#!/usr/bin/env python3

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import re


class NSEDocEvent (object):
    def __init__(self, type, text=None):
        self.type = type
        self.text = text


def nsedoc_parse_sub(text, pos):
    """Parse paragraph-level NSEDoc markup, inside of paragraphs and lists.
    Returns the position after the end of parsing followed by a list of
    events."""
    events = []
    m = re.match(r'([^\n]*?)<code>(.*?)</code>', text[pos:], re.S)
    if m:
        if m.group(1):
            events.append(NSEDocEvent("text", m.group(1).replace("\n", " ")))
        events.append(NSEDocEvent("code", m.group(2)))
        return pos + m.end(), events
    m = re.match(r'[^\n]*(\n|$)', text[pos:])
    if m:
        if m.group():
            events.append(NSEDocEvent("text", m.group().replace("\n", " ")))
        return pos + m.end(), events
    return pos, events


def nsedoc_parse(text):
    """Parse text marked up for NSEDoc. This is a generator that returns a
    sequence of NSEDocEvents. The type of the event may be "paragraph_start",
    "paragraph_end", "list_start", "list_end", "list_item_start",
    "list_item_end", "text", or "code". The types "text" and "code" have a text
    member with the text that they contain."""
    i = 0
    in_list = False

    while i < len(text):
        while i < len(text) and text[i].isspace():
            i += 1
        if i >= len(text):
            break
        yield NSEDocEvent("paragraph_start")
        while i < len(text):
            if re.match(r'\s*(\n|$)', text[i:]):
                break
            if text.startswith("* ", i):
                if not in_list:
                    yield NSEDocEvent("list_start")
                    in_list = True
                i += 2
                yield NSEDocEvent("list_item_start")
                i, events = nsedoc_parse_sub(text, i)
                for event in events:
                    yield event
                yield NSEDocEvent("list_item_end")
            else:
                if in_list:
                    yield NSEDocEvent("list_end")
                    in_list = False
                i, events = nsedoc_parse_sub(text, i)
                for event in events:
                    yield event
        if in_list:
            yield NSEDocEvent("list_end")
            in_list = False
        yield NSEDocEvent("paragraph_end")
