chain-module-sdk-rust/crates/fai-module-sdk-macros/src/lib.rs

//! Procedural macros powering `fai-module-sdk`.
//!
//! This crate exists only to host the `#[fai_module]` attribute.
//! Module authors should depend on `fai-module-sdk` (which
//! re-exports the macro), not on this crate directly.

use proc_macro::TokenStream;
use quote::quote;
use syn::{ItemFn, parse_macro_input};

/// The frozen WIT contract, embedded at proc-macro compile time.
/// The platform repo and this repo both ship a SHA-256 snapshot
/// test that fails if these copies drift.
const WIT_INLINE: &str = include_str!("../../../wit/world.wit");

/// Wrap a function with all the WASM module boilerplate.
///
/// The annotated function must have the signature:
///
/// ```ignore
/// fn invoke(ctx: Context, inputs: Inputs) -> Result<Outputs, ModuleError>
/// ```
///
/// The macro generates the `wit_bindgen::generate!` invocation,
/// the `Guest` implementation, the WIT-to-SDK conversions, and
/// the `wit_bindgen::export!` call. The function can be named
/// anything — only its signature matters.
#[proc_macro_attribute]
pub fn fai_module(_attrs: TokenStream, input: TokenStream) -> TokenStream {
    let user_fn = parse_macro_input!(input as ItemFn);
    let user_fn_name = user_fn.sig.ident.clone();
    let wit_literal = WIT_INLINE;

    let expanded = quote! {
        #user_fn

        // The WASM glue (wit_bindgen::generate!, Guest impl, export!)
        // is only emitted for the wasm32 target. Host builds skip
        // it so module crates can use crate-type = ["cdylib", "rlib"]
        // and run integration tests via `cargo test` without
        // dragging the wit_bindgen runtime onto the host target.
        #[cfg(target_arch = "wasm32")]
        #[doc(hidden)]
        mod __fai_module_sdk_internal {
            #![allow(
                    unsafe_op_in_unsafe_fn,
                    unused_imports,
                    dead_code,
                    clippy::all,
                    clippy::pedantic,
                    clippy::nursery
                )]

                ::fai_module_sdk::__rt::wit_bindgen::generate!({
                    inline: #wit_literal,
                    world: "module",
                    runtime_path: "::fai_module_sdk::__rt::wit_bindgen::rt",
                });

                use exports::fai::platform::invoke::Guest;
                use fai::platform::types::{
                    BytesValue as WitBytes,
                    FileRef as WitFileRef,
                    InvocationContext as WitContext,
                    InvocationError as WitError,
                    Payload as WitPayload,
                };

                struct Component;

                impl Guest for Component {
                    fn invoke(
                        ctx: WitContext,
                        inputs: ::std::vec::Vec<(
                            ::std::string::String,
                            WitPayload,
                        )>,
                    ) -> ::core::result::Result<
                        ::std::vec::Vec<(::std::string::String, WitPayload)>,
                        WitError,
                    > {
                        let sdk_ctx = ::fai_module_sdk::Context {
                            invocation_id: ctx.invocation_id,
                            capability_namespace: ctx.capability_namespace,
                            capability_name: ctx.capability_name,
                            deadline_ms: ctx.deadline_ms,
                        };
                        let sdk_pairs: ::std::vec::Vec<(
                            ::std::string::String,
                            ::fai_module_sdk::Payload,
                        )> = inputs
                            .into_iter()
                            .map(|(k, p)| (k, wit_payload_to_sdk(p)))
                            .collect();
                        let sdk_inputs =
                            ::fai_module_sdk::Inputs::__from_pairs(sdk_pairs);

                        match super::#user_fn_name(sdk_ctx, sdk_inputs) {
                            Ok(outputs) => {
                                let pairs = outputs.__into_pairs();
                                let wit_pairs = pairs
                                    .into_iter()
                                    .map(|(k, p)| (k, sdk_payload_to_wit(p)))
                                    .collect();
                                Ok(wit_pairs)
                            }
                            Err(e) => Err(sdk_error_to_wit(e)),
                        }
                    }
                }

                fn wit_payload_to_sdk(p: WitPayload) -> ::fai_module_sdk::Payload {
                    match p {
                        WitPayload::Text(s) => ::fai_module_sdk::Payload::Text(s),
                        WitPayload::Json(s) => ::fai_module_sdk::Payload::Json(s),
                        WitPayload::Bytes(b) => ::fai_module_sdk::Payload::Bytes(
                            ::fai_module_sdk::BytesValue {
                                mime_type: b.mime_type,
                                data: b.data,
                            },
                        ),
                        WitPayload::FileRef(f) => ::fai_module_sdk::Payload::FileRef(
                            ::fai_module_sdk::FileRef {
                                uri: f.uri,
                                mime_type: f.mime_type,
                                size_bytes: f.size_bytes,
                                sha256: f.sha256,
                            },
                        ),
                    }
                }

                fn sdk_payload_to_wit(p: ::fai_module_sdk::Payload) -> WitPayload {
                    match p {
                        ::fai_module_sdk::Payload::Text(s) => WitPayload::Text(s),
                        ::fai_module_sdk::Payload::Json(s) => WitPayload::Json(s),
                        ::fai_module_sdk::Payload::Bytes(b) => WitPayload::Bytes(WitBytes {
                            mime_type: b.mime_type,
                            data: b.data,
                        }),
                        ::fai_module_sdk::Payload::FileRef(f) => WitPayload::FileRef(WitFileRef {
                            uri: f.uri,
                            mime_type: f.mime_type,
                            size_bytes: f.size_bytes,
                            sha256: f.sha256,
                        }),
                    }
                }

                fn sdk_error_to_wit(e: ::fai_module_sdk::ModuleError) -> WitError {
                    match e {
                        ::fai_module_sdk::ModuleError::InvalidInput(s) => {
                            WitError::InvalidInput(s)
                        }
                        ::fai_module_sdk::ModuleError::PermissionDenied(s) => {
                            WitError::PermissionDenied(s)
                        }
                        ::fai_module_sdk::ModuleError::ResourceExhausted(s) => {
                            WitError::ResourceExhausted(s)
                        }
                        ::fai_module_sdk::ModuleError::DeadlineExceeded => {
                            WitError::DeadlineExceeded
                        }
                        ::fai_module_sdk::ModuleError::Internal(s) => WitError::Internal(s),
                    }
                }

            export!(Component);
        }
    };

    TokenStream::from(expanded)
}