package openai

import (
	"fmt"
	"strings"
)

// ChatMessage represents a single message within a chat completion request or response.
type ChatMessage struct {
	Role    string `json:"role"`
	Content string `json:"content"`
}

// ChatCompletionRequest encapsulates the payload for the OpenAI Chat Completions API.
type ChatCompletionRequest struct {
	Model       string        `json:"model"`
	Messages    []ChatMessage `json:"messages"`
	MaxTokens   *int          `json:"max_tokens,omitempty"`
	Temperature *float64      `json:"temperature,omitempty"`
	Stream      bool          `json:"stream,omitempty"`
}

// ChatCompletionChoice captures an individual response choice returned from the API.
type ChatCompletionChoice struct {
	Index        int         `json:"index"`
	Message      ChatMessage `json:"message"`
	FinishReason string      `json:"finish_reason"`
}

// Usage captures token accounting for a chat completion call.
type Usage struct {
	PromptTokens     int `json:"prompt_tokens"`
	CompletionTokens int `json:"completion_tokens"`
	TotalTokens      int `json:"total_tokens"`
}

// ChatCompletionResponse represents the top-level response payload from the API.
type ChatCompletionResponse struct {
	ID      string                 `json:"id"`
	Object  string                 `json:"object"`
	Choices []ChatCompletionChoice `json:"choices"`
	Usage   Usage                  `json:"usage"`
}

// ChatCompletionStreamEvent represents a single chunk in a streaming chat completion.
type ChatCompletionStreamEvent struct {
	ID           string `json:"-"`
	Role         string `json:"-"`
	Content      string `json:"-"`
	FinishReason string `json:"-"`
	Usage        *Usage `json:"-"`
	Done         bool   `json:"-"`
}

// ChatCompletionStreamHandler consumes streaming completion events.
type ChatCompletionStreamHandler func(ChatCompletionStreamEvent) error

// RequestError captures an error response returned by the API together with the HTTP status code.
type RequestError struct {
	Status   int
	Response ErrorResponse
}

// Error implements the error interface.
func (e *RequestError) Error() string {
	if e == nil {
		return ""
	}
	msg := strings.TrimSpace(e.Response.Error.Message)
	if msg == "" {
		return fmt.Sprintf("api error (status %d)", e.Status)
	}
	return fmt.Sprintf("api error (status %d): %s", e.Status, msg)
}

// StatusCode returns the originating HTTP status code.
func (e *RequestError) StatusCode() int {
	if e == nil {
		return 0
	}
	return e.Status
}

// Message returns the raw message provided by the API, if any.
func (e *RequestError) Message() string {
	if e == nil {
		return ""
	}
	return e.Response.Error.Message
}

// Type returns the OpenAI error type string, when present.
func (e *RequestError) Type() string {
	if e == nil {
		return ""
	}
	return e.Response.Error.Type
}

// APIError captures structured error responses returned by the API.
type APIError struct {
	Message string `json:"message"`
	Type    string `json:"type"`
	Param   string `json:"param"`
	Code    any    `json:"code"`
}

// ErrorResponse is returned on non-2xx responses.
type ErrorResponse struct {
	Error APIError `json:"error"`
}