Large refactor - it compiles!

This refactor splits out all conversation concerns into a new
`conversation` package. There is now a split between `conversation` and
`api`s representation of `Message`, the latter storing the minimum
information required for interaction with LLM providers. There is
necessary conversation between the two when making LLM calls.

pkg/api/api.go

@@ -0,0 +1,118 @@
+package api
+
+import (
+	"encoding/json"
+	"fmt"
+)
+
+type MessageRole string
+
+const (
+	MessageRoleSystem     MessageRole = "system"
+	MessageRoleUser       MessageRole = "user"
+	MessageRoleAssistant  MessageRole = "assistant"
+	MessageRoleToolCall   MessageRole = "tool_call"
+	MessageRoleToolResult MessageRole = "tool_result"
+)
+
+type Message struct {
+	Content     string // TODO: support multi-part messages
+	Role        MessageRole
+	ToolCalls   []ToolCall
+	ToolResults []ToolResult
+}
+
+type ToolSpec struct {
+	Name        string
+	Description string
+	Parameters  []ToolParameter
+	Impl        func(*ToolSpec, map[string]interface{}) (string, error)
+}
+
+type ToolParameter struct {
+	Name        string   `json:"name"`
+	Type        string   `json:"type"` // "string", "integer", "boolean"
+	Required    bool     `json:"required"`
+	Description string   `json:"description"`
+	Enum        []string `json:"enum,omitempty"`
+}
+
+type ToolCall struct {
+	ID         string                 `json:"id" yaml:"-"`
+	Name       string                 `json:"name" yaml:"tool"`
+	Parameters map[string]interface{} `json:"parameters" yaml:"parameters"`
+}
+
+type ToolResult struct {
+	ToolCallID string `json:"toolCallID" yaml:"-"`
+	ToolName   string `json:"toolName,omitempty" yaml:"tool"`
+	Result     string `json:"result,omitempty" yaml:"result"`
+}
+
+func NewMessageWithAssistant(content string) *Message {
+	return &Message{
+		Role:    MessageRoleAssistant,
+		Content: content,
+	}
+}
+
+func NewMessageWithToolCalls(content string, toolCalls []ToolCall) *Message {
+	return &Message{
+		Role:      MessageRoleToolCall,
+		Content:   content,
+		ToolCalls: toolCalls,
+	}
+}
+
+func (m MessageRole) IsAssistant() bool {
+	switch m {
+	case MessageRoleAssistant, MessageRoleToolCall:
+		return true
+	}
+	return false
+}
+
+func (m MessageRole) IsSystem() bool {
+	switch m {
+	case MessageRoleSystem:
+		return true
+	}
+	return false
+}
+
+// FriendlyRole returns a human friendly signifier for the message's role.
+func (m MessageRole) FriendlyRole() string {
+	switch m {
+	case MessageRoleUser:
+		return "You"
+	case MessageRoleSystem:
+		return "System"
+	case MessageRoleAssistant:
+		return "Assistant"
+	case MessageRoleToolCall:
+		return "Tool Call"
+	case MessageRoleToolResult:
+		return "Tool Result"
+	default:
+		return string(m)
+	}
+}
+
+// TODO: remove this
+type CallResult struct {
+	Message string `json:"message"`
+	Result  any    `json:"result,omitempty"`
+}
+
+func (r CallResult) ToJson() (string, error) {
+	if r.Message == "" {
+		// When message not supplied, assume success
+		r.Message = "success"
+	}
+
+	jsonBytes, err := json.Marshal(r)
+	if err != nil {
+		return "", fmt.Errorf("Could not marshal CallResult to JSON: %v\n", err)
+	}
+	return string(jsonBytes), nil
+}