/**
 * Moves favicon-shaped values out of `rich_content.thumbnailUrl` into the new
 * `faviconUrl` field.
 *
 * The extraction cascade used to end at the page's icon and then at a guessed
 * `${origin}/favicon.ico`, so `thumbnailUrl` was almost never empty — it just
 * held a 16×16 icon (or a 404) that the UI then cover-cropped into a 128×72
 * box. The cascade now stops at real artwork, and an absent `thumbnailUrl`
 * means "no artwork", which is what lets the frontend draw a placeholder.
 * This migration gives rows written before that change the same meaning.
 *
 * Purely local — it classifies the already-stored URL and makes no network
 * calls, so `accentColor` is deliberately not backfilled: the frontend derives
 * a stable hue from the hostname whenever one is missing, and
 * `refreshDumpMetadata` fetches the real color on demand.
 *
 * Idempotent: rows that already carry a `faviconUrl` are skipped, so a fresh
 * database built from schema.sql is a no-op.
 *
 * @module
 */

import type { DatabaseSync } from "node:sqlite";

/**
 * Checks whether a stored thumbnail URL is really a site icon.
 *
 * Deliberately loose. A false positive (a genuine cover image living under
 * `/assets/icons/`) renders contained on a tinted field instead of
 * cover-cropped — mildly wrong, never broken — so chasing them isn't worth the
 * extra rules.
 */
function isIconUrl(raw: string): boolean {
  let pathname: string;
  try {
    pathname = new URL(raw).pathname;
  } catch {
    return false;
  }
  return /favicon|apple-touch-icon|\/icons?\//i.test(pathname) ||
    /\.(ico|svg)$/i.test(pathname);
}

/** Applies this migration to `db`. */
export function up(db: DatabaseSync): void {
  const rows = db.prepare(
    `SELECT id, rich_content FROM dumps
      WHERE kind = 'url' AND rich_content IS NOT NULL;`,
  ).all() as { id: string; rich_content: string }[];

  const update = db.prepare(
    `UPDATE dumps SET rich_content = ? WHERE id = ?;`,
  );

  let patched = 0;
  for (const row of rows) {
    let rich: { thumbnailUrl?: string; faviconUrl?: string };
    try {
      rich = JSON.parse(row.rich_content);
    } catch {
      continue; // malformed payload — leave it untouched
    }
    if (rich.faviconUrl || !rich.thumbnailUrl) continue;
    if (!isIconUrl(rich.thumbnailUrl)) continue;

    const { thumbnailUrl: _dropped, ...rest } = rich;
    update.run(
      JSON.stringify({ ...rest, faviconUrl: rich.thumbnailUrl }),
      row.id,
    );
    patched++;
  }

  if (patched > 0) {
    console.log(
      `[migrate] 0011: reclassified ${patched} favicon thumbnail(s)`,
    );
  }
}