lsp: add tiny LRU cache for last 10 completions; ignore trailing whitespace in cache key; log cache hits; report busy with isIncomplete to prompt client retry

1 files changed, 42 insertions, 0 deletions

diff --git a/internal/lsp/completion_cache_test.go b/internal/lsp/completion_cache_test.go
new file mode 100644
index 0000000..0207a9f
--- /dev/null
+++ b/internal/lsp/completion_cache_test.go
@@ -0,0 +1,42 @@
+package lsp
+
+import (
+    "bytes"
+    "log"
+    "strings"
+    "testing"
+
+    "hexai/internal/logging"
+)
+
+func TestCompletionCache_IgnoresWhitespaceBeforeCursor(t *testing.T) {
+    var buf bytes.Buffer
+    logger := log.New(&buf, "", 0)
+    s := NewServer(bytes.NewBuffer(nil), &buf, logger, ServerOptions{})
+    logging.Bind(logger)
+    s.triggerChars = []string{" ", "."}
+    fake := &countingLLM{}
+    s.llmClient = fake
+
+    // First request with trailing spaces before cursor
+    line := "foo   "
+    p := CompletionParams{ Position: Position{ Line: 0, Character: len(line) }, TextDocument: TextDocumentIdentifier{URI: "file://x.go"} }
+    items, ok, _ := s.tryLLMCompletion(p, "", line, "", "", "", false, "")
+    if !ok || len(items) == 0 || fake.calls != 1 {
+        t.Fatalf("expected first call to invoke LLM; ok=%v len=%d calls=%d", ok, len(items), fake.calls)
+    }
+
+    // Same logical context but with a different amount of trailing whitespace
+    line2 := "foo             "
+    p2 := CompletionParams{ Position: Position{ Line: 0, Character: len(line2) }, TextDocument: TextDocumentIdentifier{URI: "file://x.go"} }
+    items2, ok2, _ := s.tryLLMCompletion(p2, "", line2, "", "", "", false, "")
+    if !ok2 || len(items2) == 0 {
+        t.Fatalf("expected cache hit to still return items")
+    }
+    if fake.calls != 1 {
+        t.Fatalf("expected cache hit to avoid LLM call; calls=%d", fake.calls)
+    }
+    if !strings.Contains(buf.String(), "completion cache hit") {
+        t.Fatalf("expected log to contain cache hit message, got: %s", buf.String())
+    }
+}