from parsimonious.grammar import Grammar

from .. import html_paths


def read_html_path(string):
    path_node = _grammar.parse(string)
    return read_html_path_node(path_node)


def read_html_path_node(path_node):
    if path_node.children[0].expr_name == "ignore":
        return html_paths.ignore
    elif path_node.children[0].children:
        return _read_html_path_elements_node(path_node.children[0].children[0])
    else:
        return html_paths.empty


def _read_html_path_elements_node(path_node):
    elements = [
        _read_element_node(child)
        for child in _repeated_children_with_separator(path_node, has_whitespace=True)
    ]
    return html_paths.path(elements)


def _read_element_node(node):
    tag_names = _read_tag_names_node(node.children[0])
    class_names = _read_class_names_node(node.children[1])
    fresh = _read_fresh_node(node.children[2])
    return html_paths.element(tag_names, class_names=class_names, fresh=fresh)


def _read_tag_names_node(node):
    return [
        child.text
        for child in _repeated_children_with_separator(node, has_whitespace=False)
    ]


def _read_class_names_node(class_names_node):
    return [
        _read_class_name_node(node)
        for node in class_names_node.children
    ]


def _read_class_name_node(node):
    return node.children[1].text


def _read_fresh_node(node):
    return len(node.children) > 0


def _repeated_children_with_separator(node, has_whitespace):
    yield node.children[0]
    
    if has_whitespace:
        sequence_node_index = 3
    else:
        sequence_node_index = 1
    
    sequence_node = node.children[1]
    for child in sequence_node.children:
        yield child.children[sequence_node_index]


grammar_text = r"""

html_path = ignore / html_path_elements?

ignore = "!"

html_path_elements = element (whitespace* ">" whitespace* element)*

element = tag_names class_name* fresh?

tag_names = identifier ("|" identifier)*

class_name = "." identifier

fresh = ":fresh"

identifier = ~"[A-Z0-9]+"i

whitespace = ~"\s"*

"""

_grammar = Grammar(grammar_text)