WASM 刮削插件开发指南

cargo new --lib my-scraper-wasm

[package]
name = "my-scraper-wasm"
version = "0.1.0"
edition = "2021"

[lib]
crate-type = ["cdylib"]

[dependencies]
serde = { version = "1.0", features = ["derive"] }
serde_json = "1.0"
# 其他依赖...

use std::ffi::{CStr, CString};
use std::os::raw::c_char;
use serde::{Deserialize, Serialize};

// 1. 定义数据结构
#[derive(Serialize)]
struct SearchResult {
    items: Vec<BookItem>,
    total: u32,
    page: u32,
    page_size: u32,
}

#[derive(Serialize)]
struct BookItem {
    id: String,
    title: String,
    author: String,
    cover_url: Option<String>,
    intro: Option<String>,
    tags: Vec<String>,
    // ... 其他字段
}

// 2. 导出 invoke 函数 (必须!)
// 它是插件与宿主交互的唯一入口
#[no_mangle]
pub extern "C" fn invoke(method_ptr: *const c_char, params_ptr: *const c_char) -> *mut c_char {
    let method = unsafe { CStr::from_ptr(method_ptr).to_string_lossy() };
    let params_json = unsafe { CStr::from_ptr(params_ptr).to_string_lossy() };

    let result = match method.as_ref() {
        "search" => handle_search(&params_json).map(|r| serde_json::to_string(&r).unwrap()),
        // 未来扩展其他方法...
        _ => Err(format!("Unknown method: {}", method)),
    };

    let response_json = match result {
        Ok(json) => json,
        Err(e) => serde_json::json!({ "error": e }).to_string(),
    };

    CString::new(response_json).unwrap().into_raw()
}

// 3. 内存管理导出 (必须!)
// 宿主环境需要分配和释放 WASM 内存以传递字符串
#[no_mangle]
pub extern "C" fn alloc(len: usize) -> *mut u8 {
    let mut buf = Vec::with_capacity(len);
    let ptr = buf.as_mut_ptr();
    std::mem::forget(buf);
    ptr
}

#[no_mangle]
pub extern "C" fn dealloc(ptr: *mut u8, len: usize) {
    unsafe {
        let _ = Vec::from_raw_parts(ptr, 0, len);
    }
}

// 4. 业务逻辑实现
fn handle_search(params_json: &str) -> Result<SearchResult, String> {
    // 解析 JSON 参数
    let params: SearchParams = serde_json::from_str(params_json).map_err(|e| e.to_string())?;
    
    // 发起 HTTP 请求 (需自行封装宿主提供的 http_request)
    let url = format!("https://api.example.com/search?q={}", params.query);
    let body = fetch_url(&url)?;
    
    // 解析响应并构造结果
    // ...
    
    // 最佳实践：如果提供了 author 筛选，在此处进行过滤或重排
    if let Some(author) = params.author {
        // ... filter logic
    }

    Ok(SearchResult { 
        items: vec![], // ...
        total: 0,
        page: params.page,
        page_size: 20
    })
}

cargo build --target wasm32-wasip1 --release

#[link(wasm_import_module = "ting_env")]
extern "C" {
    /// 发起 HTTP GET 请求，返回请求句柄（≥0）或错误码（<0）。
    fn http_request(url_ptr: *const u8, url_len: i32) -> i32;
    /// 发起 HTTP POST 请求，返回请求句柄（≥0）或错误码（<0）。
    fn http_post(url_ptr: *const u8, url_len: i32, body_ptr: *const u8, body_len: i32) -> i32;
    /// 发起带有 Bearer Token 的 HTTP GET 请求
    fn http_get_with_token(url_ptr: *const u8, url_len: i32, token_ptr: *const u8, token_len: i32) -> i32;
    /// 发起自定义 HTTP 请求（支持指定 method 和 headers JSON）
    fn http_request_with_headers(
        url_ptr: *const u8, url_len: i32,
        method_ptr: *const u8, method_len: i32,
        headers_ptr: *const u8, headers_len: i32,
        body_ptr: *const u8, body_len: i32
    ) -> i32;
    /// 获取响应体长度（字节）。
    fn http_response_size(handle: i32) -> i32;
    /// 读取响应体到缓冲区，返回实际读取的字节数（≤ len）或错误码。
    fn http_read_body(handle: i32, ptr: *mut u8, len: i32) -> i32;
}

fn fetch_url_custom(url: &str, method: &str, headers_json: &str, body_data: &[u8]) -> Result<Vec<u8>, String> {
    let handle = unsafe {
        http_request_with_headers(
            url.as_ptr(), url.len() as i32,
            method.as_ptr(), method.len() as i32,
            headers_json.as_ptr(), headers_json.len() as i32,
            body_data.as_ptr(), body_data.len() as i32
        )
    };
    
    if handle < 0 {
        return Err(format!("HTTP custom request failed: {}", -handle));
    }

    let size = unsafe { http_response_size(handle) };
    if size < 0 {
        return Err("Failed to get response size".to_string());
    }

    let mut body = vec![0u8; size as usize];
    let read = unsafe { http_read_body(handle, body.as_mut_ptr(), size) };
    if read < 0 {
        return Err("Failed to read body".to_string());
    }
    
    Ok(body)
}