"""
Inline tokenizer for mistletoe.
"""

import html
import re


# replacement for html._charref which matches only entitydefs ending with ';',
# according to the CommonMark spec.
_markdown_charref = re.compile(r'&(#[0-9]{1,7};'
                               r'|#[xX][0-9a-fA-F]{1,6};'
                               r'|[^\t\n\f <&#;]{1,32};)')
_stdlib_charref = html._charref


def tokenize(string, token_types):
    try:
        html._charref = _markdown_charref
        *token_types, fallback_token = token_types
        tokens = find_tokens(string, token_types, fallback_token)
        token_buffer = []
        if tokens:
            prev = tokens[0]
            for curr in tokens[1:]:
                prev = eval_tokens(prev, curr, token_buffer)
            token_buffer.append(prev)
        return make_tokens(token_buffer, 0, len(string), string, fallback_token)
    finally:
        html._charref = _stdlib_charref


def find_tokens(string, token_types, fallback_token):
    tokens = []
    for token_type in token_types:
        for m in token_type.find(string):
            tokens.append(ParseToken(m.start(), m.end(), m, string, token_type, fallback_token))
    return sorted(tokens)


def eval_tokens(x, y, token_buffer):
    r = relation(x, y)
    if r == 0:
        token_buffer.append(x)
        return y
    if r == 1:
        return x if x.cls.precedence >= y.cls.precedence else y
    if r == 2:
        x.append_child(y)
        return x
    return x


def eval_new_child(parent, child):
    last_child = parent.children[-1]
    r = relation(last_child, child)
    if r == 0:
        parent.children.append(child)
    elif r == 1 and last_child.cls.precedence < child.cls.precedence:
        parent.children[-1] = child
    elif r == 2:
        last_child.append_child(child)


def relation(x, y):
    if x.end <= y.start:
        return 0      # x preceeds y
    if x.end >= y.end:
        if x.parse_start <= y.start and x.parse_end >= y.end:
            return 2  # x contains y
        if x.parse_end <= y.start:
            return 3  # ignore y
    return 1          # x intersects y


def make_tokens(tokens, start, end, string, fallback_token):
    result = []
    prev_end = start
    for token in tokens:
        if token.start > prev_end:
            t = fallback_token(html.unescape(string[prev_end:token.start]))
            if t is not None:
                result.append(t)
        t = token.make()
        if t is not None:
            result.append(t)
        prev_end = token.end
    if prev_end != end:
        result.append(fallback_token(html.unescape(string[prev_end:end])))
    return result


class ParseToken:
    def __init__(self, start, end, match, string, cls, fallback_token):
        self.start = start
        self.end = end
        self.parse_start = match.start(cls.parse_group)
        self.parse_end = match.end(cls.parse_group)
        self.match = match
        self.string = string
        self.cls = cls
        self.fallback_token = fallback_token
        self.children = []

    def append_child(self, child):
        if self.cls.parse_inner:
            if not self.children:
                self.children.append(child)
            else:
                eval_new_child(self, child)

    def make(self):
        if not self.cls.parse_inner:
            return self.cls(self.match)
        children = make_tokens(self.children, self.parse_start, self.parse_end, self.string, self.fallback_token)
        token = self.cls(self.match)
        token.children = children
        return token

    def __lt__(self, other):
        return self.start < other.start

    def __repr__(self):
        pattern = '<ParseToken span=({},{}) parse_span=({},{}) cls={} children={}>'
        return pattern.format(self.start, self.end,
                              self.parse_start, self.parse_end,
                              repr(self.cls.__name__), self.children)
