#!/usr/bin/env bash

set -o pipefail

# tmux requires unrecognized OSC sequences to be wrapped with DCS tmux;
# <sequence> ST, and for all ESCs in <sequence> to be replaced with ESC ESC. It
# only accepts ESC backslash for ST.
function print_osc() {
    if [[ $TERM == screen* || $TERM == tmux* ]] ; then
        printf "\033Ptmux;\033\033]"
    else
        printf "\033]"
    fi
}

# More of the tmux workaround described above.
function print_st() {
    if [[ $TERM == screen* || $TERM == tmux* ]] ; then
        printf "\a\033\\"
    else
        printf "\a"
    fi
}

function get_b64_version() {
    if [[ -z "${BASE64_VERSION+x}" ]]; then
        BASE64_VERSION=$(base64 --version 2>&1)
        export BASE64_VERSION
    fi
}

function b64_encode() {
    get_b64_version
    if [[ $BASE64_VERSION =~ GNU ]]; then
        # Disable line wrap
        base64 -w0
    else
        base64
    fi
}

function b64_decode() {
    get_b64_version
    if [[ $BASE64_VERSION =~ fourmilab ]]; then
        BASE64_ARG=-d
    elif [[ $BASE64_VERSION =~ GNU ]]; then
        BASE64_ARG=-di
    else
        BASE64_ARG=-D
    fi
    base64 $BASE64_ARG
}

function error() {
    errcho "ERROR: $*"
}

function errcho() {
    echo "$@" >&2
}

function show_help() {
    errcho
    errcho "Usage: it2profile -s profile_name"
    errcho "       it2profile -g"
    errcho
    errcho "Change iTerm2 session profile on the fly"
    errcho
    errcho "Options:"
    errcho
    errcho "    -s      Set current iTerm2 session profile to specified profile name"
    errcho "                empty string refers to profile marked as Default"
    errcho "    -g      Get current iTerm2 session profile name"
    errcho "    -r      Reset to the session initial profile"
    errcho
}

function check_dependency() {
    if ! (builtin command -V "$1" >/dev/null 2>&1); then
        error "missing dependency: can't find $1"
        exit 1
    fi
}

# get_profile / set_profile
#
# These functions uses POSIX standard synonym for the controlling terminal
# associated with the current process group - /dev/tty. It is useful for programs 
# that wish to be sure of writing or reading data from the terminal 
# no matter how STDIN/STDOUT/STDERR has been redirected.
# 
# get_profile uses iTerm2 Session Context variable "profileName" to 
# get currently active profile name.
#
function get_profile() {
    trap 'cleanup' EXIT
    stty -echo < /dev/tty
    exec 9<> /dev/tty
    print_osc >&9
    printf "1337;ReportVariable=cHJvZmlsZU5hbWU=" >&9
    print_st >&9
    read -r -t 5 -d $'\a' iterm_response <&9
    exec 9>&-
    stty echo < /dev/tty
    [[ "$iterm_response" =~ ReportVariable= ]] || {
        error "Failed to read response from iTerm2"
        exit 2
    }
    echo "$(b64_decode <<< ${iterm_response#*=})"
}

function cleanup() {
    stty echo < /dev/tty
}

function set_profile() {
    exec 9> /dev/tty
    print_osc >&9
    printf '1337;SetProfile=%s' "$1" >&9
    print_st >&9
    exec 9>&-
}

# Show help if no arguments
if [ $# -eq 0 ]; then
    show_help
    exit
fi

check_dependency stty
check_dependency base64

# Process command line arguments
case "$1" in
    -h|--h|--help)
        show_help
        exit
        ;;
    -s|--s|--set)
        [[ $# -eq 2 ]] || {
            error "-s option requires exactly 1 argument - profile name"
            show_help
            exit 1
        }
        set_profile "$2"
        ;;
    -g|--g|--get)
        [[ $# -eq 1 ]] || {
            error "-g option does not accept any argument"
            show_help
            exit 1
        }
        get_profile
        ;;
    -r|--r|--reset)
        [[ $# -eq 1 ]] || {
            error "-r option does not accept any argument"
            show_help
            exit 1
        }
        set_profile "${ITERM_PROFILE:-}"
        ;;
    *)
        error "Unknown option: $1"
        show_help
        exit 1
        ;;
esac

exit 0