#!/usr/bin/env python3
"""Fetch and validate an immutable machine-readable Scientia glossary snapshot."""

from __future__ import annotations

import argparse
import hashlib
import html
import json
import re
import sys
import urllib.request
from collections import Counter
from dataclasses import dataclass, asdict
from datetime import datetime, timezone
from html.parser import HTMLParser
from pathlib import Path


DEFAULT_URL = "https://wiki.scientia.ru/ru/glossary"
SKILL_ROOT = Path(__file__).resolve().parent.parent
OUTPUT_ROOT = SKILL_ROOT / "references" / "terminology" / "raw" / "scientia"


def normalize_space(value: str) -> str:
    return re.sub(r"\s+", " ", html.unescape(value)).strip()


def normalize_key(value: str) -> str:
    return normalize_space(value).casefold()


@dataclass(frozen=True)
class Entry:
    source_entry_id: str
    source_revision: str
    source_order: int
    section: str
    source_section: str
    en_raw: str
    ru_raw: str
    target_url: str
    article_status: str
    row_hash: str


class GlossaryParser(HTMLParser):
    def __init__(self) -> None:
        super().__init__(convert_charrefs=True)
        self.section = "other"
        self.in_table = False
        self.in_row = False
        self.in_cell = False
        self.cells: list[str] = []
        self.cell_parts: list[str] = []
        self.link_href = ""
        self.link_status = "none"
        self.row_href = ""
        self.row_status = "none"
        self.rows: list[tuple[str, str, str, str, str]] = []

    def handle_starttag(self, tag: str, attrs: list[tuple[str, str | None]]) -> None:
        attrs_map = {key: value or "" for key, value in attrs}
        if tag == "h1" and re.fullmatch(r"[a-z]", attrs_map.get("id", ""), re.I):
            self.section = attrs_map["id"].lower()
        elif tag == "table":
            self.in_table = True
        elif tag == "tr" and self.in_table:
            self.in_row = True
            self.cells = []
            self.row_href = ""
            self.row_status = "none"
        elif tag == "td" and self.in_row:
            self.in_cell = True
            self.cell_parts = []
            self.link_href = ""
            self.link_status = "none"
        elif tag == "a" and self.in_cell:
            self.link_href = attrs_map.get("href", "")
            classes = set(attrs_map.get("class", "").split())
            if "is-valid-page" in classes:
                self.link_status = "valid"
            elif "is-invalid-page" in classes:
                self.link_status = "missing"

    def handle_endtag(self, tag: str) -> None:
        if tag == "td" and self.in_cell:
            self.cells.append(normalize_space("".join(self.cell_parts)))
            if len(self.cells) == 2:
                self.row_href = self.link_href
                self.row_status = self.link_status
            self.in_cell = False
        elif tag == "tr" and self.in_row:
            if len(self.cells) == 2 and self.cells[0] and self.cells[1]:
                self.rows.append(
                    (self.section, self.cells[0], self.cells[1], self.row_href, self.row_status)
                )
            self.in_row = False
        elif tag == "table":
            self.in_table = False

    def handle_data(self, data: str) -> None:
        if self.in_cell:
            self.cell_parts.append(data)


def fetch_html(url: str) -> bytes:
    request = urllib.request.Request(
        url,
        headers={"User-Agent": "engineering-writing-ru glossary snapshot/0.2"},
    )
    with urllib.request.urlopen(request, timeout=30) as response:
        return response.read()


def parse_entries(payload: bytes, revision: str) -> list[Entry]:
    parser = GlossaryParser()
    parser.feed(payload.decode("utf-8"))
    seen: dict[str, str] = {}
    entries: list[Entry] = []
    for order, (source_section, en_raw, ru_raw, href, status) in enumerate(parser.rows, start=1):
        key = normalize_key(en_raw)
        if key in seen:
            raise ValueError(f"Duplicate English key: {en_raw!r} and {seen[key]!r}")
        seen[key] = en_raw
        entry_id = "scientia-" + hashlib.sha256(key.encode("utf-8")).hexdigest()[:12]
        row_material = "\n".join([en_raw, ru_raw, href, status])
        row_hash = hashlib.sha256(row_material.encode("utf-8")).hexdigest()
        first_letter = re.sub(r"^[^a-z]+", "", key)
        section = first_letter[0] if first_letter else "other"
        entries.append(
            Entry(
                source_entry_id=entry_id,
                source_revision=revision,
                source_order=order,
                section=section,
                source_section=source_section,
                en_raw=en_raw,
                ru_raw=ru_raw,
                target_url=href,
                article_status=status,
                row_hash=row_hash,
            )
        )
    return entries


def validate_output_root() -> None:
    resolved_skill = SKILL_ROOT.resolve()
    resolved_output = OUTPUT_ROOT.resolve()
    if not resolved_output.is_relative_to(resolved_skill):
        raise RuntimeError(f"Refusing to write outside skill root: {resolved_output}")


def validate_existing() -> list[Entry]:
    manifest_path = OUTPUT_ROOT / "manifest.json"
    manifest = json.loads(manifest_path.read_text(encoding="utf-8"))
    snapshot_path = OUTPUT_ROOT / manifest["raw_file"]
    snapshot_text = snapshot_path.read_text(encoding="utf-8")
    if hashlib.sha256(snapshot_text.encode("utf-8")).hexdigest() != manifest["snapshot_sha256"]:
        raise ValueError("Existing snapshot hash does not match manifest")

    entries = [
        Entry(**json.loads(line))
        for line in snapshot_text.splitlines()
        if line.strip()
    ]
    if len(entries) != manifest["entry_count"]:
        raise ValueError("Existing snapshot count does not match manifest")
    if len({entry.source_entry_id for entry in entries}) != len(entries):
        raise ValueError("Duplicate source_entry_id in existing snapshot")
    if len({normalize_key(entry.en_raw) for entry in entries}) != len(entries):
        raise ValueError("Duplicate English key in existing snapshot")
    for entry in entries:
        row_material = "\n".join(
            [entry.en_raw, entry.ru_raw, entry.target_url, entry.article_status]
        )
        expected_hash = hashlib.sha256(row_material.encode("utf-8")).hexdigest()
        if expected_hash != entry.row_hash:
            raise ValueError(f"Row hash mismatch: {entry.source_entry_id}")

    lookup_script = SKILL_ROOT / "scripts" / "lookup_scientia.py"
    if not lookup_script.is_file():
        raise ValueError("Bundled lookup_scientia.py is missing")
    return entries


def compare_refreshed(payload: bytes) -> list[Entry]:
    """Compare the live table and page bytes with the immutable active snapshot."""
    local_entries = validate_existing()
    manifest = json.loads((OUTPUT_ROOT / "manifest.json").read_text(encoding="utf-8"))
    refreshed_entries = parse_entries(payload, str(manifest["source_revision"]))

    local_by_id = {entry.source_entry_id: entry for entry in local_entries}
    refreshed_by_id = {entry.source_entry_id: entry for entry in refreshed_entries}
    added = sorted(refreshed_by_id.keys() - local_by_id.keys())
    removed = sorted(local_by_id.keys() - refreshed_by_id.keys())

    def semantic_row(entry: Entry) -> tuple[object, ...]:
        return (
            entry.source_order,
            entry.section,
            entry.source_section,
            entry.en_raw,
            entry.ru_raw,
            entry.target_url,
            entry.article_status,
        )

    changed = sorted(
        entry_id
        for entry_id in local_by_id.keys() & refreshed_by_id.keys()
        if semantic_row(local_by_id[entry_id]) != semantic_row(refreshed_by_id[entry_id])
    )
    html_sha256 = hashlib.sha256(payload).hexdigest()
    html_changed = html_sha256 != manifest["html_sha256"]
    if added or removed or changed or html_changed:
        raise ValueError(
            "Scientia source drift detected: "
            f"added={len(added)}, removed={len(removed)}, changed={len(changed)}, "
            f"html_changed={str(html_changed).lower()}"
        )
    return refreshed_entries


def write_snapshot(entries: list[Entry], payload: bytes, source_url: str, revision: str) -> None:
    validate_output_root()
    OUTPUT_ROOT.mkdir(parents=True, exist_ok=True)
    snapshots_root = OUTPUT_ROOT / "snapshots"
    snapshots_root.mkdir(parents=True, exist_ok=True)
    diffs_root = OUTPUT_ROOT / "diffs"
    diffs_root.mkdir(parents=True, exist_ok=True)

    snapshot_text = "\n".join(
        json.dumps(asdict(entry), ensure_ascii=False, sort_keys=True) for entry in entries
    ) + "\n"
    safe_revision = re.sub(r"[^0-9A-Za-z._-]+", "-", revision).strip("-")
    if not safe_revision:
        raise ValueError("source revision cannot produce an empty filename")
    snapshot_path = snapshots_root / f"scientia-{safe_revision}.jsonl"
    previous_snapshots = sorted(
        path for path in snapshots_root.glob("scientia-*.jsonl") if path != snapshot_path
    )
    if snapshot_path.exists():
        existing = snapshot_path.read_text(encoding="utf-8")
        if existing != snapshot_text:
            raise RuntimeError(
                f"Immutable snapshot already exists with different content: {snapshot_path.name}"
            )
    else:
        snapshot_path.write_text(snapshot_text, encoding="utf-8", newline="\n")

    if previous_snapshots:
        previous_path = previous_snapshots[-1]
        previous_entries = {
            item["source_entry_id"]: item
            for item in (
                json.loads(line)
                for line in previous_path.read_text(encoding="utf-8").splitlines()
                if line.strip()
            )
        }
        current_entries = {entry.source_entry_id: asdict(entry) for entry in entries}
        added = sorted(current_entries.keys() - previous_entries.keys())
        removed = sorted(previous_entries.keys() - current_entries.keys())
        changed = sorted(
            key
            for key in current_entries.keys() & previous_entries.keys()
            if current_entries[key]["row_hash"] != previous_entries[key]["row_hash"]
        )
        diff = {
            "from": previous_path.name,
            "to": snapshot_path.name,
            "added": added,
            "removed": removed,
            "changed": changed,
            "requires_override_review": bool(removed or changed),
        }
        diff_name = f"{previous_path.stem}--{snapshot_path.stem}.json"
        (diffs_root / diff_name).write_text(
            json.dumps(diff, ensure_ascii=False, indent=2, sort_keys=True) + "\n",
            encoding="utf-8",
            newline="\n",
        )

    sections = Counter(
        entry.section if re.fullmatch(r"[a-z]", entry.section) else "other"
        for entry in entries
    )

    manifest = {
        "schema_version": 2,
        "source_url": source_url,
        "source_revision": revision,
        "captured_at_utc": datetime.now(timezone.utc).replace(microsecond=0).isoformat(),
        "entry_count": len(entries),
        "html_sha256": hashlib.sha256(payload).hexdigest(),
        "snapshot_sha256": hashlib.sha256(snapshot_text.encode("utf-8")).hexdigest(),
        "sections": dict(sorted(sections.items())),
        "raw_file": snapshot_path.relative_to(OUTPUT_ROOT).as_posix(),
        "runtime_lookup": "../../../../scripts/lookup_scientia.py",
        "lookup_fields": ["en_raw", "ru_raw"],
    }
    (OUTPUT_ROOT / "manifest.json").write_text(
        json.dumps(manifest, ensure_ascii=False, indent=2, sort_keys=True) + "\n",
        encoding="utf-8",
        newline="\n",
    )


def build_parser() -> argparse.ArgumentParser:
    parser = argparse.ArgumentParser()
    parser.add_argument("--url", default=DEFAULT_URL)
    parser.add_argument("--input-html", type=Path)
    parser.add_argument("--source-revision", default="2025-09-12")
    parser.add_argument("--expected-count", type=int)
    parser.add_argument("--check-only", action="store_true")
    parser.add_argument(
        "--refresh",
        action="store_true",
        help="Fetch the source even in check-only mode instead of validating the local snapshot.",
    )
    return parser


def main() -> int:
    args = build_parser().parse_args()
    if args.check_only and not args.refresh and args.input_html is None:
        entries = validate_existing()
        if args.expected_count is not None and len(entries) != args.expected_count:
            raise ValueError(f"Expected {args.expected_count} entries, found {len(entries)}")
        print(
            json.dumps(
                {
                    "entries": len(entries),
                    "sections": sorted({entry.section for entry in entries}),
                    "check_only": True,
                    "source": "local-snapshot",
                },
                ensure_ascii=False,
            )
        )
        return 0
    payload = args.input_html.read_bytes() if args.input_html else fetch_html(args.url)
    if args.check_only:
        entries = compare_refreshed(payload)
        if args.expected_count is not None and len(entries) != args.expected_count:
            raise ValueError(f"Expected {args.expected_count} entries, found {len(entries)}")
        print(
            json.dumps(
                {
                    "entries": len(entries),
                    "sections": sorted({entry.section for entry in entries}),
                    "check_only": True,
                    "source": "refreshed-source",
                    "matches_active_snapshot": True,
                },
                ensure_ascii=False,
            )
        )
        return 0

    entries = parse_entries(payload, args.source_revision)
    if args.expected_count is not None and len(entries) != args.expected_count:
        raise ValueError(f"Expected {args.expected_count} entries, found {len(entries)}")
    write_snapshot(entries, payload, args.url, args.source_revision)
    print(
        json.dumps(
            {
                "entries": len(entries),
                "sections": sorted({entry.section for entry in entries}),
                "check_only": args.check_only,
            },
            ensure_ascii=False,
        )
    )
    return 0


if __name__ == "__main__":
    try:
        raise SystemExit(main())
    except Exception as exc:
        print(f"ERROR: {exc}", file=sys.stderr)
        raise