explorer-api: renders a preview of the mix node's description in OpenGraph/Twitter format that will display in the link preview generated by social media and messenger apps

Cargo.lock

@@ -766,7 +766,7 @@ dependencies = [
 name = "config"
 version = "0.1.0"
 dependencies = [
- "handlebars",
+ "handlebars 3.5.5",
  "humantime-serde",
  "network-defaults",
  "serde",
@@ -1582,6 +1582,7 @@ name = "explorer-api"
 version = "0.1.0"
 dependencies = [
  "chrono",
+ "handlebars 4.1.3",
  "humantime-serde",
  "isocountry",
  "log",
@@ -2227,6 +2228,20 @@ dependencies = [
  "serde_json",
 ]
 
+[[package]]
+name = "handlebars"
+version = "4.1.3"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "66b09e2322d20d14bc2572401ce7c1d60b4748580a76c230ed9c1f8938f0c833"
+dependencies = [
+ "log",
+ "pest",
+ "pest_derive",
+ "quick-error 2.0.1",
+ "serde",
+ "serde_json",
+]
+
 [[package]]
 name = "hashbrown"
 version = "0.11.2"

explorer-api/Cargo.toml

@@ -20,6 +20,7 @@ okapi = { version = "0.6.0-alpha-1", features = ["derive_json_schema"] }
 rocket_okapi = "0.7.0-alpha-1"
 log = "0.4.0"
 pretty_env_logger = "0.4.0"
+handlebars = "4.1.3"
 
 mixnet-contract = { path = "../common/mixnet-contract" }
 network-defaults = { path = "../common/network-defaults" }

explorer-api/src/country_statistics/mod.rs

@@ -4,6 +4,7 @@ use reqwest::Error as ReqwestError;
 use crate::country_statistics::country_nodes_distribution::CountryNodesDistribution;
 use crate::mix_nodes::{GeoLocation, Location};
 use crate::state::ExplorerApiStateContext;
+use std::env;
 
 pub mod country_nodes_distribution;
 pub mod http;
@@ -18,18 +19,21 @@ impl CountryStatistics {
     }
 
     pub(crate) fn start(mut self) {
-        info!("Spawning task runner...");
-        tokio::spawn(async move {
-            let mut interval_timer = tokio::time::interval(std::time::Duration::from_secs(60 * 60));
-            loop {
-                // wait for the next interval tick
-                interval_timer.tick().await;
+        if env::var("DEV_MODE").is_err() {
+            info!("Spawning task runner...");
+            tokio::spawn(async move {
+                let mut interval_timer =
+                    tokio::time::interval(std::time::Duration::from_secs(60 * 60));
+                loop {
+                    // wait for the next interval tick
+                    interval_timer.tick().await;
 
-                info!("Running task...");
-                self.calculate_nodes_per_country().await;
-                info!("Done");
-            }
-        });
+                    info!("Running task...");
+                    self.calculate_nodes_per_country().await;
+                    info!("Done");
+                }
+            });
+        }
     }
 
     /// Retrieves the current list of mixnodes from the validators and calculates how many nodes are in each country

explorer-api/src/http/mod.rs

@@ -7,6 +7,7 @@ use rocket_okapi::swagger_ui::make_swagger_ui;
 use crate::country_statistics::http::country_statistics_make_default_routes;
 use crate::http::swagger::get_docs;
 use crate::mix_node::http::mix_node_make_default_routes;
+use crate::mix_node::templates::Templates;
 use crate::ping::http::ping_make_default_routes;
 use crate::state::ExplorerApiStateContext;
 
@@ -29,6 +30,8 @@ pub(crate) fn start(state: ExplorerApiStateContext) {
         .to_cors()
         .unwrap();
 
+        let templates = Templates::new();
+
         let config = rocket::config::Config::release_default();
         rocket::build()
             .configure(config)
@@ -38,6 +41,7 @@ pub(crate) fn start(state: ExplorerApiStateContext) {
             .mount("/swagger", make_swagger_ui(&get_docs()))
             .register("/", catchers![not_found])
             .manage(state)
+            .manage(templates)
             .attach(cors)
             .launch()
             .await

explorer-api/src/mix_node/http.rs

@@ -1,4 +1,5 @@
 use reqwest::Error as ReqwestError;
+use rocket::response::content::Html;
 use rocket::serde::json::Json;
 use rocket::{Route, State};
 use serde::Serialize;
@@ -6,11 +7,12 @@ use serde::Serialize;
 use mixnet_contract::{Addr, Coin, Layer, MixNode};
 
 use crate::mix_node::models::{NodeDescription, NodeStats};
+use crate::mix_node::templates::{PreviewTemplateData, Templates};
 use crate::mix_nodes::{get_mixnode_delegations, Location};
 use crate::state::ExplorerApiStateContext;
 
 pub fn mix_node_make_default_routes() -> Vec<Route> {
-    routes_with_openapi![get_delegations, get_description, get_stats, list]
+    routes_with_openapi![get_delegations, get_description, get_stats, list, preview]
 }
 
 #[derive(Clone, Debug, Serialize, JsonSchema)]
@@ -51,6 +53,34 @@ pub(crate) async fn list(
     )
 }
 
+#[openapi(tag = "mix_node")]
+#[get("/<pubkey>/preview")]
+pub(crate) async fn preview(
+    pubkey: &str,
+    templates: &State<Templates>,
+    state: &State<ExplorerApiStateContext>,
+) -> Html<String> {
+    match get_mixnode_description(pubkey, state).await {
+        Some(node_description) => {
+            // use handlebars to render an HTML output for an OpenGraph / Twitter preview - this is
+            // used in social media apps / messenger apps that show previews for links
+            match templates.render_preview(PreviewTemplateData {
+                title: node_description.name,
+                description: node_description.description,
+                url: format!(
+                    "https://testnet-milhon-explorer.nymtech.net/nym/mixnodes/{}",
+                    pubkey
+                ),
+                image_url: String::from("https://media2.giphy.com/media/pwyW4XDmtqjG8/200.gif?cid=dda24d50ae15e44c38783edc824618df68645c6af2592b28&amp;rid=200.gif&amp;ct=g"),
+            }) {
+                Ok(r) => Html(r),
+                Err(_e) => Html(String::from("Oh no, something went wrong!")),
+            }
+        }
+        None => Html(String::from("Sorry, mix node not found")),
+    }
+}
+
 #[openapi(tag = "mix_node")]
 #[get("/<pubkey>/delegations")]
 pub(crate) async fn get_delegations(pubkey: &str) -> Json<Vec<mixnet_contract::Delegation>> {
@@ -63,6 +93,13 @@ pub(crate) async fn get_description(
     pubkey: &str,
     state: &State<ExplorerApiStateContext>,
 ) -> Option<Json<NodeDescription>> {
+    get_mixnode_description(pubkey, state).await.map(Json)
+}
+
+async fn get_mixnode_description(
+    pubkey: &str,
+    state: &State<ExplorerApiStateContext>,
+) -> Option<NodeDescription> {
     match state
         .inner
         .mix_node_cache
@@ -72,7 +109,7 @@ pub(crate) async fn get_description(
     {
         Some(cache_value) => {
             trace!("Returning cached value for {}", pubkey);
-            Some(Json(cache_value))
+            Some(cache_value)
         }
         None => {
             trace!("No valid cache value for {}", pubkey);
@@ -91,7 +128,7 @@ pub(crate) async fn get_description(
                                 .mix_node_cache
                                 .set_description(pubkey, response.clone())
                                 .await;
-                            Some(Json(response))
+                            Some(response)
                         }
                         Err(e) => {
                             error!(

explorer-api/src/mix_node/mod.rs

@@ -1,3 +1,4 @@
 mod cache;
 pub(crate) mod http;
 pub(crate) mod models;
+pub(crate) mod templates;

explorer-api/src/mix_node/templates.rs

@@ -0,0 +1,73 @@
+use handlebars::{Handlebars, RenderError};
+use serde::Serialize;
+
+#[derive(Clone)]
+pub(crate) struct Templates {
+    handlebars: Handlebars<'static>,
+}
+
+impl Templates {
+    pub(crate) fn new() -> Self {
+        let mut handlebars = Handlebars::new();
+
+        assert!(handlebars
+            .register_template_string("preview", PREVIEW_TEMPLATE)
+            .is_ok());
+
+        Templates { handlebars }
+    }
+
+    pub(crate) fn render_preview(&self, data: PreviewTemplateData) -> Result<String, RenderError> {
+        self.handlebars.render("preview", &data)
+    }
+}
+
+#[derive(Clone, Debug, Serialize, JsonSchema)]
+pub(crate) struct PreviewTemplateData {
+    pub(crate) title: String,
+    pub(crate) description: String,
+    pub(crate) url: String,
+    pub(crate) image_url: String,
+}
+
+const PREVIEW_TEMPLATE: &str = r#"<!DOCTYPE html>
+<html>
+  <head>
+    <meta charset="utf-8" />
+    <meta name="viewport" content="width=device-width, initial-scale=1" />
+
+    <title>{{ title }}</title>
+    <meta name="description" content="{{ description }}">
+
+    <meta property="og:type" content="article">
+    <meta property="og:url" content="{{ url }}">
+    <meta property="og:title" content="{{ title }}">
+    <meta property="og:description" content="{{ description }}">
+    <meta property="og:image" content="{{ image_url }}">
+
+    <meta name="twitter:card" value="summary_large_image">
+    <meta name="twitter:title" value="{{ title }}">
+    <meta name="twitter:description" value="{{ description }}">
+    <meta name="twitter:image" value="{{ image_url }}">
+    <meta name="twitter:site" value="@nymtech">
+
+    <meta http-equiv="refresh" content="0;url={{url}}" />
+    
+    <style>
+    body {
+      font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, Helvetica, Arial, sans-serif, "Apple Color Emoji", "Segoe UI Emoji", "Segoe UI Symbol";
+    }
+    .meme {
+      padding-top: 20px;
+    }
+    .meme > img {
+      max-width: 200px;
+      max-height: 200px;
+    }
+    </style>
+  </head>
+  <body>
+    <h1>{{title}}</h1>
+    <div>{{description}}<div>
+  </body>
+</html>"#;