#!/usr/bin/env bash

# Argument parser for bash scripts
#
# Author: Anthony Axenov (Антон Аксенов)
# Version: 1.6
# License: MIT
# Description: https://git.axenov.dev/anthony/shell/src/branch/master/helpers/arg-parser

#purpose    Little helper to check if string matches PCRE
#argument   $1 - some string
#argument   $2 - regex
#exitcode	0 - string valid
#exitcode	1 - string is not valid
grep_match() {
    printf "%s" "$1" | grep -qE "$2" >/dev/null
}

#purpose	Find short argument or its value
#argument	$1 - (string) argument (without leading dashes; only first letter will be processed)
#argument	$2 - (number) is it flag? 1 if is, otherwise 0 or nothing
#argument	$3 - (string) variable to return value into
#                (if not specified then it will be echo'ed in stdout)
#returns    (string) 1 (if $2 == 1), value (if correct and if $2 != 1) or nothing
#usage      To get value into var:      arg v 0 myvar    or    myvalue=$(arg 'v')
#usage      To find flag into var:      arg f 1 myvar    or    flag=$(arg 'f')
#usage      To echo value:              arg v
#usage      To echo 1 if flag exists:   arg f
arg() {
    [ "$1" ] || { echo "Argument name is not specified!" >&2 && exit 1; }
    local arg_name="${1:0:1}" # first character of argument name to find
    local is_flag="$2" || 0   # 1 if we need just find a flag, 0 to get a value
    local var_name="$3" || 0  # variable name to return value into or 0 to echo it in stdout
    local value=              # initialize empty value to check if we found one later
    local arg_found=0         # marker of found argument

    for idx in "${!__RAW_ARGS__[@]}"; do # going through all args
        local arg_search=${__RAW_ARGS__[idx]} # get current argument

        # skip $arg_search if it starts with '--' or letter
        grep_match "$arg_search" "^(\w|--)" && continue

        # clear $arg_search from special and duplicate characters, e.g. 'fas-)dfs' will become 'fasd'
        local arg_chars="$(printf "%s" "$arg_search" \
            | tr -s "[$arg_search]" 2>&1 >/dev/null \
            | tr -d "[:punct:][:blank:]" 2>&1 >/dev/null)"

        # if $arg_name is not one of $arg_chars the skip it
        grep_match "-$arg_name" "^-[$arg_chars]$" || continue
        arg_found=1

        # then return '1'|'0' back into $value if we need flag or next arg value otherwise
        [ "$is_flag" = 1 ] && value=1 || value="${__RAW_ARGS__[idx+1]}"
        break
    done

    [ "$is_flag" = 1 ] && [ -z "$value" ] && value=0;

    # if value we found is empty or looks like another argument then exit with error message
    if [ "$arg_found" = 1 ] && ! grep_match "$value" "^[[:graph:]]+$" || grep_match "$value" "^--?\w+$"; then
        echo "ERROR: Argument '-$arg_name' must have correct value!" >&2 && exit 1
    fi

    # return '$value' back into $var_name (if exists) or echo in stdout
    [ "$var_name" ] && eval "$var_name='$value'" || echo "$value"
}

#purpose	Find long argument or its value
#argument	$1 - argument (without leading dashes)
#argument	$2 - (number) is it flag? 1 if is, otherwise 0 or nothing
#argument	$3 - (string) variable to return value into
#                (if not specified then it will be echo'ed in stdout)
#returns    (string) 1 (if $2 == 1), value (if correct and if $2 != 1) or nothing
#usage      To get value into var:      arg v 0 myvar    or    myvalue=$(arg 'v')
#usage      To find flag into var:      arg f 1 myvar    or    flag=$(arg 'f')
#usage      To echo value:              arg v
#usage      To echo 1 if flag exists:   arg f
argl() {
    [ "$1" ] || { echo "Argument name is not specified!" >&2 && exit 1; }
    local arg_name="$1"      # argument name to find
    local is_flag="$2" || 0  # 1 if we need just find a flag, 0 to get a value
    local var_name="$3" || 0 # variable name to return value into or 0 to echo it in stdout
    local value=             # initialize empty value to check if we found one later
    local arg_found=0        # marker of found argument

    for idx in "${!__RAW_ARGS__[@]}"; do # going through all args
        local arg_search="${__RAW_ARGS__[idx]}" # get current argument

        if [ "$arg_search" = "--$arg_name" ]; then # if current arg begins with two dashes
            # then return '1' back into $value if we need flag or next arg value otherwise
            [ "$is_flag" = 1 ] && value=1 || value="${__RAW_ARGS__[idx+1]}"
            break # stop the loop
        elif grep_match "$arg_search" "^--$arg_name=.+$"; then # check if $arg like '--foo=bar'
            # then return '1' back into $value if we need flag or part from '=' to arg's end as value otherwise
            [ "$is_flag" = 1 ] && value=1 || value="${arg_search#*=}"
            break # stop the loop
        fi
    done

    [ "$is_flag" = 1 ] && [ -z "$value" ] && value=0;

    # if value we found is empty or looks like another argument then exit with error message
    if [ "$arg_found" = 1 ] && ! grep_match "$value" "^[[:graph:]]+$" || grep_match "$value" "^--?\w+$"; then
        echo "ERROR: Argument '--$arg_name' must have correct value!" >&2 && exit 1;
    fi

    # return '$value' back into $var_name (if exists) or echo in stdout
    [ "$var_name" ] && eval "$var_name='$value'" || echo "$value"
}

################################

# This is simple examples which you can play around with.
# 1. uncomment code below
# 2. call thi sscript to see what happens:
#     /args.sh -abcd --flag1 --flag2 -e evalue -f fvalue --arg1=value1 --arg2 value2

# __RAW_ARGS__=("$@")

# arg a 1 flag_a
# echo "Flag -a has value '$flag_a'"
# echo "Flag -a has value '$(arg a 1)'"

# arg b 1 flag_b
# echo "Flag -b has value '$flag_b'"
# echo "Flag -b has value '$(arg b 1)'"

# arg c 1 flag_c
# echo "Flag -c has value '$flag_c'"
# echo "Flag -c has value '$(arg c 1)'"

# arg d 1 flag_d
# echo "Flag -d has value '$flag_d'"
# echo "Flag -d has value '$(arg d 1)'"

# argl flag1 1 flag_1
# echo "Flag --flag1 has value '$flag_1'"
# echo "Flag --flag1 has value '$(argl flag1 1)'"

# argl flag2 1 flag_2
# echo "Flag --flag2 has value '$flag_2'"
# echo "Flag --flag2 has value '$(argl flag2 1)'"

# arg e 0 arg_e
# echo "Arg -e has value '$arg_e'"
# echo "Arg -e has value '$(arg e 0)'"

# arg f 0 arg_f
# echo "Arg -f has value '$arg_f'"
# echo "Arg -f has value '$(arg f 0)'"

# argl arg1 0 arg_1
# echo "Arg --arg1 has value '$arg_1'"
# echo "Arg --arg1 has value '$(argl arg1 0)'"

# argl arg2 0 arg_2
# echo "Arg --arg2 has value '$arg_2'"
# echo "Arg --arg2 has value '$(argl arg2 0)'"