#!/usr/bin/env bash
set -e

SHIM_PATH="${RBENV_HOME}/shims"
PROTOTYPE_SHIM_PATH="${SHIM_PATH}/.rbenv-shim"

# Create the shims directory if it doesn't already exist.
mkdir -p "$SHIM_PATH"

# Ensure only one instance of rbenv-rehash is running at a time by
# setting the shell's `noclobber` option and attempting to write to
# the prototype shim file. If the file already exists, print a warning
# to stderr and exit with a non-zero status.
set -o noclobber
{ echo > "$PROTOTYPE_SHIM_PATH"
} 2>/dev/null ||
{ echo "rbenv: cannot rehash: $PROTOTYPE_SHIM_PATH exists"
  exit 1
} >&2
set +o noclobber

# If we were able to obtain a lock, register a trap to clean up the
# prototype shim when the process exits.
trap remove_prototype_shim SIGINT SIGTERM EXIT

remove_prototype_shim() {
  rm -f "$PROTOTYPE_SHIM_PATH"
}

# The prototype shim file is a script that re-execs itself, passing
# its filename and any arguments to `rbenv exec`. This file is
# hard-linked for every binary and then removed. The linking technique
# is fast, uses less disk space than unique files, and also serves as
# a locking mechanism.
create_prototype_shim() {
  cat > "$PROTOTYPE_SHIM_PATH" <<SH
#!/usr/bin/env bash
set -e
exec rbenv exec "\${0##*/}" "\$@"
SH
  chmod +x "$PROTOTYPE_SHIM_PATH"
}

# Make shims by iterating over every filename argument and creating a
# hard link from the prototype shim to a file of the same name in the
# shims directory, if one does not already exist.
make_shims() {
  local glob="$@"

  for file in $glob; do
    local shim="${file##*/}"
    [ -e "$shim" ] || ln -f "$PROTOTYPE_SHIM_PATH" "$shim"
  done
}

# Empty out the shims directory and make it the working directory.
rm -f "$SHIM_PATH"/*
cd "$SHIM_PATH"

# Create the prototype shim, then make shims for all known binaries.
create_prototype_shim
shopt -s nullglob
make_shims ../versions/*/bin/*

# Find and run any plugins that might want to make shims too.
RBENV_REHASH_PLUGINS=(/etc/rbenv.d/rehash/*.bash ${RBENV_HOME}/rbenv.d/rehash/*.bash)
shopt -u nullglob

for script in ${RBENV_REHASH_PLUGINS[@]}; do
  source $script
done