"""users.py — multi-user accounts for ani-web (PBKDF2, single json file).

CLI:  .venv/bin/python -m server.users add <username>   (password via prompt)
      .venv/bin/python -m server.users rm <username>
      .venv/bin/python -m server.users list
"""
import getpass
import hashlib
import json
import os
import re
import secrets
import time
from pathlib import Path

DATA = Path(os.environ.get("ANIWEB_DATA", Path(__file__).parent / "data"))
USERS = DATA / "users.json"
SECRET = DATA / "secret.key"
ITER = 210_000  # OWASP 2023 minimum for PBKDF2-SHA256
NAME_RE = re.compile(r"^[a-z0-9_-]{3,32}$")


def get_secret() -> bytes:
    if SECRET.exists():
        return SECRET.read_bytes()
    s = secrets.token_bytes(32)
    DATA.mkdir(exist_ok=True)
    fd = os.open(SECRET, os.O_WRONLY | os.O_CREAT | os.O_TRUNC, 0o600)
    with os.fdopen(fd, "wb") as f:
        f.write(s)
    return s


def migrate_legacy():
    """one-time: single-password era -> users.json + per-user history files."""
    cred = DATA / "credentials.json"
    if not USERS.exists() and cred.exists():
        d = json.loads(cred.read_text())
        save({"admin": {"salt": d["salt"], "hash": d["hash"], "created": time.time()}})
        cred.unlink()
    old_hist = DATA / "history.json"
    if not (DATA / "history" / "admin.json").exists() and old_hist.exists():
        (DATA / "history").mkdir(exist_ok=True)
        old_hist.rename(DATA / "history" / "admin.json")


def load() -> dict:
    try:
        return json.loads(USERS.read_text())
    except (FileNotFoundError, json.JSONDecodeError):
        return {}


def atomic_write(path, text):
    """tmp + os.replace: a crash mid-write leaves the previous file intact
    (in-place writes corrupted the file -> load() returned {} -> accounts
    or history silently vanished)."""
    tmp = path.parent / (path.name + ".tmp")
    fd = os.open(tmp, os.O_WRONLY | os.O_CREAT | os.O_TRUNC, 0o600)
    with os.fdopen(fd, "w") as f:
        f.write(text)
    os.replace(tmp, path)


def save(users: dict):
    DATA.mkdir(exist_ok=True)
    atomic_write(USERS, json.dumps(users, indent=1))


def add(username: str, password: str):
    u = username.lower()
    if not NAME_RE.match(u):
        raise ValueError("username: 3-32 chars, only a-z 0-9 _ -")
    if len(password) < 8:
        raise ValueError("password: min 8 chars")
    users = load()
    if u in users:
        raise ValueError("username already taken")
    salt = secrets.token_bytes(16)
    users[u] = {"salt": salt.hex(),
                "hash": hashlib.pbkdf2_hmac("sha256", password.encode(), salt, ITER).hex(),
                "created": time.time()}
    save(users)


def verify(username: str, password: str) -> bool:
    d = load().get(username.lower())
    if not d:
        return False
    h = hashlib.pbkdf2_hmac("sha256", password.encode(),
                            bytes.fromhex(d["salt"]), d.get("iter", ITER))
    return secrets.compare_digest(h.hex(), d["hash"])


def remove(username: str):
    u = username.lower()
    users = load()
    users.pop(u, None)
    save(users)
    (DATA / "history" / f"{u}.json").unlink(missing_ok=True)
    (DATA / "searches" / f"{u}.json").unlink(missing_ok=True)


if __name__ == "__main__":
    import sys
    cmd = sys.argv[1] if len(sys.argv) > 1 else ""
    if cmd == "add" and len(sys.argv) > 2:
        name = sys.argv[2]
        pw = getpass.getpass(f"Password for {name} (min 8 chars): ")
        if pw != getpass.getpass("Again: "):
            raise SystemExit("passwords did not match")
        try:
            add(name, pw)
        except ValueError as e:
            raise SystemExit(str(e))
        print(f"added user {name.lower()}")
    elif cmd == "rm" and len(sys.argv) > 2:
        remove(sys.argv[2])
        print(f"removed {sys.argv[2].lower()} (incl. history)")
    elif cmd == "list":
        for u in sorted(load()):
            print(u)
    else:
        print(__doc__)
        raise SystemExit(2)