from markdown_it import MarkdownIt
from markdown_it.rules_block import StateBlock
from markdown_it.rules_inline import StateInline


def substitution_plugin(
    md: MarkdownIt, start_delimiter: str = "{", end_delimiter: str = "}"
):
    """A plugin to create substitution tokens.

    These, token should be handled by the renderer.

    Example::

        {{ block }}

        a {{ inline }} b

    """

    start_char = ord(start_delimiter)
    end_char = ord(end_delimiter)

    def _substitution_inline(state: StateInline, silent: bool):
        try:
            if (
                state.srcCharCode[state.pos] != start_char
                or state.srcCharCode[state.pos + 1] != start_char
            ):
                return False
        except IndexError:
            return False

        pos = state.pos + 2
        found_closing = False
        while True:
            try:
                end = state.srcCharCode.index(end_char, pos)
            except ValueError:
                return False
            try:
                if state.srcCharCode[end + 1] == end_char:
                    found_closing = True
                    break
            except IndexError:
                return False
            pos = end + 2

        if not found_closing:
            return False

        text = state.src[state.pos + 2 : end].strip()
        state.pos = end + 2

        if silent:
            return True

        token = state.push("substitution_inline", "span", 0)
        token.block = False
        token.content = text
        token.attrSet("class", "substitution")
        token.attrSet("text", text)
        token.markup = f"{start_delimiter}{end_delimiter}"

        return True

    def _substitution_block(
        state: StateBlock, startLine: int, endLine: int, silent: bool
    ):
        startPos = state.bMarks[startLine] + state.tShift[startLine]
        end = state.eMarks[startLine]

        # if it's indented more than 3 spaces, it should be a code block
        if state.sCount[startLine] - state.blkIndent >= 4:
            return False

        lineText = state.src[startPos:end].strip()

        try:
            if (
                lineText[0] != start_delimiter
                or lineText[1] != start_delimiter
                or lineText[-1] != end_delimiter
                or lineText[-2] != end_delimiter
                or len(lineText) < 5
            ):
                return False
        except IndexError:
            return False

        text = lineText[2:-2].strip()

        # special case if multiple on same line, e.g. {{a}}{{b}}
        if (end_delimiter * 2) in text:
            return False

        state.line = startLine + 1

        if silent:
            return True

        token = state.push("substitution_block", "div", 0)
        token.block = True
        token.content = text
        token.attrSet("class", "substitution")
        token.attrSet("text", text)
        token.markup = f"{start_delimiter}{end_delimiter}"
        token.map = [startLine, state.line]

        return True

    md.block.ruler.before("fence", "substitution_block", _substitution_block)
    md.inline.ruler.before("escape", "substitution_inline", _substitution_inline)