feat(memory): implement recall scoring

codex-rs/memory/Cargo.toml

@@ -7,6 +7,7 @@ edition = { workspace = true }
 anyhow = "1"
 serde = { version = "1", features = ["derive"] }
 serde_json = "1"
+chrono = { version = "0.4", default-features = false, features = ["clock"] }
 
 [features]
 default = []

codex-rs/memory/src/recall.rs

@@ -1,4 +1,9 @@
+use crate::store::MemoryStore;
 use crate::types::MemoryItem;
+use crate::types::Status;
+use chrono::DateTime;
+use chrono::Utc;
+use std::collections::BTreeSet;
 
 pub struct RecallContext {
     pub repo_root: Option<std::path::PathBuf>,
@@ -13,9 +18,88 @@ pub struct RecallContext {
 }
 
 pub fn recall(
-    _store: &dyn crate::store::MemoryStore,
-    _prompt: &str,
-    _ctx: &RecallContext,
+    store: &dyn MemoryStore,
+    prompt: &str,
+    ctx: &RecallContext,
 ) -> anyhow::Result<Vec<MemoryItem>> {
-    todo!()
+    let now = DateTime::parse_from_rfc3339(&ctx.now_rfc3339)?.with_timezone(&Utc);
+    let tokens = tokenize(prompt);
+    let mut scored: Vec<(f32, usize, MemoryItem)> = store
+        .list(None, Some(Status::Active))?
+        .into_iter()
+        .map(|item| {
+            let mut score = overlap_score(&tokens, &tokenize(&item.content));
+            if let Some(f) = &ctx.current_file
+                && item.relevance_hints.files.iter().any(|h| f.ends_with(h))
+            {
+                score += 0.4;
+            }
+            if let Some(c) = &ctx.crate_name
+                && item.relevance_hints.crates.iter().any(|h| h == c)
+            {
+                score += 0.3;
+            }
+            if let Some(l) = &ctx.language
+                && item
+                    .relevance_hints
+                    .languages
+                    .iter()
+                    .any(|h| h.eq_ignore_ascii_case(l))
+            {
+                score += 0.2;
+            }
+            if let Some(cmd) = &ctx.command
+                && item.relevance_hints.commands.iter().any(|h| h == cmd)
+            {
+                score += 0.1;
+            }
+            let freq = 1.0 + item.counters.used_count as f32 * 0.1;
+            score *= freq;
+            if let Some(last) = &item.counters.last_used_at
+                && let Ok(dt) = DateTime::parse_from_rfc3339(last)
+            {
+                let age_days = (now - dt.with_timezone(&Utc)).num_days();
+                let decay = 0.5f32.powf(age_days as f32 / 7.0);
+                score *= decay;
+            }
+            let token_len = item.content.split_whitespace().count();
+            (score, token_len, item)
+        })
+        .collect();
+    scored.sort_by(|a, b| b.0.partial_cmp(&a.0).unwrap_or(std::cmp::Ordering::Equal));
+    let mut out = Vec::new();
+    let mut used_tokens = 0usize;
+    for (_, tokens, mut item) in scored {
+        if out.len() >= ctx.item_cap {
+            break;
+        }
+        if used_tokens + tokens > ctx.token_cap {
+            break;
+        }
+        used_tokens += tokens;
+        item.counters.used_count += 1;
+        item.counters.last_used_at = Some(ctx.now_rfc3339.clone());
+        store.update(&item)?;
+        out.push(item);
+    }
+    Ok(out)
+}
+
+fn tokenize(s: &str) -> BTreeSet<String> {
+    let mut set = BTreeSet::new();
+    for w in s.split(|c: char| !c.is_alphanumeric()) {
+        if w.is_empty() {
+            continue;
+        }
+        set.insert(w.to_ascii_lowercase());
+    }
+    set
+}
+
+fn overlap_score(a: &BTreeSet<String>, b: &BTreeSet<String>) -> f32 {
+    if a.is_empty() || b.is_empty() {
+        return 0.0;
+    }
+    let inter = a.intersection(b).count() as f32;
+    inter / a.len() as f32
 }

codex-rs/memory/tests/recall.rs

@@ -1,4 +1,140 @@
+use codex_memory::recall::RecallContext;
+use codex_memory::recall::recall;
+use codex_memory::store::MemoryStore;
+use codex_memory::types::Counters;
+use codex_memory::types::Kind;
+use codex_memory::types::MemoryItem;
+use codex_memory::types::RelevanceHints;
+use codex_memory::types::Scope;
+use codex_memory::types::Status;
+use std::collections::HashMap;
+use std::sync::Mutex;
+
+#[derive(Default)]
+struct TestStore {
+    items: Mutex<HashMap<String, MemoryItem>>,
+}
+
+impl TestStore {
+    fn new(items: Vec<MemoryItem>) -> Self {
+        let map = items.into_iter().map(|i| (i.id.clone(), i)).collect();
+        Self {
+            items: Mutex::new(map),
+        }
+    }
+}
+
+impl MemoryStore for TestStore {
+    fn add(&self, item: MemoryItem) -> anyhow::Result<()> {
+        self.items.lock().unwrap().insert(item.id.clone(), item);
+        Ok(())
+    }
+
+    fn update(&self, item: &MemoryItem) -> anyhow::Result<()> {
+        self.items
+            .lock()
+            .unwrap()
+            .insert(item.id.clone(), item.clone());
+        Ok(())
+    }
+
+    fn delete(&self, _id: &str) -> anyhow::Result<()> {
+        Ok(())
+    }
+
+    fn get(&self, id: &str) -> anyhow::Result<Option<MemoryItem>> {
+        Ok(self.items.lock().unwrap().get(id).cloned())
+    }
+
+    fn list(
+        &self,
+        _scope: Option<Scope>,
+        status: Option<Status>,
+    ) -> anyhow::Result<Vec<MemoryItem>> {
+        let items = self.items.lock().unwrap();
+        Ok(items
+            .values()
+            .filter(|i| match status.as_ref() {
+                Some(s) => i.status == *s,
+                None => true,
+            })
+            .cloned()
+            .collect())
+    }
+
+    fn archive(&self, _id: &str, _archived: bool) -> anyhow::Result<()> {
+        Ok(())
+    }
+
+    fn export(&self, _out: &mut dyn std::io::Write) -> anyhow::Result<()> {
+        Ok(())
+    }
+
+    fn import(&self, _input: &mut dyn std::io::Read) -> anyhow::Result<usize> {
+        Ok(0)
+    }
+
+    fn stats(&self) -> anyhow::Result<serde_json::Value> {
+        Ok(serde_json::json!({}))
+    }
+}
+
+fn item(id: &str, content: &str, lang: &str) -> MemoryItem {
+    MemoryItem {
+        id: id.to_string(),
+        created_at: "2024-01-01T00:00:00Z".into(),
+        updated_at: "2024-01-01T00:00:00Z".into(),
+        schema_version: 1,
+        source: "test".into(),
+        scope: Scope::Global,
+        status: Status::Active,
+        kind: Kind::Fact,
+        content: content.into(),
+        tags: vec![],
+        relevance_hints: RelevanceHints {
+            files: vec![],
+            crates: vec![],
+            languages: vec![lang.into()],
+            commands: vec![],
+        },
+        counters: Counters {
+            seen_count: 0,
+            used_count: 0,
+            last_used_at: None,
+        },
+        expiry: None,
+    }
+}
+
 #[test]
-fn placeholder() {
-    // placeholder test
+fn ranks_and_updates_counters() {
+    let a = item("1", "use cargo build for rust", "rust");
+    let b = item("2", "cargo test runs tests", "rust");
+    let c = item("3", "npm install packages", "javascript");
+    let store = TestStore::new(vec![a.clone(), b.clone(), c.clone()]);
+    let now = "2024-01-10T00:00:00Z".to_string();
+    let ctx = RecallContext {
+        repo_root: None,
+        dir: None,
+        current_file: None,
+        crate_name: None,
+        language: Some("rust".into()),
+        command: None,
+        now_rfc3339: now.clone(),
+        item_cap: 2,
+        token_cap: 50,
+    };
+    let out = recall(&store, "cargo build rust", &ctx).unwrap();
+    assert_eq!(out.len(), 2);
+    assert_eq!(out[0].id, "1");
+    assert_eq!(out[1].id, "2");
+    let a_upd = store.get("1").unwrap().unwrap();
+    assert_eq!(a_upd.counters.used_count, 1);
+    assert_eq!(a_upd.counters.last_used_at.as_deref(), Some(now.as_str()));
+    let b_upd = store.get("2").unwrap().unwrap();
+    assert_eq!(b_upd.counters.used_count, 1);
+    assert_eq!(b_upd.counters.last_used_at.as_deref(), Some(now.as_str()));
+    let c_upd = store.get("3").unwrap().unwrap();
+    assert_eq!(c_upd.counters.used_count, 0);
+    assert_eq!(c_upd.counters.last_used_at, None);
 }