[feat] modularized backend with plugin architecture, added module-api, module-host, and summarizer crates, and integrated dynamic module loading into main.rs

backend-rust/crates/modules/summarizer/Cargo.toml

@@ -0,0 +1,14 @@
+[package]
+name = "owly-news-module-summarizer"
+version.workspace = true
+edition.workspace = true
+
+[lib]
+crate-type = ["cdylib"]
+path = "src/lib.rs"
+
+[dependencies]
+anyhow = { workspace = true }
+serde = { workspace = true, features = ["derive"] }
+serde_json = { workspace = true }
+owly-news-module-api = { path = "../../module-api" }

backend-rust/crates/modules/summarizer/src/lib.rs

@@ -0,0 +1,50 @@
+use owly_news_module_api::{cstr_to_str, string_to_cstring_ptr};
+use serde::{Deserialize, Serialize};
+use std::os::raw::c_char;
+
+#[derive(Deserialize)]
+struct SummarizeReq {
+    text: String,
+    #[serde(default = "default_ratio")]
+    ratio: f32,
+}
+
+fn default_ratio() -> f32 { 0.2 }
+
+#[derive(Serialize)]
+struct SummarizeResp {
+    summary: String,
+}
+
+#[unsafe(no_mangle)]
+pub extern "C" fn module_name() -> *const c_char {
+    // IMPORTANT: string must live forever; use a const C string
+    static NAME: &str = "summarizer\0";
+    NAME.as_ptr() as *const c_char
+}
+
+#[unsafe(no_mangle)]
+pub extern "C" fn module_invoke(op: *const c_char, payload: *const c_char) -> *mut c_char {
+    // SAFETY: called by trusted host with valid pointers
+    let res = (|| -> anyhow::Result<String> {
+        let op = unsafe { cstr_to_str(op)? };
+        let payload = unsafe { cstr_to_str(payload)? };
+
+        match op {
+            "summarize" => {
+                let req: SummarizeReq = serde_json::from_str(payload)?;
+                // Placeholder summarization logic. Replace with real algorithm.
+                let words: Vec<&str> = req.text.split_whitespace().collect();
+                let take = ((words.len() as f32) * req.ratio).max(1.0).round() as usize;
+                let summary = words.into_iter().take(take).collect::<Vec<_>>().join(" ");
+                let resp = SummarizeResp { summary };
+                Ok(serde_json::to_string(&resp)?)
+            }
+            _ => anyhow::bail!("unknown op: {op}"),
+        }
+    })();
+
+    let json = res.unwrap_or_else(|e| serde_json::json!({ "error": e.to_string() }).to_string());
+
+    string_to_cstring_ptr(json)
+}