#!/bin/bash
# Recreate human users + groups with stable UIDs/GIDs, and restore the
# samba passdb from USB backup. Run during recovery BEFORE the data rsync
# so file ownership lands on the right UIDs.
#
# UIDs/GIDs MUST match what the original system used, or ZFS files end up
# owned by orphan numeric IDs. The script aborts loudly if it finds an
# existing user/group with a different UID/GID than expected — investigate
# and either rename the conflicting entry or update the constants below.
#
# Verify on a live system with:
#   id timothykim                 # check uid + primary gid
#   getent group sambagroup       # check sambagroup gid
set -euo pipefail

[ "$EUID" -eq 0 ] || { echo "must run as root" >&2; exit 1; }

SAMBAGROUP_GID=1001

# Format: username:uid:gid:shell:home_flag:supp_groups
# - gid: numeric gid for the user's primary group (group name = username)
# - home_flag: "home" creates /home/<user>, "nohome" skips it (samba-only)
# - supp_groups: comma-separated supplementary groups, or "-" for none
USERS=(
    "timothykim:1000:1000:/bin/bash:home:wheel,video,docker,sambagroup"
    "yireh:1100:1100:/sbin/nologin:nohome:sambagroup"
    "isaac:1101:1101:/sbin/nologin:nohome:sambagroup"
)

# Abort if an existing entity's numeric ID doesn't match what we expect
assert_match() {
    local label=$1 expected=$2 actual=$3
    if [ "$expected" != "$actual" ]; then
        echo "[FATAL] $label mismatch: expected $expected, got $actual" >&2
        echo "        ZFS file ownership will break if you proceed." >&2
        echo "        Either rename the conflicting entry or update this script." >&2
        exit 1
    fi
}

echo "=== sambagroup ==="
if getent group sambagroup &>/dev/null; then
    actual=$(getent group sambagroup | cut -d: -f3)
    assert_match "sambagroup gid" "$SAMBAGROUP_GID" "$actual"
    echo "[ok] sambagroup exists (gid $actual)"
else
    groupadd -g "$SAMBAGROUP_GID" sambagroup
    echo "[+] created sambagroup (gid $SAMBAGROUP_GID)"
fi

# Preflight: every supplementary group referenced must already exist.
# wheel/video are OS-default; docker is created by docker-ce install (RUNBOOK
# step 2); sambagroup was just handled above. If anything's missing, abort
# before touching users — half-applied group memberships are annoying to undo.
echo ""
echo "=== preflight: supplementary groups ==="
missing=()
for entry in "${USERS[@]}"; do
    supp=$(echo "$entry" | cut -d: -f6)
    [ "$supp" = "-" ] && continue
    IFS=, read -ra groups <<< "$supp"
    for g in "${groups[@]}"; do
        if ! getent group "$g" &>/dev/null; then
            missing+=("$g")
        fi
    done
done
if [ ${#missing[@]} -gt 0 ]; then
    # de-dupe for a cleaner error message
    uniq_missing=$(printf '%s\n' "${missing[@]}" | sort -u | tr '\n' ' ')
    echo "[FATAL] required supplementary groups missing: $uniq_missing" >&2
    echo "        likely cause: a package that creates the group hasn't been" >&2
    echo "        installed yet (e.g., docker-ce creates the docker group)." >&2
    echo "        complete RUNBOOK step 2 before running this script." >&2
    exit 1
fi
echo "[ok] all supplementary groups present"

for entry in "${USERS[@]}"; do
    IFS=: read -r u uid gid shell home_flag supp <<< "$entry"
    echo ""
    echo "=== $u ==="

    # Primary group (same name as user, pinned GID — pre-created so useradd
    # doesn't auto-assign one via USERGROUPS_ENAB)
    if getent group "$u" &>/dev/null; then
        actual=$(getent group "$u" | cut -d: -f3)
        assert_match "$u primary group gid" "$gid" "$actual"
        echo "[ok] group $u exists (gid $actual)"
    else
        groupadd -g "$gid" "$u"
        echo "[+] created group $u (gid $gid)"
    fi

    # User account
    if id "$u" &>/dev/null; then
        actual_uid=$(id -u "$u")
        actual_gid=$(id -g "$u")
        assert_match "$u uid" "$uid" "$actual_uid"
        assert_match "$u primary gid" "$gid" "$actual_gid"
        echo "[ok] $u exists (uid $actual_uid, gid $actual_gid)"
    else
        if [ "$home_flag" = "home" ]; then
            useradd -u "$uid" -g "$gid" -s "$shell" -m "$u"
        else
            useradd -u "$uid" -g "$gid" -s "$shell" -M "$u"
        fi
        echo "[+] created $u (uid $uid, gid $gid)"
    fi

    # Supplementary groups (idempotent — usermod -aG won't error on duplicates)
    if [ "$supp" != "-" ]; then
        usermod -aG "$supp" "$u"
        echo "[+] $u in supplementary groups: $supp"
    fi
done

echo ""
echo "=== samba passdb ==="
PASSDB_SRC=/mnt/backup/argento/system/samba-private
if ! mountpoint -q /mnt/backup; then
    echo "[!] /mnt/backup is not mounted — skipping samba passdb restore"
    echo "    mount the USB backup drive (RUNBOOK step 5) and re-run if you want"
    echo "    to restore preserved SMB passwords; otherwise set them manually:"
    echo "      for u in timothykim yireh isaac; do smbpasswd -a \"\$u\"; done"
elif [ -f "$PASSDB_SRC/passdb.tdb" ]; then
    install -d -m 700 /var/lib/samba/private
    cp "$PASSDB_SRC"/*.tdb /var/lib/samba/private/
    chmod 600 /var/lib/samba/private/*.tdb
    echo "[+] restored samba passdb from $PASSDB_SRC/"
else
    echo "[!] no samba passdb backup found at $PASSDB_SRC/"
    echo "    run: for u in timothykim yireh isaac; do smbpasswd -a \"\$u\"; done"
fi

echo ""
echo "=== Done ==="
echo "Next: set timothykim's Linux login password if not already (passwd timothykim)"