"""Parse Safety Alerts table from the NCMDR weekly update PDF."""

from __future__ import annotations

import io
import re
from dataclasses import dataclass

import pdfplumber

NCMDR_REF_PATTERN = re.compile(r"^SA-\d", re.IGNORECASE)


@dataclass
class SafetyAlertRow:
    ncmdr_ref: str
    detail_url: str


def _collect_refs_from_page(page) -> list[str]:
    refs: list[str] = []
    for table in page.extract_tables() or []:
        for row in table or []:
            if not row:
                continue
            for cell in row:
                if not cell:
                    continue
                text = str(cell).strip()
                if NCMDR_REF_PATTERN.match(text):
                    refs.append(text)
    return refs


def _collect_links_from_page(page) -> list[str]:
    hyperlinks = [
        h
        for h in (page.hyperlinks or [])
        if h.get("uri") and "PublishDetails" in h["uri"]
    ]
    hyperlinks.sort(key=lambda h: h.get("top", 0))
    return [h["uri"] for h in hyperlinks]


def parse_safety_alerts_from_pdf(pdf_bytes: bytes) -> list[SafetyAlertRow]:
    alerts: list[SafetyAlertRow] = []

    with pdfplumber.open(io.BytesIO(pdf_bytes)) as pdf:
        for page in pdf.pages:
            refs = _collect_refs_from_page(page)
            links = _collect_links_from_page(page)
            if not refs:
                continue

            if len(refs) != len(links):
                # Fallback: zip min length and log mismatch in importer
                pair_count = min(len(refs), len(links))
                refs = refs[:pair_count]
                links = links[:pair_count]

            for ncmdr_ref, detail_url in zip(refs, links):
                alerts.append(SafetyAlertRow(ncmdr_ref=ncmdr_ref, detail_url=detail_url))

    # Deduplicate by NCMDR ref while preserving order
    seen: set[str] = set()
    unique: list[SafetyAlertRow] = []
    for alert in alerts:
        key = alert.ncmdr_ref.strip().upper()
        if key in seen:
            continue
        seen.add(key)
        unique.append(alert)

    return unique