#!/bin/bash

set -e

SCRIPT_URL="https://git.zakscode.com/ztimson/fallback-ap/raw/branch/master/fallback-ap.sh"
INSTALL_PATH="/usr/local/bin/fallback-ap"

if [ "$EUID" -ne 0 ]; then
    echo "This installer needs to run as root, e.g.:"
    echo "  curl -sL https://git.zakscode.com/ztimson/fallback-ap/raw/branch/master/install.sh | sudo bash"
    exit 1
fi

# Ask a question; Enter accepts the default.
prompt() {
    local __var="$1" __question="$2" __default="$3" __answer=""
    read -r -p "$__question [$__default]: " __answer < /dev/tty || __answer=""
    printf -v "$__var" '%s' "${__answer:-$__default}"
}

# Like prompt, but "blank" is a legitimate value. Enter accepts the default;
# typing the clear word (e.g. "all" or "none") sets the value to empty.
prompt_blankable() {
    local __var="$1" __question="$2" __default="$3" __clear="$4" __answer=""
    read -r -p "$__question [${__default:-$__clear}]: " __answer < /dev/tty || __answer=""

    case "$__answer" in
        "")          __answer="$__default" ;;
        "$__clear")  __answer="" ;;
    esac

    printf -v "$__var" '%s' "${__answer// /}"
}

# Ask until the answer is one of the allowed choices. Enter accepts the default.
prompt_choice() {
    local __var="$1" __question="$2" __default="$3" __answer="" __opt
    shift 3

    while true; do
        read -r -p "$__question [$__default]: " __answer < /dev/tty || __answer=""
        __answer="${__answer:-$__default}"

        for __opt in "$@"; do
            if [ "$__answer" = "$__opt" ]; then
                printf -v "$__var" '%s' "$__answer"
                return 0
            fi
        done

        echo "  Please enter one of: $*"
    done
}

# Lists wireless interfaces (those with a /sys/class/net/<iface>/wireless dir).
detect_wireless() {
    local dir
    for dir in /sys/class/net/*; do
        if [ -d "$dir/wireless" ]; then
            basename "$dir"
        fi
    done
}

EXISTING_CONFIG="/etc/fallback-ap.conf"

if [ -f "$EXISTING_CONFIG" ]; then
    # shellcheck disable=SC1090
    source "$EXISTING_CONFIG"
fi

DETECTED_WIFI="$(detect_wireless | tr '\n' ' ')"
DETECTED_WIFI="${DETECTED_WIFI% }"

DEFAULT_SSID="${SAVED_SSID:-$(hostname)}"
DEFAULT_PASSWORD="${SAVED_PASSWORD:-abcd1234}"
DEFAULT_IFACE="${SAVED_IFACE:-${DETECTED_WIFI%% *}}"
DEFAULT_IFACE="${DEFAULT_IFACE:-wlan0}"
DEFAULT_CIDR="${SAVED_CIDR:-10.10.10.1/24}"
DEFAULT_DHCP_START_OCTET="${SAVED_DHCP_START_OCTET:-100}"
DEFAULT_DHCP_END_OCTET="${SAVED_DHCP_END_OCTET:-250}"
DEFAULT_MONITOR_IFACE="${SAVED_MONITOR_IFACE-}"
DEFAULT_IGNORE_IFACE="${SAVED_IGNORE_IFACE-}"
DEFAULT_CHECK_MODE="${SAVED_CHECK_MODE:-link}"
DEFAULT_CHECK_TARGETS="${SAVED_CHECK_TARGETS:-1.1.1.1 8.8.8.8}"

# --- Access point ----------------------------------------------------------------------------------------------------

[ -z "${FALLBACK_AP_SSID:-}" ]              && prompt FALLBACK_AP_SSID "Access point SSID" "$DEFAULT_SSID"
[ -z "${FALLBACK_AP_PASSWORD:-}" ]          && prompt FALLBACK_AP_PASSWORD "Access point passphrase" "$DEFAULT_PASSWORD"

if [ -z "${FALLBACK_AP_IFACE:-}" ]; then
    if [ -n "$DETECTED_WIFI" ]; then
        echo "Detected Wi-Fi interfaces: $DETECTED_WIFI"
    fi
    prompt FALLBACK_AP_IFACE "Interface to create the access point on" "$DEFAULT_IFACE"
fi

[ -z "${FALLBACK_AP_CIDR:-}" ]              && prompt FALLBACK_AP_CIDR "Access point subnet (CIDR)" "$DEFAULT_CIDR"
[ -z "${FALLBACK_AP_DHCP_START_OCTET:-}" ]  && prompt FALLBACK_AP_DHCP_START_OCTET "DHCP range start (last octet)" "$DEFAULT_DHCP_START_OCTET"
[ -z "${FALLBACK_AP_DHCP_END_OCTET:-}" ]    && prompt FALLBACK_AP_DHCP_END_OCTET "DHCP range end   (last octet)" "$DEFAULT_DHCP_END_OCTET"

# --- Connectivity monitoring -----------------------------------------------------------------------------------------
#
# The AP only starts when none of the monitored interfaces are online, and it
# is only ever created on the interface chosen above.
#
# These use "unset" (not "empty") to decide whether to ask, because an empty
# FALLBACK_AP_MONITOR_IFACE / FALLBACK_AP_IGNORE_IFACE is a valid answer
# meaning "all real interfaces" / "ignore nothing".

if [ -z "${FALLBACK_AP_MONITOR_IFACE+x}" ]; then
    echo
    echo "Which interfaces should count as 'online'? Enter a comma-separated list"
    echo "(e.g. eth0,wlan0), or 'all' for every real interface. Virtual interfaces"
    echo "(docker, veth, bridges, VPNs) are skipped automatically."
    prompt_blankable FALLBACK_AP_MONITOR_IFACE "Interfaces to monitor" "$DEFAULT_MONITOR_IFACE" "all"
fi

if [ -z "$FALLBACK_AP_MONITOR_IFACE" ] && [ -z "${FALLBACK_AP_IGNORE_IFACE+x}" ]; then
    echo
    echo "Any physical interfaces to ignore (globs allowed, e.g. enx*,usb0)?"
    prompt_blankable FALLBACK_AP_IGNORE_IFACE "Interfaces to ignore" "$DEFAULT_IGNORE_IFACE" "none"
fi

if [ -z "${FALLBACK_AP_CHECK_MODE:-}" ]; then
    echo
    echo "How should 'online' be determined?"
    echo "  link     - the interface is connected (an upstream outage keeps the AP off)"
    echo "  internet - the interface is connected AND can ping out"
    prompt_choice FALLBACK_AP_CHECK_MODE "Check mode" "$DEFAULT_CHECK_MODE" link internet
fi

if [ "$FALLBACK_AP_CHECK_MODE" = "internet" ] && [ -z "${FALLBACK_AP_CHECK_TARGETS:-}" ]; then
    prompt FALLBACK_AP_CHECK_TARGETS "Hosts to ping (space-separated)" "$DEFAULT_CHECK_TARGETS"
fi

export FALLBACK_AP_SSID FALLBACK_AP_PASSWORD FALLBACK_AP_IFACE FALLBACK_AP_CIDR FALLBACK_AP_DHCP_START_OCTET FALLBACK_AP_DHCP_END_OCTET
export FALLBACK_AP_CHECK_MODE
[ -n "${FALLBACK_AP_MONITOR_IFACE+x}" ] && export FALLBACK_AP_MONITOR_IFACE
[ -n "${FALLBACK_AP_IGNORE_IFACE+x}" ]  && export FALLBACK_AP_IGNORE_IFACE
[ -n "${FALLBACK_AP_CHECK_TARGETS+x}" ] && export FALLBACK_AP_CHECK_TARGETS

echo
echo "Downloading fallback-ap..."
curl -fsSL "$SCRIPT_URL" -o "$INSTALL_PATH"
chmod +x "$INSTALL_PATH"
echo "Running installer..."
"$INSTALL_PATH" install