Add digital output control node

For supporting the i/o extender and writing to digital outputs of
the device.

package.json

@@ -5,14 +5,17 @@
     "dependencies": {
         "dbus-native": "^0.4.0",
         "debug": "^4.3.4",
+        "exceljs": "^4.4.0",
         "lodash": "^4.17.21",
         "promise-retry": "^2.0.1",
-        "standard": "^17.1.0"
+        "standard": "^17.1.0",
+        "yargs": "^17.7.2"
     },
     "node-red": {
         "nodes": {
             "victron-client": "./src/nodes/config-client.js",
-            "victron-nodes": "./src/nodes/victron-nodes.js"
+            "victron-nodes": "./src/nodes/victron-nodes.js",
+            "victron-gpio": "./src/nodes/victron-gpio.js"
         },
         "version": ">=3.0.2"
     },

src/nodes/victron-gpio.html

@@ -0,0 +1,105 @@
+<script type="text/javascript">
+    RED.nodes.registerType('digital-output',{
+        category: 'Victron Energy',
+        color: '#4790d0',
+        defaults: {
+            name: {value:""},
+            output: {value:"", required:true}
+        },
+        inputs:1,
+        outputs:0,
+        icon: "victronenergy.svg",
+        label: function() {
+            return this.name || "Digital Output Control";
+        },
+        paletteLabel: "Digital Output Control",
+        oneditprepare: function() {
+            var node = this;
+            $.getJSON('gpio-outputs/'+this.id, function(data) {
+                var select = $('#node-input-output');
+                var warning = $('#node-warning');
+                select.empty();
+                if (data.outputs && data.outputs.length > 0) {
+                    $.each(data.outputs, function(i, output) {
+                        select.append($("<option></option>")
+                            .attr("value", output)
+                            .text("Output " + output));
+                    });
+                    select.val(node.output);
+                    warning.hide();
+                } else {
+                    select.hide();
+                    warning.show();
+                    var warningText = "<strong>Warning:</strong> NODE_RED_DBUS_ADDRESS is set";
+                    if (data.dbusAddress) {
+                        warningText += ` to "${data.dbusAddress}"`;
+                    }
+                    warningText += ". This node will not function, and no digital outputs are available. <br>Make sure NODE_RED_DBUS_ADDRESS is not set for this node to function.";
+                    warning.html(warningText);
+                }
+            }).fail(function() {
+                var select = $('#node-input-output');
+                var warning = $('#node-warning');
+                select.hide();
+                warning.show();
+                warning.html("<strong>Warning:</strong> Unable to fetch digital outputs. NODE_RED_DBUS_ADDRESS might be set, preventing this node from functioning. <br>Ensure NODE_RED_DBUS_ADDRESS is not set for this node to function.");
+            });
+        }
+    });
+</script>
+
+<script type="text/html" data-template-name="digital-output">
+    <div class="form-row">
+        <label for="node-input-name"><i class="fa fa-tag"></i> Name</label>
+        <input type="text" id="node-input-name" placeholder="Name">
+    </div>
+    <div class="form-row">
+        <label for="node-input-output"><i class="fa fa-dot-circle-o"></i> Output</label>
+        <select id="node-input-output">
+            <!-- Options will be populated dynamically -->
+        </select>
+    </div>
+    <div class="form-row">
+        <div id="node-warning" style="display: none; color: #ff8c00; margin-top: 10px;"></div>
+    </div>
+</script>
+
+<script type="text/markdown" data-help-name="digital-output">
+# Digital Output Control
+
+This node writes a 0 or 1 to a selected digital output.
+
+## Important Note
+
+This node requires the `NODE_RED_DBUS_ADDRESS` environment variable to NOT be set. If it's set, the node will not function.
+
+## Input
+
+The input should be one of the following:
+- Boolean: `true` or `false`
+- Number: `0` or `1`
+- String: `"0"` or `"1"`
+
+Any truthy value will be written as "1", and any falsy value will be written as "0".
+
+## Configuration
+
+- **Name**: Optional name for the node
+- **Output**: Select an available digital output from the dropdown list
+
+## Details
+
+The node checks for available digital outputs in the `/run/io-ext/gpiochip388/output_[1-9]/value` directory.
+
+When it receives an input, it writes the corresponding value to the selected digital output file.
+
+## Status
+
+- Green dot: Last written output and value (when successful)
+- Red ring: Indicates that `NODE_RED_DBUS_ADDRESS` is set (node will not function)
+
+## Error Handling
+
+- If `NODE_RED_DBUS_ADDRESS` is set, the node will show a warning with the set value and won't function.
+- If an invalid output is selected or there's an error writing to the file, the node will report an error.
+</script>

src/nodes/victron-gpio.js

@@ -0,0 +1,80 @@
+module.exports = function(RED) {
+    function DigitalOutputNode(config) {
+        RED.nodes.createNode(this, config);
+        var node = this;
+
+        // Check if NODE_RED_DBUS_ADDRESS is set
+        if (process.env.NODE_RED_DBUS_ADDRESS) {
+            const errorMsg = `NODE_RED_DBUS_ADDRESS is set to "${process.env.NODE_RED_DBUS_ADDRESS}". This node will not function.`;
+            node.status({fill:"red", shape:"ring", text:"DBUS Address set"});
+            node.error(errorMsg);
+            return; // Exit the function early
+        }
+
+        // Initialize node properties
+        node.gpioPath = '/run/io-ext/gpiochip388';
+        node.availableOutputs = [];
+
+        // Function to check available GPIO outputs
+        function checkAvailableOutputs() {
+            const fs = require('fs');
+            const path = require('path');
+
+            node.availableOutputs = [];
+
+            for (let i = 1; i <= 9; i++) {
+                const filePath = path.join(node.gpioPath, `output_${i}`, 'value');
+                if (fs.existsSync(filePath)) {
+                    node.availableOutputs.push(i);
+                }
+            }
+
+            // Update the dropdown options in the Node-RED editor
+            node.context().set('availableOutputs', node.availableOutputs);
+            RED.comms.publish('gpio-outputs', { id: node.id, outputs: node.availableOutputs, dbusAddress: process.env.NODE_RED_DBUS_ADDRESS });
+        }
+
+        // Check available outputs on node initialization
+        checkAvailableOutputs();
+
+        // Handle incoming messages
+        node.on('input', function(msg) {
+            const fs = require('fs');
+            const path = require('path');
+
+            const outputNumber = parseInt(config.output);
+            const value = (msg.payload === true || msg.payload === 1 || msg.payload === '1') ? '1' : '0';
+
+            if (node.availableOutputs.includes(outputNumber)) {
+                const filePath = path.join(node.gpioPath, `output_${outputNumber}`, 'value');
+
+                fs.writeFile(filePath, value, (err) => {
+                    if (err) {
+                        node.error(`Error writing to GPIO ${outputNumber}: ${err}`);
+                    } else {
+                        node.status({fill:"green", shape:"dot", text:`Output ${outputNumber}: ${value}`});
+                    }
+                });
+            } else {
+                node.error(`Invalid output number: ${outputNumber}`);
+            }
+        });
+
+        // Clean up on close
+        node.on('close', function() {
+            // Add any cleanup code here if needed
+        });
+    }
+
+    RED.nodes.registerType("digital-output", DigitalOutputNode);
+
+    // Serve the custom node configuration UI
+    RED.httpAdmin.get("/gpio-outputs/:id", RED.auth.needsPermission("digital-output.read"), function(req, res) {
+        var node = RED.nodes.getNode(req.params.id);
+        if (node && node.availableOutputs) {
+            res.json({outputs: node.availableOutputs, dbusAddress: process.env.NODE_RED_DBUS_ADDRESS});
+        } else {
+            res.status(404).end();
+        }
+    });
+}