import time
import os
import json

import torch
from torch.profiler import profile, ProfilerActivity


def synchronize():
    pass


class NullContext:
    def __enter__(self):
        pass

    def __exit__(self, exc_type, exc_val, exc_tb):
        pass


def dump_chrome_trace(f, input, trace_filename, optimize_ctx, activities, num_runs=1,
                      devices=None, kwargs_for_f=None, kwargs_for_profiler=None):
    """
    Output the chrome trace of running f(input, **kwargs_for_f) with [optimize_ctx]
    [num_runs] times to [trace_filename].

    [activities] are the activities that the profiler will record, e.g. ProfilerActivity.CUDA.
    Return total runtime without the profiler

    Outputs to trace_filename
    """

    if devices is None:
        devices = ["cuda"]

    global synchronize
    if devices != ["cpu"] and torch.cuda.is_available():
        synchronize = torch.cuda.synchronize

    if kwargs_for_f is None:
        kwargs_for_f = {}
    if kwargs_for_profiler is None:
        kwargs_for_profiler = {}

    with optimize_ctx:
        torch.manual_seed(1337)
        for _ in range(5):  # warmup runs
            f(input, **kwargs_for_f)
            synchronize()
        torch.manual_seed(1337)
        t0 = time.perf_counter()
        for _ in range(num_runs):
            f(input, **kwargs_for_f)
            synchronize()
        t1 = time.perf_counter()
    timing = t1 - t0

    with profile(activities=activities, **kwargs_for_profiler) as prof:
        with optimize_ctx:
            synchronize()
            torch.manual_seed(1337)
            for _ in range(num_runs):
                f(input, **kwargs_for_f)
                synchronize()
    prof.export_chrome_trace(trace_filename)

    return timing


def get_chrome_trace_events(filename):
    f = open(filename)
    data = json.load(f)
    events = data["traceEvents"]
    return events


def is_gpu_compute_event(event):
    global gpu_pids
    return "pid" in event and event["pid"] in gpu_pids and "ph" in event and event["ph"] == "X"


def get_sorted_gpu_events(events):
    sorted_gpu_events = []
    for event in events:
        if(not is_gpu_compute_event(event)):
            continue
        sorted_gpu_events.append(event)
    return sorted(sorted_gpu_events, key=lambda x: x["ts"])


def get_duration(sorted_gpu_events):
    if len(sorted_gpu_events) == 0:
        return 0
    event = sorted_gpu_events[0]
    current_end_time = event["ts"] + event["dur"]
    total_duration = event["dur"]
    for event in sorted_gpu_events[1:]:
        start_time = max(event["ts"], current_end_time)
        end_time = event["ts"] + event["dur"]
        total_duration = total_duration + max(end_time - start_time, 0)
        current_end_time = max(current_end_time, end_time)
    return total_duration


def get_sorted_gpu_mm_conv_events(events):
    def is_mm_conv_event(event):
        return "name" in event and ("gemm" in event["name"] or "conv" in event["name"]
                                    or "cutlass" in event["name"] or "wgrad" in event["name"])
    gpu_events = get_sorted_gpu_events(events)
    sorted_events = []
    for event in gpu_events:
        if(not is_mm_conv_event(event)):
            continue
        sorted_events.append(event)
    return sorted_events


gpu_pids = []


def compute_utilization(filename: str, total_length: float):
    """
    Process the chrome traces outputs by the pytorch profiler to compute GPU Utilization
    and percent of times spent on matmal and convolution

    Args:
        filename(str): Name of chrome traces file produced by pytorch profiler

        total_length(float): total length of the process without profiler in second

    Return:
        tuple: (GPU Utilization, percent of time spent on matmal and convolution)
    """
    events = get_chrome_trace_events(filename)

    # get pids of GPU events
    global gpu_pids
    gpu_pids = []
    for event in events:
        if "name" not in event:
            continue
        if event["name"] == 'process_labels' and "GPU" in event["args"]["labels"]:
            gpu_pids.append(event["pid"])

    total_length = total_length * 1e6
    sorted_gpu_events = get_sorted_gpu_events(events)
    utilization = get_duration(sorted_gpu_events) / total_length

    sorted_gpu_mm_conv_events = get_sorted_gpu_mm_conv_events(events)
    mm_conv_utilization = get_duration(sorted_gpu_mm_conv_events) / total_length

    return utilization, mm_conv_utilization


def benchmark_utilization(f, input, trace_folder, optimize_ctx=None, trace_file_name="tmp_chrome_trace", num_runs=1):
    """
    Benchmark the GPU Utilization and percent of time spent on matmal and convolution operations of
    running f(input, **kwargs_for_f) with [optimize_ctx] [num_runs] times.
    It will produce a chrome trace file in trace_folder/trace_file_name.json

    Example:

    ```
    def f(a):
        return a.sum()
    a = torch.rand(2**20, device="cuda")
    utilization, mm_conv_utilization = benchmark_utilization(f, a, "tmp", trace_file_name = "tmp_chrome_trace")
    ```

    Args:
        f: function to benchmark

        input: input to :attr:`f`

        trace_folder: name of the folder to store the chrome trace

        optimize_ctx: the context in which f will run

        trace_file_name: name of the dumped chrome trace file, default to "tmp_chrome_trace"

        num_runs: number of times to run f, excluding the warm-up runs, default to 1.

    Return:
        tuple: (GPU Utilization, percent of time spent on matmal and convolution)

    """
    isExist = os.path.exists(trace_folder)
    if not isExist:
        os.makedirs(trace_folder)
        print("create folder " + trace_folder)

    if optimize_ctx is None:
        optimize_ctx = NullContext()

    chrome_trace_file_name = os.path.join(trace_folder, trace_file_name + ".json")
    total_length = dump_chrome_trace(f, input, chrome_trace_file_name, optimize_ctx,
                                     [ProfilerActivity.CUDA], num_runs=num_runs, devices="cuda")
    utilization, mm_conv_utilization = compute_utilization(chrome_trace_file_name, total_length)

    return utilization, mm_conv_utilization
