[WIP] Docker Templater

script/docker-templater.sh

@@ -0,0 +1,122 @@
+#!/usr/bin/env bash
+# Export Variables so they can be picked up by envsubst
+set -ae
+TEMPLATE_SRC=$1;
+DOCKER_DATA=$2;
+
+NETWORK_NAME="${NETWORK_NAME:-proxy}"
+
+# "NetworkSettings"
+
+# Import Template
+# Required Variables:
+# - TEMPLATE :: The template string which will be read by envsubst
+# Optional Variables:
+# - WRAP_START :: String to prepend in front of the mapped template result
+# - WRAP_END :: String to append to the mapped template result
+# - SEPARATOR :: String/Charater to separate TEMPLATE lines (DEFAULT: \n)
+# - OUT :: if set the result will be written to $OUT instead of stdout
+# Optional Functions:
+# - label_hook :: modify/override label query results
+# - template_hook :: hook to verify/modify template rsults (0 => OK; 1 => SKIP)
+
+if [ -f "${TEMPLATE_SRC}" ]
+then
+    source "${TEMPLATE_SRC}"
+    if [ -z "${TEMPLATE}" ]
+    then
+        echo "[ERR]: Template \"${TEMPLATE_SRC}\" does define a template string."
+        exit 1
+    fi
+else
+    echo "[ERR]: No such File \"${TEMPLATE_SRC}\".";
+    exit 1
+fi
+
+# Check Hooks
+if type label_hook 2>/dev/null | grep -q "label_hook is a function"
+then
+    RUN_LABEL_HOOK=true
+else
+    RUN_LABEL_HOOK=false
+fi
+
+if type template_hook 2>/dev/null | grep -q "template_hook is a function"
+then
+    RUN_TEMPLATE_HOOK=true
+else
+    RUN_TEMPLATE_HOOK=false
+fi
+
+if [ -z "${SEPARATOR+.}" ]
+then
+    SEPARATOR='\n'
+fi
+
+for row in $(jq -r '.[] | @base64' <<< "${DOCKER_DATA}")
+do
+    CONTAINER_DATA=$(base64 --decode <<< "${row}");
+    # Set non Label values
+    if [ -z "${LOCAL_IP}" ]
+    then
+        LOCAL_IP=$(jq -r '.NetworkSettings.Networks | if has($ENV.NETWORK_NAME) then .[$ENV.NETWORK_NAME].IPAddress else first(.[].IPAddress) end' <<< "${CONTAINER_DATA}");
+    fi
+    # export LOCAL_IP
+
+    # Read Label values
+    CONTAINER_LABELS=$(jq '.Labels' <<< "${CONTAINER_DATA}");
+    for var in $(envsubst -v "${TEMPLATE}")
+    do
+        if [ -z "${!var}" ]
+        then
+            VAR_LABEL=$(tr '[:upper:]_' '[:lower:].' <<< "${var}")
+            LABEL_VAL=$(jq --arg KEY "${VAR_LABEL}" -r 'if has($KEY) then .[$KEY] else "" end' <<< "${CONTAINER_LABELS}")
+
+            if [ -n "${LABEL_VAL}" ]
+            then
+                declare "${var}"="${LABEL_VAL}";
+            fi
+        fi
+    done
+
+    if ${RUN_LABEL_HOOK}
+    then
+        label_hook
+    fi
+
+    PARTIAL_RESULT="$(envsubst <<< "${TEMPLATE}")";
+    # Verify template result if check_template is defined
+    if ${RUN_TEMPLATE_HOOK}
+    then
+        if template_hook
+        then
+            # FIX with printf
+            RESULT+="${PARTIAL_RESULT}"
+        fi
+    else
+        RESULT=$(printf '%s' "${RESULT}" "${RESULT:+$SEPARATOR}" "${PARTIAL_RESULT}")
+    fi
+
+    # Unset label-environment variables for next container
+    for var in $(envsubst -v "${TEMPLATE}")
+    do
+        if [ "${var}" != "LOCAL_IP" ]
+        then
+            unset "${!var}"
+        fi
+    done
+done
+
+RESULT="${WRAP_START}${RESULT}${WRAP_END}"
+
+
+if [ -z "${OUT}" ]
+then
+    printf "%b\n" "${RESULT}";
+else
+    if ! diff --brief "${OUT}" - > /dev/null 2>&1 <<< "${RESULT}"
+    then
+        printf "Template Task: '%s' has been written to: '%s'\n" "${TEMPLATE_SRC}" "${OUT}"
+        printf "%b\n" "${RESULT}" > "${OUT}";
+    fi
+fi