const db = getDb("cache.sqlite");
db.table(
  "blob_assets",
  /* SQL */ `
  CREATE TABLE IF NOT EXISTS blob_assets (
    hash TEXT PRIMARY KEY,
    refs INTEGER NOT NULL DEFAULT 0
  );
`,
);

/**
 * Uncompressed files are read directly from the media store root.  Compressed
 * files are stored as `<compress store>/<first 2 chars of hash>/<hash>` Since
 * multiple files can share the same hash, the number of references is tracked
 * so that when a file is deleted, the compressed data is only removed when all
 * references are gone.
 */
export class BlobAsset {
  /** sha1 of the contents */
  hash!: string;
  refs!: number;

  decrementOrDelete() {
    BlobAsset.decrementOrDelete(this.hash);
  }

  static get(hash: string) {
    return getQuery.get(hash);
  }
  static putOrIncrement(hash: string) {
    ASSERT(hash.length === 40);
    putOrIncrementQuery.get(hash);
    return BlobAsset.get(hash)!;
  }
  static decrementOrDelete(hash: string) {
    ASSERT(hash.length === 40);
    decrementQuery.run(hash);
    return deleteQuery.run(hash).changes > 0;
  }
}

const getQuery = db.prepare<[hash: string]>(/* SQL */ `
    SELECT * FROM blob_assets WHERE hash = ?;
`).as(BlobAsset);
const putOrIncrementQuery = db.prepare<[hash: string]>(/* SQL */ `
    INSERT INTO blob_assets (hash, refs) VALUES (?, 1)
    ON CONFLICT(hash) DO UPDATE SET refs = refs + 1;
`);
const decrementQuery = db.prepare<[hash: string]>(/* SQL */ `
    UPDATE blob_assets SET refs = refs - 1 WHERE hash = ? AND refs > 0;
`);
const deleteQuery = db.prepare<[hash: string]>(/* SQL */ `
    DELETE FROM blob_assets WHERE hash = ? AND refs <= 0;
`);

import { getDb } from "#sitegen/sqlite";