"""
documents.py - the document shelf behind /documents.

Files live OUTSIDE the repo at /srv/scout-website-assets/docs, bind-mounted
read-only at /docs, the same arrangement as the photos. PDFs never bloat a
clone, and publishing one is a file drop plus a manifest line - no rebuild,
no redeploy.

manifest.json sits beside the files and maps a STABLE SLUG to a filename. That
indirection is the point: next year's permission slip can replace this year's
without breaking a link already printed on a flyer or sitting in somebody's
inbox.

Documents are served THROUGH the app, never from a static mount. Anything
under /app/static is public forever. Serving through a route means that when
member login exists, gating a document is one change in visible() and not a
single URL moves.

visibility:
    "public"    anyone, and listed on /documents.
    "unlisted"  served at its slug to anyone holding the link, but kept off the
                index and sent with X-Robots-Tag: noindex. For internal papers
                that need a durable link before member login exists. This is
                obscurity, not access control: treat an unlisted link as
                forwardable, because it is.
    "members"   reserved for the login that does not exist yet. Until it does,
                these are hidden AND unservable, returning 404 rather than 403,
                because a 403 advertises a document we cannot actually gate yet.
"""

import datetime
import json
import os
import re
from pathlib import Path

DOCS_DIR = Path(os.environ.get("DOCS_DIR", "/docs"))
MANIFEST = DOCS_DIR / "manifest.json"

# Slugs are the public contract. Keep them boring and permanent.
SLUG_RE = re.compile(r"^[a-z0-9][a-z0-9-]{0,63}$")

EMPTY = {"categories": [], "documents": []}

# extension -> (badge label, media type). Anything unlisted downloads as a blob.
KINDS = {
    ".pdf":  ("PDF",  "application/pdf"),
    ".doc":  ("DOC",  "application/msword"),
    ".docx": ("DOC",  "application/vnd.openxmlformats-officedocument.wordprocessingml.document"),
    ".xls":  ("XLS",  "application/vnd.ms-excel"),
    ".xlsx": ("XLS",  "application/vnd.openxmlformats-officedocument.spreadsheetml.sheet"),
    ".ppt":  ("PPT",  "application/vnd.ms-powerpoint"),
    ".pptx": ("PPT",  "application/vnd.openxmlformats-officedocument.presentationml.presentation"),
    ".csv":  ("CSV",  "text/csv"),
    ".txt":  ("TXT",  "text/plain; charset=utf-8"),
    ".md":   ("TXT",  "text/plain; charset=utf-8"),
    ".ics":  ("ICS",  "text/calendar; charset=utf-8"),
    ".jpg":  ("IMG",  "image/jpeg"),
    ".jpeg": ("IMG",  "image/jpeg"),
    ".png":  ("IMG",  "image/png"),
    ".zip":  ("ZIP",  "application/zip"),
}

# Browsers should open these in a tab; the rest download.
INLINE = {".pdf", ".txt", ".md", ".jpg", ".jpeg", ".png"}

_cache = {"key": None, "value": EMPTY}


def _stat_key():
    try:
        st = MANIFEST.stat()
    except OSError:
        return None
    return (st.st_mtime_ns, st.st_size)


def _clean(raw):
    """Drop anything malformed rather than serving a half-valid shelf."""
    cats, seen_cat = [], set()
    for c in raw.get("categories") or []:
        cid = str(c.get("id", "")).strip()
        if not cid or cid in seen_cat:
            continue
        seen_cat.add(cid)
        cats.append({
            "id": cid,
            "title": str(c.get("title") or cid).strip(),
            "blurb": str(c.get("blurb") or "").strip(),
        })

    docs, seen_slug = [], set()
    for d in raw.get("documents") or []:
        slug = str(d.get("slug", "")).strip().lower()
        name = str(d.get("file", "")).strip()
        if not SLUG_RE.match(slug) or slug in seen_slug or not name:
            continue
        # Path traversal guard: the resolved file must sit inside DOCS_DIR.
        path = (DOCS_DIR / name).resolve()
        try:
            inside = path.is_relative_to(DOCS_DIR.resolve())
        except AttributeError:  # pragma: no cover - Python < 3.9
            inside = str(path).startswith(str(DOCS_DIR.resolve()) + os.sep)
        if not inside:
            continue
        seen_slug.add(slug)
        vis = str(d.get("visibility") or "public").strip().lower()
        unit = str(d.get("unit") or "both").strip().lower()
        docs.append({
            "slug": slug,
            "file": name,
            "path": path,
            "title": str(d.get("title") or slug).strip(),
            "description": str(d.get("description") or "").strip(),
            "category": str(d.get("category") or "").strip(),
            "unit": unit if unit in ("pack", "troop", "both") else "both",
            "visibility": vis if vis in ("public", "unlisted", "members") else "members",
            "updated": str(d.get("updated") or "").strip(),
        })
    return {"categories": cats, "documents": docs}


def manifest():
    """Reload only when manifest.json actually changed on disk."""
    key = _stat_key()
    if key != _cache["key"]:
        if key is None:
            _cache["value"] = EMPTY
        else:
            try:
                with MANIFEST.open(encoding="utf-8") as fh:
                    _cache["value"] = _clean(json.load(fh))
            except Exception as e:
                print("DOCUMENTS: manifest unreadable: %s" % e, flush=True)
                _cache["value"] = EMPTY
        _cache["key"] = key
    return _cache["value"]


def visible(doc):
    """The single gate on SERVING. Member login plugs in here and nowhere else."""
    return doc.get("visibility") in ("public", "unlisted") and doc["path"].is_file()


def listed(doc):
    """The separate, weaker question of whether it appears on the index."""
    return doc.get("visibility") == "public" and visible(doc)


def noindex(doc):
    """Unlisted documents should not turn up in a search result."""
    return doc.get("visibility") == "unlisted"


def listing():
    """Listed documents grouped into their categories, in manifest order."""
    m = manifest()
    docs = [d for d in m["documents"] if listed(d)]
    known = {c["id"] for c in m["categories"]}
    groups = []
    for cat in m["categories"]:
        rows = [d for d in docs if d["category"] == cat["id"]]
        if rows:
            groups.append((cat, rows))
    loose = [d for d in docs if d["category"] not in known]
    if loose:
        groups.append(({"id": "", "title": "Everything else", "blurb": ""}, loose))
    return groups


def find(slug):
    slug = (slug or "").strip().lower()
    if not SLUG_RE.match(slug):
        return None
    for d in manifest()["documents"]:
        if d["slug"] == slug:
            return d if visible(d) else None
    return None


def kind(doc):
    return KINDS.get(doc["path"].suffix.lower(), ("FILE", "application/octet-stream"))


def disposition(doc):
    return "inline" if doc["path"].suffix.lower() in INLINE else "attachment"


def size_text(doc):
    try:
        n = doc["path"].stat().st_size
    except OSError:
        return ""
    if n < 1024:
        return "%d B" % n
    if n < 1024 * 1024:
        return "%d KB" % round(n / 1024)
    return "%.1f MB" % (n / 1024 / 1024)


def updated_text(doc):
    """Manifest date wins; otherwise the file's own mtime, which cannot lie."""
    stamp = doc.get("updated")
    if stamp:
        try:
            return datetime.date.fromisoformat(stamp).strftime("%b %-d, %Y")
        except ValueError:
            return stamp
    try:
        ts = doc["path"].stat().st_mtime
    except OSError:
        return ""
    return datetime.date.fromtimestamp(ts).strftime("%b %-d, %Y")