fancier error handling for config

src/config.rs

@@ -1,11 +1,14 @@
 use std::{
     env::{self, VarError},
+    error::Error,
     fmt::Debug,
     path::PathBuf,
     str::FromStr,
     time::Duration,
 };
 
+use anyhow::{anyhow, Context};
+
 pub struct Config {
     pub capture_images: bool,
     pub capture_audio_duration: Option<f64>,
@@ -22,37 +25,62 @@ pub struct Config {
 
 const VAR_PREFIX: &str = "SCREENCAP_BOT_";
 
-fn get_var(name: &str) -> Result<String, VarError> {
-    env::var(VAR_PREFIX.to_string() + name)
-}
-
-fn parse_var<E: Debug, T: FromStr<Err = E>>(name: &str) -> Result<T, VarError> {
-    get_var(name).map(|s| {
-        s.parse()
-            .unwrap_or_else(|e| panic!("Failed to parse {}{}: {:?}", VAR_PREFIX, name, e))
-    })
-}
-
-fn expect_var(name: &str) -> String {
-    get_var(name).unwrap_or_else(|_| panic!("{}{} must be set", VAR_PREFIX, name))
-}
-
-pub fn load() -> Config {
-    let capture_images = parse_var("CAPTURE_IMAGES").unwrap_or(true);
-
-    Config {
-        capture_images,
-        capture_audio_duration: parse_var("CAPTURE_AUDIO_DURATION").ok(),
-        shows_file: parse_var("SHOWS_FILE").unwrap_or(PathBuf::from("./shows.yaml")),
-        global_tags: get_var("GLOBAL_TAGS")
-            .map(|s| s.split(',').map(String::from).collect())
-            .unwrap_or_default(),
-        post_interval: Duration::from_secs(parse_var("POST_INTERVAL").unwrap_or_default()),
-        cohost_email: expect_var("COHOST_EMAIL"),
-        cohost_password: expect_var("COHOST_PASSWORD"),
-        cohost_page: expect_var("COHOST_PAGE"),
-        cohost_draft: parse_var("COHOST_DRAFT").unwrap_or(false),
-        cohost_cw: parse_var("COHOST_CW").unwrap_or(capture_images),
-        eighteen_plus: parse_var("18PLUS").unwrap_or(false),
+fn get_var(name: &str) -> anyhow::Result<Option<String>> {
+    let var_name = VAR_PREFIX.to_string() + name;
+    match env::var(&var_name) {
+        Ok(v) => Ok(Some(v)),
+        Err(VarError::NotPresent) => Ok(None),
+        Err(e) => Err(e).with_context(|| format!("Failed to read variable {}", var_name)),
     }
 }
+
+fn parse_var<E: Debug + Send + Sync + Error + 'static, T: FromStr<Err = E>>(
+    name: &str,
+) -> anyhow::Result<Option<T>> {
+    get_var(name)?
+        .map(|s| {
+            s.parse()
+                .with_context(|| format!("Failed to parse variable {}{}", VAR_PREFIX, name))
+        })
+        .transpose()
+}
+
+fn require_var(name: &str) -> anyhow::Result<String> {
+    get_var(name)?.ok_or_else(|| anyhow!("{}{} must be set", VAR_PREFIX, name))
+}
+
+pub fn load() -> anyhow::Result<Config> {
+    let capture_images = parse_var("CAPTURE_IMAGES")?.unwrap_or(true);
+
+    let capture_audio_duration = parse_var("CAPTURE_AUDIO_DURATION")?;
+    if let Some(d) = capture_audio_duration {
+        if d <= 0.0 {
+            return Err(anyhow!(
+                "{}CAPTURE_AUDIO_DURATION cannot be <= 0",
+                VAR_PREFIX
+            ));
+        }
+    }
+
+    if let (false, None) = (capture_images, capture_audio_duration) {
+        return Err(anyhow!(
+            "At least one of image capture and audio capture must be enabled!"
+        ));
+    }
+
+    Ok(Config {
+        capture_images,
+        capture_audio_duration,
+        shows_file: parse_var("SHOWS_FILE")?.unwrap_or_else(|| PathBuf::from("./shows.yaml")),
+        global_tags: get_var("GLOBAL_TAGS")?
+            .map(|s| s.split(',').map(String::from).collect())
+            .unwrap_or_default(),
+        post_interval: Duration::from_secs(parse_var("POST_INTERVAL")?.unwrap_or_default()),
+        cohost_email: require_var("COHOST_EMAIL")?,
+        cohost_password: require_var("COHOST_PASSWORD")?,
+        cohost_page: require_var("COHOST_PAGE")?,
+        cohost_draft: parse_var("COHOST_DRAFT")?.unwrap_or(false),
+        cohost_cw: parse_var("COHOST_CW")?.unwrap_or(capture_images),
+        eighteen_plus: parse_var("18PLUS")?.unwrap_or(false),
+    })
+}

src/main.rs

@@ -27,13 +27,7 @@ async fn main() -> anyhow::Result<()> {
 
     let mut rng = rand::thread_rng();
 
-    let conf = config::load();
-
-    if let (false, None) = (conf.capture_images, conf.capture_audio_duration) {
-        return Err(anyhow!(
-            "At least one of image capture and audio capture must be enabled!"
-        ));
-    }
+    let conf = config::load()?;
 
     info!("Loading shows from {}", conf.shows_file.display());
     let shows = shows::load(&conf.shows_file).with_context(|| {
@@ -110,6 +104,12 @@ async fn post_random_capture<R: Rng>(
         Some(d) => media_info.duration_secs - d,
         None => media_info.duration_secs,
     };
+    if max_timestamp < 0.0 {
+        return Err(anyhow!(
+            "Media file {} is too short to take audio clip!",
+            file.display()
+        ));
+    }
     let timestamp = max_timestamp * rng.sample::<f64, _>(Standard);
     let formatted_timestamp = format_timestamp(timestamp, Some(media_info.duration_secs));
     info!("Taking capture at {}", formatted_timestamp);