#!/usr/bin/env python

"""%prog [options] shellpath dirpath

Pulls performance data on parsing via the js shell.
Displays the average number of milliseconds it took to parse each file.

For comparison, something apparently approximating a t-test is performed:
"Faster" means that:

    t_baseline_goodrun = (t_baseline_avg - t_baseline_stddev)
    t_current_badrun = (t_current_avg + t_current_stddev)
    t_current_badrun < t_baseline_goodrun

Effectively, a bad run from the current data is better than a good run from the
baseline data, we're probably faster. A similar computation is used for
determining the "slower" designation.

Arguments:
  shellpath             executable JavaScript shell
  dirpath               directory filled with parsilicious js files
"""

from __future__ import print_function

import math
import optparse
import os
import subprocess as subp
import sys
from string import Template

try:
    import compare_bench
except ImportError:
    compare_bench = None


_DIR = os.path.dirname(__file__)
JS_CODE_TEMPLATE = Template("""
if (typeof snarf !== 'undefined') read = snarf
var contents = read("$filepath");
for (var i = 0; i < $warmup_run_count; i++)
    parse(contents);
var results = [];
for (var i = 0; i < $real_run_count; i++) {
    var start = new Date();
    parse(contents);
    var end = new Date();
    results.push(end - start);
}
print(results);
""")


def gen_filepaths(dirpath, target_ext='.js'):
    for filename in os.listdir(dirpath):
        if filename.endswith(target_ext):
            yield os.path.join(dirpath, filename)


def avg(seq):
    return sum(seq) / len(seq)


def stddev(seq, mean):
    diffs = ((float(item) - mean) ** 2 for item in seq)
    return math.sqrt(sum(diffs) / len(seq))


def bench(shellpath, filepath, warmup_runs, counted_runs, stfu=False):
    """Return a list of milliseconds for the counted runs."""
    assert '"' not in filepath
    code = JS_CODE_TEMPLATE.substitute(filepath=filepath,
                                       warmup_run_count=warmup_runs,
                                       real_run_count=counted_runs)
    proc = subp.Popen([shellpath, '-e', code], stdout=subp.PIPE)
    stdout, _ = proc.communicate()
    milliseconds = [float(val) for val in stdout.split(',')]
    mean = avg(milliseconds)
    sigma = stddev(milliseconds, mean)
    if not stfu:
        print('Runs:', [int(ms) for ms in milliseconds])
        print('Mean:', mean)
        print('Stddev: {:.2f} ({:.2f}% of mean)'.format(
            sigma, sigma / mean * 100))
    return mean, sigma


def parsemark(filepaths, fbench, stfu=False):
    """:param fbench: fbench(filename) -> float"""
    bench_map = {} # {filename: (avg, stddev)}
    for filepath in filepaths:
        filename = os.path.split(filepath)[-1]
        if not stfu:
            print('Parsemarking {}...'.format(filename))
        bench_map[filename] = fbench(filepath)
    print('{')
    for i, (filename, (avg, stddev)) in enumerate(bench_map.iteritems()):
        assert '"' not in filename
        fmt = '    {:30s}: {{"average_ms": {:6.2f}, "stddev_ms": {:6.2f}}}'
        if i != len(bench_map) - 1:
            fmt += ','
        filename_str = '"{}"'.format(filename)
        print(fmt.format(filename_str, avg, stddev))
    print('}')
    return dict((filename, dict(average_ms=avg, stddev_ms=stddev))
                for filename, (avg, stddev) in bench_map.iteritems())


def main():
    parser = optparse.OptionParser(usage=__doc__.strip())
    parser.add_option('-w', '--warmup-runs', metavar='COUNT', type=int,
                      default=5,
                      help='used to minimize test instability [%default]')
    parser.add_option('-c', '--counted-runs', metavar='COUNT', type=int,
                      default=50,
                      help='timed data runs that count towards the average'
                      ' [%default]')
    parser.add_option('-s', '--shell', metavar='PATH',
                      help='explicit shell location; when omitted, will look'
                      ' in likely places')
    parser.add_option('-b', '--baseline', metavar='JSON_PATH',
                      dest='baseline_path',
                      help='json file with baseline values to '
                      'compare against')
    parser.add_option('-q', '--quiet', dest='stfu', action='store_true',
                      default=False,
                      help='only print JSON to stdout [%default]')
    options, args = parser.parse_args()
    try:
        shellpath = args.pop(0)
    except IndexError:
        parser.print_help()
        print()
        print('error: shellpath required', file=sys.stderr)
        return -1
    try:
        dirpath = args.pop(0)
    except IndexError:
        parser.print_help()
        print()
        print('error: dirpath required', file=sys.stderr)
        return -1
    if not shellpath or not os.path.exists(shellpath):
        print('error: could not find shell:', shellpath, file=sys.stderr)
        return -1
    if options.baseline_path:
        if not os.path.isfile(options.baseline_path):
            print('error: baseline file does not exist', file=sys.stderr)
            return -1
        if not compare_bench:
            print('error: JSON support is missing, cannot compare benchmarks',
                  file=sys.stderr)
            return -1
    benchfile = lambda filepath: bench(shellpath, filepath,
                                       options.warmup_runs,
                                       options.counted_runs,
                                       stfu=options.stfu)
    bench_map = parsemark(gen_filepaths(dirpath), benchfile, options.stfu)
    if options.baseline_path:
        compare_bench.compare_immediate(bench_map, options.baseline_path)
    return 0


if __name__ == '__main__':
    sys.exit(main())