package model

import (
	"encoding/json"
)

// openAIChatResponse is the JSON body returned by /chat/completions, for both
// the non-streaming payload and each SSE stream chunk.
type openAIChatResponse struct {
	ID      string         `json:"id"`
	Model   string         `json:"model"`
	Choices []openAIChoice `json:"choices"`
	Usage   *openAIUsage   `json:"usage,omitempty"`
}

// openAIChoice is one candidate completion.
type openAIChoice struct {
	Index        int                   `json:"index"`
	Message      openAIResponseMessage `json:"message"`
	Delta        *openAIDelta          `json:"delta,omitempty"`
	FinishReason string                `json:"finish_reason,omitempty"`
}

// openAIResponseMessage is the assistant message inside a non-streaming choice.
type openAIResponseMessage struct {
	Role      string           `json:"role"`
	Content   string           `json:"content"`
	ToolCalls []openAIToolCall `json:"tool_calls,omitempty"`
}

// openAIDelta is the incremental payload inside a stream chunk. Reasoning content
// (OpenAI o-series / DeepSeek / DashScope) arrives in ReasoningContent; streaming
// function calls arrive in ToolCalls, accumulated per fragment index.
type openAIDelta struct {
	Role             string                `json:"role"`
	Content          string                `json:"content"`
	ReasoningContent string                `json:"reasoning_content"`
	ToolCalls        []openAIToolCallDelta `json:"tool_calls"`
}

// openAIToolCallDelta is one streaming function-call fragment. OpenAI emits a
// sequence of these sharing the same Index: the ID and Function.Name usually
// arrive once (in the first fragment) while Function.Arguments streams across
// fragments.
type openAIToolCallDelta struct {
	Index    int              `json:"index"`
	ID       string           `json:"id"`
	Function openAIToolCallFn `json:"function"`
}

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

func responseFromWire(wire *openAIChatResponse) Response {
	out := Response{Model: wire.Model}
	if len(wire.Choices) > 0 {
		text := wire.Choices[0].Message.Content
		out.Content = text
		out.Message = Message{Role: RoleAssistant, Content: []Content{{Type: ContentTypeText, Text: text}}}
		out.StopReason = wire.Choices[0].FinishReason
		for _, tc := range wire.Choices[0].Message.ToolCalls {
			args := map[string]any{}
			if tc.Function.Arguments != "" {
				_ = json.Unmarshal([]byte(tc.Function.Arguments), &args)
			}
			out.ToolCalls = append(out.ToolCalls, ToolCall{Name: tc.Function.Name, ID: tc.ID, Args: args})
		}
	}
	if u := wire.Usage; u != nil {
		out.PromptTokens = u.PromptTokens
		out.CompletionTokens = u.CompletionTokens
		out.TotalTokens = u.TotalTokens
	}
	return out
}