import re
from dataclasses import dataclass

from menu import MenuItem

TODO_PATH = "TODO.md"

_HEADER = """# HPE 1810 switch scrape TODO

Regenerate with `python discover.py`. Edit the "Want it?" column by hand;
"Implemented?" is updated by the assistant when an extractor exists.

"""
_TABLE_HEADER = "| Menu Item | URL | Want it? | Implemented? |\n|---|---|---|---|\n"
_ROW_RE = re.compile(r"^\|\s*(.*?)\s*\|\s*(.*?)\s*\|\s*(.*?)\s*\|\s*(.*?)\s*\|\s*$")


@dataclass
class TodoRow:
    label: str
    url: str
    want: str = ""
    implemented: str = ""


def parse_existing(path: str = TODO_PATH) -> list[TodoRow]:
    """Read existing TODO.md's table into a list, preserving duplicate urls
    (e.g. two menu entries, "Home" and "System Description", pointing at the
    same page) so a round trip through refresh_todo()/mark_implemented()
    never silently drops one of them."""
    try:
        with open(path, encoding="utf-8") as f:
            text = f.read()
    except FileNotFoundError:
        return []

    rows: list[TodoRow] = []
    for line in text.splitlines():
        m = _ROW_RE.match(line)
        if not m:
            continue
        label, url, want, implemented = m.groups()
        if label in ("Menu Item", "---"):
            continue
        rows.append(TodoRow(label=label, url=url, want=want, implemented=implemented))
    return rows


def merge(discovered: list[MenuItem], existing: list[TodoRow]) -> list[TodoRow]:
    # Keyed by (label, url): a url can legitimately appear under more than
    # one label (see docstring above), so url alone isn't a safe lookup key.
    prior_by_key = {(row.label, row.url): row for row in existing}
    seen_keys = set()
    rows: list[TodoRow] = []

    for item in discovered:
        if not item.href:
            continue
        key = (item.label, item.href)
        seen_keys.add(key)
        prior = prior_by_key.get(key)
        if prior is not None:
            rows.append(TodoRow(label=item.label, url=item.href, want=prior.want, implemented=prior.implemented))
        else:
            rows.append(TodoRow(label=item.label, url=item.href))

    for row in existing:
        if (row.label, row.url) not in seen_keys:
            rows.append(row)

    return rows


def render(rows: list[TodoRow]) -> str:
    lines = [_HEADER, _TABLE_HEADER]
    for row in rows:
        lines.append(f"| {row.label} | {row.url} | {row.want} | {row.implemented} |\n")
    return "".join(lines)


def refresh_todo(discovered: list[MenuItem], path: str = TODO_PATH) -> None:
    existing = parse_existing(path)
    rows = merge(discovered, existing)
    with open(path, "w", encoding="utf-8") as f:
        f.write(render(rows))


def mark_implemented(url: str, path: str = TODO_PATH) -> None:
    """Flip Implemented? to 'yes' for every row matching url (there may be
    more than one label pointing at the same page, e.g. Home/System
    Description both -> SysDescription.html)."""
    existing = parse_existing(path)
    matched = [row for row in existing if row.url == url]
    if not matched:
        raise KeyError(f"No TODO row found for url {url!r}")
    for row in matched:
        row.implemented = "yes"
    with open(path, "w", encoding="utf-8") as f:
        f.write(render(existing))