import { BadRequestException } from '@nestjs/common';
import {
  activityPosterResizeTarget,
  activityPosterTemplateTooLarge,
} from '@dukang/shared-types';
import sharp from 'sharp';

const JPEG_QUALITY = 85;

export type ActivityPosterUploadPrepared = {
  buffer: Buffer;
  mimeType: string;
  width: number;
  height: number;
  originalWidth: number;
  originalHeight: number;
  compressed: boolean;
};

function resolveOutputMime(hasAlpha: boolean, inputMime?: string): string {
  if (hasAlpha) return 'image/png';
  if (inputMime === 'image/webp') return 'image/jpeg';
  if (inputMime?.startsWith('image/')) return inputMime;
  return 'image/jpeg';
}

async function encodeImage(
  pipeline: sharp.Sharp,
  mimeType: string,
): Promise<Buffer> {
  if (mimeType === 'image/png') {
    return pipeline.png().toBuffer();
  }
  if (mimeType === 'image/jpeg' || mimeType === 'image/jpg') {
    return pipeline.jpeg({ quality: JPEG_QUALITY }).toBuffer();
  }
  if (mimeType === 'image/webp') {
    return pipeline.webp({ quality: JPEG_QUALITY }).toBuffer();
  }
  return pipeline.jpeg({ quality: JPEG_QUALITY }).toBuffer();
}

export async function prepareActivityPosterUpload(input: {
  buffer: Buffer;
  mimeType?: string;
}): Promise<ActivityPosterUploadPrepared> {
  if (!input.buffer?.length) {
    throw new BadRequestException('活动图文件为空');
  }
  if (input.mimeType && !input.mimeType.startsWith('image/')) {
    throw new BadRequestException('活动图仅支持图片文件');
  }

  const meta = await sharp(input.buffer, { failOn: 'none' }).metadata();
  if (!meta.width || !meta.height) {
    throw new BadRequestException('活动图无法读取尺寸，请换一张图片');
  }

  const originalWidth = meta.width;
  const originalHeight = meta.height;
  const resizeTarget = activityPosterResizeTarget(originalWidth, originalHeight);

  if (!resizeTarget) {
    return {
      buffer: input.buffer,
      mimeType: input.mimeType || 'image/jpeg',
      width: originalWidth,
      height: originalHeight,
      originalWidth,
      originalHeight,
      compressed: false,
    };
  }

  const hasAlpha = meta.hasAlpha === true;
  const outputMime = resolveOutputMime(hasAlpha, input.mimeType);
  const buffer = await encodeImage(
    sharp(input.buffer, { failOn: 'none' }).resize(resizeTarget.width, resizeTarget.height, {
      fit: 'inside',
      withoutEnlargement: true,
    }),
    outputMime,
  );
  const metaOut = await sharp(buffer).metadata();
  const width = metaOut.width ?? resizeTarget.width;
  const height = metaOut.height ?? resizeTarget.height;

  if (activityPosterTemplateTooLarge(width, height)) {
    throw new BadRequestException('活动图压缩后仍超出尺寸限制，请换一张较小的图片');
  }

  return {
    buffer,
    mimeType: outputMime,
    width,
    height,
    originalWidth,
    originalHeight,
    compressed: true,
  };
}