feat: cost-guarded resumable index build (sample smoke + full)

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

src/bin/alpha_id.rs

@@ -52,9 +52,48 @@ fn main() {
     let cfg = Config::load(&cli.config).expect("config");
     match cli.cmd {
         Cmd::Index { sample, full, confirm } => {
+            use alpha_id::embed::{EmbeddingStore, build_corpus_embeddings, estimate};
+            use alpha_id::ionos::IonosClient;
             let p = Pipeline::load(&cfg).expect("load");
-            eprintln!("Loaded {} entries, {} ICD metas. (sample={:?} full={} confirm={})",
+            let texts: Vec<String> = p.entries.iter().map(|e| e.text.clone()).collect();
-                p.entries.len(), p.meta.len(), sample, full, confirm);
+            let client = IonosClient::new(&cfg.ionos_base_url, &cfg.token_path)
+                .expect("ionos client (token?)");
+            let store = EmbeddingStore::open(&cfg.index_dir, &cfg.embed_model).expect("store");
+
+            let subset: Vec<String> = match sample {
+                Some(n) => texts.iter().take(n).cloned().collect(),
+                None => texts.clone(),
+            };
+
+            if sample.is_some() {
+                let est = estimate(&subset);
+                eprintln!("SMOKE: embedding {} sample texts ({} chars)…", est.items, est.chars);
+                let n = build_corpus_embeddings(&client, &store, &cfg.embed_model, &subset, 32)
+                    .expect("sample embed failed");
+                let dim = store.get(&subset[0]).map(|v| v.len()).unwrap_or(0);
+                eprintln!("SMOKE OK: embedded {n}, vector dim = {dim}. \
+                           Inspect, then run `index --full --confirm`.");
+                return;
+            }
+
+            if full {
+                let pending: Vec<String> = texts.iter().filter(|t| !store.has(t)).cloned().collect();
+                let est = estimate(&pending);
+                eprintln!("FULL RUN: {} of {} texts not yet embedded ({} chars). \
+                           This calls IONOS and costs money.", est.items, texts.len(), est.chars);
+                if !confirm {
+                    eprintln!("Refusing without --confirm. Re-run: \
+                               `alpha-id index --full --confirm`");
+                    std::process::exit(2);
+                }
+                let n = build_corpus_embeddings(&client, &store, &cfg.embed_model, &texts, 32)
+                    .expect("full embed failed");
+                eprintln!("FULL RUN done: {n} newly embedded, {} total cached.",
+                    texts.iter().filter(|t| store.has(t)).count());
+                return;
+            }
+
+            eprintln!("Specify --sample N (smoke test first) or --full --confirm.");
         }
         Cmd::Suggest { input, mode, top, billable_only, valid_only, exclude_exotic, chapters, json } => {
             let p = Pipeline::load(&cfg).expect("load");

src/embed.rs

@@ -62,6 +62,23 @@ fn hex(b: &[u8]) -> String {
     b.iter().map(|x| format!("{:02x}", x)).collect()
 }
 
+/// Embed all `texts` not yet cached, in batches. Resumable: a crash
+/// leaves cached vectors intact; rerun continues from the gap.
+pub fn build_corpus_embeddings(
+    client: &IonosClient, store: &EmbeddingStore, model: &str,
+    texts: &[String], batch: usize,
+) -> Result<usize, AppError> {
+    let pending: Vec<String> = texts.iter()
+        .filter(|t| !store.has(t))
+        .cloned()
+        .collect();
+    let mut done = 0;
+    for chunk in pending.chunks(batch.max(1)) {
+        done += embed_batch(client, store, model, chunk)?;
+    }
+    Ok(done)
+}
+
 /// Embed a batch via IONOS, persisting each result. Only `texts` not
 /// already cached should be passed (caller filters via `has`).
 pub fn embed_batch(

tests/index_build_tests.rs

@@ -0,0 +1,32 @@
+use alpha_id::embed::{EmbeddingStore, build_corpus_embeddings};
+use alpha_id::ionos::IonosClient;
+use std::io::Write;
+
+#[test]
+fn build_embeds_only_missing_and_is_resumable() {
+    let server = tiny_http::Server::http("127.0.0.1:0").unwrap();
+    let url = format!("http://{}", server.server_addr());
+    let h = std::thread::spawn(move || {
+        // Only 1 HTTP request is made: both texts fit in a single batch (batch=8).
+        // The second build_corpus_embeddings call finds everything cached and
+        // makes zero requests, so the server only needs to serve once.
+        for _ in 0..1 {
+            if let Ok(req) = server.recv() {
+                let body = r#"{"data":[{"embedding":[0.1,0.2]},{"embedding":[0.3,0.4]}]}"#;
+                req.respond(tiny_http::Response::from_string(body)).ok();
+            }
+        }
+    });
+    let mut tf = tempfile::NamedTempFile::new().unwrap();
+    write!(tf, "tok").unwrap();
+    let client = IonosClient::new(&url, tf.path().to_str().unwrap()).unwrap();
+    let dir = tempfile::tempdir().unwrap();
+    let store = EmbeddingStore::open(dir.path().to_str().unwrap(), "BAAI/bge-m3").unwrap();
+    let texts = vec!["a".to_string(), "b".to_string()];
+
+    let n1 = build_corpus_embeddings(&client, &store, "BAAI/bge-m3", &texts, 8).unwrap();
+    assert_eq!(n1, 2);
+    let n2 = build_corpus_embeddings(&client, &store, "BAAI/bge-m3", &texts, 8).unwrap();
+    assert_eq!(n2, 0);
+    h.join().ok();
+}