From 947118def11db76241118096d17a7a82a9b83ebe Mon Sep 17 00:00:00 2001
From: Michael Zhang <mail@mzhang.io>
Date: Sun, 23 Jun 2024 13:56:45 -0500
Subject: [PATCH] wip

---
 crates/panorama-app-sdk/src/lib.rs     | 33 ++++++++++++++++++++------
 crates/panorama-core/src/state/apps.rs | 26 ++++++++++++++------
 2 files changed, 45 insertions(+), 14 deletions(-)

diff --git a/crates/panorama-app-sdk/src/lib.rs b/crates/panorama-app-sdk/src/lib.rs
index 58fbfc0..68a8c3d 100644
--- a/crates/panorama-app-sdk/src/lib.rs
+++ b/crates/panorama-app-sdk/src/lib.rs
@@ -1,24 +1,42 @@
-use std::ffi::CString;
+// Reference for FFI closures
+// https://adventures.michaelfbryan.com/posts/rust-closures-in-ffi/
 
-use sys::RegisterCallback;
+use std::ffi::{c_char, c_void, CString};
 
 pub mod sys {
-  use std::ffi::c_char;
+  use std::ffi::{c_char, c_void};
 
-  use crate::RegisterContext;
-
-  pub type RegisterCallback = fn(*mut RegisterContext) -> ();
+  use crate::RegisterCallback;
 
   extern "C" {
     pub fn register_endpoint(
       url_len: u64,
       url: *const c_char,
       callback: *mut RegisterCallback,
+      callback_data: *mut c_void,
     );
   }
 }
 
 pub struct RegisterContext {}
+pub type RegisterCallback = fn(*mut RegisterContext) -> ();
+
+unsafe extern "C" fn register_endpoint_callback_trampoline<F>(
+  context: *mut RegisterContext,
+  register_callback: *mut c_void,
+) where
+  F: FnMut(*mut RegisterContext),
+{
+  let register_callback = &mut *(register_callback as *mut F);
+  register_callback(context);
+}
+
+pub fn get_trampoline<F>(_closure: &F) -> RegisterCallback
+where
+  F: FnMut(*mut RegisterCallback),
+{
+  register_endpoint_callback_trampoline::<F>
+}
 
 pub fn register_endpoint(
   url: impl AsRef<str>,
@@ -31,7 +49,8 @@ pub fn register_endpoint(
     sys::register_endpoint(
       url.len() as u64,
       url_cstr.into_raw(),
-      &mut callback2 as *mut RegisterCallback,
+      register_endpoint_callback_trampoline,
+      &mut callback2 as *mut _ as *mut c_void,
     )
   };
   println!("Result: {:?}", result);
diff --git a/crates/panorama-core/src/state/apps.rs b/crates/panorama-core/src/state/apps.rs
index a9ee076..ebae6db 100644
--- a/crates/panorama-core/src/state/apps.rs
+++ b/crates/panorama-core/src/state/apps.rs
@@ -3,13 +3,11 @@ use std::{
   fs::{self, File},
   io::Read,
   path::{Path, PathBuf},
-  sync::Arc,
 };
 
 use anyhow::{Context as _, Result};
-use serde_yaml::Value;
 use wasmtime::{
-  Caller, Config, Engine, Linker, Memory, MemoryType, Module, Store,
+  AsContext, Caller, Config, Engine, Linker, Memory, Module, Store,
 };
 use wasmtime_wasi::WasiCtxBuilder;
 
@@ -115,10 +113,9 @@ impl AppState {
         println!("WTF? {url_len} {url}");
         let mem = caller.get_export("memory").and_then(|e| e.into_memory());
         if let Some(mem) = mem {
-          let mut buffer = vec![0; url_len as usize];
-          mem.read(caller, url as usize, &mut buffer);
-          let string = String::from_utf8(buffer);
-          println!("{:?}", string);
+          let result =
+            read_utf_8string(&mut caller, &mem, url_len as usize, url as usize);
+          println!("{:?}", result);
         }
         // println!("my host state is: {}", caller.data());
       },
@@ -141,3 +138,18 @@ impl AppState {
     Ok(())
   }
 }
+
+fn read_utf_8string<C>(
+  c: C,
+  mem: &Memory,
+  len: usize,
+  offset: usize,
+) -> Result<String>
+where
+  C: AsContext,
+{
+  let mut buffer = vec![0; len];
+  mem.read(c, offset, &mut buffer)?;
+  let string = String::from_utf8(buffer)?;
+  Ok(string)
+}