"""Python part of the warnings subsystem."""

import sys


__all__ = ["warn", "warn_explicit", "showwarning",
           "formatwarning", "filterwarnings", "simplefilter",
           "resetwarnings", "catch_warnings"]

def showwarning(message, category, filename, lineno, file=None, line=None):
    """Hook to write a warning to a file; replace if you like."""
    msg = WarningMessage(message, category, filename, lineno, file, line)
    _showwarnmsg_impl(msg)

def formatwarning(message, category, filename, lineno, line=None):
    """Function to format a warning the standard way."""
    msg = WarningMessage(message, category, filename, lineno, None, line)
    return _formatwarnmsg_impl(msg)

def _showwarnmsg_impl(msg):
    file = msg.file
    if file is None:
        file = sys.stderr
        if file is None:
            # sys.stderr is None when run with pythonw.exe:
            # warnings get lost
            return
    text = _formatwarnmsg(msg)
    try:
        file.write(text)
    except OSError:
        # the file (probably stderr) is invalid - this warning gets lost.
        pass

def _formatwarnmsg_impl(msg):
    s =  ("%s:%s: %s: %s\n"
          % (msg.filename, msg.lineno, msg.category.__name__,
             msg.message))

    if msg.line is None:
        try:
            import linecache
            line = linecache.getline(msg.filename, msg.lineno)
        except Exception:
            # When a warning is logged during Python shutdown, linecache
            # and the import machinery don't work anymore
            line = None
            linecache = None
    else:
        line = msg.line
    if line:
        line = line.strip()
        s += "  %s\n" % line

    if msg.source is not None:
        try:
            import tracemalloc
            tb = tracemalloc.get_object_traceback(msg.source)
        except Exception:
            # When a warning is logged during Python shutdown, tracemalloc
            # and the import machinery don't work anymore
            tb = None

        if tb is not None:
            s += 'Object allocated at (most recent call first):\n'
            for frame in tb:
                s += ('  File "%s", lineno %s\n'
                      % (frame.filename, frame.lineno))

                try:
                    if linecache is not None:
                        line = linecache.getline(frame.filename, frame.lineno)
                    else:
                        line = None
                except Exception:
                    line = None
                if line:
                    line = line.strip()
                    s += '    %s\n' % line
    return s

# Keep a reference to check if the function was replaced
_showwarning_orig = showwarning

def _showwarnmsg(msg):
    """Hook to write a warning to a file; replace if you like."""
    try:
        sw = showwarning
    except NameError:
        pass
    else:
        if sw is not _showwarning_orig:
            # warnings.showwarning() was replaced
            if not callable(sw):
                raise TypeError("warnings.showwarning() must be set to a "
                                "function or method")

            sw(msg.message, msg.category, msg.filename, msg.lineno,
               msg.file, msg.line)
            return
    _showwarnmsg_impl(msg)

# Keep a reference to check if the function was replaced
_formatwarning_orig = formatwarning

def _formatwarnmsg(msg):
    """Function to format a warning the standard way."""
    try:
        fw = formatwarning
    except NameError:
        pass
    else:
        if fw is not _formatwarning_orig:
            # warnings.formatwarning() was replaced
            return fw(msg.message, msg.category,
                      msg.filename, msg.lineno, line=msg.line)
    return _formatwarnmsg_impl(msg)

def filterwarnings(action, message="", category=Warning, module="", lineno=0,
                   append=False):
    """Insert an entry into the list of warnings filters (at the front).

    'action' -- one of "error", "ignore", "always", "default", "module",
                or "once"
    'message' -- a regex that the warning message must match
    'category' -- a class that the warning must be a subclass of
    'module' -- a regex that the module name must match
    'lineno' -- an integer line number, 0 matches all warnings
    'append' -- if true, append to the list of filters
    """
    import re
    assert action in ("error", "ignore", "always", "default", "module",
                      "once"), "invalid action: %r" % (action,)
    assert isinstance(message, str), "message must be a string"
    assert isinstance(category, type), "category must be a class"
    assert issubclass(category, Warning), "category must be a Warning subclass"
    assert isinstance(module, str), "module must be a string"
    assert isinstance(lineno, int) and lineno >= 0, \
           "lineno must be an int >= 0"
    _add_filter(action, re.compile(message, re.I), category,
            re.compile(module), lineno, append=append)

def simplefilter(action, category=Warning, lineno=0, append=False):
    """Insert a simple entry into the list of warnings filters (at the front).

    A simple filter matches all modules and messages.
    'action' -- one of "error", "ignore", "always", "default", "module",
                or "once"
    'category' -- a class that the warning must be a subclass of
    'lineno' -- an integer line number, 0 matches all warnings
    'append' -- if true, append to the list of filters
    """
    assert action in ("error", "ignore", "always", "default", "module",
                      "once"), "invalid action: %r" % (action,)
    assert isinstance(lineno, int) and lineno >= 0, \
           "lineno must be an int >= 0"
    _add_filter(action, None, category, None, lineno, append=append)

def _add_filter(*item, append):
    # Remove possible duplicate filters, so new one will be placed
    # in correct place. If append=True and duplicate exists, do nothing.
    if not append:
        try:
            filters.remove(item)
        except ValueError:
            pass
        filters.insert(0, item)
    else:
        if item not in filters:
            filters.append(item)
    _filters_mutated()

def resetwarnings():
    """Clear the list of warning filters, so that no filters are active."""
    filters[:] = []
    _filters_mutated()

class _OptionError(Exception):
    """Exception used by option processing helpers."""
    pass

# Helper to process -W options passed via sys.warnoptions
def _processoptions(args):
    for arg in args:
        try:
            _setoption(arg)
        except _OptionError as msg:
            print("Invalid -W option ignored:", msg, file=sys.stderr)

# Helper for _processoptions()
def _setoption(arg):
    import re
    parts = arg.split(':')
    if len(parts) > 5:
        raise _OptionError("too many fields (max 5): %r" % (arg,))
    while len(parts) < 5:
        parts.append('')
    action, message, category, module, lineno = [s.strip()
                                                 for s in parts]
    action = _getaction(action)
    message = re.escape(message)
    category = _getcategory(category)
    module = re.escape(module)
    if module:
        module = module + '$'
    if lineno:
        try:
            lineno = int(lineno)
            if lineno < 0:
                raise ValueError
        except (ValueError, OverflowError):
            raise _OptionError("invalid lineno %r" % (lineno,))
    else:
        lineno = 0
    filterwarnings(action, message, category, module, lineno)

# Helper for _setoption()
def _getaction(action):
    if not action:
        return "default"
    if action == "all": return "always" # Alias
    for a in ('default', 'always', 'ignore', 'module', 'once', 'error'):
        if a.startswith(action):
            return a
    raise _OptionError("invalid action: %r" % (action,))

# Helper for _setoption()
def _getcategory(category):
    import re
    if not category:
        return Warning
    if re.match("^[a-zA-Z0-9_]+$", category):
        try:
            cat = eval(category)
        except NameError:
            raise _OptionError("unknown warning category: %r" % (category,))
    else:
        i = category.rfind(".")
        module = category[:i]
        klass = category[i+1:]
        try:
            m = __import__(module, None, None, [klass])
        except ImportError:
            raise _OptionError("invalid module name: %r" % (module,))
        try:
            cat = getattr(m, klass)
        except AttributeError:
            raise _OptionError("unknown warning category: %r" % (category,))
    if not issubclass(cat, Warning):
        raise _OptionError("invalid warning category: %r" % (category,))
    return cat


def _is_internal_frame(frame):
    """Signal whether the frame is an internal CPython implementation detail."""
    filename = frame.f_code.co_filename
    return 'importlib' in filename and '_bootstrap' in filename


def _next_external_frame(frame):
    """Find the next frame that doesn't involve CPython internals."""
    frame = frame.f_back
    while frame is not None and _is_internal_frame(frame):
        frame = frame.f_back
    return frame


# Code typically replaced by _warnings
def warn(message, category=None, stacklevel=1, source=None):
    """Issue a warning, or maybe ignore it or raise an exception."""
    # Check if message is already a Warning object
    if isinstance(message, Warning):
        category = message.__class__
    # Check category argument
    if category is None:
        category = UserWarning
    if not (isinstance(category, type) and issubclass(category, Warning)):
        raise TypeError("category must be a Warning subclass, "
                        "not '{:s}'".format(type(category).__name__))
    # Get context information
    try:
        if stacklevel <= 1 or _is_internal_frame(sys._getframe(1)):
            # If frame is too small to care or if the warning originated in
            # internal code, then do not try to hide any frames.
            frame = sys._getframe(stacklevel)
        else:
            frame = sys._getframe(1)
            # Look for one frame less since the above line starts us off.
            for x in range(stacklevel-1):
                frame = _next_external_frame(frame)
                if frame is None:
                    raise ValueError
    except ValueError:
        globals = sys.__dict__
        lineno = 1
    else:
        globals = frame.f_globals
        lineno = frame.f_lineno
    if '__name__' in globals:
        module = globals['__name__']
    else:
        module = "<string>"
    filename = globals.get('__file__')
    if filename:
        fnl = filename.lower()
        if fnl.endswith(".pyc"):
            filename = filename[:-1]
    else:
        if module == "__main__":
            try:
                filename = sys.argv[0]
            except AttributeError:
                # embedded interpreters don't have sys.argv, see bug #839151
                filename = '__main__'
        if not filename:
            filename = module
    registry = globals.setdefault("__warningregistry__", {})
    warn_explicit(message, category, filename, lineno, module, registry,
                  globals, source)

def warn_explicit(message, category, filename, lineno,
                  module=None, registry=None, module_globals=None,
                  source=None):
    lineno = int(lineno)
    if module is None:
        module = filename or "<unknown>"
        if module[-3:].lower() == ".py":
            module = module[:-3] # XXX What about leading pathname?
    if registry is None:
        registry = {}
    if registry.get('version', 0) != _filters_version:
        registry.clear()
        registry['version'] = _filters_version
    if isinstance(message, Warning):
        text = str(message)
        category = message.__class__
    else:
        text = message
        message = category(message)
    key = (text, category, lineno)
    # Quick test for common case
    if registry.get(key):
        return
    # Search the filters
    for item in filters: