package ai

import "context"

// Message represents a single message in a conversation.
type Message struct {
	Role       string      `json:"role"` // "system", "user", "assistant", "tool"
	Content    string      `json:"content"`
	ToolCalls  []ToolCall  `json:"tool_calls,omitempty"`
	ToolCallID string      `json:"tool_call_id,omitempty"`
	Name       string      `json:"name,omitempty"`
}

// ToolCall represents a function call requested by the model.
type ToolCall struct {
	ID       string `json:"id"`
	Function struct {
		Name      string `json:"name"`
		Arguments string `json:"arguments"`
	} `json:"function"`
}

// Tool describes a tool available to the model.
type Tool struct {
	Name        string                 `json:"name"`
	Description string                 `json:"description"`
	Parameters  map[string]interface{} `json:"parameters"`
}

// Response is the result from a provider.
type Response struct {
	Content   string     `json:"content"`
	ToolCalls []ToolCall `json:"tool_calls,omitempty"`
	Model     string     `json:"model"`
	Usage     Usage      `json:"usage"`
}

// Usage tracks token usage.
type Usage struct {
	PromptTokens     int `json:"prompt_tokens"`
	CompletionTokens int `json:"completion_tokens"`
	TotalTokens      int `json:"total_tokens"`
}

// StreamChunk is a piece of a streamed response.
type StreamChunk struct {
	Content   string     `json:"content,omitempty"`
	ToolCalls []ToolCall `json:"tool_calls,omitempty"`
	Done      bool       `json:"done"`
	Error     error      `json:"-"`
}

// Provider is the interface that all AI backends must implement.
type Provider interface {
	// Chat sends messages and returns a complete response.
	Chat(ctx context.Context, messages []Message, tools []Tool) (*Response, error)

	// StreamChat sends messages and returns a channel of streamed chunks.
	StreamChat(ctx context.Context, messages []Message, tools []Tool) (<-chan StreamChunk, error)

	// Name returns the provider's display name.
	Name() string

	// Models returns the list of available model names.
	Models() []string
}