import re
from typing import TYPE_CHECKING, Any, Dict, List, Match, Union

from ..core import BlockState
from ..helpers import LINK_LABEL
from ..util import unikey

if TYPE_CHECKING:
    from ..block_parser import BlockParser
    from ..core import BaseRenderer, InlineState
    from ..inline_parser import InlineParser
    from ..markdown import Markdown

__all__ = ["footnotes"]

_PARAGRAPH_SPLIT = re.compile(r"\n{2,}")
# https://michelf.ca/projects/php-markdown/extra/#footnotes
REF_FOOTNOTE = (
    r"^(?P<footnote_lead> {0,3})"
    r"\[\^(?P<footnote_key>" + LINK_LABEL + r")]:[ \t]"
    r"(?P<footnote_text>[^\n]*(?:\n+|$)"
    r"(?:(?P=footnote_lead) {1,3}(?! )[^\n]*\n+)*"
    r")"
)

INLINE_FOOTNOTE = r"\[\^(?P<footnote_key>" + LINK_LABEL + r")\]"


def parse_inline_footnote(inline: "InlineParser", m: Match[str], state: "InlineState") -> int:
    key = unikey(m.group("footnote_key"))
    ref = state.env.get("ref_footnotes")
    if ref and key in ref:
        notes = state.env.get("footnotes")
        if not notes:
            notes = []
        if key not in notes:
            notes.append(key)
            state.env["footnotes"] = notes
        state.append_token({"type": "footnote_ref", "raw": key, "attrs": {"index": notes.index(key) + 1}})
    else:
        state.append_token({"type": "text", "raw": m.group(0)})
    return m.end()


def parse_ref_footnote(block: "BlockParser", m: Match[str], state: BlockState) -> int:
    ref = state.env.get("ref_footnotes")
    if not ref:
        ref = {}

    key = unikey(m.group("footnote_key"))
    if key not in ref:
        ref[key] = m.group("footnote_text")
        state.env["ref_footnotes"] = ref
    return m.end()


def parse_footnote_item(block: "BlockParser", key: str, index: int, state: BlockState) -> Dict[str, Any]:
    ref = state.env.get("ref_footnotes")
    if not ref:
        raise ValueError("Missing 'ref_footnotes'.")
    text = ref[key]

    lines = text.splitlines()
    second_line = None
    for second_line in lines[1:]:
        if second_line:
            break

    if second_line:
        spaces = len(second_line) - len(second_line.lstrip())
        pattern = re.compile(r"^ {" + str(spaces) + r",}", flags=re.M)
        text = pattern.sub("", text).strip()
        items = _PARAGRAPH_SPLIT.split(text)
        children = [{"type": "paragraph", "text": s} for s in items]
    else:
        text = text.strip()
        children = [{"type": "paragraph", "text": text}]
    return {"type": "footnote_item", "children": children, "attrs": {"key": key, "index": index}}


def md_footnotes_hook(
    md: "Markdown", result: Union[str, List[Dict[str, Any]]], state: BlockState
) -> Union[str, List[Dict[str, Any]]]:
    notes = state.env.get("footnotes")
    if not notes:
        return result

    children = [parse_footnote_item(md.block, k, i + 1, state) for i, k in enumerate(notes)]
    state = BlockState()
    state.tokens = [{"type": "footnotes", "children": children}]
    output = md.render_state(state)
    return result + output  # type: ignore[operator]


def render_footnote_ref(renderer: "BaseRenderer", key: str, index: int) -> str:
    i = str(index)
    html = '<sup class="footnote-ref" id="fnref-' + i + '">'
    return html + '<a href="#fn-' + i + '">' + i + "</a></sup>"


def render_footnotes(renderer: "BaseRenderer", text: str) -> str:
    return '<section class="footnotes">\n<ol>\n' + text + "</ol>\n</section>\n"


def render_footnote_item(renderer: "BaseRenderer", text: str, key: str, index: int) -> str:
    i = str(index)
    back = '<a href="#fnref-' + i + '" class="footnote">&#8617;</a>'
    text = text.rstrip()[:-4] + back + "</p>"
    return '<li id="fn-' + i + '">' + text + "</li>\n"


def footnotes(md: "Markdown") -> None:
    """A mistune plugin to support footnotes, spec defined at
    https://michelf.ca/projects/php-markdown/extra/#footnotes

    Here is an example:

    .. code-block:: text

        That's some text with a footnote.[^1]

        [^1]: And that's the footnote.

    It will be converted into HTML:

    .. code-block:: html

        <p>That's some text with a footnote.<sup class="footnote-ref" id="fnref-1"><a href="#fn-1">1</a></sup></p>
        <section class="footnotes">
        <ol>
        <li id="fn-1"><p>And that's the footnote.<a href="#fnref-1" class="footnote">&#8617;</a></p></li>
        </ol>
        </section>

    :param md: Markdown instance
    """
    md.inline.register(
        "footnote",
        INLINE_FOOTNOTE,
        parse_inline_footnote,
        before="link",
    )
    md.block.register(
        "ref_footnote",
        REF_FOOTNOTE,
        parse_ref_footnote,
        before="ref_link",
    )
    md.after_render_hooks.append(md_footnotes_hook)

    if md.renderer and md.renderer.NAME == "html":
        md.renderer.register("footnote_ref", render_footnote_ref)
        md.renderer.register("footnote_item", render_footnote_item)
        md.renderer.register("footnotes", render_footnotes)