// Package provider defines the interface that LLM backend implementations must satisfy.
package provider

import "context"

// Message is the provider-level message representation.
type Message struct {
	Role       string
	Content    string
	Images     []Image
	Audio      []Audio
	ToolCalls  []ToolCall
	ToolCallID string
}

// Image represents an image attachment at the provider level.
type Image struct {
	URL         string
	Base64      string
	ContentType string
}

// Audio represents an audio attachment at the provider level.
type Audio struct {
	URL         string
	Base64      string
	ContentType string
}

// ToolCall represents a tool invocation requested by the model.
type ToolCall struct {
	ID        string
	Name      string
	Arguments string // raw JSON
}

// ToolDef defines a tool available to the model.
type ToolDef struct {
	Name        string
	Description string
	Schema      map[string]any // JSON Schema
}

// Request is a completion request at the provider level.
type Request struct {
	Model       string
	Messages    []Message
	Tools       []ToolDef
	Temperature *float64
	MaxTokens   *int
	TopP        *float64
	Stop        []string
}

// Response is a completion response at the provider level.
type Response struct {
	Text      string
	ToolCalls []ToolCall
	Usage     *Usage
}

// Usage captures token consumption.
type Usage struct {
	InputTokens  int
	OutputTokens int
	TotalTokens  int
}

// StreamEventType identifies the kind of stream event.
type StreamEventType int

const (
	StreamEventText      StreamEventType = iota // Text content delta
	StreamEventToolStart                        // Tool call begins
	StreamEventToolDelta                        // Tool call argument delta
	StreamEventToolEnd                          // Tool call complete
	StreamEventDone                             // Stream complete
	StreamEventError                            // Error occurred
)

// StreamEvent represents a single event in a streaming response.
type StreamEvent struct {
	Type      StreamEventType
	Text      string
	ToolCall  *ToolCall
	ToolIndex int
	Error     error
	Response  *Response
}

// Provider is the interface that LLM backends implement.
type Provider interface {
	// Complete performs a non-streaming completion.
	Complete(ctx context.Context, req Request) (Response, error)

	// Stream performs a streaming completion, sending events to the channel.
	// The provider MUST close the channel when done.
	// The provider MUST send exactly one StreamEventDone as the last non-error event.
	Stream(ctx context.Context, req Request, events chan<- StreamEvent) error
}