Uncompress files, with autodetection of algorithm

Hi Everyone, this is my first bash script ever. I would really appreciate it if you could provide me with some comments and insights regarding correct function use, logic implementation, and a lead to how to implement the recursive functionality described in the script's body. Thanks a lot!

    #!/bin/bash
    #
    # The following is a script designed to unpack 4 different compression types.
    # 
    # Known compression type files are unpacked, otherwise, the script ignores them.
    #
    # The script accepts a file or a list of files, 2 flags which are -v (for verbose) and -r ( for recursive but currently not functional).
    #
    # The execution syntax is: unpack [-v] [-r] file [file...]
    #
    # !!!!! Didn't come up with a way to isolate the functionality of -r without code duplication.!!!!!!!!!!!!!!!!
    
    
    decomp_files=0      # Counts decompressed files.
    failed_decomp=0     # Counts filed decompression attempts.
    is_verbose=false    # States if -v was used (true if used).
    is_unpackable=false # States if the can be decompressed.
    
# The function is responsible for detecting if the parameter provided to the script is a file or not.
# If it's a file, it isolates the type of compression and checks if the -v option is set.
    function detect_file_type() {
        
        for file in $@
        do
            if [ -f "$file" ]
            then
                # print & isolate compression type
                comp_type=`file $file | awk '{print $2}'` 
                decompress $file $comp_type
                
                if ( $is_verbose && ! $is_unpackable) 
                then
                    printf "Ignoring ${file}\n"
                elif ( $is_verbose && $is_unpackable )
                then
                    printf "Unpacking ${file}\n"
                fi
            fi
        done
        
        #TOOO: Add logical functionality to: "if file is directory -> cd inside -> repeat".
        
        printf "Decompressed $decomp_files archive(s)\n"
    }
     
# The function decompresses the file with the right binary after its identification.
# Invoked by the detect_file_type function.
    function decompress () {
        case $comp_type in
        
            "gzip")
                gzip --decompress $file
                ((decomp_files++))
                is_unpackable=true
                ;;
            "bzip2")
                bunzip2 --decompress $file
                ((decomp_files++))
                is_unpackable=true
                ;;
            "Zip")
                unzip $file
                ((decomp_files++))
                is_unpackable=true
                ;;
            "compress'd")
                uncompress $file
                ((decomp_files++))
                is_unpackable=true
                ;;
            *)
                ((failed_decomp++))
                is_unpackable=false
                ;;
        esac
    }
    
# This is the first function to be executed.
# The function checks for the optional flags and assigns the corresponding variables accordingly.
    function main () {
        # Check if the script was executed with parameters.
        if [[ -z "${@}" ]]
        then
            printf "Command structure: unpack [-r] [-v] file [file...]\n"
            exit 1
        fi
        
        if [ "$1" = "-v" ] || [ "$2" = "-v" ]
        then
            is_verbose=true
        fi
    
        if [ "$1" = "-r" ] || [ "$2" = "-r" ]
        then
            is_recursive=true
        fi 
        
        detect_file_type $@
    }
    
    main $@