#!/usr/bin/python
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# License Version 1.0. (the "License"); you may not use this file except in
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# Original Developer. In addition, Exhibit A has been modified to be consistent
# with Exhibit B.
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# the specific language governing rights and limitations under the License.
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# The Original Code is reddit.
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# the Original Code is reddit Inc.
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"""Check for new style guide violations in the current branch.

This script is meant to be used in a CI process to ensure that new changes
do not violate PEP-8, PEP-257, or any of the validity checks of pyflakes.

"""
import argparse
import collections
import difflib
import logging
import lxml.etree as etree
import os
import re
import subprocess
import sys


DEVNULL = open("/dev/null", "w")
TOOLS = collections.OrderedDict((
    ('pep8', ["pep8", "--repeat"]),
    ('pep257', ["pep257"]),
    ('pyflakes', ["pyflakes"]),
))


# Match *.py and *.pyx
PYFILE = re.compile(r".*\.pyx?$")


def assert_tools_available():
    """Check if the external binaries needed are available or exit."""
    for tool in TOOLS.values():
        binary = tool[0]
        try:
            subprocess.check_call(["which", binary], stdout=DEVNULL)
        except subprocess.CalledProcessError:
            logging.error("command %r not found. please install it!", binary)
            sys.exit(1)


def assert_not_dirty():
    """Check if there are uncommitted changes in the repo and exit if so."""
    try:
        subprocess.check_call(["git", "diff",
                               "--no-ext-diff", "--quiet", "--exit-code"])
    except subprocess.CalledProcessError:
        logging.error("you have uncommitted changes. please commit them!")
        sys.exit(1)


def _parse_ref(ref):
    """Return the result of git rev-parse on the given ref."""
    ref = subprocess.check_output(["git", "rev-parse", ref])
    return ref.strip()


def get_current_ref():
    """Return the most descriptive name possible of the current HEAD."""
    try:
        ref = subprocess.check_output(["git", "symbolic-ref", "HEAD"]).strip()
        return ref[len("refs/heads/"):]
    except subprocess.CalledProcessError:
        return _parse_ref("HEAD")


def get_upstream_ref():
    """Return the ref that this topic branch is based on."""
    return _parse_ref("master@{upstream}")


def get_merge_base():
    upstream = get_upstream_ref()
    current = get_current_ref()
    output = subprocess.check_output(['git', 'merge-base', upstream, current])
    return output.strip()


def get_root():
    """Return the root directory of this git project."""
    return os.path.dirname(_parse_ref("--git-dir"))


def check_ref_out(ref):
    """Ask git to check out the specified ref."""
    try:
        subprocess.check_call(
            ["git", "checkout", ref],
            stdout=DEVNULL,
            stderr=DEVNULL,
        )
    except subprocess.CalledProcessError:
        logging.error("failed to check out %s", ref)
        sys.exit(1)


def walk_workspace():
    root = get_root()
    files = subprocess.check_output(['git', 'ls-files', '--full-name',
                                     '--', root])
    for filename in files.splitlines():
        yield os.path.join(root, filename)


def select_files(files):
    for f in files:
        if re.match(PYFILE, f):
            yield f
        else:
            try:
                with open(f) as f_:
                    first = f_.readline()
                    if first.startswith('#!') and 'python' in first:
                        yield f
            except (IOError, OSError):
                logging.exception("Unable to check-code against %s", f)


def extract_errtype(violation, tool):
    """Based on a line of `tool`'s output, return the kind of infraction.

    Mostly relevant for pep8, which has various kinds of infractions,
    such as E501 for line too long.

    """
    if tool == 'pep8':
        # E501 line too long (91 characters)
        errtype, sep, message = violation.partition(" ")
        if not sep:
            errtype = 'PEP8'
    elif tool == 'pep257':
        errtype = 'PEP257'
    elif tool == 'pyflakes':
        errtype = 'pyflakes'
    return errtype


def make_test_class(tool, filepath):
    no_ext, ext = os.path.splitext(filepath)
    test_class_suffix = no_ext.replace(os.path.sep, '_')
    return tool + '.' + test_class_suffix


def extract_line_info(reportline, filepath, tool):
    if tool == 'pep257' and reportline.startswith('Note: checks'):
        return None
    file_info, sep, violation = reportline.partition(": ")
    if not sep:
        return None
    file_info = file_info.split(":")
    if len(file_info) < 2:
        logging.warn("I don't understand this report line: %r", reportline)
        line_num = ''
    else:
        line_num = file_info[1]
    report_entry = {
        'file': filepath,
        'test_class': make_test_class(tool, filepath),
        'line': line_num,
        'violation': violation,
        'errtype': extract_errtype(violation, tool),
        'tool': tool,
    }
    return report_entry


def generate_report(toolname, files=None):
    if not files:
        files = walk_workspace()

    report = []
    for filepath in select_files(files):
        command = TOOLS[toolname] + [filepath]
        logging.info(" ".join(command))
        process = subprocess.Popen(
            command,
            stdout=subprocess.PIPE,
            stderr=subprocess.STDOUT,
        )

        lines = process.communicate()[0].splitlines()
        ws_root = get_root()
        ws_filepath = os.path.relpath(filepath, ws_root)
        for line in lines:
            line = extract_line_info(line, ws_filepath, toolname)
            if line:
                report.append(line)
    return report


def generate_all_reports(ref=None, files=None):
    """Run the tools on the specified files and return errors / warnings."""
    if ref:
        check_ref_out(ref)

    report = collections.OrderedDict.fromkeys(TOOLS.keys())
    for tool in TOOLS:
        report[tool] = generate_report(tool, files)

    return report


def get_changed_files(old_ref, new_ref):
    """Return a list of files that have changed from one ref to another."""
    root = get_root()
    changed_files_text = subprocess.check_output(["git", "diff", "--name-only",
                                                  old_ref, new_ref])
    changed_files = changed_files_text.splitlines()
    return [os.path.join(root, x) for x in changed_files]


def diffable(report):
    """Convert the report to a list of lines that are reasonably 'diffable'.

    That is, standard diff tools should be able to identify new or fixed
    violations by comparing results of this function

    """
    updated = []
    for toolname, violations in report.iteritems():
        updated.append(toolname)
        updated.extend('%(file)s %(violation)s' % v for v in violations)
        updated.append('')
    return updated


def human(report):
    """Convert the report to a list of human useful lines."""
    updated = []
    for toolname, violations in report.iteritems():
        updated.append(toolname)
        updated.extend('%(file)s:%(line)s %(violation)s' % v
                       for v in violations)
        updated.append('')
    return updated


def junitize(report):
    """Convert the report into JUnit style XML.

    This allows the report to be consumed by tools that consume JUnit reports

    The style used here is: each file is a <testsuite>; each violation
    will be a <testcase> (always failed) whose "classname" shall be the tool
    used (e.g., pep8) and "name" shall be the type of violation and line
    number. Any additional information shall be included as the <failure>
    message.

    """
    by_file = {}
    for violations in report.itervalues():
        for violation in violations:
            file_errors = by_file.setdefault(violation['file'], [])
            file_errors.append(violation)
    violations = etree.Element("testsuites")
    for filename in by_file:
        file_errs = etree.SubElement(violations, "testsuite")
        for violation in by_file[filename]:
            entry = etree.SubElement(file_errs, "testcase")
            entry.attrib['classname'] = violation['test_class']
            entry.attrib['name'] = violation['line']
            error_info = etree.SubElement(entry, "failure")
            error_info.attrib['message'] = violation['violation']
            error_info.attrib['type'] = violation['errtype']
    return violations


def make_errname(violation):
    """Create a unique "test name" for this violation."""
    name = '.'.join((violation['errtype'], violation['line']))
    return name


def diff_report(options):
    if options.check_dirty:
        assert_not_dirty()

    current_ref = get_current_ref()
    base_ref = get_merge_base()
    if options.files:
        files = options.files
    else:
        files = get_changed_files(base_ref, current_ref)
        logging.debug("files changed: %r", files)

    try:
        new_report = diffable(generate_all_reports(current_ref, files))
        logging.debug("new report:\n%r", new_report)
        old_report = diffable(generate_all_reports(base_ref, files))
        logging.debug("old report:\n%r", old_report)
    finally:
        check_ref_out(current_ref)

    return difflib.unified_diff(old_report, new_report)


def regression_report(options):
    added, removed = 0, 0
    for line in diff_report(options):
        line = line.strip()
        if line == "+++" or line == "---":
            continue
        if line.startswith("+"):
            added += 1
        elif line.startswith("-"):
            removed += 1

    if added:
        print >> options.out, "added %d issues" % added
    if removed:
        print >> options.out, "removed %d issues!" % removed

    return 1 if added else 0


def junit_report(options):
    report = generate_all_reports(files=options.files)
    junit = junitize(report)
    print >> options.out, etree.tostring(junit, pretty_print=True)


def human_report(options):
    if options.full:
        report = human(generate_all_reports(files=options.files))
    else:
        files = (options.files or
                 get_changed_files(get_merge_base(), get_current_ref()))
        logging.debug("changed files: %r", files)
        report = human(generate_all_reports(files=files))
    for line in report:
        print >> options.out, line


def parse_args(args):
    parser = argparse.ArgumentParser(description="Report on python problems")
    parser.add_argument('--dirty', dest='check_dirty', action='store_false',
                        help="Skip the dirty workspace check.")
    parser.add_argument('-O', dest='out', type=argparse.FileType('w'),
                        default=sys.stdout, help="Write the report to OUT"
                        " instead of stdout.")
    parser.add_argument('--verbose', '-v', action='count', dest='verbosity',
                        help="Show verbose reporting messages.",
                        default=0)
    parser.add_argument('--quiet', '-q', action='count', default=0,
                        help="Reduce verbosity")
    parser.add_argument('--full', action='store_true', help="When generating"
                        " a {report}, show all files, not just changed ones.")
    parser.add_argument('report', choices=('junit', 'regression', 'report'))
    parser.add_argument('files', nargs='*', metavar='FILE')
    options = parser.parse_args(args)
    set_up_logging(options.verbosity - options.quiet)
    logging.debug("Options: %r", options)
    return options


def set_up_logging(verbosity):
    levels = {-2: logging.ERROR, -1: logging.WARN, 0: logging.INFO,
              1: logging.DEBUG}
    max_level = max(levels.keys())
    min_level = min(levels.keys())
    verbosity = min(verbosity, max_level)
    verbosity = max(verbosity, min_level)
    level = levels[verbosity]
    format_ = '%(levelname)s %(message)s'
    logging.basicConfig(level=level, format=format_)


def main():
    options = parse_args(sys.argv[1:])
    if options.report == 'regression':
        command = regression_report
    elif options.report == 'junit':
        command = junit_report
    elif options.report == 'report':
        command = human_report
    assert_tools_available()
    sys.exit(command(options))

if __name__ == "__main__":
    main()