"""Site settings in the Blancco preferences: set in the webapp, not in XML.

Three values differ per site and are filled into our preferences.xml:
  business_location  printed on every erasure report (the site)
  wifi_ssid          the Wi-Fi Blancco joins to license erasures in the GE
  wifi_password      Blancco cloud (the imaging LAN has no internet)
A fourth, the password of the blancco Samba account in <network_share>,
comes from services/share_accounts.py (Tools > Share accounts).

They live in UPDATES_DIR/blancco/site-settings.json (0600, root). The repo's
playbook/blancco-preferences.xml carries none of them; the playbook installs
it as WEB_ROOT/blancco/preferences.repo.xml and this module renders the
served WEB_ROOT/blancco/preferences.xml from it. The same values are applied
whenever a new Blancco release is staged (blancco_update.apply_prefs), so an
update keeps them.

The playbook seeds the settings from site-vars.yml (site_name,
blancco_wifi_ssid, blancco_wifi_password) only while no settings file exists:
after install the webapp page (Updates > Blancco releases) is the place to
change them, and a playbook re-run never overwrites them.

    python3 -m services.blancco_prefs render [--seed]
        --seed reads BLANCCO_SEED_LOCATION / _SSID / _PASSWORD from the
        environment (not argv: the password stays out of ps).
"""

import json
import os
import re
import sys
from xml.sax.saxutils import escape

import config
from services import updates_common as uc

FIELDS = ("business_location", "wifi_ssid", "wifi_password")
DEFAULTS = {"business_location": "", "wifi_ssid": "INTERNETACCESS", "wifi_password": ""}

_LOCATION = re.compile(rb"(<business_location>)[^<]*(</business_location>)")
_WIRELESS = re.compile(
    rb'(<wireless>\s*<enabled>[^<]*</enabled>\s*<ssid encrypted="false">)[^<]*'
    rb'(</ssid>\s*<password encrypted="false">)[^<]*(</password>)')
# The report share login: the blancco Samba account (Tools > Share accounts).
_SHARE = re.compile(
    rb'(<network_share>\s*<username encrypted="false">blancco</username>\s*'
    rb'<password encrypted="false">)[^<]*(</password>)')


def settings_path():
    return os.path.join(uc.state_dir("blancco"), "site-settings.json")


def repo_prefs_path():
    return os.path.join(config.WEB_ROOT, "blancco", "preferences.repo.xml")


def served_prefs_path():
    return os.path.join(config.WEB_ROOT, "blancco", "preferences.xml")


def load():
    data = uc.read_json(settings_path(), None)
    out = dict(DEFAULTS)
    if isinstance(data, dict):
        for k in FIELDS:
            if isinstance(data.get(k), str):
                out[k] = data[k]
    return out


def exists():
    return os.path.isfile(settings_path())


def _clean(value, field):
    value = (value or "").strip()
    if len(value) > 128:
        raise ValueError(f"{field} is too long (128 characters at most)")
    if any(ord(c) < 32 for c in value):
        raise ValueError(f"{field} has control characters")
    return value


def save(business_location, wifi_ssid, wifi_password=None):
    """Store the settings. wifi_password None (or '') keeps the stored one."""
    cur = load()
    new = {
        "business_location": _clean(business_location, "Business location"),
        "wifi_ssid": _clean(wifi_ssid, "Wi-Fi network"),
        "wifi_password": cur["wifi_password"] if not wifi_password else _clean(wifi_password, "Wi-Fi password"),
    }
    if not new["wifi_ssid"]:
        raise ValueError("Wi-Fi network (SSID) cannot be empty")
    path = settings_path()
    tmp = path + ".tmp"
    fd = os.open(tmp, os.O_WRONLY | os.O_CREAT | os.O_TRUNC, 0o600)
    with os.fdopen(fd, "w") as f:
        json.dump(new, f, indent=2)
    os.replace(tmp, path)
    return new


def apply(xml, settings=None):
    """Our preferences (bytes) with the site settings filled in. Values are
    XML-escaped; the replacement is a function, so nothing in them is read
    as a regex group reference."""
    s = settings or load()
    from services import share_accounts
    share_pw = escape(share_accounts.load()["blancco"]).encode("utf-8")
    loc = escape(s["business_location"] or "Unnamed site").encode("utf-8")
    ssid = escape(s["wifi_ssid"]).encode("utf-8")
    pw = escape(s["wifi_password"]).encode("utf-8")
    out, n = _LOCATION.subn(lambda m: m.group(1) + loc + m.group(2), xml)
    if n != 1:
        raise ValueError("preferences have no single <business_location> element")
    out, n = _WIRELESS.subn(lambda m: m.group(1) + ssid + m.group(2) + pw + m.group(3), out)
    if n != 1:
        raise ValueError("preferences have no single <wireless> ssid/password block")
    out, n = _SHARE.subn(lambda m: m.group(1) + share_pw + m.group(2), out)
    if n != 1:
        raise ValueError("preferences have no single <network_share> login for blancco")
    return out


def render():
    """Write the served preferences.xml from the repo copy + settings, when it
    changes. Returns True if the file was written."""
    with open(repo_prefs_path(), "rb") as f:
        base = f.read()
    data = apply(base)
    # Same guard the playbook and the Blancco page apply: well-formed XML.
    import xml.etree.ElementTree as ET
    ET.fromstring(data)
    path = served_prefs_path()
    try:
        with open(path, "rb") as f:
            if f.read() == data:
                return False
    except OSError:
        pass
    tmp = path + ".tmp"
    with open(tmp, "wb") as f:
        f.write(data)
    os.chmod(tmp, 0o644)
    os.replace(tmp, path)
    return True


def public():
    """For the page: the settings without the password."""
    s = load()
    return {"business_location": s["business_location"], "wifi_ssid": s["wifi_ssid"],
            "wifi_password_set": bool(s["wifi_password"]), "configured": exists()}


def main(argv):
    if not argv or argv[0] != "render":
        print(__doc__)
        return 2
    if "--seed" in argv[1:] and not exists():
        save(os.environ.get("BLANCCO_SEED_LOCATION", ""),
             os.environ.get("BLANCCO_SEED_SSID", "") or DEFAULTS["wifi_ssid"],
             os.environ.get("BLANCCO_SEED_PASSWORD", ""))
        print("seeded site settings from site-vars")
    s = load()
    changed = render()
    print("CHANGED" if changed else "UNCHANGED")
    if not s["business_location"]:
        print("WARNING: business_location is empty: reports say 'Unnamed site'")
    if not s["wifi_password"]:
        print(f"WARNING: no Wi-Fi password for '{s['wifi_ssid']}': Blancco cannot license erasures")
    return 0


if __name__ == "__main__":
    sys.exit(main(sys.argv[1:]))