update ErrorCode, status, lifecycle

include/lidarlib/lidar.hpp

@@ -1,4 +1,5 @@
 #pragma once
+#include "lidarlib/error.hpp"
 #include <cstdint>
 #include <vector>
 #include <string>
@@ -83,14 +84,28 @@ class Lidar {
 public:
     virtual ~Lidar() = default;
 
-    virtual bool open() = 0;
+    // ErrorCode::Ok on success. Calling open() on an already-open instance
+    // returns AlreadyOpen and leaves the connection untouched.
+    virtual ErrorCode open() = 0;
+    // Idempotent: safe to call before open() or more than once.
     virtual void close() = 0;
-    // Block until one full scan; false on error/timeout. timeout_ms = 0 → block
-    // indefinitely. No default on purpose: drivers differ (OLEI 1000, SICK 2000).
+    // Block until one full scan; false on error/timeout (see last_error()).
+    // timeout_ms = 0 → block indefinitely. No default on purpose: drivers
+    // differ (OLEI 1000, SICK 2000).
     virtual bool recv_scan(ScanResult& out, int timeout_ms) = 0;
     virtual void set_scan_callback(ScanCallback cb) = 0;
     virtual bool spin_once() = 0;
     virtual const char* detected_model() const = 0;
+
+    virtual bool is_open() const = 0;
+    // Status of the most recent open()/recv_scan()/spin_once() call.
+    ErrorCode last_error() const { return last_error_; }
+
+protected:
+    ErrorCode set_error(ErrorCode e) { last_error_ = e; return e; }
+
+private:
+    ErrorCode last_error_ = ErrorCode::Ok;
 };
 
 // OLEI UDP driver.
@@ -109,11 +124,12 @@ public:
     Driver(const Driver&)            = delete;
     Driver& operator=(const Driver&) = delete;
 
-    bool open() override;
+    ErrorCode open() override;
     void close() override;
     bool recv_scan(ScanResult& out, int timeout_ms = 1000) override;
     void set_scan_callback(ScanCallback cb) override { cb_ = std::move(cb); }
     bool spin_once() override;
+    bool is_open() const override { return sock_fd_ >= 0; }
 
     // Model name read from the Family B/C header; "AUTO" until one is seen.
     const char* detected_model() const override { return detected_model_name_.c_str(); }