Extra Chill Link Pages #4 in Social & Sharing

Owner-neutral Link Pages storage and operation runtime for the Extra Chill network.

Runtime contract

The plugin loads its generic API synchronously from the exact plugin basename extrachill-link-pages/extrachill-link-pages.php. Consumers may validate EC_LINK_PAGES_RUNTIME_API_VERSION === '3' and ec_link_pages_runtime_ready() === true before registering adapters. The API is therefore available before plugins_loaded priority 20.

Compatibility is deliberate: EC_LINK_PAGE_POST_TYPE remains the legacy storage slug artist_link_page, and EC_LINK_PAGE_OWNER_META_KEY remains _ec_link_page_owner_reference. Existing posts, IDs, slugs, metadata, site ownership, routes, and rendering remain untouched.

Owner adapter contract

Owner plugins keep authorization and management operations in an operation provider, but delegate generic persistence to:

• ec_read_link_page_persistence( int $link_page_id, array $overrides = array() )
• ec_save_link_page_persistence( int $link_page_id, array $data )
• ec_save_link_page_persistence_composed( int $link_page_id, array $data, callable $finalizer )
• ec_create_owned_link_page( string|array $owner, string $title, string $slug, bool $force = false )
• ec_provision_owned_link_page( string|array $owner, string $title, string $slug, bool $force = false, ?callable $precondition = null )
• ec_provision_owned_link_page_composed( string|array $owner, string $title, string $slug, callable $finalizer, bool $force = false, ?callable $precondition = null )

The create primitive validates the canonical owner, rejects an occupied slug, verifies that WordPress did not suffix the requested slug, assigns the owner, and deletes the new post if assignment fails. Existing owner records are returned unless $force is true. Owner adapters may maintain reciprocal legacy metadata around this primitive, but generic storage does not know that policy. The provisioning primitive serializes by canonical owner and returns array( 'link_page_id' => int, 'created' => bool ). Its optional precondition runs inside the owner lock immediately before lookup or creation; the historical create wrapper continues returning only the integer ID.

On multisite, canonical storage resolves in this order: a valid EC_LINK_PAGE_STORAGE_BLOG_ID configuration constant, the ec_link_page_storage_blog_id filter, then the persisted network option. The constant supports fresh network activation before host plugins can register runtime filters.

The composed save finalizer receives ( $link_page_id, $persistence ); the composed provision finalizer receives ( $link_page_id, $owner_reference ) for new, force-replaced, and existing exact owner pages. Finalizers return exactly true or WP_Error. Both run under the exact Link Page lock before any generic success hook. On failure, generic save metadata is restored or a newly created page is removed; an existing page remains unchanged. The finalizer owns compensation for state outside the generic Link Page storage snapshots.

Public display is registered with ec_register_link_page_public_projection_provider( $name, $callback, $priority = 10 ). The callback receives a local context containing link_page_id, parsed owner, owner_reference, public_url, and request scalar data. It returns null when it does not own the reference, otherwise one strict projection:

array(
    'display_title'    => 'Required title',
    'bio'              => '',
    'profile_img_url'  => '',
    'social_links'     => array(),
    'social_renderer'  => null, // callable( $links, $position, $context ): string
    'management_url'   => '',
    'body_attributes'  => array(),
    'seo'              => array(),
    'tracking_url'     => '',
    'components'       => array(), // before_header, after_header, after_links, footer
    'assets'           => null, // callable( $context, $projection ): true|WP_Error
)

Component slots contain ordered callback arrays. Provider and component calls are context-checked and exceptions fail closed. A live provider takes precedence; when no provider is loaded, ec_save_link_page_public_projection_snapshot() and ec_read_link_page_public_projection_snapshot() provide the versioned, owner-checksummed, serializable fallback. The public renderer makes no HTTP request to discover owner data.

The Artist companion must validate API version 3, add the new function signatures, register a public provider, and delegate its existing management callbacks to generic persistence. It must stop loading its old public runtime before both plugins run together. Historical Artist-named query variables, body attributes, and the extrachill_artist_link_page_minimal_head hook remain only as documented compatibility identifiers; the companion supplies its historical body attributes and optional domain components.

The CPT's structural registration settings and English labels remain unchanged. The standalone plugin intentionally owns label translation through the extrachill-link-pages text domain; this is a translation-ownership change, not a storage, capability, rewrite, or public-routing change.

Deployment order

1. Deploy the Artist Platform compatibility handoff while its bundled fallback remains available.
2. Install and activate Extra Chill Link Pages on the same site or network scope.
3. On that activation request, this plugin accepts already-loaded fallback symbols and avoids duplicate CPT registration.
4. On subsequent requests, Artist Platform detects the exact active basename, defers the generic runtime and CPT, then registers its external adapters at plugins_loaded priority 20.

This rolling handoff intentionally does not add a hard Requires Plugins header to Artist Platform yet: WordPress would prevent deploying that compatibility build before this new plugin exists. After the rolling transition is complete, Artist Platform can declare Requires Plugins: extrachill-link-pages.

Multisite lifecycle

Successful activation persists the explicitly resolved canonical storage blog in the network option ec_link_page_storage_blog_id. Runtime resolution checks an explicit filter first and then that validated option. Network activation with neither source fails closed. Activation and deactivation touch only that storage site and restore the caller's exact multisite context. Query, switch, callback, context-restoration, and runtime-contract failures are exposed as WP_Error, logged, published through ec_link_pages_runtime_error, and shown in site and network admin notices. Activation terminates on such an error so WordPress does not report a broken runtime as successfully activated.

Deactivation unregisters the standalone-owned legacy storage type before flushing affected sites, so standalone rewrites are removed rather than re-created. During the rolling transition, Artist Platform fallback may resume on the next request. That fallback must re-establish its rewrites through Artist Platform's existing activation or rewrite lifecycle; this plugin does not load or invoke the fallback during deactivation. Deactivation deliberately preserves the canonical storage option because fallback code may still own records there; silently deleting it could fork subsequent storage ownership.