feat: add lockfile

opencode-attach

@@ -1,7 +1,48 @@
 #!/bin/sh
 set -eu
 
+LOCKFILE="${OPENCODE_ATTACH_LOCK:-/tmp/opencode-attach.lock}"
+
 : "${OPENCODE_SERVER_PASSWORD:?OPENCODE_SERVER_PASSWORD is required}"
 : "${OPENCODE_API_URL:?OPENCODE_API_URL is required}"
 
+cleanup_lock() {
+    if [ -f "$LOCKFILE" ]; then
+        existing_pid=$(cat "$LOCKFILE" 2>/dev/null || true)
+        [ "$existing_pid" = "$$" ] && rm -f "$LOCKFILE"
+    fi
+}
+
+kill_existing_instance() {
+    if [ ! -f "$LOCKFILE" ]; then
+        return
+    fi
+
+    existing_pid=$(cat "$LOCKFILE" 2>/dev/null || true)
+    if [ -z "$existing_pid" ] || [ "$existing_pid" = "$$" ]; then
+        rm -f "$LOCKFILE"
+        return
+    fi
+
+    if kill -0 "$existing_pid" 2>/dev/null; then
+        kill "$existing_pid" 2>/dev/null
+        for _ in 1 2 3 4 5; do
+            if ! kill -0 "$existing_pid" 2>/dev/null; then
+                break
+            fi
+            sleep 1
+        done
+        if kill -0 "$existing_pid" 2>/dev/null; then
+            kill -9 "$existing_pid" 2>/dev/null || true
+        fi
+    fi
+
+    rm -f "$LOCKFILE"
+}
+
+trap cleanup_lock INT TERM EXIT
+
+kill_existing_instance
+printf '%s\n' "$$" > "$LOCKFILE"
+
 exec opencode attach -p "${OPENCODE_SERVER_PASSWORD}" "${OPENCODE_API_URL}" "$@"