SnapOtter/apps/api/src/routes/tools/vectorize.ts

import { z } from "zod";
import sharp from "sharp";
import potrace from "potrace";
import type { FastifyInstance } from "fastify";
import { randomUUID } from "node:crypto";
import { writeFile } from "node:fs/promises";
import { join, basename } from "node:path";
import { createWorkspace } from "../../lib/workspace.js";

const settingsSchema = z.object({
  colorMode: z.enum(["bw", "color"]).default("bw"),
  threshold: z.number().min(0).max(255).default(128),
  detail: z.enum(["low", "medium", "high"]).default("medium"),
});

function traceImage(
  buffer: Buffer,
  options: { threshold: number; turdSize: number; color?: string },
): Promise<string> {
  return new Promise((resolve, reject) => {
    potrace.trace(buffer, options, (err: Error | null, svg: string) => {
      if (err) reject(err);
      else resolve(svg);
    });
  });
}

function posterize(
  buffer: Buffer,
  options: { steps: number; threshold: number },
): Promise<string> {
  return new Promise((resolve, reject) => {
    potrace.posterize(buffer, options, (err: Error | null, svg: string) => {
      if (err) reject(err);
      else resolve(svg);
    });
  });
}

export function registerVectorize(app: FastifyInstance) {
  app.post(
    "/api/v1/tools/vectorize",
    async (request, reply) => {
      let fileBuffer: Buffer | null = null;
      let filename = "output";
      let settingsRaw: 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);
            }
            fileBuffer = Buffer.concat(chunks);
            filename = basename(part.filename ?? "output").replace(/\.[^.]+$/, "");
          } else if (part.fieldname === "settings") {
            settingsRaw = 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 (!fileBuffer || fileBuffer.length === 0) {
        return reply.status(400).send({ error: "No image file provided" });
      }

      let settings: z.infer<typeof settingsSchema>;
      try {
        const parsed = settingsRaw ? JSON.parse(settingsRaw) : {};
        const result = settingsSchema.safeParse(parsed);
        if (!result.success) {
          return reply.status(400).send({ error: "Invalid settings", details: result.error.issues });
        }
        settings = result.data;
      } catch {
        return reply.status(400).send({ error: "Settings must be valid JSON" });
      }

      try {
        // Convert to BMP-compatible format for potrace (PNG)
        const pngBuffer = await sharp(fileBuffer)
          .grayscale()
          .png()
          .toBuffer();

        const turdSize = settings.detail === "low" ? 10 : settings.detail === "high" ? 1 : 4;

        let svg: string;

        if (settings.colorMode === "color") {
          // Color mode: posterize
          svg = await posterize(pngBuffer, {
            steps: settings.detail === "low" ? 3 : settings.detail === "high" ? 8 : 5,
            threshold: settings.threshold,
          });
        } else {
          // B&W mode: simple trace
          svg = await traceImage(pngBuffer, {
            threshold: settings.threshold,
            turdSize,
          });
        }

        const svgBuffer = Buffer.from(svg, "utf-8");
        const outFilename = `${filename}.svg`;
        const jobId = randomUUID();
        const workspacePath = await createWorkspace(jobId);
        const outputPath = join(workspacePath, "output", outFilename);
        await writeFile(outputPath, svgBuffer);

        return reply.send({
          jobId,
          downloadUrl: `/api/v1/download/${jobId}/${encodeURIComponent(outFilename)}`,
          originalSize: fileBuffer.length,
          processedSize: svgBuffer.length,
          svgPreview: svg.length < 50000 ? svg : undefined,
        });
      } catch (err) {
        return reply.status(422).send({
          error: "Vectorization failed",
          details: err instanceof Error ? err.message : "Unknown error",
        });
      }
    },
  );
}