""" Class for recording and reporting deprecations
"""

import functools
import warnings
import re

_LEADING_WHITE = re.compile(r'^(\s*)')


class ExpiredDeprecationError(RuntimeError):
    """ Error for expired deprecation

    Error raised when a called function or method has passed out of its
    deprecation period.
    """
    pass


def _ensure_cr(text):
    """ Remove trailing whitespace and add carriage return

    Ensures that `text` always ends with a carriage return
    """
    return text.rstrip() + '\n'


def _add_dep_doc(old_doc, dep_doc):
    """ Add deprecation message `dep_doc` to docstring in `old_doc`

    Parameters
    ----------
    old_doc : str
        Docstring from some object.
    dep_doc : str
        Deprecation warning to add to top of docstring, after initial line.

    Returns
    -------
    new_doc : str
        `old_doc` with `dep_doc` inserted after any first lines of docstring.
    """
    dep_doc = _ensure_cr(dep_doc)
    if not old_doc:
        return dep_doc
    old_doc = _ensure_cr(old_doc)
    old_lines = old_doc.splitlines()
    new_lines = []
    for line_no, line in enumerate(old_lines):
        if line.strip():
            new_lines.append(line)
        else:
            break
    next_line = line_no + 1
    if next_line >= len(old_lines):
        # nothing following first paragraph, just append message
        return old_doc + '\n' + dep_doc
    indent = _LEADING_WHITE.match(old_lines[next_line]).group()
    dep_lines = [indent + L for L in [''] + dep_doc.splitlines() + ['']]
    return '\n'.join(new_lines + dep_lines + old_lines[next_line:]) + '\n'


class Deprecator(object):
    """ Class to make decorator marking function or method as deprecated

    The decorated function / method will:

    * Raise the given `warning_class` warning when the function / method gets
      called, up to (and including) version `until` (if specified);
    * Raise the given `error_class` error when the function / method gets
      called, when the package version is greater than version `until` (if
      specified).

    Parameters
    ----------
    version_comparator : callable
        Callable accepting string as argument, and return 1 if string
        represents a higher version than encoded in the `version_comparator`, 0
        if the version is equal, and -1 if the version is lower.  For example,
        the `version_comparator` may compare the input version string to the
        current package version string.
    warn_class : class, optional
        Class of warning to generate for deprecation.
    error_class : class, optional
        Class of error to generate when `version_comparator` returns 1 for a
        given argument of ``until`` in the ``__call__`` method (see below).
    """

    def __init__(self,
                 version_comparator,
                 warn_class=DeprecationWarning,
                 error_class=ExpiredDeprecationError):
        self.version_comparator = version_comparator
        self.warn_class = warn_class
        self.error_class = error_class

    def is_bad_version(self, version_str):
        """ Return True if `version_str` is too high

        Tests `version_str` with ``self.version_comparator``

        Parameters
        ----------
        version_str : str
            String giving version to test

        Returns
        -------
        is_bad : bool
            True if `version_str` is for version below that expected by
            ``self.version_comparator``, False otherwise.
        """
        return self.version_comparator(version_str) == -1

    def __call__(self, message, since='', until='',
                 warn_class=None, error_class=None):
        """ Return decorator function function for deprecation warning / error

        Parameters
        ----------
        message : str
            Message explaining deprecation, giving possible alternatives.
        since : str, optional
            Released version at which object was first deprecated.
        until : str, optional
            Last released version at which this function will still raise a
            deprecation warning.  Versions higher than this will raise an
            error.
        warn_class : None or class, optional
            Class of warning to generate for deprecation (overrides instance
            default).
        error_class : None or class, optional
            Class of error to generate when `version_comparator` returns 1 for a
            given argument of ``until`` (overrides class default).

        Returns
        -------
        deprecator : func
            Function returning a decorator.
        """
        warn_class = warn_class if warn_class else self.warn_class
        error_class = error_class if error_class else self.error_class
        messages = [message]
        if (since, until) != ('', ''):
            messages.append('')
        if since:
            messages.append('* deprecated from version: ' + since)
        if until:
            messages.append('* {0} {1} as of version: {2}'.format(
                "Raises" if self.is_bad_version(until) else "Will raise",
                error_class,
                until))
        message = '\n'.join(messages)

        def deprecator(func):

            @functools.wraps(func)
            def deprecated_func(*args, **kwargs):
                if until and self.is_bad_version(until):
                    raise error_class(message)
                warnings.warn(message, warn_class, stacklevel=2)
                return func(*args, **kwargs)

            deprecated_func.__doc__ = _add_dep_doc(deprecated_func.__doc__,
                                                   message)
            return deprecated_func

        return deprecator
