Struct MiddlewareHandler 

pub struct MiddlewareHandler {
    pub engine: Arc<Engine>,
    pub file_path: String,
    pub ast: AST,
}

Handler for a single Rhai middleware script.

Why the AST is compiled once at startup

Rhai offers both “compile on every evaluation” and “compile once, re-run the AST” modes. Middleware is invoked on the hot path (every request), so we keep the compiled AST alongside the Engine and only evaluate at request time. This trades a small amount of memory for a large throughput win and keeps parse errors as startup failures instead of per-request 500s.

The Engine is wrapped in Arc so that MiddlewareHandler can be cloned cheaply into each request task without deep-cloning the interpreter state.

Fields

engine: Arc<Engine>

file_path: String

ast: AST

Implementations

impl MiddlewareHandler

pub fn new(file_path: &str) -> ServerResult<Self>

Compile a middleware script from disk into a reusable handler.

Returns an AppError on either a missing file or a compile-time Rhai parse error. Callers treat both as startup-time failures — we deliberately do not try to recover by, say, skipping the offending script, because silently ignoring a misconfigured middleware would produce confusing request-time behaviour.

pub async fn handle( &self, request_url_path: &str, request_body_json_value: Option<&Value>, request_headers: &HeaderMap, ) -> Option<Result<Response<BoxBody>, Error>>

Evaluate the middleware for one request.

Returns:

• Some(Ok(response)) — the script decided to handle the request and produced a response.
• Some(Err(_)) — the script tried to handle the request but the response could not be built (e.g. invalid header value).
• None — the script returned a value that is neither a string nor a map, which is the convention for “let the next layer handle it”.

Why errors here are logged and converted, not propagated

A Rhai runtime error during per-request evaluation is a script bug, not a startup config bug. Turning it into an AppError would force the whole process down, which is the opposite of what an HTTP server should do. We instead log and fall through to the next handler, producing an HTTP response rather than aborting.

Trait Implementations

impl Clone for MiddlewareHandler

fn clone(&self) -> MiddlewareHandler

Returns a duplicate of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.