#!/bin/bash
# Author: Alexander Epstein https://github.com/alexanderepstein

base=""
exchangeTo=""
currentVersion="1.11.1"
configuredClient=""

## This function determines which http get tool the system has installed and returns an error if there isnt one
getConfiguredClient()
{
    if  command -v curl &>/dev/null ; then
      configuredClient="curl"
    elif command -v wget &>/dev/null ; then
      configuredClient="wget"
    elif command -v fetch &>/dev/null ; then
      configuredClient="fetch"
    else
      echo "Error: This tool reqires either curl, wget, or fetch to be installed."
      return 1
    fi

}

## Allows to call the users configured client without if statements everywhere
httpGet()
{
  case "$configuredClient" in
    curl) curl -A curl -s "$@";;
    wget) wget -qO- "$@";;
    fetch) fetch -o "...";;
  esac
}

checkValidCurrency()
{
  if [[ $1 != "AUD" && $1 != "BGN" && $1 != "BRL" \
      && $1 != "CAD" && $1 != "CHF" && $1 != "CNY" && $1 != "CZK" && $1 != "DKK" \
      && $1 != "EUR" && $1 != "GBP" && $1 != "HKD" && $1 != "HRK" && $1 != "HUF" \
      && $1 != "IDR" && $1 != "ILS" && $1 != "INR" && $1 != "JPY" && $1 != "KRW" \
      && $1 != "MXN" && $1 != "MYR" && $1 != "NOK" && $1 != "NZD" && $1 != "PHP" \
      && $1 != "PLN" && $1 != "RON" && $1 != "RUB" && $1 != "SEK" && $1 != "SGD" \
    && $1 != "THB" && $1 != "TRY" && $1 != "USD" && $1 != "ZAR" ]];then
    echo "1"
  else
    echo "0"
  fi
}

## Grabs the base currency from the user and validates it with all the possible currency
## types available on the API and guides user through input (doesnt take in arguments)
getBase()
{
  echo -n "What is the base currency: "
  read -r base
  base=$(echo $base | tr /a-z/ /A-Z/)
  if [[ $(checkValidCurrency $base) == "1"  ]];then
    unset base
    echo "Invalid base currency"
    getBase
  fi
}
## Checks base currency from the user and validates it with all the possible currency
## types available on the API (requires argument)
checkBase()
{
  base=$1
  base=$(echo $base | tr /a-z/ /A-Z/)
  if [[ $(checkValidCurrency $base) == "1" ]];then
    unset base
    echo "Invalid base currency"
    exit 1
  fi
}

## Grabs the exchange to currency from the user and validates it with all the possible currency
## types available on the API and guides user through input (doesnt take in arguments)
getExchangeTo()
{
  echo -n "What currency to exchange to: "
  read -r exchangeTo
  exchangeTo=$(echo $exchangeTo | tr /a-z/ /A-Z/)
  if [[ $(checkValidCurrency $exchangeTo) == "1" ]];then
    echo "Invalid exchange currency"
    unset exchangeTo
    getExchangeTo
  fi
}

## Grabs the exchange to currency from the user and validates it with all the possible currency
## types available on the API (requires arguments)
checkExchangeTo()
{
  exchangeTo=$1
  exchangeTo=$(echo $exchangeTo | tr /a-z/ /A-Z/)
  if [[ $(checkValidCurrency $exchangeTo) == "1" ]];then
    echo "Invalid exchange currency"
    unset exchangeTo
    exit 1
  fi
}

## Get the amount that will be exchanged and validate that the user has entered a number (decimals are allowed)
## doesnt take in argument, it guides user through input
getAmount()
{
  echo -n "What is the amount being exchanged: "
  read -r amount
  if [[ ! "$amount" =~ ^[0-9]+(\.[0-9]+)?$ ]]
  then
    echo "The amount has to be a number"
    unset amount
    getAmount
  fi
}

## Get the amount that will be exchanged
## validate that the user has entered a number (decimals are allowed and requires argument)
checkAmount()
{
  amount=$1
  if [[ ! "$amount" =~ ^[0-9]+(\.[0-9]+)?$ ]]
  then
    echo "The amount has to be a number"
    unset amount
    exit 1
  fi
}

checkInternet()
{
  echo -e "GET http://google.com HTTP/1.0\n\n" | nc google.com 80 > /dev/null 2>&1
  if [ $? -eq 0 ]; then
    return 0
  else
    echo "Error: no active internet connection" >&2
    return 1
  fi
}

## Grabs the exchange rate and does the math for converting the currency
convertCurrency()
{
  exchangeRate=$(httpGet "http://api.fixer.io/latest?base=$base&symbols=$exchangeTo" | grep -Eo "[0-9]*[.][0-9]*") > /dev/null
  exchangeAmount=$(echo "$exchangeRate * $amount" | bc  )
  echo
  echo "========================="
  echo "| $base to $exchangeTo"
  echo "| Rate: $exchangeRate"
  echo "| $base: $amount"
  echo "| $exchangeTo: $exchangeAmount"
  echo "========================="
}

update()
{
  # Author: Alexander Epstein https://github.com/alexanderepstein
  # Update utility version 1.2.0
  # To test the tool enter in the defualt values that are in the examples for each variable
  repositoryName="Bash-Snippets" #Name of repostiory to be updated ex. Sandman-Lite
  githubUserName="alexanderepstein" #username that hosts the repostiory ex. alexanderepstein
  nameOfInstallFile="install.sh" # change this if the installer file has a different name be sure to include file extension if there is one
  latestVersion=$(httpGet https://api.github.com/repos/$githubUserName/$repositoryName/tags | grep -Eo '"name":.*?[^\\]",'| head -1 | grep -Eo "[0-9.]+" ) #always grabs the tag without the v option

  if [[ $currentVersion == "" || $repositoryName == "" || $githubUserName == "" || $nameOfInstallFile == "" ]];then
    echo "Error: update utility has not been configured correctly." >&2
    exit 1
  elif [[ $latestVersion == "" ]];then
    echo "Error: no active internet connection" >&2
    exit 1
  else
    if [[ "$latestVersion" != "$currentVersion" ]]; then
      echo "Version $latestVersion available"
      echo -n "Do you wish to update $repositoryName [Y/n]: "
      read -r answer
      if [[ "$answer" == "Y" || "$answer" == "y" ]] ;then
        cd  ~ || { echo 'Update Failed' ; exit 1 ; }
        if [[ -d  ~/$repositoryName ]]; then rm -r -f $repositoryName  ||  { echo "Permissions Error: try running the update as sudo"; exit 1; } ; fi
        git clone "https://github.com/$githubUserName/$repositoryName" || { echo "Couldn't download latest version" ; exit 1; }
        cd $repositoryName ||  { echo 'Update Failed' ; exit 1 ;}
        git checkout "v$latestVersion" 2> /dev/null || git checkout "$latestVersion" 2> /dev/null || echo "Couldn't git checkout to stable release, updating to latest commit."
        chmod a+x install.sh #this might be necessary in your case but wasnt in mine.
        ./$nameOfInstallFile "update" || exit 1
        cd ..
        rm -r -f $repositoryName ||  { echo "Permissions Error: update succesfull but cannot delete temp files located at ~/$repositoryName delete this directory with sudo"; exit 1; }
      else
        exit 1
      fi
    else
      echo "$repositoryName is already the latest version"
    fi
  fi

}


usage()
{
  echo "Currency"
  echo "Description: A realtime currency converter."
  echo "   With no flags it will guide you through the currency exchange"
  echo "Usage: currency or currency [flag] or currency [base] [exchangeTo] [amount]"
  echo "  -u Update Bash-Snippet Tools"
  echo "  -h Show the help"
  echo "  -v Get the tool version"
  echo "Supported Currencies:"
  echo " _______________________"
  echo "| AUD | BGN | BRL | CAD |"
  echo "| CHF | CNY | CZK | DKK |"
  echo "| EUR | GBP | HKD | HRK |"
  echo "| HUF | IDR | ILS | INR |"
  echo "| JPY | KRW | MXN | MYR |"
  echo "| NOK | NZD | PHP | PLN |"
  echo "| RON | RUB | SEK | SGD |"
  echo "| THB | TRY | USD | ZAR |"
  echo " _______________________"
  echo "Examples:"
  echo "  currency EUR USD 12.35"
  echo "  currency"
}

getConfiguredClient || exit 1
checkInternet || exit 1 # check if we have a valid internet connection if this isnt true the rest of the script will not work so stop here

while getopts "uvh" opt; do
  case $opt in
    \?)
      echo "Invalid option: -$OPTARG" >&2
      exit 1
    ;;
    h)
      usage
      exit 0
    ;;
    v)
      echo "Version $currentVersion"
      exit 0
    ;;
    u)
      update
      exit 0
    ;;
    :)
      echo "Option -$OPTARG requires an argument." >&2
      exit 1
    ;;
  esac
done

if [[ $# == 0 ]]; then
  getBase # get base currency
  getExchangeTo # get exchange to currency
  getAmount # get the amount to be converted
  convertCurrency # grab the exhange rate and perform the conversion
  exit 0
elif [[ $# == "1" ]]; then
  if [[ $1 == "update" ]];then
    update
  elif [[ $1 == "help" ]]; then
    usage
  else
    echo "Not a valid argument"
    usage
    exit 1
  fi
elif [[ $# == "2" ]]; then
  echo "Not a valid argument"
  usage
  exit 1
elif [[ $# == "3" ]];then
  checkBase $1
  checkExchangeTo $2
  checkAmount $3
  convertCurrency
  exit 0
fi