Build [quickjs-wasi](https://github.com/second-state/wasmedge-quickjs)
===
# 1. clone project

# new a workspace
$ makedir wasm && cd wasm

# quickjs-wasi rust binding
wasm/$ git clone https://github.com/second-state/wasmedge-quickjs.git

# quickjs-wasi
wasm/$ git clone https://github.com/second-state/quickjs-wasi.git

## wasmedge-quickjs
This is quickjs-wasi's rust binding. It is a rust project.
It is majorly using wasi's libquickjs.a generated by quickjs-wasi to compile rust code to qjs.wasm to use javascript in wasm. This is majorly to meet the need of Rust developers who are unfamiliar with C to extend quickjs in wasm.

## quickjs-wasi
This library is quickjs being changed based on wasi and some features of quickjs have been deleted.

It is majorly used to provide wasmedge-quickjs with
* Static library
`wasmedge-quickjs/lib/libquickjs.a`
* Rust binging of quickjs's C api
`wasmedge-quickjs/lib/binding.rs`

### build
> Usually this is not needed.
> This section can be skipped.

**1、Generate qjs.c and qjscalc.c**

quickjs-wasi$ make

This repl.c and qjscalc.c is the bytecode generated with the corresponding javascript file, mainly working as the repl feature of quickjs. This will be needed in the following compilation.

**2、Generate qjs.wasm**
> wasi-sdk(12) should be installed

quickjs-wasi$ ./build_wasi.sh

This is a standard wasm compiled by quickjs. It can run directly.

# run quickjs repl

quickjs-wasi$ wasmedge --dir=.:. qjs.wasm

QuickJS - Type "\h" for help
qjs > print('hello')
print('hello')
hello
undefined
qjs > 

**3. Generate libquickjs.a & binding.rs**
> Rust bindgen needs to be installed

quickjs-wasi$ cd lib
quickjs-wasi/lib$ ./build_lib.sh
# move to wasmedge-quickjs/lib/
cp libquickjs.a ../../wasmedge-quickjs/lib/
cp binding.rs ../../wasmedge-quickjs/lib/

`wapper.c` has custom function. Majorly
* Packaged static functions of C
* Packaged some macro into functions

`wapper.h` define exported function.
It will be used by `bindgen` in ./build_lib.sh to generate `binding.rs`.

>If a certain program is better to be implemented by C instead of rust, we can tweak `wapper.*` then re-generate to `libquickjs.a` and `binding.rs`.

# 2. build [quickjs-wasi.wasm]
> cargo-wasi extension needs to be installed
> `cargo install cargo-wasi`
> an easy-to-compile command

## Compile a standard quickjs-wasi.wasm

wasmedge-quickjs/$ cargo wasi build --release

wasmedge-quickjs/$ echo "print('hello')" > example_js/hello.js

wasmedge-quickjs/$ wasmedge --dir=.:. target/wasm32-wasi/release/quickjs-rs-wasi.wasm example_js/hello.js
hello
wasmedge-quickjs/$

## Compile quickjs-wasi.wasm + http
This is a http-client feautre extended with [wasmedge_wasi_socket](https://github.com/second-state/wasmedge_wasi_socket) .

wasmedge-quickjs/$ cargo wasi build --features=http --release
wasmedge-quickjs/$ wasmedge --dir=.:. target/wasm32-wasi/release/quickjs-rs-wasi.wasm example_js/http.js
haha
add: 3
get-test
200
{"Connection":"close","Server":"gunicorn/19.9.0","Content-Length":"310","Content-Type":"application/json","Access-Control-Allow-Origin":"*","Access-Control-Allow-Credentials":"true","D
ate":"Sat, 28 Aug 2021 21:50:49 GMT"}
{
  "args": {
    "a": "123"
  },
  "headers": {
    "A": "b",
    "C": "1,2,3",
    "Host": "54.198.109.87",
    "Referer": "http://54.198.109.87/get?a=123",
    "X-Amzn-Trace-Id": "Root=1-612aafb9-74d3c8cc45407da9317ca34d"
  },
  "origin": "36.155.117.30",
  "url": "http://54.198.109.87/get?a=123"
}

delete-test
200
{"Access-Control-Allow-Origin":"*","Date":"Sat, 28 Aug 2021 21:50:50 GMT","Content-Length":"379","Server":"gunicorn/19.9.0","Content-Type":"application/json","Access-Control-Allow-Cred
entials":"true","Connection":"close"}
{
  "args": {
    "a": "123"
  },
  "data": "haha=1",
  "files": {},
  "form": {},
  "headers": {
    "Content-Length": "6",
    "Host": "54.198.109.87",
    "Referer": "http://54.198.109.87/delete?a=123",
    "X-Amzn-Trace-Id": "Root=1-612aafba-3b5865be294e90da4ea88cb4"
  },
  "json": null,
  "origin": "36.155.117.30",
  "url": "http://54.198.109.87/delete?a=123"
}

wasmedge-quickjs/$

For specific user guide for http-client, please refer to
`wasmedge-quickjs/example_js/http.js`

## Compile quickjs-wasi.wasm + img
This is an image feature extended with [image-rs](https://github.com/image-rs/image).

Core code: wasmedge-quickjs/src/quickjs_sys/img_module.rs

wasmedge-quickjs/$ cargo wasi build --features=img --release
wasmedge-quickjs/$ wasmedge --dir=.:. target/wasm32-wasi/release/quickjs-rs-wasi.wasm example_js/img_demo.js
start load image
buf: [object ArrayBuffer]
279434
new image from memory
rgba pixels len 40000
rgb pixels len 30000
luma pixels len 10000
wasmedge-quickjs/$ ls example_js/
add.js  bird.png  bird_luma.png  bird_new_1.png  bird_new_2.jpg  http_demo.js  img_demo.js  tensorflow_demo  tensorflow_lite_demo
wasmedge-quickjs/$

Among these, `bird_luma.png bird_new_1.png bird_new_2.jpg` are the newly generated images.

This image library is the dependency of tensorflow.

## Compile quickjs-wasi.wasm + tensorflow

This is an extension of tensorflow feature with [wasmedge_tensorflow_interface](https://github.com/second-state/wasmedge_tensorflow_interface) as reference.

Core code: wasmedge-quickjs/src/quickjs_sys/tensorflow_module.rs

wasmedge-quickjs/$ cargo wasi build --features=tensorflow --release

**tensorflow classify**

wasmedge-quickjs/$ wasmedge-tensorflow --dir=.:. target/wasm32-wasi/release/quickjs-rs-wasi.wasm example_js/tensorflow_demo/main.js
label index: 23
confidence: 0.6699743270874023
wasmedge-quickjs/$

This is a tensorflow model for animal image classification.
Index 23 is labeled **bald eagle** with a confidence of 0.6699 (max=1.0).

**tensorflow-lite classify**

wasmedge-quickjs/$ wasmedge-tensorflow --dir=.:. target/wasm32-wasi/release/quickjs-rs-wasi.wasm example_js/tensorflow_lite_demo/main.js
label index: 258
confidence: 0.8941176470588236
wasmedge-quickjs/$

This is a tensorflow model for animal image classification.
Index 258 is labeled **Hot dog** with a confidence of 0.8941176470588236 (max=1.0).

# 3. Extend quickjs
This part mainly explains how quickjs can be extended. How to deliver what C can achieve with rust. Developers can refer to image_module and tensorflow module to extend,

## How to extend HTTP to quickjs
> Core code: wasmedge-quickjs/src/quickjs_sys/http_module.rs

This part shows how to write a quickjs module using javascript and rust.

// http_module.rs

// This function will add a http module to ctx
pub(super) fn init_module_http(ctx: &mut Context) {  
    unsafe { 
    let ctx = ctx.ctx;
    // The javascript part of http module is used to wrap the code written by rust
    let init_js = include_str!("../../js_lib/http.js");
    // Get globalThis object
	let global = get_global(ctx);
	
  // Generate a new javascript function from http_module::get
// And set it to global as http_get attribute
// So you can use globalThis['http_get'](...) in javascript
// to call the http_module::get function.
// This is mainly for js_lib/http.js to use.
	set(ctx,"http_get",global,new_function(ctx, "http_get", Some(get)));
	...

	// Execute javascript code in ctx 
	let mut val = JS_Eval(
	ctx,  
	// The javascript code to be executed
	// here is our package code
	make_c_string(init_js).as_ptr(),  
	init_js.len(),  
	// filename, which is in the code of the javascript user
	// import * from'http' 'http' in the end
	make_c_string("http").as_ptr() as *const i8,
	// Use Module type to execute, it will generate a module
	JS_EVAL_TYPE_MODULE as i32,
	); 
	// This way, the javascript code executed in the following ctx,
// You can import * from'http' to use the http-client function packaged in http_module.rs.
  // Delete the function we set up earlier from globalThis.
  // Otherwise, javascript users can also use globalThis['http_get'](...)
super::delete(ctx, "http_get", global);
	super::delete(ctx, "http_get", global);  
	...
 
	// If the execution result of JS_Eval is an exception
	if JS_IsException_real(val) > 0 {
	// dump this exception
		js_std_dump_error(ctx);
	}
  // Because js is the gc mechanism of reference counting
  // We need to free memory in this function
  // The corresponding function to increase the reference count is JS_DupV
	JS_FreeValue_real(ctx, val);  
	JS_FreeValue_real(ctx, global);
 }
}

unsafe fn parse_response(  
    ctx: *mut JSContext,  
  r: Result<http_req::response::Response, http_req::error::Error>,  
  body: &[u8],  
) -> JSValue {...}

unsafe fn parse_headers(  
    ctx: *mut JSContext,  
  req: &mut http_req::request::Request,  
  header: JSValue,  
) -> Result<(), JSValue> {...}

unsafe fn parse_body(ctx: *mut JSContext, body: JSValue) -> Vec<u8> {...}

pub extern "C" fn get(  
    ctx: *mut JSContext,  
  this_val: JSValue,  
  argc: ::std::os::raw::c_int,  
  argv: *mut JSValue,  
) -> JSValue {...}

pub extern "C" fn post(  
    ctx: *mut JSContext,  
  this_val: JSValue,  
  argc: ::std::os::raw::c_int,  
  argv: *mut JSValue,  
) -> JSValue {...}

pub extern "C" fn put(  
    ctx: *mut JSContext,  
  this_val: JSValue,  
  argc: ::std::os::raw::c_int,  
  argv: *mut JSValue,  
) -> JSValue {...}

  
pub extern "C" fn patch(  
    ctx: *mut JSContext,  
  this_val: JSValue,  
  argc: ::std::os::raw::c_int,  
  argv: *mut JSValue,  
) -> JSValue {...}

pub extern "C" fn delete(  
    ctx: *mut JSContext,  
  this_val: JSValue,  
  argc: ::std::os::raw::c_int,  
  argv: *mut JSValue,  
) -> JSValue {...}

## How to extend Tensorflow to quickjs
> Core code: wasmedge-quickjs/src/quickjs_sys/tensorflow_module.rs

// tensorflow_module.rs

// import wasm host function
mod wasmedge_tensorflow {...}

pub mod tensorflow {...}

pub mod tensorflow_lite {
	use super::wasmedge_tensorflow::*;
	use crate::quickjs_sys::*;  
	use std::path::Path;
	struct TensorflowLiteSession {
		context: u64,
		data: Vec<u8>,
	}
	
    impl Drop for TensorflowLiteSession {  
        fn drop(&mut self) {  
            unsafe {
	            wasmedge_tensorflowlite_delete_session(self.context);
	        }  
        }
    }
  
    impl TensorflowLiteSession {  
        pub fn new_from_path<T: AsRef<Path>>(path: T) -> Result<Self, String> {...}
        pub unsafe fn add_input(&mut self, name: &str, tensor_buf: *const u8, tensor_buf_len: u32) {...}  
        pub unsafe fn run(&mut self) {...} 
        pub unsafe fn get_output(&self, name: &str) -> Vec<u8> {...}  
	}

	// bind function  
	// Wrap the rust function into the form of javascript native input and output parameters.
// Complete the extraction of parameters and the wrapping of return value here
	
	unsafe extern "C" fn bind_add_input(
		ctx: *mut JSContext,
		this_val: JSValue,  
		argc: ::std::os::raw::c_int,  
		argv: *mut JSValue,  
	) -> JSValue {...}
    
    unsafe extern "C" fn bind_run(
	    ctx: *mut JSContext,  
		this_val: JSValue,  
		argc: ::std::os::raw::c_int,  
		argv: *mut JSValue,  
	) -> JSValue {...}
  
    unsafe extern "C" fn bind_get_output(  
        ctx: *mut JSContext,  
		this_val: JSValue,  
		argc: ::std::os::raw::c_int,  
		argv: *mut JSValue,  
	) -> JSValue {...}
  
    // bind to quickjs  
    
    // Important function
    // This function is called when our newly created Class object is gc, that is, when the reference count returns to zero.
     // We need to free memory in this function
	unsafe extern "C" fn js_finalizer(rt: *mut JSRuntime, val: JSValue) {
		// Additional memory data of this object will be obtained, a *void
		let s = JS_GetOpaque(val, JS_CLASS_ID) as *mut TensorflowLiteSession;
		if !s.is_null() {
			// Back to the life cycle of rust and be released.
			Box::from_raw(s);
		}
    }
    
    // Important function
    // This function implements how to convert a rust object to JSValue
    unsafe fn Session_to_JSValue(
	    ctx: *mut JSContext,
		session: Box<TensorflowLiteSession>,
	) -> JSValue {
		let obj = JS_NewObjectClass(ctx, JS_CLASS_ID as i32);  
		if JS_IsException_real(obj) > 0 {
			return obj;
		}
		// Important! Leak the memory of rust and escape the life cycle of rust.
        let ptr_data = Box::leak(session);
        JS_SetOpaque(obj, (ptr_data as *mut TensorflowLiteSession).cast());
        obj
    }
  
	// Important function!
	// This function will be registered as the constructor of our custom class
    unsafe extern "C" fn js_ctor(
	    ctx: *mut JSContext,  
		new_target: JSValue,  
		argc: ::std::os::raw::c_int,  
		argv: *mut JSValue,
	) -> JSValue {  
        if argv.is_null() || argc == 0 {
	        return js_throw_error(ctx, "argv is empty");
	    }
        let param = *argv;
        let session = if JS_IsString_real(param) > 0 {
		    let path = match to_string(ctx, param) {  
	            Ok(path) => path,
	            Err(e) => return js_throw_error(ctx, e),
	        };  
			let session = match TensorflowLiteSession::new_from_path(path) {  
                Ok(s) => s,
                Err(e) => return js_throw_error(ctx, e),
	        };
			Box::new(session)  
        } else {  
            return js_throw_error(ctx, "param error");
        };
        return Session_to_JSValue(ctx, session);
	}
	
	// For storing class_id
	pub static mut JS_CLASS_ID: JSClassID = 0;
	// For storing class's constructor, majorly used as JS_IsInstanceOf
	pub static mut JS_CLASS: JSValue = 0;
	// class definition
	static mut JS_CLASS_DEF: JSClassDef = JSClassDef {
		class_name: "TensorflowSession\0".as_ptr() as *const i8,
		finalizer: Some(js_finalizer),
		gc_mark: None,
		call: None,
		exotic: ::std::ptr::null_mut(),
	};
	// class method list
	// Defined the class method name the javascript user can see
	static mut JS_PROTO_FUNCS: [JSCFunctionListEntry; 3] = [
		CFUNC_DEF!("add_input\0", bind_add_input, 2),  
		CFUNC_DEF!("run\0", bind_run, 0),  
		CFUNC_DEF!("get_output\0", bind_get_output, 1),
	];
	
	// module init
	unsafe extern "C" fn js_module_init(
		ctx: *mut JSContext,
        m: *mut JSModuleDef,
	) -> ::std::os::raw::c_int {
		// Create a class_id in js
		JS_NewClassID(&mut JS_CLASS_ID);
		// Bind a JSClassDef to this class_id
		JS_NewClass(JS_GetRuntime(ctx), JS_CLASS_ID, &JS_CLASS_DEF);
		
		let proto = JS_NewObject(ctx);
		JS_SetPropertyFunctionList(
			ctx,
			proto,  
			JS_PROTO_FUNCS.as_ptr(),  
			JS_PROTO_FUNCS.len() as i32,
		);
		// Generate a constructor
		JS_CLASS = JS_NewCFunction2(
			ctx,  
			Some(js_ctor),  
			make_c_string("TensorflowLiteSession").as_ptr(),  
			1,
			JSCFunctionEnum_JS_CFUNC_constructor,
			0,
		);
		// Set up custom constructor of class
		JS_SetConstructor(ctx, JS_CLASS, proto);
		// Set up custom proto of class
		JS_SetClassProto(ctx, JS_CLASS_ID, proto);
		
		// Set up export in module
		// Here, the exported is the constructor exported of Class
		JS_SetModuleExport(
			ctx,
			m,
			make_c_string("TensorflowLiteSession").as_ptr(),
			JS_CLASS,
		);
		0
	}
	
	// new Module
	// Create a new JSModule in CTX
	pub unsafe fn init_module_tensorflow_lite(ctx: *mut JSContext) -> *mut JSModuleDef {
		let name = make_c_string("tensorflow_lite");
		let m = JS_NewCModule(ctx, name.as_ptr(), Some(js_module_init));
		if m.is_null() {
			return m;
		}
		JS_AddModuleExport(ctx, m, make_c_string("TensorflowLiteSession").as_ptr());  
		return m;
	}
}