libtemplate:Refactor

The new version is no longer dependent on the overly-complex config
library. Now we make use of bash environment variables to do template
variable replacement.

Function has also been cleaned up a bit. All variables are now declared
and commented before they are initialized and used.

1 files changed, 40 insertions, 11 deletions

diff --git a/lib/template.sh b/lib/template.sh
index f9fc825..ae1dde5 100644
--- a/lib/template.sh
+++ b/lib/template.sh
@@ -17,12 +17,15 @@
 # along with this program.  If not, see <http://www.gnu.org/licenses/>.
 #
 
-source ${LIBDIR}/config.sh
 
 #
 # Provides *very* basic templating functionality. Interpolates basic jinja
 # variable syntax ( "{{ variable }}" ).
 #
+# Template variables are replaced with matching bash environment variabes. This
+# means that template variables can only contain upper case, lower case,
+# numbers, underscores. All non-conforming variables are ignored.
+#
 # @param src  Path to template file to interpolate
 # @param dest Destination to copy the interpolated template to
 #
@@ -30,17 +33,43 @@ function template {
   local src=${1:-}
   local dest=${2:-}
 
-  local delim=$'\001'
-  local tmp=$(mktemp tmp.template.XXXXXXXX)
+  local _delim    # Regex delimiter (use an uncommon character please)
+  local _tmp      # Path to the tmp copy of the original template file
+  local _oldifs   # Old value of IFS (for changing it back)
+  local _filevars # List of valid variable references found in the template file
+  local _varstr   # Template string calling the variable (eg: {{ varname }})
+  local _varname  # Name of the actual variable (eg: {{ varname }} == varname)
 
-  cp -p ${src} ${tmp}
-  for key in ${!configs[@]}; do
-    sed -i "s${delim}{{ ${key} }}${delim}${configs[$key]}${delim}g" ${tmp}
-  done
+  # Pick a really weird delimiter to avoid possible regex conflict
+  _delim=$'\001'
+
+  # Copy the template to a temp location so we don't work on the original
+  _tmp=$(mktemp tmp.template.XXXXXXXX)
+  cp -p ${src} ${_tmp}
+
+  # Read all unique template variables specified in the file
+  _filevars=("$( grep -o '{{ [_[:alnum:]]\+ }}' ${_tmp} | sort | uniq)")
 
-  # Create parent directory if it doesn't yet exist
-  [[ ! -d $(dirname ${dest}) ]] &&  mkdir -p $(dirname ${dest})
+  _oldifs=${IFS}
+  IFS=$'\n'
+  for _varstr in ${_filevars[@]}; do
+    # Strip '{{ ' and ' }}' from varstr to get variable name
+    _varname="${_varstr:3:-3}"
+
+    # Skip any unset but referenced variables
+    if [ -z "${!_varname}" ]; then
+      printf \
+        "WARN: Template variable '%s' is referenced but is unset.\n" \
+        ${_varname} >&2
+      continue
+    fi
+
+    # If variable is set, then find and replace
+    sed -i "s${_delim}${_varstr}${_delim}${!_varname}${_delim}g" "${_tmp}"
+  done
+  IFS=${_oldifs}
 
-  # Move the modified version into place
-  mv ${tmp} ${dest}
+  # Move the modified version into place, creating any leading dirs if necessary
+  install -D "${_tmp}" "${dest}"
+  rm -f "${_tmp}"
 }