SnapOtter/apps/api/src/routes/tools/erase-object.ts

import { randomUUID } from "node:crypto";
import { writeFile } from "node:fs/promises";
import { basename, join } from "node:path";
import { inpaint } from "@stirling-image/ai";
import type { FastifyInstance, FastifyReply, FastifyRequest } from "fastify";
import { validateImageBuffer } from "../../lib/file-validation.js";
import { createWorkspace } from "../../lib/workspace.js";
import { updateSingleFileProgress } from "../progress.js";

/**
 * Object eraser / inpainting route.
 * Accepts an image and a mask image, erases masked areas.
 */
export function registerEraseObject(app: FastifyInstance) {
  app.post("/api/v1/tools/erase-object", async (request: FastifyRequest, reply: FastifyReply) => {
    let imageBuffer: Buffer | null = null;
    let maskBuffer: Buffer | null = null;
    let filename = "image";
    let clientJobId: string | null = null;

    try {
      const parts = request.parts();
      for await (const part of parts) {
        if (part.type === "file") {
          const chunks: Buffer[] = [];
          for await (const chunk of part.file) {
            chunks.push(chunk);
          }
          const buf = Buffer.concat(chunks);
          if (part.fieldname === "mask") {
            maskBuffer = buf;
          } else {
            imageBuffer = buf;
            filename = basename(part.filename ?? "image");
          }
        } else if (part.fieldname === "clientJobId") {
          clientJobId = part.value as string;
        }
      }
    } catch (err) {
      return reply.status(400).send({
        error: "Failed to parse multipart request",
        details: err instanceof Error ? err.message : String(err),
      });
    }

    if (!imageBuffer || imageBuffer.length === 0) {
      return reply.status(400).send({ error: "No image file provided" });
    }
    if (!maskBuffer || maskBuffer.length === 0) {
      return reply.status(400).send({
        error: "No mask image provided. Upload a mask as a second file with fieldname 'mask'",
      });
    }

    const imageValidation = await validateImageBuffer(imageBuffer);
    if (!imageValidation.valid) {
      return reply.status(400).send({ error: `Invalid image: ${imageValidation.reason}` });
    }
    const maskValidation = await validateImageBuffer(maskBuffer);
    if (!maskValidation.valid) {
      return reply.status(400).send({ error: `Invalid mask: ${maskValidation.reason}` });
    }

    try {
      const jobId = randomUUID();
      const workspacePath = await createWorkspace(jobId);

      // Save input
      const inputPath = join(workspacePath, "input", filename);
      await writeFile(inputPath, imageBuffer);

      // Process
      const jobIdForProgress = clientJobId;
      const onProgress = jobIdForProgress
        ? (percent: number, stage: string) => {
            updateSingleFileProgress({
              jobId: jobIdForProgress,
              phase: "processing",
              stage,
              percent,
            });
          }
        : undefined;

      const resultBuffer = await inpaint(
        imageBuffer,
        maskBuffer,
        join(workspacePath, "output"),
        onProgress,
      );

      // Save output
      const outputFilename = `${filename.replace(/\.[^.]+$/, "")}_erased.png`;
      const outputPath = join(workspacePath, "output", outputFilename);
      await writeFile(outputPath, resultBuffer);

      if (clientJobId) {
        updateSingleFileProgress({
          jobId: clientJobId,
          phase: "complete",
          percent: 100,
        });
      }

      return reply.send({
        jobId,
        downloadUrl: `/api/v1/download/${jobId}/${encodeURIComponent(outputFilename)}`,
        originalSize: imageBuffer.length,
        processedSize: resultBuffer.length,
      });
    } catch (err) {
      return reply.status(422).send({
        error: "Object erasing failed",
        details: err instanceof Error ? err.message : "Unknown error",
      });
    }
  });
}