write a config module

src/config.gleam

@@ -0,0 +1,78 @@
+import envoy
+import glaml
+import gleam/result
+import simplifile
+
+pub type Config {
+  Config(mqtt_host: String, mqtt_user: String, mqtt_pw: String, jwt_key: String)
+}
+
+fn load_file() -> Result(String, String) {
+  simplifile.read("config.yml")
+  |> result.map_error(fn(_) { "Failed to read config.yml" })
+}
+
+fn parse_yaml(contents: String) -> Result(glaml.Document, String) {
+  use docs <- result.try(
+    glaml.parse_string(contents)
+    |> result.map_error(fn(_) { "Failed to parse config.yml" }),
+  )
+
+  case docs {
+    [doc] -> Ok(doc)
+    _ -> Error("Expected exactly one YAML document in config.yml")
+  }
+}
+
+fn compile_config(doc: glaml.Document) -> Result(Config, String) {
+  let root = glaml.document_root(doc)
+
+  // Extract values from YAML
+  use mqtt_host_result <- result.try(
+    glaml.select_sugar(root, "mqtt.host")
+    |> result.map_error(fn(_) { "mqtt.host not found in config.yml" }),
+  )
+  use mqtt_user_result <- result.try(
+    glaml.select_sugar(root, "mqtt.user")
+    |> result.map_error(fn(_) { "mqtt.user not found in config.yml" }),
+  )
+  use jwt_key_result <- result.try(
+    glaml.select_sugar(root, "jwt_key")
+    |> result.map_error(fn(_) { "jwt_key not found in config.yml" }),
+  )
+
+  // Extract strings from nodes
+  case mqtt_host_result, mqtt_user_result, jwt_key_result {
+    glaml.NodeStr(host), glaml.NodeStr(user), glaml.NodeStr(key) -> {
+      let yaml_config =
+        Config(
+          mqtt_host: host,
+          mqtt_user: user,
+          mqtt_pw: "placeholder",
+          jwt_key: key,
+        )
+
+      // Override with env vars
+      let final_config =
+        Config(
+          mqtt_host: envoy.get("MQTT_HOST")
+            |> result.unwrap(yaml_config.mqtt_host),
+          mqtt_user: envoy.get("MQTT_USER")
+            |> result.unwrap(yaml_config.mqtt_user),
+          mqtt_pw: envoy.get("MQTT_PW")
+            |> result.unwrap(yaml_config.mqtt_pw),
+          jwt_key: envoy.get("JWT_KEY")
+            |> result.unwrap(yaml_config.jwt_key),
+        )
+
+      Ok(final_config)
+    }
+    _, _, _ -> Error("Config values must be strings in config.yml")
+  }
+}
+
+pub fn load_config() -> Result(Config, String) {
+  use file_content <- result.try(load_file())
+  use doc <- result.try(parse_yaml(file_content))
+  compile_config(doc)
+}

src/weather_portal.gleam

@@ -1,5 +1,17 @@
+import config
 import gleam/io
 
 pub fn main() -> Nil {
-  io.println("Hello from weather_portal!")
+  case config.load_config() {
+    Ok(cfg) -> {
+      io.println("Config loaded successfully!")
+      io.println("MQTT Host: " <> cfg.mqtt_host)
+      io.println("MQTT User: " <> cfg.mqtt_user)
+      io.println("MQTT PW: " <> cfg.mqtt_pw)
+      io.println("JWT Key: " <> cfg.jwt_key)
+    }
+    Error(err) -> {
+      io.println("Failed to load config: " <> err)
+    }
+  }
 }