#!/bin/bash

# Originally written by anon, modified

BLUE='\033[34m'
GREEN='\033[32m'
BOLD='\033[1m'
NORMAL='\033[0m'

MARKNAME="@BAKE"
MARK="${MARKNAME} "
MARKSTR="${BLUE}${MARKNAME}${NORMAL}"
 
enable -n echo
 
usage() {
    IFSTR="${GREEN}<input_file>${NORMAL}"
    echo -e "${BOLD}Usage: $0 <input_file>${NORMAL}" >&2
    echo -e "\t$0 runs the value of ${MARKSTR}." >&2
    echo -e "\tThe point of this script is ease to compialation of single source file (toy) programs." >&2
    echo -e "\tThe value of ${MARKSTR} is read from ${IFSTR} in is whatever comes after '${MARK}' until the end of the line." >&2
    echo -e "\tInside the value of ${MARKSTR} all mentions of special placeholders are replaced:" >&2
    echo -e "\t\t${BLUE}\$@${NORMAL} - ${IFSTR}"
    echo -e "\t\t${BLUE}\$*${NORMAL} - ${IFSTR} with the last extension cut off"
    echo -e "\t\t${BLUE}\$+${NORMAL} - All remaining arguments"
}

if [[ $# -lt 1 ]]; then
    usage
    exit 1
fi
 
if [[ $1 == "-h" ]] || [[ $1 == "--help" ]]; then
    usage
    exit 0
fi

run=1
if [[ $1 == "-n" ]] || [[ $1 == "--dry-run" ]]; then
    if [[ $# -lt 2 ]]; then
        usage
        exit 1
    fi
    run=0
    shift 1
fi

input_file=$1
shift 1
 
if [[ ! -f $input_file ]]; then
    echo -e "Input file '$input_file' does not exist." >&2
    exit 1
fi

line=$(grep "$MARK" "$input_file" | head -1)
line=${line//\$@/$input_file}
line=${line//\$\*/${input_file%.*}}
line=${line//\$+/$@}

if [[ -n $line ]]; then
    command="${line#*${MARK}}"
    echo "Exec: $command"
    if [[ $run -eq 1 ]]; then
        echo "Output:"
        eval "$command"
    fi
else
    echo -e "${MARKSTR} is not defined." >&2
fi