import { FORMATS } from "../formats.js";
import { fromOpenAIFinish } from "./finishReason.js";

// Shared OpenAI-Chat → Claude-Messages shape conversion.
//
// Lives in `concerns/` (not chatCore/) because BOTH the non-streaming handler
// and the forced-SSE→JSON handler need it, and importing it from
// nonStreamingHandler.js into sseToJsonHandler.js would create a circular
// import (nonStreamingHandler already imports parseSSEToOpenAIResponse from
// sseToJsonHandler).

function parseToolArguments(value) {
  if (!value) return {};
  if (typeof value === "object") return value;
  try {
    return JSON.parse(value);
  } catch {
    return {};
  }
}

function openAICompletionToClaudeMessage(responseBody) {
  if (!responseBody?.choices?.[0]) return responseBody;
  const choice = responseBody.choices[0];
  const message = choice.message || {};
  const content = [];

  const reasoning = message.reasoning_content || message.provider_specific_fields?.reasoning_content || "";
  if (reasoning) {
    content.push({ type: "thinking", thinking: reasoning });
  }
  if (typeof message.content === "string" && message.content.length > 0) {
    content.push({ type: "text", text: message.content });
  }
  for (const toolCall of message.tool_calls || []) {
    const fn = toolCall.function || {};
    content.push({
      type: "tool_use",
      id: toolCall.id || `toolu_${Date.now()}_${content.length}`,
      name: fn.name || toolCall.name || "",
      input: parseToolArguments(fn.arguments || toolCall.arguments),
    });
  }
  if (content.length === 0) content.push({ type: "text", text: "" });

  const usage = responseBody.usage || {};
  return {
    id: String(responseBody.id || `msg_${Date.now()}`).replace(/^chatcmpl-/, ""),
    type: "message",
    role: "assistant",
    model: responseBody.model || "unknown",
    content,
    stop_reason: fromOpenAIFinish(choice.finish_reason, FORMATS.CLAUDE),
    stop_sequence: null,
    usage: {
      input_tokens: usage.prompt_tokens || usage.input_tokens || 0,
      output_tokens: usage.completion_tokens || usage.output_tokens || 0,
    },
  };
}

/**
 * Convert an OpenAI Chat Completions body into the Claude Messages shape when
 * the client speaks Anthropic (sourceFormat=CLAUDE) but the provider replied
 * OpenAI JSON. Shape-aware guard: Claude-shaped bodies pass through untouched.
 */
export function toClaudeMessageShape(responseBody) {
  if (!responseBody || responseBody.type === "message") return responseBody;
  if (responseBody?.choices) return openAICompletionToClaudeMessage(responseBody);
  return responseBody;
}

/** Export the raw converter for tests that want it directly. */
export { openAICompletionToClaudeMessage };