Migrate a User Library Between Streaming Platforms

import fs from "node:fs";

const API_KEY = process.env.SONOVAULT_API_KEY!;
const BASE    = "https://api.sonovault.now/v1";
const BATCH   = 100;

type Platform = "spotify" | "applemusic" | "tidal" | "beatport" | "discogs" | "musicbrainz";

interface Migration {
  source: Platform;        // where the IDs came from
  target: Platform;        // where you're going
  inputIds: string[];
}

interface Outcome {
  sourceId: string;
  targetId: string | null;
  status:   "matched" | "missing_on_target" | "unresolved";
  title?:   string;
}

async function migrate({ source, target, inputIds }: Migration): Promise<Outcome[]> {
  const outcomes: Outcome[] = [];

  for (let i = 0; i < inputIds.length; i += BATCH) {
    const chunk = inputIds.slice(i, i + BATCH);

    const res  = await fetch(`${BASE}/tracks/resolve`, {
      method:  "POST",
      headers: { "x-api-key": API_KEY, "content-type": "application/json" },
      body:    JSON.stringify({
        input_type: `${source}_id`,
        items:      chunk,
      }),
    });
    const data = await res.json();

    for (let j = 0; j < chunk.length; j++) {
      const sourceId = chunk[j];
      const result   = data.results[j];

      if (result.status !== "matched") {
        outcomes.push({ sourceId, targetId: null, status: "unresolved" });
        continue;
      }

      const targetLink = result.links.find((l: { source: string }) => l.source === target);
      outcomes.push({
        sourceId,
        targetId: targetLink?.external_id ?? null,
        status:   targetLink ? "matched" : "missing_on_target",
        title:    result.track?.title,
      });
    }
    console.log(`Resolved ${Math.min(i + BATCH, inputIds.length)} / ${inputIds.length}`);
  }

  return outcomes;
}

// Example: Spotify → Tidal
const spotifyIds = fs.readFileSync("./spotify-library.txt", "utf-8").trim().split("\n");
const outcomes   = await migrate({ source: "spotify", target: "tidal", inputIds: spotifyIds });

const matched     = outcomes.filter(o => o.status === "matched");
const missing     = outcomes.filter(o => o.status === "missing_on_target");
const unresolved  = outcomes.filter(o => o.status === "unresolved");

console.log(`Matched: ${matched.length}`);
console.log(`Missing on Tidal: ${missing.length}`);
console.log(`Unresolved: ${unresolved.length}`);

fs.writeFileSync("./tidal-ids.txt", matched.map(o => o.targetId).join("\n"));
fs.writeFileSync("./missing-on-tidal.json", JSON.stringify(missing, null, 2));

// A user-facing summary you can show before initiating the destination write.

function renderReport(outcomes: Outcome[], target: Platform) {
  const total      = outcomes.length;
  const matched    = outcomes.filter(o => o.status === "matched").length;
  const missing    = outcomes.filter(o => o.status === "missing_on_target");
  const unresolved = outcomes.filter(o => o.status === "unresolved");

  return [
    `${matched} of ${total} tracks ready to import to ${target}.`,
    missing.length    && `${missing.length} not available on ${target}:`,
    ...missing.slice(0, 10).map(o => `  - ${o.title ?? o.sourceId}`),
    unresolved.length && `${unresolved.length} couldn't be identified at all.`,
  ].filter(Boolean).join("\n");
}