import OpenAI from "openai";
import * as fs from "fs";
import * as path from "path";
import { StoryConfig } from "./config";

let openaiClient: OpenAI | null = null;
function getOpenAI(): OpenAI {
  if (!openaiClient) {
    openaiClient = new OpenAI({ apiKey: process.env.OPENAI_API_KEY });
  }
  return openaiClient;
}

const allowedSizesValues = [
  "256x256",
  "512x512",
  "1024x1024",
  "1536x1024",
  "1024x1536",
  "1792x1024",
  "1024x1792",
] as const;
type AllowedSize = (typeof allowedSizesValues)[number];

function pickImageSize(resolution?: string): AllowedSize {
  if (!resolution) return "1024x1024";
  const match = resolution.match(/^(\d+)x(\d+)$/);
  if (!match) return "1024x1024";
  const width = parseInt(match[1], 10);
  const height = parseInt(match[2], 10);
  if (!Number.isFinite(width) || !Number.isFinite(height)) return "1024x1024";
  if (width === height) return "1024x1024";
  const landscapeCandidates: AllowedSize[] = ["1536x1024", "1792x1024"];
  const portraitCandidates: AllowedSize[] = ["1024x1536", "1024x1792"];
  return width > height ? landscapeCandidates[0] : portraitCandidates[0];
}

export async function generateImage(
  storyName: string,
  storyConfig: StoryConfig,
  chunk: string,
  chunkIndex: number,
  imageIndex: number
): Promise<string> {
  const imagePath = path.join("stories", storyName, "images", `chunk_${chunkIndex}_img${imageIndex}.png`);
  const prompt = `${(storyConfig.config.image_style_prompts || "").trim()}

Illustration for the following passage:
"${chunk.slice(0, 500)}"`;

  const size = pickImageSize(storyConfig.config.export_settings?.resolution);

  const response = await getOpenAI().images.generate({
    model: "dall-e-3",
    prompt,
    n: 1,
    size,
    response_format: "b64_json",
  });

  if (!response.data?.[0].b64_json) {
    throw new Error("Image data not found in response");
  }

  const imageBase64 = response.data[0].b64_json;
  const imageBuffer = Buffer.from(imageBase64, "base64");
  fs.writeFileSync(imagePath, imageBuffer);

  return imagePath;
}