#!/usr/bin/env python3
#
# Copyright 2017 gRPC authors.
#
# 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.
""" Computes the diff between two qps runs and outputs significant results """

import argparse
import json
import multiprocessing
import os
import shutil
import subprocess
import sys

import qps_scenarios
import tabulate

sys.path.append(
    os.path.join(os.path.dirname(sys.argv[0]), '..', 'microbenchmarks',
                 'bm_diff'))
import bm_speedup

sys.path.append(
    os.path.join(os.path.dirname(sys.argv[0]), '..', '..', 'run_tests',
                 'python_utils'))
import check_on_pr


def _args():
    argp = argparse.ArgumentParser(description='Perform diff on QPS Driver')
    argp.add_argument('-d',
                      '--diff_base',
                      type=str,
                      help='Commit or branch to compare the current one to')
    argp.add_argument(
        '-l',
        '--loops',
        type=int,
        default=4,
        help='Number of loops for each benchmark. More loops cuts down on noise'
    )
    argp.add_argument('-j',
                      '--jobs',
                      type=int,
                      default=multiprocessing.cpu_count(),
                      help='Number of CPUs to use')
    args = argp.parse_args()
    assert args.diff_base, "diff_base must be set"
    return args


def _make_cmd(jobs):
    return ['make', '-j', '%d' % jobs, 'qps_json_driver', 'qps_worker']


def build(name, jobs):
    shutil.rmtree('qps_diff_%s' % name, ignore_errors=True)
    subprocess.check_call(['git', 'submodule', 'update'])
    try:
        subprocess.check_call(_make_cmd(jobs))
    except subprocess.CalledProcessError as e:
        subprocess.check_call(['make', 'clean'])
        subprocess.check_call(_make_cmd(jobs))
    os.rename('bins', 'qps_diff_%s' % name)


def _run_cmd(name, scenario, fname):
    return [
        'qps_diff_%s/opt/qps_json_driver' % name, '--scenarios_json', scenario,
        '--json_file_out', fname
    ]


def run(name, scenarios, loops):
    for sn in scenarios:
        for i in range(0, loops):
            fname = "%s.%s.%d.json" % (sn, name, i)
            subprocess.check_call(_run_cmd(name, scenarios[sn], fname))


def _load_qps(fname):
    try:
        with open(fname) as f:
            return json.loads(f.read())['qps']
    except IOError as e:
        print(("IOError occurred reading file: %s" % fname))
        return None
    except ValueError as e:
        print(("ValueError occurred reading file: %s" % fname))
        return None


def _median(ary):
    assert (len(ary))
    ary = sorted(ary)
    n = len(ary)
    if n % 2 == 0:
        return (ary[(n - 1) / 2] + ary[(n - 1) / 2 + 1]) / 2.0
    else:
        return ary[n / 2]


def diff(scenarios, loops, old, new):
    old_data = {}
    new_data = {}

    # collect data
    for sn in scenarios:
        old_data[sn] = []
        new_data[sn] = []
        for i in range(loops):
            old_data[sn].append(_load_qps("%s.%s.%d.json" % (sn, old, i)))
            new_data[sn].append(_load_qps("%s.%s.%d.json" % (sn, new, i)))

    # crunch data
    headers = ['Benchmark', 'qps']
    rows = []
    for sn in scenarios:
        mdn_diff = abs(_median(new_data[sn]) - _median(old_data[sn]))
        print(('%s: %s=%r %s=%r mdn_diff=%r' %
               (sn, new, new_data[sn], old, old_data[sn], mdn_diff)))
        s = bm_speedup.speedup(new_data[sn], old_data[sn], 10e-5)
        if abs(s) > 3 and mdn_diff > 0.5:
            rows.append([sn, '%+d%%' % s])

    if rows:
        return tabulate.tabulate(rows, headers=headers, floatfmt='+.2f')
    else:
        return None


def main(args):
    build('new', args.jobs)

    if args.diff_base:
        where_am_i = subprocess.check_output(
            ['git', 'rev-parse', '--abbrev-ref', 'HEAD']).decode().strip()
        subprocess.check_call(['git', 'checkout', args.diff_base])
        try:
            build('old', args.jobs)
        finally:
            subprocess.check_call(['git', 'checkout', where_am_i])
            subprocess.check_call(['git', 'submodule', 'update'])

    run('new', qps_scenarios._SCENARIOS, args.loops)
    run('old', qps_scenarios._SCENARIOS, args.loops)

    diff_output = diff(qps_scenarios._SCENARIOS, args.loops, 'old', 'new')

    if diff_output:
        text = '[qps] Performance differences noted:\n%s' % diff_output
    else:
        text = '[qps] No significant performance differences'
    print(('%s' % text))
    check_on_pr.check_on_pr('QPS', '```\n%s\n```' % text)


if __name__ == '__main__':
    args = _args()
    main(args)