# Licensed under the Apache License: http://www.apache.org/licenses/LICENSE-2.0
# For details: https://bitbucket.org/ned/coveragepy/src/default/NOTICE.txt

"""Miscellaneous stuff for coverage.py."""

import errno
import hashlib
import inspect
import locale
import os
import sys
import types

from coverage import env
from coverage.backward import string_class, to_bytes, unicode_class

ISOLATED_MODULES = {}


def isolate_module(mod):
    """Copy a module so that we are isolated from aggressive mocking.

    If a test suite mocks os.path.exists (for example), and then we need to use
    it during the test, everything will get tangled up if we use their mock.
    Making a copy of the module when we import it will isolate coverage.py from
    those complications.
    """
    if mod not in ISOLATED_MODULES:
        new_mod = types.ModuleType(mod.__name__)
        ISOLATED_MODULES[mod] = new_mod
        for name in dir(mod):
            value = getattr(mod, name)
            if isinstance(value, types.ModuleType):
                value = isolate_module(value)
            setattr(new_mod, name, value)
    return ISOLATED_MODULES[mod]

os = isolate_module(os)


# Use PyContracts for assertion testing on parameters and returns, but only if
# we are running our own test suite.
if env.TESTING:
    from contracts import contract              # pylint: disable=unused-import
    from contracts import new_contract

    try:
        # Define contract words that PyContract doesn't have.
        new_contract('bytes', lambda v: isinstance(v, bytes))
        if env.PY3:
            new_contract('unicode', lambda v: isinstance(v, unicode_class))
    except ValueError:
        # During meta-coverage, this module is imported twice, and PyContracts
        # doesn't like redefining contracts. It's OK.
        pass
else:                                           # pragma: not covered
    # We aren't using real PyContracts, so just define a no-op decorator as a
    # stunt double.
    def contract(**unused):
        """Dummy no-op implementation of `contract`."""
        return lambda func: func


def nice_pair(pair):
    """Make a nice string representation of a pair of numbers.

    If the numbers are equal, just return the number, otherwise return the pair
    with a dash between them, indicating the range.

    """
    start, end = pair
    if start == end:
        return "%d" % start
    else:
        return "%d-%d" % (start, end)


def format_lines(statements, lines):
    """Nicely format a list of line numbers.

    Format a list of line numbers for printing by coalescing groups of lines as
    long as the lines represent consecutive statements.  This will coalesce
    even if there are gaps between statements.

    For example, if `statements` is [1,2,3,4,5,10,11,12,13,14] and
    `lines` is [1,2,5,10,11,13,14] then the result will be "1-2, 5-11, 13-14".

    """
    pairs = []
    i = 0
    j = 0
    start = None
    statements = sorted(statements)
    lines = sorted(lines)
    while i < len(statements) and j < len(lines):
        if statements[i] == lines[j]:
            if start is None:
                start = lines[j]
            end = lines[j]
            j += 1
        elif start:
            pairs.append((start, end))
            start = None
        i += 1
    if start:
        pairs.append((start, end))
    ret = ', '.join(map(nice_pair, pairs))
    return ret


def expensive(fn):
    """A decorator to indicate that a method shouldn't be called more than once.

    Normally, this does nothing.  During testing, this raises an exception if
    called more than once.

    """
    if env.TESTING:
        attr = "_once_" + fn.__name__

        def _wrapped(self):
            """Inner function that checks the cache."""
            if hasattr(self, attr):
                raise Exception("Shouldn't have called %s more than once" % fn.__name__)
            setattr(self, attr, True)
            return fn(self)
        return _wrapped
    else:
        return fn


def bool_or_none(b):
    """Return bool(b), but preserve None."""
    if b is None:
        return None
    else:
        return bool(b)


def join_regex(regexes):
    """Combine a list of regexes into one that matches any of them."""
    return "|".join("(?:%s)" % r for r in regexes)


def file_be_gone(path):
    """Remove a file, and don't get annoyed if it doesn't exist."""
    try:
        os.remove(path)
    except OSError as e:
        if e.errno != errno.ENOENT:
            raise


def output_encoding(outfile=None):
    """Determine the encoding to use for output written to `outfile` or stdout."""
    if outfile is None:
        outfile = sys.stdout
    encoding = (
        getattr(outfile, "encoding", None) or
        getattr(sys.__stdout__, "encoding", None) or
        locale.getpreferredencoding()
    )
    return encoding


class Hasher(object):
    """Hashes Python data into md5."""
    def __init__(self):
        self.md5 = hashlib.md5()

    def update(self, v):
        """Add `v` to the hash, recursively if needed."""
        self.md5.update(to_bytes(str(type(v))))
        if isinstance(v, string_class):
            self.md5.update(to_bytes(v))
        elif isinstance(v, bytes):
            self.md5.update(v)
        elif v is None:
            pass
        elif isinstance(v, (int, float)):
            self.md5.update(to_bytes(str(v)))
        elif isinstance(v, (tuple, list)):
            for e in v:
                self.update(e)
        elif isinstance(v, dict):
            keys = v.keys()
            for k in sorted(keys):
                self.update(k)
                self.update(v[k])
        else:
            for k in dir(v):
                if k.startswith('__'):
                    continue
                a = getattr(v, k)
                if inspect.isroutine(a):
                    continue
                self.update(k)
                self.update(a)

    def hexdigest(self):
        """Retrieve the hex digest of the hash."""
        return self.md5.hexdigest()


def _needs_to_implement(that, func_name):
    """Helper to raise NotImplementedError in interface stubs."""
    if hasattr(that, "_coverage_plugin_name"):
        thing = "Plugin"
        name = that._coverage_plugin_name
    else:
        thing = "Class"
        klass = that.__class__
        name = "{klass.__module__}.{klass.__name__}".format(klass=klass)

    raise NotImplementedError(
        "{thing} {name!r} needs to implement {func_name}()".format(
            thing=thing, name=name, func_name=func_name
            )
        )


class CoverageException(Exception):
    """An exception specific to coverage.py."""
    pass


class NoSource(CoverageException):
    """We couldn't find the source for a module."""
    pass


class NoCode(NoSource):
    """We couldn't find any code at all."""
    pass


class NotPython(CoverageException):
    """A source file turned out not to be parsable Python."""
    pass


class ExceptionDuringRun(CoverageException):
    """An exception happened while running customer code.

    Construct it with three arguments, the values from `sys.exc_info`.

    """
    pass