#!/bin/bash

NC='\033[0m'
RED='\033[0;31m'
GREEN='\033[0;32m'
YELLOW='\033[0;33m'

msg_info() {
    echo -e "${GREEN}[INFO] $1${NC}"
}

msg_warn() {
    echo -e "${YELLOW}[WARN] $1${NC}"
}

msg_error() {
    echo -e "${RED}[ERROR] $1${NC}"
}

print_help() {
    echo
    echo "tsession - a poor man's session handler for tmux"
    echo
    echo "USAGE:"
    echo "    tsession [ls|list]"
    echo "    tsession a|attach [-m|--dmenu|<session>]"
    echo "    tsession l|load [-d|--detach] {<session> ...}"
    echo "    tsession h|help"
    echo
    echo "where:"
    echo "    ls | list:"
    echo "        list available sessions (default if no argument is"
    echo "        provided)"
    echo "    a | attach:"
    echo "        attach to an existing session (compatible with"
    echo "        'target-session' syntax defined in the TMux manual)."
    echo "        If the -m|--dmenu flag is used sessions can be"
    echo "        selected with dmenu. Defaults to dmenu if no argument"
    echo "        is provided."
    echo "    l | load:"
    echo "        start list of sessions. Terminal attaches to last"
    echo "        sessions provided (use -d|--detach to detach from all"
    echo "        provided sessions)"
    echo "    h | help:"
    echo "        print this help"
    echo
}

COMMAND=${1:-list}
shift

mkdir -p "$TMUX_SESSIONS"
case $COMMAND in
    ls|list)
        ls "$TMUX_SESSIONS" | sed 's|\.tmux$||'
        ;;
    a|attach)
        # Defaults to dmenu prompt.
        arg=${1:-'--dmenu'}
        case $arg in
            -m|--dmenu)
                # Retrieve existing sessions
                sessions=$(tmux ls -F "#S" 2>/dev/null)
                # Choose one with dmenu
                # It seems like the windowid changes between pipe
                # commands; this means that WINDOWID needs to be
                # computed exacly when dmenu is called.
                session=$(echo -e "TERM\nNEW\n$sessions" | WINDOWID=`xdotool getwindowfocus` dmenu -i -l 10 -h 16 -p "Session:" -e $WINDOWID)
                # Attach to selected session
                case $session in
                    "")
                        # Do nothing... command aborted.
                        ;;
                    "TERM")
                        # Open a simple term window without Tmux.
                        bash
                        ;;
                    "NEW")
                        # Create a new tmux session
                        tmux new -s `date +'S%m%d%H%M%S'` -n main 2>$HOME/ciaone
                        ;;
                    *)
                        # Attach to an existing Tmux session
                        # TODO: forcing the shell to be interactive
                        # seems to be the only way to make Base16 colors
                        # work properly when attaching to an existing
                        # session. There might be a better way...
                        bash -ic "tmux attach -t $session"
                        ;;
                    esac
                ;;
            *)
                tmux has-session -t "$arg" && \
                    bash -ic "tmux attach -t $arg" || \
                    bash
                ;;
        esac
        ;;
    l|load)
        if [ -d "$TMUX_SESSIONS" ];
        then
            sessions=()
            attach="true"
            # Collect requested sessions
            while [[ $# -gt 0 ]]
            do
                case $1 in
                    -d|--detach)
                        attach="false"
                        ;;
                    *)
                        sessions+=("$1")
                        ;;
                esac
                shift
            done
            # Tmux digest file path.
            dpath="$TMUX_SESSIONS/.tmux.digests"
            for s in "${sessions[@]}"
            do
                # Tmux session file path.
                spath="$TMUX_SESSIONS/$s.tmux"
                if [ -x "$spath" ]; then 
                    # If a tmux session file exists, check if it is
                    # genuine comparing its digest with a set of
                    # approved digests. If the file is not among the
                    # approved ones, prompt the user for approval;
                    # execute the file otherwise.
                    # Code inspired by:
                    # https://github.com/wincent/wincent/blob/f7c51dfd808ea78ec10d6501eaa28f0a5b4796e9/roles/dotfiles/files/.zsh/functions#L41-L80
                    digest="$(openssl sha512 "$spath")"
                    if ! grep -qs "$digest" "$dpath" ; then
                        cat "$spath"
                        echo
                        read -n 1 -p \
                            "Trust this tmux session file? [y/N] " \
                            reply
                        echo
                        if [[ ! $reply =~ ^[yY]$ ]]; then 
                            msg_error "$spath not trusted"
                            continue
                        fi
                        echo "$digest" >> "$dpath"
                    fi
                    # Execute the TMux config file
                    "$spath" && \
                        last_session=$(awk -F "=" '/^SESSION/{ print $NF }' $spath) ; \
                        last_window=$(awk -F "=" '/^WINDOW/{ print $NF }' $spath)
                else
                    msg_warn "session \"$s\" not found"
                fi
            done
            # Attach to the latest session created.
            if [ "$attach" = "true" ] && [ -z "$TMUX" ]; then
                tmux attach -t "$last_session:$last_window"
            fi
        fi
        ;;
    h|help)
        print_help
        ;;
    *)
        msg_error "$COMMAND: invalid command"
        print_help
        exit 1
        ;;
esac