# Copyright 2015 The Chromium OS Authors. All rights reserved.
# Use of this source code is governed by a BSD-style license that can be
# found in the LICENSE file.

import collections
import logging
import re
import six

from autotest_lib.client.bin import utils
from autotest_lib.client.common_lib import error


def get_histogram_text(tab, histogram_name):
    """
     This returns contents of the given histogram.

     @param tab: object, Chrome tab instance
     @param histogram_name: string, name of the histogram
     @returns string: contents of the histogram
     """
    docEle = 'document.documentElement'
    tab.Navigate('chrome://histograms/%s' % histogram_name)
    tab.WaitForDocumentReadyStateToBeComplete()
    raw_text = tab.EvaluateJavaScript('{0} && {0}.innerText'.format(docEle))
    # extract the contents of the histogram
    histogram = raw_text[raw_text.find('Histogram:'):].strip()
    if histogram:
        logging.debug('chrome://histograms/%s:\n%s', histogram_name, histogram)
    else:
        logging.debug('No histogram is shown in chrome://histograms/%s',
                      histogram_name)
    return histogram


def loaded(tab, histogram_name, pattern):
    """
     Checks if the histogram page has been fully loaded.

     @param tab: object, Chrome tab instance
     @param histogram_name: string, name of the histogram
     @param pattern: string, required text to look for
     @returns re.MatchObject if the given pattern is found in the text
              None otherwise

     """
    return re.search(pattern, get_histogram_text(tab, histogram_name))


def  verify(cr, histogram_name, histogram_bucket_value):
    """
     Verifies histogram string and success rate in a parsed histogram bucket.
     The histogram buckets are outputted in debug log regardless of the
     verification result.

     Full histogram URL is used to load histogram. Example Histogram URL is :
     chrome://histograms/Media.GpuVideoDecoderInitializeStatus

     @param cr: object, the Chrome instance
     @param histogram_name: string, name of the histogram
     @param histogram_bucket_value: int, required bucket number to look for
     @raises error.TestError if histogram is not successful

     """
    bucket_pattern = '\n' + str(histogram_bucket_value) + '.*100\.0%.*'
    error_msg_format = ('{} not loaded or histogram bucket not found '
                        'or histogram bucket found at < 100%')
    tab = cr.browser.tabs.New()
    msg = error_msg_format.format(histogram_name)
    utils.poll_for_condition(lambda: loaded(tab, histogram_name, bucket_pattern
                                            ),
                             exception=error.TestError(msg),
                             sleep_interval=1)


def is_bucket_present(cr,histogram_name, histogram_bucket_value):
    """
     This returns histogram succes or fail to called function

     @param cr: object, the Chrome instance
     @param histogram_name: string, name of the histogram
     @param histogram_bucket_value: int, required bucket number to look for
     @returns True if histogram page was loaded and the bucket was found.
              False otherwise

     """
    try:
        verify(cr, histogram_name, histogram_bucket_value)
    except error.TestError:
        return False
    else:
        return True


def is_histogram_present(cr, histogram_name):
    """
     This checks if the given histogram is present and non-zero.

     @param cr: object, the Chrome instance
     @param histogram_name: string, name of the histogram
     @returns True if histogram page was loaded and the histogram is present
              False otherwise

     """
    histogram_pattern = 'Histogram: '+ histogram_name + ' recorded ' + \
                        r'[1-9][0-9]*' + ' samples'
    tab = cr.browser.tabs.New()
    try:
        utils.poll_for_condition(lambda: loaded(tab, histogram_name,
                                                histogram_pattern),
                                 timeout=2,
                                 sleep_interval=0.1)
        return True
    except utils.TimeoutError:
        # the histogram is not present, and then returns false
        return False


def get_histogram(cr, histogram_name):
    """
     This returns contents of the given histogram.

     @param cr: object, the Chrome instance
     @param histogram_name: string, name of the histogram
     @returns string: contents of the histogram

     """
    tab = cr.browser.tabs.New()
    return get_histogram_text(tab, histogram_name)


def parse_histogram(histogram_text):
    """
     Parses histogram text into bucket structure.

     @param histogram_text: histogram raw text.
     @returns dict(bucket_value, bucket_count)
     """
    # Match separator line, e.g. "1   ..."
    RE_SEPEARTOR = re.compile(r'\d+\s+\.\.\.')
    # Match bucket line, e.g. "2  --O  (46 = 1.5%) {46.1%}"
    RE_BUCKET = re.compile(r'(\d+)\s+\-*O\s+\((\d+) = (\d+\.\d+)%\).*')
    result = {}
    for line in histogram_text.splitlines():
        if RE_SEPEARTOR.match(line):
            continue
        m = RE_BUCKET.match(line)
        if m:
            result[int(m.group(1))] = int(m.group(2))
    return result


def subtract_histogram(minuend, subtrahend):
    """
     Subtracts histogram: minuend - subtrahend

     @param minuend: histogram bucket dict from which another is to be
                     subtracted.
     @param subtrahend: histogram bucket dict to be subtracted from another.
     @result difference of the two histograms in bucket dict. Note that
             zero-counted buckets are removed.
     """
    result = collections.defaultdict(int, minuend)
    for k, v in six.iteritems(subtrahend):
        result[k] -= v

    # Remove zero counted buckets.
    return {k: v for k, v in six.iteritems(result) if v}


def expect_sole_bucket(histogram_differ, bucket, bucket_name, timeout=10,
                       sleep_interval=1):
    """
     Returns true if the given bucket solely exists in histogram differ.

     @param histogram_differ: a HistogramDiffer instance used to get histogram
            name and histogram diff multiple times.
     @param bucket: bucket value.
     @param bucket_name: bucket name to be shown on error message.
     @param timeout: timeout in seconds.
     @param sleep_interval: interval in seconds between getting diff.
     @returns True if the given bucket solely exists in histogram.
     @raises TestError if bucket doesn't exist or other buckets exist.
     """
    timer = utils.Timer(timeout)
    histogram = {}
    histogram_name = histogram_differ.histogram_name
    while timer.sleep(sleep_interval):
        histogram = histogram_differ.end()
        if histogram:
            break

    if bucket not in histogram:
        raise error.TestError('Expect %s has %s. Histogram: %r' %
                              (histogram_name, bucket_name, histogram))
    if len(histogram) > 1:
        raise error.TestError('%s has bucket other than %s. Histogram: %r' %
                              (histogram_name, bucket_name, histogram))
    return True


def poll_histogram_grow(histogram_differ, timeout=2, sleep_interval=0.1):
    """
     Polls histogram to see if it grows within |timeout| seconds.

     @param histogram_differ: a HistogramDiffer instance used to get histogram
            name and histogram diff multiple times.
     @param timeout: observation timeout in seconds.
     @param sleep_interval: interval in seconds between getting diff.
     @returns (True, histogram_diff) if the histogram grows.
              (False, {}) if it does not grow in |timeout| seconds.
     """
    timer = utils.Timer(timeout)
    while timer.sleep(sleep_interval):
        histogram_diff = histogram_differ.end()
        if histogram_diff:
            return (True, histogram_diff)
    return (False, {})


class HistogramDiffer(object):
    """
     Calculates a histogram's progress between begin() and end().

     Usage:
       differ = HistogramDiffer(cr, 'Media.GpuVideoDecoderError')
       ....
       diff_gvd_error = differ.end()
     """

    def __init__(self, cr, histogram_name, begin=True):
        """
          Constructor.

          @param: cr: object, the Chrome instance
          @param: histogram_name: string, name of the histogram
          @param: begin: if set, calls begin().
          """
        self.cr = cr
        self.histogram_name = histogram_name
        self.begin_histogram_text = ''
        self.end_histogram_text = ''
        self.begin_histogram = {}
        self.end_histogram = {}
        if begin:
            self.begin()

    def _get_histogram(self):
        """
          Gets current histogram bucket.

          @returns (dict(bucket_value, bucket_count), histogram_text)
          """
        tab = self.cr.browser.tabs.New()
        text = get_histogram_text(tab, self.histogram_name)
        tab.Close()
        return (parse_histogram(text), text)

    def begin(self):
        """
          Takes a histogram snapshot as begin_histogram.
          """
        (self.begin_histogram,
         self.begin_histogram_text) = self._get_histogram()
        logging.debug('begin histograms/%s: %r\nraw_text: %s',
                      self.histogram_name, self.begin_histogram,
                      self.begin_histogram_text)

    def end(self):
        """
          Takes a histogram snapshot as end_histogram.

          @returns self.diff()
          """
        self.end_histogram, self.end_histogram_text = self._get_histogram()
        logging.debug('end histograms/%s: %r\nraw_text: %s',
                      self.histogram_name, self.end_histogram,
                      self.end_histogram_text)
        diff = subtract_histogram(self.end_histogram, self.begin_histogram)
        logging.debug('histogram diff: %r', diff)
        return diff