#!/usr/bin/env bash

# Max length of the OSC 52 sequence.
: "${OSC52_MAX_SEQUENCE:=100000}"
# Whether to disable tmux/screen DCS escape sequences
: "${OSC52_NO_DCS:=0}"

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

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

    cat << EOF
Usage: $0 [options] [string]
Send an arbitrary string to the terminal clipboard using the OSC 52 escape
sequence as specified in xterm:
  https://invisible-island.net/xterm/ctlseqs/ctlseqs.html#h3-Operating-System-Commands
  Section "Operating System Commands", Ps => 52.
The data can either be read from stdin:
  $ echo "hello world" | $0
Or specified on the command line:
  $ $0 "hello world"
Options:
  -h, --help    This screen.
  -d, --no-dcs  Disable tmux/screen specific DCS sequences, only use OSC 52
  -f, --force   Ignore max byte limit (${OSC52_MAX_SEQUENCE})
  --            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'
}

osc52_seq() {
    printf '%s' "$1"
}

print_seq() {
    local seq="$1"

    if [ "${OSC52_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 "${seq}"
            ;;
        *)
            osc52_seq "${seq}"
            ;;
    esac
}

b64enc() {
    base64 | tr -d '\n'
}

copy() {
    local str
    if [ $# -eq 0 ]; then
        str="$(b64enc)"
    else
        str="$(printf '%s' "$1" | b64enc)"
    fi

    if [ "${OSC52_MAX_SEQUENCE}" -gt 0 ]; then
        local len=${#str}
        if [ "${len}" -gt "${OSC52_MAX_SEQUENCE}" ]; then
            die "selection too long to send to terminal:" \
                "${OSC52_MAX_SEQUENCE} limit, ${len} attempted"
        fi
    fi

    print_seq "$(printf '\033]52;c;%s\a' "${str}")"
}

main() {
    set -e

    local args=()
    while [ $# -gt 0 ]; do
        case $1 in
            -h | --help)
                usage
                ;;
            -f | --force)
                OSC52_MAX_SEQUENCE=0
                ;;
            -d | --no-dcs)
                OSC52_NO_DCS=1
                ;;
            --)
                shift
                args+=("$@")
                break
                ;;
            -*)
                usage "Unknown option: $1"
                ;;
            *)
                args+=("$1")
                ;;
        esac
        shift
    done

    if [ "${#args[@]}" -gt 1 ]; then
        usage "Only supply one argument"
    fi

    copy "${args[@]}"
}

main "$@"