#!/usr/bin/env bash

usage() {
    cat <<EOS >&2
    $(help_synopsis "${BASE_SOURCE[0]}" "[options] <command> <commandoptions>")

    --conf=<path>           Path for alternative nix-script.rc file. Default: ~/.nix-script.rc
    -l | --list-commands    List all available commands
    -v                      Be verbose
    -d                      Debugging output (enables -v)
    -h                      Show this help and exit

$(help_rcvars                                                       \
"RC_CONFIG  - Path of your system configuration (git) directory"    \
"RC_NIXPKGS - Path of your nixpkgs clone"
)

$(help_end)
EOS
}

RC=~/.nix-script.rc
LIST_COMMANDS=0
VERBOSE=0

source $(dirname ${BASH_SOURCE[0]})/nix-utils.sh

SHIFT_ARGS=0

#
# Increase the SHIFT_ARGS variable
#
shift_one_more() {
    SHIFT_ARGS=$(( SHIFT_ARGS + 1 ))
}

#
# Shift N times the arguments, so:
#
#  shift_n 5 a b c d e f
#
# will print "f"
#
shift_n() {
    for n in `seq 0 $1`; do shift; done
    echo $*
}

#
# Parse the arguments for this script
#
for cmd
do
    case $cmd in
    --conf=*)
        RC=$(echo $cmd | sed 's,^--conf\=,,')
        dbg "RC = $RC"
        [[ ! -e $RC ]] && stderr "RC file '$RC' does not exist" && exit 1
        shift_one_more
        ;;

    "--list-commands" )
        LIST_COMMANDS=1
        shift_one_more
        ;;

    "-l" )
        LIST_COMMANDS=1
        shift_one_more
        ;;

    "-v" )
        export VERBOSE=1
        stdout "Verbose now"
        shift_one_more
        ;;

    "-d")
        export VERBOSE=1
        export DEBUG=1
        stdout "Debugging enabled. Implicitely turned on verbosity"
        shift_one_more
        ;;

    "-h" )
        usage
        exit 1
        ;;

    * )
        if [ ! -n $(script_for $cmd) ]
        then
            stderr "Unknown flag / command '$cmd'"
            exit 1
        else
            if [ -z "$COMMAND" ]
            then
                stdout "Found command: '$cmd'"
                COMMAND=$cmd
                shift_one_more
            fi
            break
        fi
    esac
done

if [[ ! -f "$RC" ]]
then
    dbg "No configuration file, setting up (empty) default values"

    RC_CONFIG=""
    RC_NIXPKGS=""
    RC_SWITCH_DEFAULT_TAG_FLAGS=""
    RC_SWITCH_DEFAULT_TAG_FLAGS_NIXPKGS=""
else
    dbg "Configuration file found. Sourcing: '$RC'"
    source $RC
fi

dbg "RC_CONFIG = '$RC_CONFIG'"
dbg "RC_NIXPKGS = '$RC_NIXPKGS'"

if [ $LIST_COMMANDS -eq 1 ]
then
    dbg "Listing commands"
    caller_util_list_subcommands_for "nix-script"
    exit 0
fi

[ -z "$COMMAND" ] && stderr "No command given" && exit 1

dbg "Searching for script for '$COMMAND'"
SCRIPT=$(script_for $COMMAND)
dbg "Script is: $SCRIPT"

#
# Error checking whether the script is available and executable.
#
[ ! -f $SCRIPT ]   && stderr "Not available: $COMMAND -> $SCRIPT" && exit 1
[[ ! -x $SCRIPT ]] && stderr "Not executeable: $SCRIPT"           && exit 1

dbg "Parsing args for '$COMMAND'"
SCRIPT_ARGS=$(shift_n $SHIFT_ARGS $*)

#
# execute the script with its arguments
#
stdout "Calling: '$SCRIPT $SCRIPT_ARGS'"
RC=$RC RC_CONFIG=$RC_CONFIG RC_NIXPKGS=$RC_NIXPKGS exec bash $SCRIPT $SCRIPT_ARGS