Preamble 
 railspg [-h] [-c] [-u] [-e] new <project_name>

This program generates a basic rails project where all generated databases (development, test and production) are
postgres. The outcome is otherwise equivalent to the default 'rails new <project_name>'

      -h: get help
      -c: Create databases. If (1) postgres username and unix/Ubuntu username are identical
          (2) An env variable is set to posgres password, databases may be created.
          By default, the env variable name is POSTGRES_PASSWORD. 
          If the databases are NOT created, run 'rake db:create:all' after program execution.
      -u: change username. The default username is the current unix/Ubuntu username
      -e: set postgres password environment variable name. Useful if the env variable name is other than default

    REQUIREMENTS
       (1) Set up a postgres user with the same name as the current unix/Ununtu login name
               sudo -u postgres createuser -s <unix_ubuntu_username>
               sudo -u postgres psql
               \\password <unix_ubuntu_username>
       (2) Set env variable. You may need to execute the following prior to running the program. 
              POSTGRES_PASSWORD='my_postgres_password'
              export POSTGRES_PASSWORD'
          Or, include the following line in your .bashrc file
              export POSTGRES_PASSWORD='my_postgres_password'

    EXAMPLE USAGE
      railspg new <project_name>
      ralspg -c new <project_name> 
      railspg -cu <username> -e PG_PASSWORD new <project name>
END
}

#!/bin/bash
##declarations
#declare all_args="${@}"
declare whoami="$(whoami)"
declare myusername=${whoami}
declare -i  createdb=0
declare grep_project_name=""
#declare script_name=${0##*/}
declare password_env_var_string="POSTGRES_PASSWORD"

## Functions

is_rails_installed () {
   declare railsv="$(rails -v)"
   declare railsgrep="$(echo ${railsv} | grep -c '^Rails')"

   if [[ ${railsgrep} -eq 1 ]]; then
       echo "${railsv} detected. OK"
   else
       echo "No version of Rails detected. Check your system with 'rails -v'"
       exit 1
   fi
}

postgres_gem_installed? () {
   declare pg="$(gem list | grep -c '^pg')"

   if [[ ${pg} -eq 0 ]]; then
       echo "Postgres gem not detected Make sure that 'gem install pg' succeeds before continuing"
       exit 1
   fi
}

user_choice () {
    read -p  "Databases will not be created. Do you wish to continue? [Y/n]?" userchoice
      if [[ $userchoice == "Y" ||  $userchoice == "Yes" ]]; then
        echo "OK"
      else
        echo "Exiting at user request"
        exit 1
      fi
  }

credentials_check () {
  if [[  ${myusername} != ${whoami} ]]; then
    echo "username and login name do not correspond"
    user_choice
    createdb=0
  else
   echo "Username OK"
  fi
}

env_variable_check () {
  if [[  $(env  | grep -c ^${1}=) -ne 0 ]]; then
    echo "Env variable OK"
  else
    echo "Password 'env' variable not properly set"
    user_choice
    createdb=0
  fi
}

verify_postgres_login () {
    declare md5_encrypted_psql_credentials=$(echo -n ${psql_password}${myusername} |  md5sum)
    declare psql_login_status="$(psql  -d postgres -c 'select * from pg_shadow' |cut -d \| -f 7 | grep -c  ${md5_encrypted_psql_credentials})"
  if [[ ${psql_login_status} -eq 1 ]]; then
    echo "login psql succesful"
  else
    echo "cannot login to psql. Check username and password"
    user_choice
    createdb=0
  fi
}

usage () {
cat <<END

 railspg [-h] [-c] [-u] [-e] new <project_name>

This program generates a basic rails project where all generated databases (development, test and production) are
postgres. The outcome is otherwise equivalent to the default 'rails new <project_name>'

      -h: get help
      -c: Create databases. If (1) postgres username and unix/Ubuntu username are identical
          (2) An env variable is set to posgres password, databases may be created.
          By default, the env variable name is POSTGRES_PASSWORD. 
          If the databases are NOT created, run 'rake db:create:all' after program execution.
      -u: change username. The default username is the current unix/Ubuntu username
      -e: set postgres password environment variable name. Useful if the env variable name is other than default

    REQUIREMENTS
       (1) Set up a postgres user with the same name as the current unix/Ununtu login name
               sudo -u postgres createuser -s <unix_ubuntu_username>
               sudo -u postgres psql
               \\password <unix_ubuntu_username>
       (2) Set env variable. You may need to execute the following prior to running the program. 
              POSTGRES_PASSWORD='my_postgres_password'
              export POSTGRES_PASSWORD'
          Or, include the following line in your .bashrc file
              export POSTGRES_PASSWORD='my_postgres_password'

    EXAMPLE USAGE
      railspg new <project_name>
      ralspg -c new <project_name> 
      railspg -cu <username> -e PG_PASSWORD new <project name>
END
}

postgres_help () {
   echo "hello from em"
}

## Set options
while getopts ":chhhu:e:" opt; do
 case $opt in
    c)
     createdb=1
      ;;
    h)
     usage | less
     exit 1
      ;;
    hh)
     postgres_help
     exit 1
      ;;
    u)
     myusername=${OPTARG}
      ;;
    e)
      password_env_var_string=${OPTARG}
      ;;
  esac
done

shift $(( ${OPTIND} - 1 ))

##  Declarations
declare myrails="${2}"
if [[ ${myrails} ]];then
  declare grep_project_name="$(ls | grep -c ^${myrails}$)"
fi
declare compulsoryargs="${@}"
declare devexists="$(psql -lqt | cut -d \| -f 1 | grep -w ${myrails}_development | wc -l)"
declare prodexists="$(psql -lqt | cut -d \| -f 1 | grep -w ${myrails}_production | wc -l)"
declare testexists="$(psql -lqt | cut -d \| -f 1 | grep -w ${myrails}_test | wc -l)"
declare psql_password=$(env | grep $password_env_var_string  | cut -d \= -f 2)

## Checks and tests
# Does the app name already exist?
if [[ ${grep_project_name} -ne 0 ]]; then
  echo "The project name ${2} already exists"
  exit 1
fi
# is the first compulsory argument 'new'?
if [[ $1 != new ]]; then
  echo "The first compulsory argument must be the keyword 'new'"
  exit 1
fi
# are there exactly two compulsory arguments? 
if [[ $# != 2 ]]; then
  echo " Argument error. The program requires exactly two compulsory arguments, ${#} detected"
  exit 1
fi

is_rails_installed 
postgres_gem_installed? 

# Should the databases be created?
if [[  ${createdb} == 1  ]]; then
   credentials_check
   env_variable_check ${password_env_var_string}
   verify_postgres_login
fi
# Do databases already exist?
if [[ ${devexists} == 1 || ${prodexists} == 1 || ${testexists} == 1 ]]; then
  if [[ ${devexists} == 1 ]]; then
    echo "Database ${myrails}_development already exists" 
  fi
  if [[ ${testexists} == 1 ]]; then
    echo "Database ${myrails}_test already exists" 
  fi
  if [[ ${prodexists} == 1 ]]; then
    echo "Database ${myrails}_production already exists" 
  fi
echo "railspg -h for help"
exit 1
fi

## Program code begins here
set -x
rails new ${myrails} -d postgresql && cd ${myrails}  && bundle install
cd config && sed -i '/pool:/a \ \ timeout:\ 5000' database.yml

sed -i "/${myrails}_development/a \ \ username: ${myusername}\n\ \ \
password: <%= ENV[\'${password_env_var_string}\'] %>\n\ \ \
host: localhost\n\ \ port: 5432" database.yml

sed -i "/${myrails}_test/a \ \ username: ${myusername}\n\ \ \
password: <%= ENV[\'${password_env_var_string}\'] %>\n\ \ \
host: localhost\n\ \ port: 5432" database.yml

sed -i "/${myrails}_production/{n;N;d}" database.yml
sed -i "/${myrails}_production/a \ \ username: ${myusername}\n\ \ \
password: <%= ENV[\'${password_env_var_string}\'] %>" database.yml
cd ..
set +x

# create the databases
if [[  $createdb -eq 1 ]]; then
    rake db:create:all
    echo "Databases created OK"
fi