"""Module for placeholders processing."""

# Placeholders (taken from Python-Markdown)
from __future__ import annotations


STX = '\u0002'
''' "Start of Text" marker for placeholder templates. '''
ETX = '\u0003'
''' "End of Text" marker for placeholder templates. '''
INLINE_PLACEHOLDER_PREFIX = f'{STX}klzzwxh:'


def build_placeholder(num: int) -> str:
    """Return a placeholder."""
    return f'{INLINE_PLACEHOLDER_PREFIX}{num}{ETX}'


def escape_placeholders(text: str) -> str:
    """Escape placeholders in the given text."""
    return text.replace(STX, f'\\{STX}').replace(ETX, f'\\{ETX}')


def unescape_placeholders(text: str) -> str:
    """Unescape placeholders in the given text."""
    return text.replace(f'\\{STX}', STX).replace(f'\\{ETX}', ETX)


def save_placeholder(
        placeholders_contents: list[tuple[str, str]],
        text_to_include: str,
) -> str:
    """Save the included text and return the placeholder."""
    inclusion_index = len(placeholders_contents)
    placeholder = build_placeholder(inclusion_index)
    placeholders_contents.append((placeholder, text_to_include))
    return placeholder