#!/usr/bin/env bash

# Whether to disable tmux/screen DCS escape sequences
: "${OSC777_NO_DCS:=0}"

die() {
    echo "ERROR: $*"
    exit 1
}

usage() {
    if [ $# -gt 0 ]; then
        exec 1>&2
    fi

    cat << EOF
Usage: $0 [options] <title> <message>
Send a notification (title and message) to the host system using the OSC 777
escape sequence:
Options:
  -h, --help    This screen.
  -d, --no-dcs  Disable tmux/screen specific DCS sequences, only use OSC 777
  --            Stop options processing
EOF

    if [ $# -gt 0 ]; then
        echo
        die "$@"
    else
        exit 0
    fi
}

tmux_seq() {
    # shellcheck disable=1003
    printf '\033Ptmux;\033%s\033\\' "$1"
}

screen_seq() {
    # Screen limits the length of string sequences, so we have to break it up.
    # Going by the screen history:
    #   (v4.2.1) Apr 2014 - today: 768 bytes
    #   Aug 2008 - Apr 2014 (v4.2.0): 512 bytes
    #   ??? - Aug 2008 (v4.0.3): 256 bytes
    local limit=768
    # We go 4 bytes under the limit because we're going to insert two bytes
    # before (\eP) and 2 bytes after (\e\) each string.
    printf '%s' "$1" |
        sed -E "s:.{$((limit - 4))}:&\n:g" |
        sed -E -e 's:^:\x1bP:' -e 's:$:\x1b\\:' |
        tr -d '\n'
}

osc777_seq() {
    printf '%s' "$1"
}

print_seq() {
    local seq="$1"

    if [ "${OSC777_NO_DCS}" != 0 ]; then
        # Override TERM to avoid tmux/screen DCS escape logic
        TERM=dummy
    fi

    case ${TERM-} in
        screen*)
            # Since tmux defaults to setting TERM=screen, special case it.
            if [ -n "${TMUX-}" ]; then
                tmux_seq "${seq}"
            else
                screen_seq "${seq}"
            fi
            ;;
        tmux*)
            tmux_seq "${seq}"
            ;;
        *)
            osc777_seq "${seq}"
            ;;
    esac
}

notify() {
    local title=$1
    local message=$2

    # shellcheck disable=1003
    print_seq "$(printf '\033]777;notify;%s;%s\e\\' "${title}" "${message}")"
}

main() {
    set -e

    local args=()
    while [ $# -gt 0 ]; do
        case $1 in
            -h | --help)
                usage
                ;;
            -d | --no-dcs)
                OSC777_NO_DCS=1
                ;;
            --)
                shift
                args+=("$@")
                break
                ;;
            -*)
                usage "Unknown option: $1"
                ;;
            *)
                args+=("$1")
                ;;
        esac
        shift
    done

    if [ "${#args[@]}" -ne 2 ]; then
        usage "Supply exactly two arguments"
    fi

    notify "${args[@]}"
}

main "$@"