#!/bin/bash
# I used this in a context where gettext couldn't be used.
# I tested it on Bash version 3 and 4 on the following systems:
#   MacOS, Debian, MSYS (Mingw), cygwin.

# Available languages
languages=(EN FR)

# Strings
msgExample=(
    "This is an example message."
    "Ceci est un message exemple..."
)

msgExampleArgs=(
    "Please refer to the document #{0} for details on this problem."
    "Veuillez vous référer au document n°{0} pour des détails concernant ce problème."
)

# =========
# FUNCTIONS

## getLanguage()
# Usage: getLanguage
# Description:
#   Function that attempts to return the uppercase two (or three)
#   letters language code corresponding to the current system locale. If it
#   fails, it will return its default value (EN).
function getLanguage() {
    local defaultLang="EN"

    local lang=""
    local systemName="$(uname)"

    case $(uname) in
        Darwin)
            # MacOS
            lang="$(defaults read -g AppleLocale \
                        | cut -d '_' -f1 \
                        | tr '[:lower:]' '[:upper:]')"
            ;;
        *)
            lang=$(echo "$LANG" | cut -d '_' -f1 | tr '[:lower:]' '[:upper:]')
            ;;
    esac

    # Fallback to our default language if we were unable to get a langauge
    if [[ -z "$lang" ]]; then
        lang="$defaultLang"
    fi

    echo "$lang"
}

## getString()
# Usage: getString STRING_NAME [ARGS...]
# Description:
#   Returns the string corresponding to the given STRING_NAME. That name should
#   match the name of the shell variable that contains the strings array.
#
#   If args are given, they will be used as substitutes to the {x} values in the
#   string. Eg: first arg will replace the {0} value, second one the {1}, etc.
#
#   The previous declaration of a 'languages' array is expected. It should
#   contain the uppercase two (or three) letters language identifier (such as
#   FR). The strings arrays should be organized using that same order for the
#   translations of a string.
function getString() {
    # Declare the lang index according to the user language, if it was not
    # done yet.
    if [[ -z "${langIndex+x}" ]]; then
        # Find out user's language and use it to set the strings to be used
        # for the runtime of this script.
        local usrLang="$(getLanguage)"

        # Now get the index that we are going to use for the strings out of
        # the position of our language in the 'languages' array.
        local currentIndex=0
        langIndex=0
        for lang in "${languages[@]}"; do
            if [[ "$usrLang" = "$lang" ]]; then
                langIndex=$currentIndex
                break
            fi
            currentIndex=$(($currentIndex + 1))
        done
    fi

    # Now get the string according to the index we set to be used.
    msgName="${1}[$langIndex]"
    str="${!msgName}"
    shift

    # Substitute its placeholders using our arguments.
    paramNo=0
    while [[ $# -gt 0 ]]; do
        str="$(echo "$str" | sed "s/{${paramNo}}/${1}/g")"
        paramNo=$(($paramNo + 1))
        shift
    done

    echo "$str"
}

# =======
# EXAMPLE

echo "$(getString msgExample)"
echo "$(getString msgExampleArgs 54671)"