import { existsSync, mkdirSync } from 'node:fs';
import { dirname, join } from 'node:path';

import { SUPPORTED_MEDIA_EXTENSIONS } from '../constants.js';
import type { Result } from '../types/result.js';
import { getErrorMessage } from './errors.js';
import { getFileExtension } from './extension.js';
import { write } from './file.js';
import { fetchImage } from './network.js';

export async function downloadImage(
  src: string,
  rootPath: string
): Promise<Result<[string, string]>> {
  if (src.startsWith('data:image/')) {
    return { success: true, data: [src, src] };
  }
  try {
    let filename = await writeImageToFile(src, rootPath);
    filename = filename.replace(process.cwd(), '');
    return { success: true, data: [src, filename] };
  } catch (error) {
    if (error instanceof Error) {
      return { success: false, message: error.message };
    } else {
      return {
        success: false,
        message: `${src} - an unknown error occurred downloading this image`,
      };
    }
  }
}

async function writeImageToFile(src: string, rootPath: string): Promise<string> {
  const filename = removeMetadataFromImageSrc(src);
  const imagePath = join(rootPath, filename);
  const shortenedFilename = filename.length > 36 ? `...${filename.slice(-36)}` : filename;

  if (!isValidImageSrc(filename)) {
    throw new Error(`${shortenedFilename} - file extension not supported`);
  }

  if (existsSync(imagePath)) {
    return imagePath;
  }

  try {
    mkdirSync(dirname(imagePath), { recursive: true });
  } catch (error) {
    throw new Error(`${imagePath} - failed to create directory`);
  }

  try {
    const imageData = await fetchImage(src);
    write(imagePath, imageData);
    return imagePath;
  } catch (error) {
    const errorMessage = getErrorMessage(error);
    throw new Error(`${shortenedFilename} - failed to download file from source${errorMessage}`);
  }
}

export function isValidImageSrc(src: string) {
  if (!src) {
    return false;
  }

  const ext = getFileExtension(src);
  if (ext && !SUPPORTED_MEDIA_EXTENSIONS.includes(ext)) {
    return false;
  }

  return true;
}

export function getFilenameBeforeMetadata(src: string, ext: string): string {
  const lengthUntilMetadata = src.indexOf(`.${ext}`) + `.${ext}`.length;
  return src.slice(0, lengthUntilMetadata);
}

export function removeMetadataFromImageSrc(src: string): string {
  let filename = '';
  if (src.includes('gitbook/image')) {
    for (const ext of SUPPORTED_MEDIA_EXTENSIONS) {
      if (src.includes(`.${ext}`)) {
        filename = getFilenameBeforeMetadata(src, ext);
      }
    }
  }

  if (!filename) {
    if (src.startsWith('http')) {
      src = new URL(src).pathname;
    }
    filename =
      decodeURIComponent(
        src
          .split('#')[0]!
          .split('?')[0]!
          .replace(/[\/]{2,}/g, '/')
      ).replace(/(?:_{2,}|[\s%#&{}\\<>*?$!'":@+`|=])/g, '-') || 'image';
    return filename;
  }

  return filename.split('%2F').slice(4).join('%2F');
}