Add lookup_env_var to get environment Variable

ferron-common/src/util/lookup_env_var.rs

@@ -0,0 +1,70 @@
+use std::env;
+use anyhow::bail;
+
+pub fn lookup_env_value(conf_string: String) -> anyhow::Result<String> {
+    if !conf_string.starts_with("{env:") {
+        bail!("String '{}' does not start with '{{env:'", conf_string);
+    }
+
+    // Search Index of "{env:"
+    if let Some(index_lb) = conf_string.find("{env:") {
+        // Search for ending "}"
+        if let Some(index_rb_afterlb) = conf_string[index_lb + 5..].find("}") {
+            return get_env_val(
+                conf_string[index_lb + 5..index_lb + 5 + index_rb_afterlb].to_string(),
+            );
+        } else {
+            bail!("No closing '}}' found in string '{}'", conf_string);
+        }
+    }
+
+    // If not an env prefix return the string
+    Ok(conf_string)
+}
+
+pub fn get_env_val(conf_key: String) -> anyhow::Result<String> {
+    match env::var(conf_key.clone()) {
+        Ok(val) => return Ok(val),
+        Err(e) => bail!("couldn't find ENV-Key >>{conf_key}<< {e}"),
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn lala_get_env_var() {
+        let result = get_env_val("LALA".to_string());
+        assert!(
+            result.is_err(),
+            "couldn't find ENV-Key >>LALA<< environment variable not found"
+        );
+    }
+
+    #[test]
+    fn home_get_env_var() {
+        let result = get_env_val("HOME".to_string());
+        assert!(result.is_ok(), "Found 'HOME'");
+    }
+
+    #[test]
+    fn missing_get_env_key() {
+        let result = lookup_env_value("LALA".to_string());
+        assert!(result.is_err(), "Not found LALA");
+    }
+
+    #[test]
+    fn success_lookup_env_value() {
+        let result = lookup_env_value("{env:HOME}".to_string());
+        assert!(result.is_ok(), "Get successfully 'HOME' ENV");
+    }
+    #[test]
+    fn failed_lookup_env_value() {
+        let result = lookup_env_value("{envA:HOME}".to_string());
+        assert!(
+            result.is_err(),
+            "couldn't find ENV-Key >>:HOME<< environment variable not found"
+        );
+    }
+}