"""
Docstrings are another source of information for functions and classes.
:mod:`jedi.evaluate.dynamic` tries to find all executions of functions, while
the docstring parsing is much easier. There are two different types of
docstrings that |jedi| understands:

- `Sphinx <http://sphinx-doc.org/markup/desc.html#info-field-lists>`_
- `Epydoc <http://epydoc.sourceforge.net/manual-fields.html>`_

For example, the sphinx annotation ``:type foo: str`` clearly states that the
type of ``foo`` is ``str``.

As an addition to parameter searching, this module also provides return
annotations.
"""

import re
from itertools import chain
from textwrap import dedent

from jedi.evaluate.cache import memoize_default
from jedi.parser import Parser
from jedi.common import indent_block

DOCSTRING_PARAM_PATTERNS = [
    r'\s*:type\s+%s:\s*([^\n]+)',  # Sphinx
    r'\s*@type\s+%s:\s*([^\n]+)',  # Epydoc
]

DOCSTRING_RETURN_PATTERNS = [
    re.compile(r'\s*:rtype:\s*([^\n]+)', re.M),  # Sphinx
    re.compile(r'\s*@rtype:\s*([^\n]+)', re.M),  # Epydoc
]

REST_ROLE_PATTERN = re.compile(r':[^`]+:`([^`]+)`')


@memoize_default(None, evaluator_is_first_arg=True)
def follow_param(evaluator, param):
    func = param.parent_function
    param_str = _search_param_in_docstr(func.raw_doc, str(param.get_name()))
    return _evaluate_for_statement_string(evaluator, param_str, param.get_parent_until())


def _search_param_in_docstr(docstr, param_str):
    """
    Search `docstr` for a type of `param_str`.

    >>> _search_param_in_docstr(':type param: int', 'param')
    'int'
    >>> _search_param_in_docstr('@type param: int', 'param')
    'int'
    >>> _search_param_in_docstr(
    ...   ':type param: :class:`threading.Thread`', 'param')
    'threading.Thread'
    >>> _search_param_in_docstr('no document', 'param') is None
    True

    """
    # look at #40 to see definitions of those params
    patterns = [re.compile(p % re.escape(param_str))
                for p in DOCSTRING_PARAM_PATTERNS]
    for pattern in patterns:
        match = pattern.search(docstr)
        if match:
            return _strip_rst_role(match.group(1))

    return None


def _strip_rst_role(type_str):
    """
    Strip off the part looks like a ReST role in `type_str`.

    >>> _strip_rst_role(':class:`ClassName`')  # strip off :class:
    'ClassName'
    >>> _strip_rst_role(':py:obj:`module.Object`')  # works with domain
    'module.Object'
    >>> _strip_rst_role('ClassName')  # do nothing when not ReST role
    'ClassName'

    See also:
    http://sphinx-doc.org/domains.html#cross-referencing-python-objects

    """
    match = REST_ROLE_PATTERN.match(type_str)
    if match:
        return match.group(1)
    else:
        return type_str


def _evaluate_for_statement_string(evaluator, string, module):
    code = dedent("""
    def pseudo_docstring_stuff():
        '''Create a pseudo function for docstring statements.'''
    %s
    """)
    if string is None:
        return []

    for element in re.findall('((?:\w+\.)*\w+)\.', string):
        # Try to import module part in dotted name.
        # (e.g., 'threading' in 'threading.Thread').
        string = 'import %s\n' % element + string

    p = Parser(code % indent_block(string), no_docstr=True)
    pseudo_cls = p.module.subscopes[0]
    try:
        stmt = pseudo_cls.statements[-1]
    except IndexError:
        return []

    # Use the module of the param.
    # TODO this module is not the module of the param in case of a function
    # call. In that case it's the module of the function call.
    # stuffed with content from a function call.
    pseudo_cls.parent = module
    definitions = evaluator.eval_statement(stmt)
    it = (evaluator.execute(d) for d in definitions)
    # TODO Executing tuples does not make sense, people tend to say
    # `(str, int)` in a type annotation, which means that it returns a tuple
    # with both types.
    # At this point we just return the classes if executing wasn't possible,
    # i.e. is a tuple.
    return list(chain.from_iterable(it)) or definitions


@memoize_default(None, evaluator_is_first_arg=True)
def find_return_types(evaluator, func):
    def search_return_in_docstr(code):
        for p in DOCSTRING_RETURN_PATTERNS:
            match = p.search(code)
            if match:
                return _strip_rst_role(match.group(1))

    type_str = search_return_in_docstr(func.raw_doc)
    return _evaluate_for_statement_string(evaluator, type_str, func.get_parent_until())
