rorpc_parse/codegen/

orpc.rs

//! Code generation for the `#[rorpc(method, path)]` attribute macro.
//!
//! Parses the attribute arguments, analyses the handler signature, and emits:
//! - The original function unchanged
//! - An `inventory::submit!` for `HandlerMetadata`
//! - An `inventory::submit!` for `HandlerRegistration` (Axum router factory)
//! - `inventory::submit!` blocks for `SchemaRegistration` fallback schemas

use proc_macro2::TokenStream;
use quote::quote;
use syn::{
    Expr, ExprLit, ItemFn, Lit, MetaNameValue, Token,
    parse::{Parse, ParseStream},
    punctuated::Punctuated,
};

use crate::{
    errors::{Error, Result, type_display},
    functions::extract_handler_signature,
    types::{JSON, QUERY, RESULT, innermost_custom_type, is_primitive, try_extract_wrapper},
};

// ---------------------------------------------------------------------------
// OrpcArgs — parsed from #[orpc(method = "...", path = "...", stream_event = TypePath)]
// ---------------------------------------------------------------------------

/// Parsed arguments for the `#[orpc(...)]` attribute.
pub struct OrpcArgs {
    pub method: String,
    pub path: String,
    pub stream_event: Option<syn::Type>,
}

const VALID_KEYS: &[&str] = &["method", "path", "stream_event"];

impl Parse for OrpcArgs {
    fn parse(input: ParseStream) -> syn::Result<Self> {
        let pairs = Punctuated::<MetaNameValue, Token![,]>::parse_terminated(input)?;

        let mut method = None;
        let mut path = None;
        let mut stream_event = None;

        for pair in &pairs {
            let key = pair
                .path
                .get_ident()
                .map(|i| i.to_string())
                .unwrap_or_default();

            let span = pair
                .path
                .get_ident()
                .map(|i| i.span())
                .unwrap_or_else(proc_macro2::Span::call_site);

            match key.as_str() {
                "method" => {
                    if let Expr::Lit(ExprLit {
                        lit: Lit::Str(s), ..
                    }) = &pair.value
                    {
                        method = Some(s.value().to_uppercase());
                    } else {
                        return Err(syn::Error::new(
                            span,
                            Error::invalid_attr_value(
                                span,
                                &key,
                                "a string literal",
                                "non-string expression",
                            )
                            .to_string(),
                        ));
                    }
                }
                "path" => {
                    if let Expr::Lit(ExprLit {
                        lit: Lit::Str(s), ..
                    }) = &pair.value
                    {
                        path = Some(s.value());
                    } else {
                        return Err(syn::Error::new(
                            span,
                            Error::invalid_attr_value(
                                span,
                                &key,
                                "a string literal",
                                "non-string expression",
                            )
                            .to_string(),
                        ));
                    }
                }
                "stream_event" => {
                    // Accept a type path: stream_event = StreamEvent
                    if let Expr::Path(expr_path) = &pair.value {
                        let type_path = syn::TypePath {
                            attrs: vec![],
                            qself: expr_path.qself.clone(),
                            path: expr_path.path.clone(),
                        };
                        stream_event = Some(syn::Type::Path(type_path));
                    } else {
                        return Err(syn::Error::new(
                            span,
                            "stream_event must be a type path (e.g., StreamEvent or module::StreamEvent)",
                        ));
                    }
                }
                _ => {
                    return Err(syn::Error::new(
                        span,
                        Error::unknown_key(span, &key, VALID_KEYS).to_string(),
                    ));
                }
            }
        }

        let method = method.ok_or_else(|| {
            syn::Error::new(
                proc_macro2::Span::call_site(),
                Error::missing_required_attr(
                    proc_macro2::Span::call_site(),
                    "method",
                    "add `method = \"GET\"` to #[rorpc]",
                )
                .to_string(),
            )
        })?;

        let path = path.ok_or_else(|| {
            syn::Error::new(
                proc_macro2::Span::call_site(),
                Error::missing_required_attr(
                    proc_macro2::Span::call_site(),
                    "path",
                    "add `path = \"/your/route\"` to #[rorpc]",
                )
                .to_string(),
            )
        })?;

        Ok(OrpcArgs {
            method,
            path,
            stream_event,
        })
    }
}

// ---------------------------------------------------------------------------
// expand_orpc
// ---------------------------------------------------------------------------

/// Generate the full expansion for `#[orpc(method, path)] async fn handler(...)`.
///
/// Returns the original function unchanged plus all inventory registrations.
pub fn expand_orpc(args: OrpcArgs, func: ItemFn) -> TokenStream {
    match try_expand_orpc(args, func) {
        Ok(ts) => ts,
        Err(e) => e.to_compile_error(),
    }
}

fn try_expand_orpc(args: OrpcArgs, func: ItemFn) -> Result<TokenStream> {
    let sig = extract_handler_signature(&func)?;

    let fn_name = &func.sig.ident;
    let fn_name_str = sig.fn_name.as_str();
    let method = &args.method;
    let path = &args.path;

    let output_type_str = type_display(&sig.output_type);

    let error_type_token = match &sig.error_type {
        Some(ty) => {
            let s = type_display(ty);
            quote! { Some(#s) }
        }
        None => quote! { None },
    };

    let stream_event_token = match &args.stream_event {
        Some(ty) => {
            let s = type_display(ty);
            quote! { Some(#s) }
        }
        None => quote! { None },
    };

    let input_type_str = match &sig.input_type {
        Some(ty) => type_display(ty),
        None => "()".to_string(),
    };

    let query_type_token = match &sig.query_type {
        Some(ty) => {
            let s = type_display(ty);
            quote! { Some(#s) }
        }
        None => quote! { None },
    };

    let registration = emit_handler_registration(fn_name, method, path, &sig.state_type);
    let schema_registrations = emit_schema_registrations(&func);

    Ok(quote! {
        #func

        ::rorpc::inventory::submit! {
            ::rorpc::HandlerMetadata {
                name: #fn_name_str,
                method: #method,
                path: #path,
                input_type_name: #input_type_str,
                query_type_name: #query_type_token,
                output_type_name: #output_type_str,
                module_path: ::std::module_path!(),
                error_type_name: #error_type_token,
                stream_event_type_name: #stream_event_token,
            }
        }

        #registration
        #schema_registrations
    })
}

// ---------------------------------------------------------------------------
// Handler registration factory
// ---------------------------------------------------------------------------

fn emit_handler_registration(
    fn_name: &syn::Ident,
    method: &str,
    path: &str,
    state_type: &Option<syn::Type>,
) -> TokenStream {
    if let Some(state_ty) = state_type {
        quote! {
            ::rorpc::inventory::submit! {
                ::rorpc::HandlerRegistration {
                    path: #path,
                    method: #method,
                    factory: |state: ::std::sync::Arc<dyn ::std::any::Any + Send + Sync>| {
                        use ::axum::routing::{delete, get, patch, post, put};
                        let method_router = match #method {
                            "GET"    => get(#fn_name),
                            "POST"   => post(#fn_name),
                            "PUT"    => put(#fn_name),
                            "PATCH"  => patch(#fn_name),
                            "DELETE" => delete(#fn_name),
                            _        => post(#fn_name),
                        };
                        if let Some(typed_state) = state.downcast_ref::<#state_ty>() {
                            ::axum::Router::new()
                                .route(#path, method_router)
                                .with_state(typed_state.clone())
                        } else {
                            ::axum::Router::new()
                        }
                    },
                }
            }
        }
    } else {
        quote! {
            ::rorpc::inventory::submit! {
                ::rorpc::HandlerRegistration {
                    path: #path,
                    method: #method,
                    factory: |_state: ::std::sync::Arc<dyn ::std::any::Any + Send + Sync>| {
                        use ::axum::routing::{delete, get, patch, post, put};
                        let method_router = match #method {
                            "GET"    => get(#fn_name),
                            "POST"   => post(#fn_name),
                            "PUT"    => put(#fn_name),
                            "PATCH"  => patch(#fn_name),
                            "DELETE" => delete(#fn_name),
                            _        => post(#fn_name),
                        };
                        ::axum::Router::new().route(#path, method_router)
                    },
                }
            }
        }
    }
}

// ---------------------------------------------------------------------------
// Schema registrations — z.unknown() fallback for types without #[derive(ZodTs)]
// ---------------------------------------------------------------------------

fn emit_schema_registrations(func: &ItemFn) -> TokenStream {
    let mut seen = std::collections::HashSet::new();
    let mut registrations = Vec::new();

    // Collect candidate types from Json<T> and Query<T> params and return type
    let mut candidates: Vec<&syn::Type> = Vec::new();

    for arg in &func.sig.inputs {
        if let syn::FnArg::Typed(pat_type) = arg {
            // Check for Json<T>
            if let Some(m) = try_extract_wrapper(&pat_type.ty, JSON)
                && let Some(inner) = m.first_type()
            {
                candidates.push(inner);
            }
            // Check for Query<T>
            if let Some(m) = try_extract_wrapper(&pat_type.ty, QUERY)
                && let Some(inner) = m.first_type()
            {
                candidates.push(inner);
            }
        }
    }

    if let syn::ReturnType::Type(_, ty) = &func.sig.output {
        // Handle both Json<T> and Result<Json<T>, E>
        if let Some(m) = try_extract_wrapper(ty, JSON) {
            if let Some(inner) = m.first_type() {
                candidates.push(inner);
            }
        } else if let Some(result_m) = try_extract_wrapper(ty, RESULT)
            && let Some(first) = result_m.first_type()
            && let Some(json_m) = try_extract_wrapper(first, JSON)
            && let Some(inner) = json_m.first_type()
        {
            candidates.push(inner);
        }
    }

    for ty in candidates {
        if let Some(custom_ty) = innermost_custom_type(ty) {
            if is_primitive(custom_ty) {
                continue;
            }
            let name = type_display(custom_ty);
            if !seen.insert(name.clone()) {
                continue;
            }
            let fallback = format!(
                "z.unknown() /* add #[derive(ZodTs)] to {} for a real schema */",
                name
            );
            registrations.push(quote! {
                ::rorpc::inventory::submit! {
                    ::rorpc::SchemaRegistration {
                        type_name: #name,
                        zod_ts: || #fallback.to_string(),
                        dependent_types: || vec![],
                    }
                }
            });
        }
    }

    quote! { #(#registrations)* }
}

// ---------------------------------------------------------------------------
// Tests
// ---------------------------------------------------------------------------

#[cfg(test)]
mod tests {
    use super::*;
    use syn::parse_quote;

    #[test]
    fn parse_stream_event_type_path() {
        // Test that stream_event = StreamEvent (without quotes) parses correctly
        let args: OrpcArgs = syn::parse_quote! {
            method = "GET", path = "/stream", stream_event = StreamEvent
        };

        assert_eq!(args.method, "GET");
        assert_eq!(args.path, "/stream");
        assert!(args.stream_event.is_some());

        // Verify type_display produces the correct string
        let ty = args.stream_event.unwrap();
        let type_str = crate::errors::type_display(&ty);
        assert_eq!(type_str, "StreamEvent");
    }

    #[test]
    fn parse_stream_event_qualified_path() {
        // Test that stream_event = crate::models::StreamEvent works
        let args: OrpcArgs = syn::parse_quote! {
            method = "GET", path = "/stream", stream_event = crate::models::StreamEvent
        };

        assert!(args.stream_event.is_some());
        let ty = args.stream_event.unwrap();
        let type_str = crate::errors::type_display(&ty);
        assert_eq!(type_str, "crate::models::StreamEvent");
    }

    #[test]
    fn parse_without_stream_event() {
        // Test that stream_event is optional
        let args: OrpcArgs = syn::parse_quote! {
            method = "POST", path = "/create"
        };

        assert_eq!(args.method, "POST");
        assert_eq!(args.path, "/create");
        assert!(args.stream_event.is_none());
    }

    #[test]
    fn stream_event_type_converts_to_string_literal() {
        // This is the critical test for the bug fix
        // Verify that when we generate the metadata, stream_event becomes a string literal
        let args: OrpcArgs = syn::parse_quote! {
            method = "GET", path = "/stream", stream_event = StreamEvent
        };

        let func: syn::ItemFn = parse_quote! {
            async fn stream_test() -> Sse<impl Stream<Item = Event>> {
                todo!()
            }
        };

        let result = try_expand_orpc(args, func);
        assert!(result.is_ok(), "expand_orpc should succeed");

        // Check that the generated code contains Some("StreamEvent") as a string literal
        let tokens = result.unwrap().to_string();

        // quote! serialises with spaces between tokens, so `Some("StreamEvent")` becomes
        // `Some ("StreamEvent")`. Check the field name and the quoted value separately.
        assert!(
            tokens.contains("stream_event_type_name") && tokens.contains(r#""StreamEvent""#),
            "Generated code should contain stream_event_type_name: Some(\"StreamEvent\"), got: {}",
            tokens
        );
        // Also assert it is NOT a bare identifier (which would be a type error at compile time)
        assert!(
            !tokens.contains("Some (StreamEvent)") && !tokens.contains("Some(StreamEvent)"),
            "stream_event_type_name must be a string literal, not a bare identifier"
        );
    }
}