Init repo

.gitignore

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+target
+result*

Cargo.toml

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+[package]
+name = "berlinerbaeder-exporter"
+version = "0.1.0"
+edition = "2021"
+
+[dependencies]
+axum = "0.7.5"
+reqwest = { version = "0.12.5", features = ["json"] }
+serde = { version = "1.0.204", features = ["derive"] }
+serde_json = "1.0.120"
+tokio = { version = "1.38.0", features = ["rt-multi-thread"] }

flake.lock

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+{
+  "nodes": {
+    "nixpkgs": {
+      "locked": {
+        "lastModified": 1720768451,
+        "narHash": "sha256-EYekUHJE2gxeo2pM/zM9Wlqw1Uw2XTJXOSAO79ksc4Y=",
+        "owner": "NixOS",
+        "repo": "nixpkgs",
+        "rev": "7e7c39ea35c5cdd002cd4588b03a3fb9ece6fad9",
+        "type": "github"
+      },
+      "original": {
+        "owner": "NixOS",
+        "ref": "nixos-unstable",
+        "repo": "nixpkgs",
+        "type": "github"
+      }
+    },
+    "root": {
+      "inputs": {
+        "nixpkgs": "nixpkgs"
+      }
+    }
+  },
+  "root": "root",
+  "version": 7
+}

flake.nix

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+{
+  inputs = {
+    nixpkgs.url = "github:NixOS/nixpkgs/nixos-unstable";
+  };
+  outputs = { self, nixpkgs, ... }: {
+    packages.x86_64-linux = let
+      pkgs = import nixpkgs {
+        system = "x86_64-linux";
+      };
+    in {
+      berlinerbaeder-exporter = pkgs.rustPlatform.buildRustPackage rec {
+        pname = "berlinerbaeder-exporter";
+        version = "0.1.0";
+
+        src = ./.;
+
+        nativeBuildInputs = [
+          pkgs.pkg-config
+        ];
+
+        buildInputs = [
+          pkgs.openssl
+        ];
+
+        cargoLock.lockFile = ./Cargo.lock;
+
+      };
+      default = self.packages.x86_64-linux.berlinerbaeder-exporter;
+    };
+
+    hydraJobs = {
+      inherit (self)
+        packages;
+    };
+  };
+}
+

src/main.rs

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+use axum::{
+    routing::get,
+    Router,
+};
+
+use serde::{
+    Deserialize,
+    Serialize,
+};
+
+#[derive(Serialize, Deserialize)]
+struct TrafficDataThresholds {
+    level: i64,
+    threshold: i64,
+    color: String,
+    description: String,
+}
+
+#[derive(Serialize, Deserialize)]
+struct TrafficDataItem {
+    id: String,
+    level: i64,
+    color: Option<String>,
+    description: Option<String>,
+    counter: Option<i64>,
+    automatic: bool,
+    thresholds: Vec<TrafficDataThresholds>,
+}
+
+#[tokio::main]
+async fn main() {
+    let app = Router::new()
+        .route("/", get(route_index))
+        .route("/metrics", get(route_metrics));
+
+    let listener = tokio::net::TcpListener::bind("[::]:3000").await.unwrap();
+    println!("Server listening on: http://{}", listener.local_addr().unwrap());
+
+    axum::serve(listener, app).await.unwrap();
+}
+
+async fn route_index() -> String {
+    return String::from("Prometheus exporter for Berlinerbaeder occupancy");
+}
+
+async fn route_metrics() -> Result<String, String> {
+    let client = reqwest::Client::new();
+    let trafficdata_req = client.get(String::from("https://www.berlinerbaeder.de/traffic/trafficdata.json"))
+        .send().await
+        .map_err(|_err| String::from("trafficdata API cannot be fetched"))?;
+    
+    if trafficdata_req.status() != reqwest::StatusCode::OK {
+        return Err(String::from("Unexpected response from trafficdata API"));
+    }
+
+    let trafficdata_body = trafficdata_req.text().await
+        .map_err(|_err| "Cannot read body of trafficdata API")?;
+
+    let trafficdata: Vec<TrafficDataItem> = serde_json::from_str(trafficdata_body.as_str())
+        .map_err(|err| format!("{}", err))?;
+
+    let mut out = String::new();
+
+    for bad in trafficdata {
+        out.push_str(&format!("berlinerbaeder_occupation{{bad=\"{}\"}} {}\n", bad.id, bad.counter.unwrap_or(-1)));
+    }
+
+    return Ok(out);
+}