discount tutorial part 2 implemented

Author: nickwesselman

.graphqlrc.cjs

@@ -26,6 +26,7 @@ function getProjects(path) {
 
 const projects = {
     ...getProjects("sample-apps/discounts-tutorial/extensions"),
+    ...getProjects("sample-apps/discounts/extensions"),
     ...getProjects("checkout/rust/delivery-customization"),
     ...getProjects("checkout/rust/payment-customization"),
     ...getProjects("discounts/rust/order-discounts"),

.vscode/settings.json

@@ -8,6 +8,7 @@
       "discounts/rust/product-discounts/fixed-amount/Cargo.toml",
       "discounts/rust/shipping-discounts/default/Cargo.toml",
       "discounts/rust/shipping-discounts/fixed-amount/Cargo.toml",
-      "sample-apps/discounts-tutorial/extensions/volume/Cargo.toml"
+      "sample-apps/discounts-tutorial/extensions/volume/Cargo.toml",
+      "sample-apps/discounts/extensions/product-discount/Cargo.toml"
     ]
   }

sample-apps/discounts/extensions/product-discount/input.graphql

@@ -10,4 +10,9 @@ query Input {
       }
     }
   }
+  discountNode {
+    metafield(namespace: "discounts-tutorial", key: "function-configuration") {
+      value
+    }
+  }
 }

sample-apps/discounts/extensions/product-discount/src/main.rs

@@ -1,33 +1,63 @@
 use shopify_function::prelude::*;
 use shopify_function::Result;
 
-use serde::{Serialize};
+use serde::{Deserialize, Serialize};
 
 // Use the shopify_function crate to generate structs for the function input and output
 generate_types!(
     query_path = "./input.graphql",
     schema_path = "./schema.graphql"
 );
 
-// Use the shopify_function crate to declare your function entrypoint
+// Create a structure that matches the JSON structure that you'll use for your configuration
+#[derive(Serialize, Deserialize, PartialEq)]
+#[serde(rename_all(deserialize = "camelCase"))]
+struct Configuration {
+    pub quantity: i64,
+    pub percentage: f64,
+}
+
+impl Configuration {
+    const DEFAULT_QUANTITY: i64 = 999;
+    const DEFAULT_PERCENTAGE: f64 = 0.0;
+
+    // Parse the JSON metafield value using serde
+    fn from_str(value: &str) -> Self {
+        serde_json::from_str(value).expect("Unable to parse configuration value from metafield")
+    }
+}
+
+impl Default for Configuration {
+    fn default() -> Self {
+        Configuration {
+            quantity: Self::DEFAULT_QUANTITY,
+            percentage: Self::DEFAULT_PERCENTAGE,
+        }
+    }
+}
+
 #[shopify_function]
 fn function(input: input::ResponseData) -> Result<output::FunctionResult> {
     let no_discount = output::FunctionResult {
         discounts: vec![],
         discount_application_strategy: output::DiscountApplicationStrategy::FIRST,
     };
 
-    // Iterate all the lines in the cart to create discount targets
+    // Get the configuration from the metafield on your function owner
+    let config = match input.discount_node.metafield {
+        Some(input::InputDiscountNodeMetafield { value }) =>
+            Configuration::from_str(&value),
+        None => return Ok(no_discount),
+    };
+
     let targets = input.cart.lines
         .iter()
-        // Only include cart lines with a quantity higher than two
-        .filter(|line| line.quantity >= 2)
-        // Only include cart lines with a targetable product variant
+        // Use the configured quantity instead of a hardcoded value
+        .filter(|line| line.quantity >= config.quantity)
         .filter_map(|line| match &line.merchandise {
             input::InputCartLinesMerchandise::ProductVariant(variant) => Some(variant),
             input::InputCartLinesMerchandise::CustomProduct => None,
         })
-        // Use the variant id to create a discount target
         .map(|variant| output::Target {
             product_variant: Some(output::ProductVariantTarget {
                 id: variant.id.to_string(),
@@ -37,22 +67,19 @@ fn function(input: input::ResponseData) -> Result<output::FunctionResult> {
         .collect::<Vec<output::Target>>();
 
     if targets.is_empty() {
-        // You can use STDERR for debug logs in your function
         eprintln!("No cart lines qualify for volume discount.");
         return Ok(no_discount);
     }
 
-    // The shopify_function crate serializes your function result and writes it to STDOUT
     Ok(output::FunctionResult {
         discounts: vec![output::Discount {
             message: None,
-            // Apply the discount to the collected targets
             targets,
-            // Define a percentage-based discount
+            // Use the configured percentage instead of a hardcoded value
             value: output::Value {
                 fixed_amount: None,
                 percentage: Some(output::Percentage {
-                    value: "10.0".to_string()
+                    value: config.percentage.to_string()
                 })
             }
         }],