UI writer abstraction instead of printlns everywhere

crates/g3-core/src/ui_writer.rs

@@ -0,0 +1,66 @@
+/// Interface for UI output operations
+/// This trait abstracts all UI operations to allow different implementations
+/// (console, TUI, web, etc.) without coupling the core logic to specific output methods.
+pub trait UiWriter: Send + Sync {
+    /// Print a simple message
+    fn print(&self, message: &str);
+    
+    /// Print a message with a newline
+    fn println(&self, message: &str);
+    
+    /// Print without newline (for progress indicators)
+    fn print_inline(&self, message: &str);
+    
+    /// Print a system prompt section
+    fn print_system_prompt(&self, prompt: &str);
+    
+    /// Print a context window status message
+    fn print_context_status(&self, message: &str);
+    
+    /// Print a tool execution header
+    fn print_tool_header(&self, tool_name: &str);
+    
+    /// Print a tool argument
+    fn print_tool_arg(&self, key: &str, value: &str);
+    
+    /// Print tool output header
+    fn print_tool_output_header(&self);
+    
+    /// Print a tool output line
+    fn print_tool_output_line(&self, line: &str);
+    
+    /// Print tool output summary (when output is truncated)
+    fn print_tool_output_summary(&self, hidden_count: usize);
+    
+    /// Print tool execution timing
+    fn print_tool_timing(&self, duration_str: &str);
+    
+    /// Print the agent prompt indicator
+    fn print_agent_prompt(&self);
+    
+    /// Print agent response inline (for streaming)
+    fn print_agent_response(&self, content: &str);
+    
+    /// Flush any buffered output
+    fn flush(&self);
+}
+
+/// A no-op implementation for when UI output is not needed
+pub struct NullUiWriter;
+
+impl UiWriter for NullUiWriter {
+    fn print(&self, _message: &str) {}
+    fn println(&self, _message: &str) {}
+    fn print_inline(&self, _message: &str) {}
+    fn print_system_prompt(&self, _prompt: &str) {}
+    fn print_context_status(&self, _message: &str) {}
+    fn print_tool_header(&self, _tool_name: &str) {}
+    fn print_tool_arg(&self, _key: &str, _value: &str) {}
+    fn print_tool_output_header(&self) {}
+    fn print_tool_output_line(&self, _line: &str) {}
+    fn print_tool_output_summary(&self, _hidden_count: usize) {}
+    fn print_tool_timing(&self, _duration_str: &str) {}
+    fn print_agent_prompt(&self) {}
+    fn print_agent_response(&self, _content: &str) {}
+    fn flush(&self) {}
+}