#!/bin/bash

#####################################################################
# Substitutes the given environment variables in the given files.
# Parameters:
# $1: Comma-delimited list of file paths
# $2: Comma-delimited list of environment variables
# $3: File path to index.html (optional)
#####################################################################

echo 'Substituting environment variables...'

# The first parameter is a comma-delimited list of paths to files which should be substituted
if [[ -z $1 ]]; then
  echo 'ERROR: No target files given.'
  exit 1
fi

# The second parameter is a comma-delimited list of environment variable names
if [[ -z $2 ]]; then
  echo 'ERROR: No environment variables given.'
  exit 1
fi

# Add trailing slash to $BASE_HREF if needed
if [[ "$2" == *"BASE_HREF"* ]]; then
  length=${#BASE_HREF}
  last_char=${BASE_HREF:length-1:1}
  [[ $last_char != "/" ]] && BASE_HREF="$BASE_HREF/"; :
fi

# Convert "VAR1,VAR2,VAR3,..." to "\$VAR1 \$VAR2 \$VAR3 ..."
env_list="\\\$${2//,/ \\\$}"  # "\" and "$" are escaped as "\\" and "\$"
for file_path in ${1//,/ }
do
  echo "replacing $env_list in $file_path"

  # Replace strings in the given file(s) in env_list
  envsubst "$env_list" < "$file_path" > "$file_path".tmp && mv "$file_path".tmp "$file_path"

  echo '...'
done

echo 'Finished substituting environment variables.'
for env_var in ${2//,/ }
do
  echo "$env_var = ${!env_var}"
done

# The third parameter is the path to the index.html file
# Rewrite base href in index.html.
# Use @ as a sed delimiter because $BASE_HREF will contain a / character
if [[ -z $3 ]]; then
  # Execute all other commands with parameters
  exit 0
else
  #  Wait a second in case envsubst needs more time
  sleep 1
  sed -i -e 's@<base href\=\"\/\">@<base href\=\"'"$BASE_HREF"'\">@' "$3"

  # Execute all other commands with parameters
  exec "${@:4}"
fi