"""Generating content for autodoc using typehints"""

import re
from collections import OrderedDict
from typing import Any, Dict, Iterable, Set, cast

from docutils import nodes
from docutils.nodes import Element

from sphinx import addnodes
from sphinx.application import Sphinx
from sphinx.util import inspect, typing


def record_typehints(app: Sphinx, objtype: str, name: str, obj: Any,
                     options: Dict, args: str, retann: str) -> None:
    """Record type hints to env object."""
    if app.config.autodoc_typehints_format == 'short':
        mode = 'smart'
    else:
        mode = 'fully-qualified'

    try:
        if callable(obj):
            annotations = app.env.temp_data.setdefault('annotations', {})
            annotation = annotations.setdefault(name, OrderedDict())
            sig = inspect.signature(obj, type_aliases=app.config.autodoc_type_aliases)
            for param in sig.parameters.values():
                if param.annotation is not param.empty:
                    annotation[param.name] = typing.stringify(param.annotation, mode)
            if sig.return_annotation is not sig.empty:
                annotation['return'] = typing.stringify(sig.return_annotation, mode)
    except (TypeError, ValueError):
        pass


def merge_typehints(app: Sphinx, domain: str, objtype: str, contentnode: Element) -> None:
    if domain != 'py':
        return
    if app.config.autodoc_typehints not in ('both', 'description'):
        return

    try:
        signature = cast(addnodes.desc_signature, contentnode.parent[0])
        if signature['module']:
            fullname = '.'.join([signature['module'], signature['fullname']])
        else:
            fullname = signature['fullname']
    except KeyError:
        # signature node does not have valid context info for the target object
        return

    annotations = app.env.temp_data.get('annotations', {})
    if annotations.get(fullname, {}):
        field_lists = [n for n in contentnode if isinstance(n, nodes.field_list)]
        if field_lists == []:
            field_list = insert_field_list(contentnode)
            field_lists.append(field_list)

        for field_list in field_lists:
            if app.config.autodoc_typehints_description_target == "all":
                modify_field_list(field_list, annotations[fullname])
            else:
                augment_descriptions_with_types(field_list, annotations[fullname])


def insert_field_list(node: Element) -> nodes.field_list:
    field_list = nodes.field_list()
    desc = [n for n in node if isinstance(n, addnodes.desc)]
    if desc:
        # insert just before sub object descriptions (ex. methods, nested classes, etc.)
        index = node.index(desc[0])
        node.insert(index - 1, [field_list])
    else:
        node += field_list

    return field_list


def modify_field_list(node: nodes.field_list, annotations: Dict[str, str]) -> None:
    arguments: Dict[str, Dict[str, bool]] = {}
    fields = cast(Iterable[nodes.field], node)
    for field in fields:
        field_name = field[0].astext()
        parts = re.split(' +', field_name)
        if parts[0] == 'param':
            if len(parts) == 2:
                # :param xxx:
                arg = arguments.setdefault(parts[1], {})
                arg['param'] = True
            elif len(parts) > 2:
                # :param xxx yyy:
                name = ' '.join(parts[2:])
                arg = arguments.setdefault(name, {})
                arg['param'] = True
                arg['type'] = True
        elif parts[0] == 'type':
            name = ' '.join(parts[1:])
            arg = arguments.setdefault(name, {})
            arg['type'] = True
        elif parts[0] == 'rtype':
            arguments['return'] = {'type': True}

    for name, annotation in annotations.items():
        if name == 'return':
            continue

        arg = arguments.get(name, {})
        if not arg.get('type'):
            field = nodes.field()
            field += nodes.field_name('', 'type ' + name)
            field += nodes.field_body('', nodes.paragraph('', annotation))
            node += field
        if not arg.get('param'):
            field = nodes.field()
            field += nodes.field_name('', 'param ' + name)
            field += nodes.field_body('', nodes.paragraph('', ''))
            node += field

    if 'return' in annotations and 'return' not in arguments:
        field = nodes.field()
        field += nodes.field_name('', 'rtype')
        field += nodes.field_body('', nodes.paragraph('', annotation))
        node += field


def augment_descriptions_with_types(
    node: nodes.field_list,
    annotations: Dict[str, str],
) -> None:
    fields = cast(Iterable[nodes.field], node)
    has_description = set()  # type: Set[str]
    has_type = set()  # type: Set[str]
    for field in fields:
        field_name = field[0].astext()
        parts = re.split(' +', field_name)
        if parts[0] == 'param':
            if len(parts) == 2:
                # :param xxx:
                has_description.add(parts[1])
            elif len(parts) > 2:
                # :param xxx yyy:
                name = ' '.join(parts[2:])
                has_description.add(name)
                has_type.add(name)
        elif parts[0] == 'type':
            name = ' '.join(parts[1:])
            has_type.add(name)
        elif parts[0] in ('return', 'returns'):
            has_description.add('return')
        elif parts[0] == 'rtype':
            has_type.add('return')

    # Add 'type' for parameters with a description but no declared type.
    for name in annotations:
        if name in ('return', 'returns'):
            continue
        if name in has_description and name not in has_type:
            field = nodes.field()
            field += nodes.field_name('', 'type ' + name)
            field += nodes.field_body('', nodes.paragraph('', annotations[name]))
            node += field

    # Add 'rtype' if 'return' is present and 'rtype' isn't.
    if 'return' in annotations:
        if 'return' in has_description and 'return' not in has_type:
            field = nodes.field()
            field += nodes.field_name('', 'rtype')
            field += nodes.field_body('', nodes.paragraph('', annotations['return']))
            node += field


def setup(app: Sphinx) -> Dict[str, Any]:
    app.connect('autodoc-process-signature', record_typehints)
    app.connect('object-description-transform', merge_typehints)

    return {
        'version': 'builtin',
        'parallel_read_safe': True,
        'parallel_write_safe': True,
    }
