// Package chatcmpl describes the OpenAI-compatible Chat Completions
// protocol spoken by upstream providers.
package chatcmpl

import "encoding/json"

// Request is a Chat Completions request body.
type Request struct {
	Model         string         `json:"model"`
	Messages      []Message      `json:"messages"`
	MaxTokens     int            `json:"max_tokens,omitempty"`
	Temperature   *float64       `json:"temperature,omitempty"`
	TopP          *float64       `json:"top_p,omitempty"`
	Stop          []string       `json:"stop,omitempty"`
	Stream        bool           `json:"stream,omitempty"`
	StreamOptions *StreamOptions `json:"stream_options,omitempty"`
	Tools         []Tool         `json:"tools,omitempty"`
	ToolChoice    any            `json:"tool_choice,omitempty"`
}

// StreamOptions toggles the usage chunk at the end of a stream.
type StreamOptions struct {
	IncludeUsage bool `json:"include_usage"`
}

// Message is one Chat Completions message. Content is either a string or
// a []ContentPart.
type Message struct {
	Role       string     `json:"role"`
	Content    any        `json:"content"`
	ToolCalls  []ToolCall `json:"tool_calls,omitempty"`
	ToolCallID string     `json:"tool_call_id,omitempty"`
}

// ContentPart is one part of a multi-modal message.
type ContentPart struct {
	Type     string    `json:"type"`
	Text     string    `json:"text,omitempty"`
	ImageURL *ImageURL `json:"image_url,omitempty"`
}

// ImageURL references an image, usually as a data URL.
type ImageURL struct {
	URL string `json:"url"`
}

// Tool is a function tool definition.
type Tool struct {
	Type     string       `json:"type"`
	Function ToolFunction `json:"function"`
}

// ToolFunction is the payload of a function tool.
type ToolFunction struct {
	Name        string          `json:"name"`
	Description string          `json:"description,omitempty"`
	Parameters  json.RawMessage `json:"parameters,omitempty"`
}

// ToolCall is a function call requested by the model.
type ToolCall struct {
	ID       string           `json:"id"`
	Type     string           `json:"type"`
	Function ToolCallFunction `json:"function"`
	Index    int              `json:"index,omitempty"`
}

// ToolCallFunction holds the name and the accumulated JSON arguments.
type ToolCallFunction struct {
	Name      string `json:"name"`
	Arguments string `json:"arguments"`
}

// Response is a non-streaming Chat Completions response body.
type Response struct {
	ID      string   `json:"id"`
	Object  string   `json:"object"`
	Model   string   `json:"model"`
	Choices []Choice `json:"choices"`
	Usage   *Usage   `json:"usage,omitempty"`
	Error   *Error   `json:"error,omitempty"`
}

// Choice is one completion choice.
type Choice struct {
	Index        int     `json:"index"`
	Message      Message `json:"message"`
	FinishReason string  `json:"finish_reason"`
}

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

// Error is an upstream error payload.
type Error struct {
	Message string `json:"message"`
	Type    string `json:"type"`
	Code    any    `json:"code,omitempty"`
}

// StreamChunk is one SSE data payload of a streaming response.
type StreamChunk struct {
	ID      string        `json:"id"`
	Choices []ChunkChoice `json:"choices"`
	Usage   *Usage        `json:"usage,omitempty"`
}

// ChunkChoice is one choice inside a stream chunk.
type ChunkChoice struct {
	Index        int     `json:"index"`
	Delta        Delta   `json:"delta"`
	FinishReason *string `json:"finish_reason"`
}

// Delta is the incremental payload of a stream chunk.
type Delta struct {
	Role      string     `json:"role,omitempty"`
	Content   *string    `json:"content,omitempty"`
	ToolCalls []ToolCall `json:"tool_calls,omitempty"`
}