From 417a339cf5f86f5b90f8b72eab8ede517e269d10 Mon Sep 17 00:00:00 2001
From: reubenmiller <reuben.d.miller@gmail.com>
Date: Tue, 3 Mar 2026 22:40:38 +0100
Subject: [PATCH] feat: add an experimental flow params plugin

---
 nfpm.yaml                           |  5 +++
 src/inventory-scripts/70_FlowParams | 24 +++++++++++++++
 src/parameter_update.sh             | 18 +++++++++--
 src/plugins/flow_params             | 47 +++++++++++++++++++++++++++++
 4 files changed, 91 insertions(+), 3 deletions(-)
 create mode 100755 src/inventory-scripts/70_FlowParams
 create mode 100755 src/plugins/flow_params

diff --git a/nfpm.yaml b/nfpm.yaml
index 789fc9f..e39c12e 100644
--- a/nfpm.yaml
+++ b/nfpm.yaml
@@ -37,6 +37,11 @@ contents:
     file_info:
       mode: 0755
 
+  - src: ./src/inventory-scripts/70_FlowParams
+    dst: /usr/share/tedge-inventory/scripts.d/
+    file_info:
+      mode: 0755
+
   - src: ./src/c8y_ParameterUpdate.template
     dst: /etc/tedge/operations/c8y/
     file_info:
diff --git a/src/inventory-scripts/70_FlowParams b/src/inventory-scripts/70_FlowParams
new file mode 100755
index 0000000..f2c143e
--- /dev/null
+++ b/src/inventory-scripts/70_FlowParams
@@ -0,0 +1,24 @@
+#!/bin/sh
+set -e
+
+# NOTE: The flow should probably be in charge of publishing its own values rather than relying on this mechanism to get and update the values
+# in the cloud
+
+TEDGE_CONFIG_DIR=${TEDGE_CONFIG_DIR:-/etc/tedge}
+MAPPERS_DIR="$TEDGE_CONFIG_DIR/mappers"
+
+find "$MAPPERS_DIR" -name params.toml | while read -r PARAMS_FILE; do
+    VALUES=$(jq --raw-input '[ inputs
+  | gsub("\r$"; "")
+  | split(" = "; "")
+  | select(length == 2)
+  | {(.[0]): (.[1] | fromjson)}
+] | add' "$PARAMS_FILE")
+
+    FLOW_DIR_RELATIVE=$(dirname "${PARAMS_FILE#"$MAPPERS_DIR"/}")
+    MAPPER=$(echo "$FLOW_DIR_RELATIVE" | cut -d/ -f1)
+    NAME=$(echo "$FLOW_DIR_RELATIVE" | cut -d/ -f3-)
+    if [ -n "$NAME" ]; then
+        tedge mqtt pub --retain "te/device/main///twin/flow_params_${MAPPER}_$NAME" "$VALUES"
+    fi
+done
diff --git a/src/parameter_update.sh b/src/parameter_update.sh
index dd50032..2c4fbc8 100755
--- a/src/parameter_update.sh
+++ b/src/parameter_update.sh
@@ -17,12 +17,24 @@ set_parameters() {
     TYPE="$1"
     PARAMETERS="$2"
 
-    if [ ! -x "$PARAMETER_PLUGINS/$TYPE" ]; then
-        echo "Could not find a matching parameter plugin. path=$PARAMETER_PLUGINS/$TYPE" >&2
+    case "$TYPE" in
+        flow_params_*)
+            # Special case where a single parameter plugin is responsible for managing all flow parameters
+            # since flows can't write the values to file themselves
+            COMMON_TYPE=flow_params
+            ;;
+        *)
+            COMMON_TYPE="$TYPE"
+            ;;
+    esac
+
+    if [ ! -x "$PARAMETER_PLUGINS/$COMMON_TYPE" ]; then
+        echo "Could not find a matching parameter plugin. path=$PARAMETER_PLUGINS/$COMMON_TYPE" >&2
         exit 1
     fi
 
-    "$PARAMETER_PLUGINS/$TYPE" set "$PARAMETERS"
+    echo "Running plugin: \"$PARAMETER_PLUGINS/$COMMON_TYPE\" set \"$PARAMETERS\" \"$TYPE\"" >&2
+    "$PARAMETER_PLUGINS/$COMMON_TYPE" set "$PARAMETERS" "$TYPE"
 }
 
 case "$COMMAND" in
diff --git a/src/plugins/flow_params b/src/plugins/flow_params
new file mode 100755
index 0000000..e322dce
--- /dev/null
+++ b/src/plugins/flow_params
@@ -0,0 +1,47 @@
+#!/bin/sh
+set -e
+COMMAND="$1"
+shift
+
+TEDGE_CONFIG_DIR="${TEDGE_CONFIG_DIR:-/etc/tedge}"
+
+update_parameters() {
+    MESSAGE="$1"
+    MESSAGE_TYPE="$2"
+
+    # Write to the params.
+    MAPPER=$(echo "$MESSAGE_TYPE" | cut -d_ -f3)
+    NAME=$(echo "$MESSAGE_TYPE" | cut -d_ -f4-)
+
+    FLOW_DIR="$TEDGE_CONFIG_DIR/mappers/$MAPPER/flows/$NAME"
+    if [ ! -d "$FLOW_DIR" ]; then
+        echo "Flow directory does not exist. path=$FLOW_DIR" >&2
+        exit 1
+    fi
+
+    # convert json to key/value and write it to the params.toml file
+    echo "Writing to the flows params.toml file. path=$FLOW_DIR/params.toml" >&2
+    echo "$MESSAGE" | jq -r 'to_entries|map("\(.key) = \(.value|tojson)")|.[]' | sudo tedge-write "$FLOW_DIR/params.toml"
+
+    # Note: manually update the digital twin property though normally this is done by the Device Parameter microservice
+    # as sending the 408 message is actually harder than just updating the digital twin value
+    tedge mqtt pub -r "te/device/main///twin/$MESSAGE_TYPE" "${MESSAGE}"
+}
+
+get() {
+    echo "{}"
+}
+
+case "$COMMAND" in
+    init)
+        ;;
+    set)
+        update_parameters "$@"
+        ;;
+    get)
+        ;;
+    *)
+        echo "Unknown command. name=$COMMAND" >&2
+        exit 1
+        ;;
+esac