#!/usr/bin/env python2.7
#
# 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 qps_scenarios
import shutil
import subprocess
import sys
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 comment_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, 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, e:
        print("IOError occurred reading file: %s" % fname)
        return None
    except ValueError, 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']).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)
    comment_on_pr.comment_on_pr('```\n%s\n```' % text)


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