import { Kysely, sql } from 'kysely';

/**
 * DocAdenice backlink table (R3.2).
 *
 * Stores directed edges: source_page_id -> target_page_id.
 * Populated by the BacklinkIndexerService each time a page is saved.
 *
 * link_type discriminates the relationship:
 *   - 'wikilink'        : [[Page Title]] or [[Page Title|alias]] syntax
 *   - 'mention'         : @mention node (entityType = 'page' from Docmost Mention)
 *   - 'database_embed'  : R3.1.c databaseView node that references a page embed
 *
 * context_excerpt: ~200 chars of surrounding text captured at index time for
 * the "Linked references" panel preview. Nullable — populated when text context
 * is extractable.
 *
 * UNIQUE(source_page_id, target_page_id, link_type) ensures the indexer can
 * do a simple DELETE-then-INSERT (full reindex per save) without duplicates.
 *
 * Idempotent: ifNotExists on every CREATE so re-runs never fail.
 */
export async function up(db: Kysely<any>): Promise<void> {
  await db.schema
    .createTable('acadenice_backlink')
    .ifNotExists()
    .addColumn('id', 'uuid', (col) =>
      col.primaryKey().defaultTo(sql`gen_random_uuid()`),
    )
    .addColumn('source_page_id', 'uuid', (col) =>
      col.notNull().references('pages.id').onDelete('cascade'),
    )
    .addColumn('target_page_id', 'uuid', (col) =>
      col.notNull().references('pages.id').onDelete('cascade'),
    )
    .addColumn('link_type', 'varchar(20)', (col) =>
      col
        .notNull()
        .check(
          sql`link_type IN ('wikilink', 'mention', 'database_embed')`,
        ),
    )
    .addColumn('context_excerpt', 'text')
    .addColumn('created_at', 'timestamptz', (col) =>
      col.notNull().defaultTo(sql`now()`),
    )
    .addColumn('updated_at', 'timestamptz', (col) =>
      col.notNull().defaultTo(sql`now()`),
    )
    .addColumn('workspace_id', 'uuid', (col) =>
      col.notNull().references('workspaces.id').onDelete('cascade'),
    )
    .addUniqueConstraint('acadenice_backlink_source_target_type_unique', [
      'source_page_id',
      'target_page_id',
      'link_type',
    ])
    .execute();

  await db.schema
    .createIndex('idx_backlink_target')
    .ifNotExists()
    .on('acadenice_backlink')
    .column('target_page_id')
    .execute();

  await db.schema
    .createIndex('idx_backlink_source')
    .ifNotExists()
    .on('acadenice_backlink')
    .column('source_page_id')
    .execute();

  await db.schema
    .createIndex('idx_backlink_workspace')
    .ifNotExists()
    .on('acadenice_backlink')
    .column('workspace_id')
    .execute();
}

export async function down(db: Kysely<any>): Promise<void> {
  await db.schema.dropTable('acadenice_backlink').ifExists().execute();
}