ubuntu-based-kiosk/menus/addon_anki_sync.sh

#!/bin/bash
################################################################################
# menus/addon_anki_sync.sh - "Anki Sync Server" addon.
#
# Self-hosted flashcard sync, as an alternative to AnkiWeb - lets Anki
# desktop and AnkiDroid clients on the LAN sync their collection (any
# note type: simple vocab/math-fact cards or complex custom templates)
# against this kiosk instead of ankiweb.net. Standard Anki-format decks
# import/export as .apkg from the desktop client; Quizlet sets round-trip
# through Anki via tab-separated text (Quizlet's own export/import), so
# this server doesn't need to know anything about that format itself -
# it only syncs whatever collection the client already has.
#
# Installed the officially documented way (docs.ankiweb.net/sync-server.html):
# the real "anki" package from PyPI, run headless as `python -m
# anki.syncserver` - no Qt/GUI deps, since that module never imports the
# desktop app's aqt package. Runs in its own venv under $ANKI_SYNC_DIR
# (lib/config.sh) as $KIOSK_USER, same shape as menus/addon_webui.sh's
# Node app: an EnvironmentFile under $ANKI_SYNC_ENV_DIR feeding a
# systemd unit's ExecStart, both parameterized so tests can point them
# at a scratch directory instead of the real system.
#
# Unlike webui.env, anki-sync.env holds plaintext sync passwords
# (SYNC_USER1=user:pass, ... - the only form the upstream server
# accepts), so it's written chmod 600/root:root rather than left at the
# default `sudo tee` mode - systemd reads EnvironmentFile as root before
# dropping to User=$KIOSK_USER, so the service never needs read access
# to it itself.
#
# No login/HTTPS beyond that account+password, same caveat as every
# other plain self-hosted addon here (CUPS, LMS, Web UI): fine on a
# trusted LAN, put it behind a reverse proxy with TLS if it needs to be
# reachable beyond one.
#
# Depends on: lib/menu.sh, lib/config.sh being sourced first.
################################################################################

anki_sync_is_installed() {
    [[ -f "$SYSTEMD_DIR/kiosk-anki-sync.service" ]]
}

anki_sync_is_active() {
    systemctl is-active --quiet kiosk-anki-sync
}

anki_sync_env_file() {
    echo "$ANKI_SYNC_ENV_DIR/anki-sync.env"
}

anki_sync_port() {
    sudo grep -oP '^SYNC_PORT=\K.*' "$(anki_sync_env_file)" 2>/dev/null || echo "8080"
}

# No `|| echo 0` here: `grep -c` on a file with zero matches still
# prints "0" to stdout while exiting non-zero, so chaining `||` would
# run *both* branches and return "0\n0" - the pattern menus/
# addon_webui.sh's webui_port() uses safely only works because `-oP`
# prints nothing at all on no match.
anki_sync_user_count() {
    local count
    count=$(sudo grep -c '^SYNC_USER[0-9]\+=' "$(anki_sync_env_file)" 2>/dev/null)
    echo "${count:-0}"
}

addon_anki_sync_status() {
    if anki_sync_is_installed && anki_sync_is_active; then
        echo "Anki Sync Server: running at http://$(get_ip_address):$(anki_sync_port)/"
        echo "  Sync users: $(anki_sync_user_count)"
    elif anki_sync_is_installed; then
        echo "Anki Sync Server: installed but not running"
    else
        echo "Anki Sync Server: not installed"
    fi
}

addon_anki_sync_menu_builder() {
    if anki_sync_is_installed; then
        MENU_LABELS=("Add another sync user" "Change port" "Restart service" "Uninstall")
        MENU_HANDLERS=(action_anki_sync_add_user action_anki_sync_reconfigure_port action_anki_sync_restart action_anki_sync_uninstall)
    else
        MENU_LABELS=("Install Anki Sync Server")
        MENU_HANDLERS=(action_anki_sync_install)
    fi
}

addon_anki_sync_menu() {
    run_menu "ANKI SYNC SERVER" addon_anki_sync_menu_builder addon_anki_sync_status
}

################################################################################
# Shared install helpers
################################################################################

anki_sync_ask_username() {
    local default="$1"
    local uname
    while true; do
        uname=$(ask_text "Username" "$default")
        if [[ -z "$uname" ]]; then
            echo "❌ Username cannot be empty" >&2
            continue
        fi
        if [[ "$uname" == *:* ]]; then
            echo "❌ Username cannot contain ':'" >&2
            continue
        fi
        echo "$uname"
        return 0
    done
}

# Prompts twice (masked) and returns the password once both entries
# match - same shape as menus/lockout.sh's prompt_and_hash_password,
# but returned as plain text (not hashed): the upstream sync server
# authenticates against the plaintext SYNC_USERn value itself.
anki_sync_ask_password() {
    local pass1 pass2
    while true; do
        read -r -s -p "Password for $1: " pass1
        echo
        read -r -s -p "Confirm password: " pass2
        echo

        if [[ -z "$pass1" ]]; then
            echo "❌ Password cannot be empty"
            continue
        fi
        if [[ "$pass1" != "$pass2" ]]; then
            echo "❌ Passwords do not match"
            continue
        fi
        echo "$pass1"
        return 0
    done
}

anki_sync_write_base_env() {
    local port="$1"
    sudo mkdir -p "$ANKI_SYNC_ENV_DIR"
    sudo tee "$(anki_sync_env_file)" > /dev/null <<EOF
SYNC_BASE=${ANKI_SYNC_DIR}/data
SYNC_HOST=0.0.0.0
SYNC_PORT=${port}
EOF
    sudo chown root:root "$(anki_sync_env_file)"
    sudo chmod 600 "$(anki_sync_env_file)"
}

anki_sync_append_user_line() {
    local index="$1" username="$2" password="$3"
    echo "SYNC_USER${index}=${username}:${password}" | sudo tee -a "$(anki_sync_env_file)" > /dev/null
}

anki_sync_write_unit_file() {
    sudo tee "$SYSTEMD_DIR/kiosk-anki-sync.service" > /dev/null <<EOF
[Unit]
Description=Anki Sync Server
After=network.target

[Service]
Type=simple
User=${KIOSK_USER}
EnvironmentFile=${ANKI_SYNC_ENV_DIR}/anki-sync.env
ExecStart=${ANKI_SYNC_DIR}/bin/python -m anki.syncserver
Restart=on-failure
RestartSec=5

[Install]
WantedBy=multi-user.target
EOF
}

################################################################################
# Actions
################################################################################

action_anki_sync_install() {
    echo
    echo "This installs a self-hosted Anki sync server (the official"
    echo "'python -m anki.syncserver', from the 'anki' package on PyPI)"
    echo "so Anki desktop / AnkiDroid on your LAN can sync flashcards to"
    echo "this kiosk instead of AnkiWeb. Plain vocab/math-fact cards and"
    echo "complex custom note types both sync fine - it just stores"
    echo "whatever collection the client already has. Quizlet decks"
    echo "still need to go through Anki's own tab-separated import first"
    echo "(File > Import in the desktop app) - this server only syncs"
    echo "the resulting collection."
    echo
    ask_yes_no "Install the Anki Sync Server?" "n" || { echo "Cancelled"; return; }

    echo "Installing python3-venv..."
    if ! sudo apt-get update -qq || ! sudo apt-get install -y python3-venv python3-pip; then
        log_error "Failed to install python3-venv/python3-pip"
        return 1
    fi

    echo "Creating virtual environment..."
    sudo mkdir -p "$ANKI_SYNC_DIR"
    sudo chown -R "$KIOSK_USER:$KIOSK_USER" "$ANKI_SYNC_DIR"
    if ! sudo -u "$KIOSK_USER" python3 -m venv "$ANKI_SYNC_DIR"; then
        log_error "Failed to create virtual environment"
        return 1
    fi

    # Debian/Ubuntu's python3-venv doesn't always bootstrap pip into a
    # fresh venv on its own (ensurepip behavior varies by release) - fall
    # back to ensurepip explicitly rather than failing the whole install
    # over it.
    if ! sudo -u "$KIOSK_USER" test -x "$ANKI_SYNC_DIR/bin/pip"; then
        sudo -u "$KIOSK_USER" "$ANKI_SYNC_DIR/bin/python" -m ensurepip --upgrade
    fi

    echo "Installing the 'anki' package (this can take a minute)..."
    if ! sudo -u "$KIOSK_USER" "$ANKI_SYNC_DIR/bin/pip" install --upgrade pip anki; then
        log_error "pip install anki failed"
        return 1
    fi

    echo
    echo "Set up the first sync account (used by Anki clients to log in):"
    local username password port
    username=$(anki_sync_ask_username "kiosk")
    password=$(anki_sync_ask_password "$username")
    port=$(ask_integer "Port to listen on" "8080" 1024 65535)

    sudo mkdir -p "$ANKI_SYNC_DIR/data"
    sudo chown "$KIOSK_USER:$KIOSK_USER" "$ANKI_SYNC_DIR/data"

    anki_sync_write_base_env "$port"
    anki_sync_append_user_line 1 "$username" "$password"
    anki_sync_write_unit_file

    if enable_and_start_units kiosk-anki-sync; then
        sudo ufw allow "${port}/tcp" comment 'Anki Sync Server' 2>/dev/null || true
        log_success "Anki Sync Server installed: http://$(get_ip_address):${port}/"
        echo "  In Anki desktop: Preferences > Network > Self-hosted sync server"
        echo "  Log in with: $username"
    else
        log_error "Installed but failed to start - check: sudo journalctl -u kiosk-anki-sync -n 50"
        return 1
    fi
}

action_anki_sync_add_user() {
    echo
    local next_index
    next_index=$(( $(anki_sync_user_count) + 1 ))

    local username password
    username=$(anki_sync_ask_username "user${next_index}")
    password=$(anki_sync_ask_password "$username")

    anki_sync_append_user_line "$next_index" "$username" "$password"
    sudo systemctl restart kiosk-anki-sync
    log_success "Added sync user: $username"
}

action_anki_sync_reconfigure_port() {
    echo
    local current_port
    current_port=$(anki_sync_port)
    local port
    port=$(ask_integer "Port to listen on" "$current_port" 1024 65535)

    if [[ "$port" == "$current_port" ]]; then
        echo "No change"
        return
    fi

    sudo sed -i "s/^SYNC_PORT=.*/SYNC_PORT=${port}/" "$(anki_sync_env_file)"
    sudo systemctl restart kiosk-anki-sync
    sudo ufw allow "${port}/tcp" comment 'Anki Sync Server' 2>/dev/null || true
    log_success "Anki Sync Server now listening on port ${port}"
}

action_anki_sync_restart() {
    sudo systemctl restart kiosk-anki-sync
    sleep 1
    if anki_sync_is_active; then
        log_success "Anki Sync Server restarted"
    else
        log_error "Anki Sync Server failed to restart - check: sudo journalctl -u kiosk-anki-sync -n 50"
        return 1
    fi
}

action_anki_sync_uninstall() {
    echo
    ask_yes_no "Uninstall the Anki Sync Server? This deletes the synced collection data on this kiosk." "n" || { echo "Cancelled"; return; }
    anki_sync_do_uninstall
}

# The actual removal, no prompt - shared with Complete Uninstall so that
# operation doesn't need to re-implement teardown a second time.
anki_sync_do_uninstall() {
    sudo systemctl stop kiosk-anki-sync 2>/dev/null || true
    sudo systemctl disable kiosk-anki-sync 2>/dev/null || true
    sudo rm -f "$SYSTEMD_DIR/kiosk-anki-sync.service"
    sudo systemctl daemon-reload 2>/dev/null || true
    sudo rm -rf "$ANKI_SYNC_ENV_DIR" "$ANKI_SYNC_DIR"
    log_success "Anki Sync Server removed"
}