Fixes #14: Managing errors

text/Issue 14 - Managing errors.md

@@ -0,0 +1,55 @@
+# What's the problem we're trying to solve ?
+
+* Display errors to the user in the web application
+* Give hints to the user about how to fix these errors
+* Only the foxbox should know how to handle errors (example: automatically restart an adapter ?)
+
+# Concrete issue: starting adapters
+
+For reference, here is the current code: https://github.com/fxbox/foxbox/blob/998b6e0e1e1fd3cba3b711783eaa7000c2f66a0d/src/adapters/mod.rs#L61-L69
+
+Basically we unwrap on any error. Some adapters are not returning an Error for some errors because of this.
+
+The end-user can't see panics because he only accesses the app through a web browser.
+So we need another way to log the error instead and let the user act on it (especially
+we might need to be able to restart the foxbox from the browser -- but this is for another issue, I think).
+
+# Some solutions
+
+## 1. Error levels
+
+* init methods return a taxonomied error enum.
+* this error would show error levels: eg: Warn, Fatal, Critical.
+* this error would contain the cause. The cause should be a real error that implements Display/Debug/Error.
+* the box would log the result somewhere the user can look at (but this can be in a separate RFC). For now we could simply log warnings and panic at fatal and critical errors.
+
+```rust
+#[derive(Debug, Clone, Copy)]
+enum ErrorLevel {
+  Warn,
+  Fatal,
+  Critical,
+}
+
+#[derive(Debug)]
+enum Error {
+  AdapterStartError { level: ErrorLevel, cause: Error },
+  CannotCreateTLSCert { level: ErrorLevel, cause: Error },
+  ...
+}
+
+use std::error;
+impl error::Error for Error {
+...
+}
+```
+
+Adapter init methods could return a Taxonomy-defined method that would be automatically converted to a Foxbox' error using a `From<TaxError>` implementation.
+
+## 2. Custom Logger
+
+* we replace env_logger with a logger that would keep the logs in a central place to display it through a web browser
+* the adapters init function directly uses this to log what needs to be logged
+* the adapters init function returns a Error only for Critical errors.
+
+Q: how to scale to other errors ?