package memory

import "github.com/enmanuel/agents/pkg/llm"

// Window is an immutable sliding window of conversation messages for a single room.
type Window struct {
	messages []llm.Message
	maxSize  int
}

// NewWindow creates an empty window with the given capacity.
func NewWindow(maxSize int) Window {
	return Window{maxSize: maxSize}
}

// Append returns a new Window with the message added, dropping the oldest
// messages if capacity is exceeded.
func (w Window) Append(msg llm.Message) Window {
	msgs := make([]llm.Message, len(w.messages), len(w.messages)+1)
	copy(msgs, w.messages)
	msgs = append(msgs, msg)
	if len(msgs) > w.maxSize {
		msgs = msgs[len(msgs)-w.maxSize:]
	}
	return Window{messages: msgs, maxSize: w.maxSize}
}

// ToLLMMessages returns a copy of the window contents as []llm.Message.
func (w Window) ToLLMMessages() []llm.Message {
	out := make([]llm.Message, len(w.messages))
	copy(out, w.messages)
	return out
}

// Len returns the number of messages in the window.
func (w Window) Len() int {
	return len(w.messages)
}

// Clear returns an empty window with the same capacity.
func (w Window) Clear() Window {
	return NewWindow(w.maxSize)
}