()
            if end_time - start_time >= timeout:
                return []


selectors.DefaultSelector = ReplacementEpollSelector


class Aergia(object):

    # a key-value pair where keys represent frame metadata (see
    # Aergia.frame_to_string) and values represent number of times
    # sampled.
    samples = defaultdict(lambda: [0, 0])
    # number of times samples have been collected
    total_samples = 0

    # the timestamp recorded last signal
    last_signal_time = 0.0

    def __init__(self, signal_interval):
        signal.signal(signal.SIGPROF,
                      self.cpu_signal_handler)
        signal.setitimer(signal.ITIMER_PROF,
                         signal_interval,
                         signal_interval)

    @staticmethod
    def start():
        atexit.register(Aergia.exit_handler)
        Aergia.last_signal_time = Aergia.gettime()

    @staticmethod
    def exit_handler():
        Aergia.print_samples()
        Aergia.disable_signals()

    @staticmethod
    def print_samples():
        '''Pretty-print profiling results.'''
        if Aergia.total_samples > 0:
            print("FILE\tFUNC\tPERC\tACTUAL+CALCULATED=SECONDS")
            for key in Aergia.sort_samples(Aergia.samples):
                Aergia.print_sample(key)
        else:
            print("No samples were gathered. If you are using concurrency, "
                  "this is likely a bug and you may run the profiler again.")

    @staticmethod
    def print_sample(key):
        '''Pretty-print a single sample.'''
        sig_intv = Aergia.get_sampling_interval()
        value = Aergia.samples[key]
        tot = Aergia.sum_sample(value)
        print(f"{key} :\t{tot * 100 / Aergia.total_samples:.3f}%"
              f"\t({value[0]:.3f} + {value[1]:.3f} ="
              f" {tot*sig_intv:.6f} seconds)")

    @staticmethod
    def disable_signals():
        signal.signal(signal.ITIMER_PROF, signal.SIG_IGN)
        signal.setitimer(signal.ITIMER_PROF, 0)

    @staticmethod
    def cpu_signal_handler(sig, frame):
        sig_intv = Aergia.get_sampling_interval()
        elapsed_since_last_signal = Aergia.gettime() - \
            Aergia.last_signal_time
        c_time_norm = (elapsed_since_last_signal - sig_intv) / \
            sig_intv

        keys = Aergia.compute_frames_to_record()
        for key in keys:
            Aergia.samples[Aergia.frame_to_string(key)][0] += \
                elapsed_since_last_signal
            Aergia.samples[Aergia.frame_to_string(key)][1] += c_time_norm
            Aergia.total_samples += elapsed_since_last_signal / \
                sig_intv
        Aergia.last_signal_time = Aergia.gettime()

    @staticmethod
    def compute_frames_to_record():
        '''Collects all stack frames that Aergia actually processes.'''
        frames = []
        if Aergia.is_event_loop_running():
            frames = Aergia.get_current_idle_tasks()

        # Process all the frames to remove ones we aren't going to track.
        new_frames = []
        for frame in frames:
            if frame is None:
                continue
            fname = frame.f_code.co_filename
            # Record samples only for files we care about.
            if (len(fname)) == 0:
                # 'eval/compile' gives no f_code.co_filename.  We have
                # to look back into the outer frame in order to check
                # the co_filename.
                fname = frame.f_back.f_code.co_filename
            while not Aergia.should_trace(fname):
                # Walk the stack backwards until we hit a frame that
                # IS one we should trace (if there is one).  i.e., if
                # it's in the code being profiled, and it is just
                # calling stuff deep in libraries.
                if frame:
                    frame = cast(FrameType, frame.f_back)
                else:
                    break
                if frame:
                    fname = frame.f_code.co_filename
            if frame:
                new_frames.append(frame)
        return new_frames

    @staticmethod
    def get_current_idle_tasks():
        '''Obtains the stack of frames of all currently idle tasks.'''
        curr_task = asyncio.current_task()
        return [
            task.get_coro().cr_frame
            for task in asyncio.all_tasks()
            if task is not curr_task
        ]

    @staticmethod
    def frame_to_string(frame):
        '''Pretty-prints a frame as a function/file name and a line number.
        Additionally used as a key for tallying lines.'''
        co = frame.f_code
        func_name = co.co_name
        line_no = frame.f_lineno
        filename = co.co_filename
        return filename + ':' + str(line_no) + '\t' + func_name

    @staticmethod
    def should_trace(filename):
        '''Returns FALSE if filename is uninteresting to the user.'''
        # FIXME Assume GuixSD. Makes filtering easy
        if '/gnu/store' in filename:
            return False
        if 'site-packages' in filename:
            return False
        if filename[0] == '<':
            return False
        if 'aergia' in filename:
            return False
        return True

    @staticmethod
    def is_event_loop_running() -> bool:
        '''Returns TRUE if there is an exent loop running. This is what
        `asyncio.get_event_loop()' did, before it was deprecated in 3.12'''
        return asyncio.get_event_loop_policy()._local._loop is not None

    @staticmethod
    def sort_samples(sample_dict):
        '''Returns SAMPLE_DICT in descending order by number of samples.'''
        return {k: v for k, v in sorted(sample_dict.items(),
                                        key=lambda item: Aergia.sum_sample(
                                            item[1]),
                                        reverse=True)}

    @staticmethod
    def sum_sample(sample):
        return sample[0] + sample[1]

    @staticmethod
    def gettime():
        '''returns the wallclock time'''
        return time.time()

    @staticmethod
    def get_sampling_interval():
        '''returns the current sampling interval'''
        return signal.getitimer(signal.ITIMER_PROF)[-1]


the_globals = {
    '__name__': '__main__',
    '__doc__': None,
    '__package__': None,
    '__loader__': globals()['__loader__'],
    '__spec__': None,
    '__annotations__': {},
    '__builtins__': globals()['__builtins__'],
    '__file__': None,
    '__cached__': None,
}


def parse_arguments():
    '''Parse CLI args'''
    parser = argparse.ArgumentParser(
        usage='%(prog)s [args] script [args]'
    )

    parser.add_argument('-i', '--interval',
                        help='The minimum amount of time inbetween \
                        samples in seconds.',
                        metavar='',
                        default=0.01)
    parser.add_argument('script', help='A python script to run.')
    parser.add_argument('s_args', nargs=argparse.REMAINDER,
                        help='python script args')

    return parser.parse_args()


def main():
    args = parse_arguments()

    sys.argv = [args.script] + args.s_args
    try:
        with open(args.script, 'rb') as fp:
            code = compile(fp.read(), args.script, "exec")
            Aergia(args.interval).start()
            exec(code, the_globals)
    except Exception:
        traceback.print_exc()


if __name__ == "__main__":
    main()