import { Knex } from "knex";

/**
 * Rebuilds `sdk_cache` for per-entity last-content dedupe.
 *
 * The original table keyed rows by (type, content-hash) as insert-only set
 * membership: "have we ever sent this exact content within the TTL window?".
 * That cannot express a value returning to a previously-seen state (A -> B -> A),
 * so a corrective write whose content matches an earlier one is silently deduped.
 *
 * The new shape stores one row per (type, entity_key) holding that entity's last
 * content hash, so dedupe becomes "does this differ from what we last sent for
 * this entity?". The SDK cache is ephemeral (rebuilt from migrations on each
 * container start), so there is no data to preserve — we drop and recreate.
 */
export async function up(knex: Knex): Promise<void> {
  await knex.schema.dropTableIfExists("sdk_cache");
  await knex.schema.createTable("sdk_cache", (table) => {
    table.increments("id");
    table.string("type").notNullable().index();
    table.string("entity_key").notNullable();
    table.string("content_hash").notNullable();
    // Epoch milliseconds; compared directly against Date.now() in removeExpiredObjects.
    // Indexed so TTL cleanup is a range scan rather than a full table scan.
    table.bigInteger("updated_at").notNullable().index();
    table.unique(["type", "entity_key"]); // one row per entity
  });
}

export async function down(knex: Knex): Promise<void> {
  await knex.schema.dropTableIfExists("sdk_cache");
  await knex.schema.createTable("sdk_cache", (table) => {
    table.increments("id");
    table.string("type").notNullable().index();
    table.string("key").notNullable();
    table.timestamp("created_at").defaultTo(knex.fn.now());
    table.unique(["type", "key"]);
  });
}