# backend/file_chat.py — historique de discussion (#169, #190)
"""Chat history persisted under ``data/chats/``.

One JSON document per ``(vault, path)`` pair, keyed by a SHA-256 of both so
the filename never carries user-controlled path separators. Writes are
atomic (tmp + move) and the message list is capped at
:data:`MAX_MESSAGES` to bound growth.

#190 adds the **general chat**: the same store addressed with the reserved
sentinels (:data:`GLOBAL_VAULT` / :data:`GLOBAL_PATH`), so no second
implementation. Messages may carry an ``attachment`` (image/video/url)
uploaded under ``data/chat_uploads/``.
"""

from __future__ import annotations

import hashlib
import html
import json
import logging
import re
import shutil
import time
import uuid
from pathlib import Path
from typing import Any

import httpx

logger = logging.getLogger("obsigate.file_chat")

CHAT_DIR = Path("data/chats")
MAX_MESSAGES = 500  # retention ceiling per file (oldest dropped first)
MAX_TEXT = 4000  # characters per message

# #190 — general (non file-bound) conversation, stored like any other one.
GLOBAL_VAULT = "__global__"
GLOBAL_PATH = "general"

# #191 — private (2 users) conversations reuse the same store: the vault is
# the reserved sentinel and the path is the sorted username pair, so the
# storage key never depends on who asks.
DM_VAULT = "__dm__"

# #190 — attachments (image/video) live outside the vaults.
UPLOAD_DIR = Path("data/chat_uploads")
MAX_UPLOAD_BYTES = 25 * 1024 * 1024  # 25 MB per attachment
ALLOWED_ATTACH_EXT = {
    ".png", ".jpg", ".jpeg", ".gif", ".webp", ".svg",
    ".mp4", ".webm", ".ogg", ".mov", ".m4v",
}

# #191 — link preview fetch budget
PREVIEW_TIMEOUT = 5.0  # seconds
PREVIEW_MAX_BYTES = 512 * 1024  # only the head of the page is parsed


def _chat_file(vault: str, path: str) -> Path:
    """Return the chat file for *(vault, path)* (hashed, traversal-proof)."""
    CHAT_DIR.mkdir(parents=True, exist_ok=True)
    key = hashlib.sha256(f"{vault}\0{path}".encode()).hexdigest()[:32]
    return CHAT_DIR / f"{key}.json"


def _read(vault: str, path: str) -> dict[str, Any]:
    """Load the raw chat document (empty structure when missing/corrupt)."""
    file = _chat_file(vault, path)
    if not file.exists():
        return {"vault": vault, "path": path, "messages": []}
    try:
        doc = json.loads(file.read_text(encoding="utf-8"))
        if not isinstance(doc.get("messages"), list):
            raise TypeError("messages is not a list")  # caught by the handler below
        return doc
    except Exception as e:
        logger.error("Failed to read chat for %s/%s: %s", vault, path, e)
        return {"vault": vault, "path": path, "messages": []}


def _write(file: Path, doc: dict[str, Any]) -> None:
    """Atomically persist *doc* (tmp file + rename)."""
    try:
        tmp = file.with_suffix(".tmp")
        tmp.write_text(json.dumps(doc, ensure_ascii=False, indent=1), encoding="utf-8")
        shutil.move(str(tmp), str(file))
    except Exception as e:
        logger.error("Failed to write chat %s: %s", file.name, e)


def get_messages(vault: str, path: str) -> list[dict[str, Any]]:
    """Return the chat history for *(vault, path)* (chronological)."""
    return list(_read(vault, path).get("messages", []))


def add_message(
    vault: str,
    path: str,
    user: str,
    text: str,
    attachment: dict[str, Any] | None = None,
    preview: dict[str, Any] | None = None,
) -> dict[str, Any]:
    """Append a message and persist it. Returns the stored message.

    The list is capped at :data:`MAX_MESSAGES` (oldest dropped first).
    *attachment* (#190) is ``{name, url, mime, kind}`` for image/video/url;
    *preview* (#191) is the OpenGraph card of the first URL in *text*.
    """
    text = (text or "").strip()[:MAX_TEXT]
    msg: dict[str, Any] = {
        "id": uuid.uuid4().hex[:12],
        "user": user or "anonyme",
        "text": text,
        "ts": time.time(),
    }
    if attachment:
        msg["attachment"] = attachment
    if preview:
        msg["preview"] = preview
    doc = _read(vault, path)
    return _append(vault, path, doc, msg)


def _append(
    vault: str,
    path: str,
    doc: dict[str, Any],
    msg: dict[str, Any],
) -> dict[str, Any]:
    """Cap, persist and return *msg* (shared by file and global chats)."""
    messages = list(doc.get("messages", []))
    messages.append(msg)
    if len(messages) > MAX_MESSAGES:
        messages = messages[-MAX_MESSAGES:]
    doc["messages"] = messages
    _write(_chat_file(vault, path), doc)
    return msg


# --- #191 : messages privés (2 utilisateurs) -------------------------------

def dm_path(user_a: str, user_b: str) -> str:
    """Storage path for the private conversation between two users.

    The pair is sorted so both participants address the same document.
    """
    return "|".join(sorted([user_a, user_b]))


def get_dm_messages(user_a: str, user_b: str) -> list[dict[str, Any]]:
    """Return the private history between two users (chronological)."""
    return get_messages(DM_VAULT, dm_path(user_a, user_b))


def add_dm_message(
    user_a: str,
    user_b: str,
    author: str,
    text: str,
    attachment: dict[str, Any] | None = None,
    preview: dict[str, Any] | None = None,
) -> dict[str, Any]:
    """Append a private message. Returns the stored message."""
    return add_message(DM_VAULT, dm_path(user_a, user_b), author, text, attachment, preview)


# --- #191 : suppression -----------------------------------------------------

def delete_message(vault: str, path: str, message_id: str) -> bool:
    """Remove one message from a conversation. True when it existed."""
    doc = _read(vault, path)
    messages = list(doc.get("messages", []))
    kept = [m for m in messages if m.get("id") != message_id]
    if len(kept) == len(messages):
        return False
    doc["messages"] = kept
    _write(_chat_file(vault, path), doc)
    return True


# --- #190 : chat général (conversation centrale, hors fichier) -------------

def get_global_messages() -> list[dict[str, Any]]:
    """Return the general-chat history (chronological)."""
    return get_messages(GLOBAL_VAULT, GLOBAL_PATH)


def add_global_message(
    user: str,
    text: str,
    attachment: dict[str, Any] | None = None,
    preview: dict[str, Any] | None = None,
) -> dict[str, Any]:
    """Append a message to the general chat. Returns the stored message."""
    return add_message(GLOBAL_VAULT, GLOBAL_PATH, user, text, attachment, preview)


def save_attachment(filename: str, data: bytes) -> dict[str, Any]:
    """Persist an uploaded attachment under :data:`UPLOAD_DIR`.

    Returns ``{name, url, mime, kind}``. The stored name is a fresh UUID
    (never the client name), the extension must be in
    :data:`ALLOWED_ATTACH_EXT` and the size is capped at
    :data:`MAX_UPLOAD_BYTES`.

    Raises:
        ValueError: extension refused, empty file or size exceeded.
    """
    ext = Path(filename or "").suffix.lower()
    if ext not in ALLOWED_ATTACH_EXT:
        raise ValueError(f"extension refusée : {ext or '(aucune)'}")
    if not data:
        raise ValueError("fichier vide")
    if len(data) > MAX_UPLOAD_BYTES:
        raise ValueError(f"fichier trop lourd (max {MAX_UPLOAD_BYTES // (1024 * 1024)} MB)")
    UPLOAD_DIR.mkdir(parents=True, exist_ok=True)
    name = f"{uuid.uuid4().hex}{ext}"
    (UPLOAD_DIR / name).write_bytes(data)
    kind = "video" if ext in {".mp4", ".webm", ".ogg", ".mov", ".m4v"} else "image"
    return {
        "name": name,
        "url": f"/api/chat/attachment/{name}",
        "mime": _MIME_BY_EXT.get(ext, "application/octet-stream"),
        "kind": kind,
    }


# --- #191 : link preview ----------------------------------------------------

_URL_RE = re.compile(r"https?://[^\s<>\"']+")
_PREVIEW_CACHE: dict[str, dict[str, Any] | None] = {}
PREVIEW_CACHE_MAX = 200


def _og(content: str, prop: str) -> str:
    """Extract one OpenGraph/``<title>`` value from an HTML head (regex)."""
    for pattern in (
        rf'<meta[^>]+(?:property|name)="{prop}"[^>]+content="([^"]*)"',
        rf'<meta[^>]+content="([^"]*)"[^>]+(?:property|name)="{prop}"',
    ):
        m = re.search(pattern, content, re.IGNORECASE)
        if m:
            return html.unescape(m.group(1)).strip()[:300]
    if prop == "og:title":
        m = re.search(r"<title[^>]*>([^<]*)</title>", content, re.IGNORECASE)
        if m:
            return html.unescape(m.group(1)).strip()[:300]
    return ""


def build_preview(text: str) -> dict[str, Any] | None:
    """Fetch OpenGraph metadata for the first URL in *text* (#191).

    SSRF-guarded (reuses the web-tool guard), size/time capped, cached in a
    bounded dict. Returns ``{url, title, description, image, site}`` or
    ``None`` when there is no URL / the fetch fails (never raises: a dead
    link must not block the message).
    """
    m = _URL_RE.search(text or "")
    if not m:
        return None
    url = m.group(0).rstrip(".,;:!?)")
    if url in _PREVIEW_CACHE:
        cached = _PREVIEW_CACHE[url]
        return dict(cached) if cached else None
    try:
        from backend.tools.web import USER_AGENT, _assert_public_http_url

        _assert_public_http_url(url)
        resp = httpx.get(
            url,
            headers={"User-Agent": USER_AGENT, "Accept": "text/html,*/*"},
            timeout=PREVIEW_TIMEOUT,
            follow_redirects=True,
        )
        if resp.status_code >= 400:
            raise ValueError(f"HTTP {resp.status_code}")
        body = resp.text[:PREVIEW_MAX_BYTES]
        preview = {
            "url": url,
            "title": _og(body, "og:title") or _og(body, "og:site_name"),
            "description": _og(body, "og:description"),
            "image": _og(body, "og:image"),
            "site": _og(body, "og:site_name") or (url.split("/")[2] if "/" in url[8:] else url),
        }
        if not preview["title"]:
            raise ValueError("pas de titre")
    except Exception as e:
        logger.debug("link preview failed for %s: %s", url, e)
        preview = None
    if len(_PREVIEW_CACHE) >= PREVIEW_CACHE_MAX:
        _PREVIEW_CACHE.pop(next(iter(_PREVIEW_CACHE)))  # oldest first (dict order)
    _PREVIEW_CACHE[url] = preview
    return dict(preview) if preview else None


def attachment_path(name: str) -> Path | None:
    """Resolve an attachment by its stored name (UUID+ext only, no traversal)."""
    p = Path(name)
    if p.name != name or p.suffix.lower() not in ALLOWED_ATTACH_EXT:
        return None
    file = UPLOAD_DIR / p.name
    return file if file.exists() else None


# Extension → MIME (literals only; ``mimetypes`` guesses poorly for a few).
_MIME_BY_EXT = {
    ".png": "image/png",
    ".jpg": "image/jpeg",
    ".jpeg": "image/jpeg",
    ".gif": "image/gif",
    ".webp": "image/webp",
    ".svg": "image/svg+xml",
    ".mp4": "video/mp4",
    ".webm": "video/webm",
    ".ogg": "video/ogg",
    ".mov": "video/quicktime",
    ".m4v": "video/x-m4v",
}