syntax = "proto3";

package chatto.api.v1;

import "buf/validate/validate.proto";
import "google/protobuf/timestamp.proto";

// Request to fetch server-side link preview metadata for a URL.
message FetchLinkPreviewRequest {
  // URL to preview.
  string url = 1 [
    (buf.validate.field).string.min_len = 1,
    (buf.validate.field).string.max_len = 2048
  ];
}

// Link preview metadata used by message composers and room timeline events.
//
// Clients should treat optional metadata as unavailable when absent. Message
// creation accepts only the preview_token returned by FetchLinkPreview, not
// client-provided metadata fields.
message LinkPreview {
  // Previewed URL.
  string url = 1;
  // Page or embed title.
  optional string title = 2;
  // Page or embed description.
  optional string description = 3;
  // Preview image URL, when available.
  optional string image_url = 4;
  // Existing server asset ID for the preview image, when cached or stored with
  // the message.
  optional string image_asset_id = 5;
  // Site name, when known.
  optional string site_name = 6;
  // Embed provider or type, when recognized.
  optional string embed_type = 7;
  // Provider-specific embed ID, when recognized.
  optional string embed_id = 8;
  // Structured, provider-neutral social-post data for native rendering.
  SocialPostPreview social_post = 9;
}

// Bounded, provider-neutral social-post data used for native preview cards.
message SocialPostPreview {
  // Stable lowercase provider identifier, such as "bluesky".
  string provider = 1;
  // Author shown on the post.
  SocialPostAuthor author = 2;
  // Plain-text post body.
  string text = 3;
  // Post publication time.
  google.protobuf.Timestamp published_at = 4;
  // Images attached directly to the post, in display order.
  repeated SocialPostImage images = 5;
  // Website card embedded in the post, when present.
  SocialPostExternalLink external_link = 6;
  // Provider-supplied content warning, when present.
  optional string content_warning = 7;
  // Canonical URL for this post. Always set for quoted posts; the outer post
  // may also use LinkPreview.url.
  string url = 8;
  // Post quoted by this post, when present. Quotes inside this snapshot are
  // omitted so preview size and rendering depth remain bounded.
  SocialPostPreview quoted_post = 9;
}

// Author shown on a social-post preview.
message SocialPostAuthor {
  // Author display name.
  string display_name = 1;
  // Provider-native handle without a leading at-sign when applicable.
  string handle = 2;
  // Locally served author avatar URL, when available.
  optional string avatar_url = 3;
  // Locally stored author avatar asset ID, when available.
  optional string avatar_asset_id = 4;
}

// One image attached directly to a social post.
message SocialPostImage {
  // Locally served image URL.
  string url = 1;
  // Locally stored image asset ID.
  string asset_id = 2;
  // Author-provided alternative text.
  optional string alt = 3;
  // Source aspect-ratio width, when known.
  optional uint32 width = 4;
  // Source aspect-ratio height, when known.
  optional uint32 height = 5;
}

// Website card embedded in a social post.
message SocialPostExternalLink {
  // Destination URL.
  string url = 1;
  // Card title, when available.
  optional string title = 2;
  // Card description, when available.
  optional string description = 3;
  // Locally served card image URL, when available.
  optional string image_url = 4;
  // Locally stored card image asset ID, when available.
  optional string image_asset_id = 5;
}

// Result of fetching link preview metadata.
message FetchLinkPreviewResponse {
  // Preview metadata, or absent when the URL cannot be previewed.
  LinkPreview preview = 1;
  // Short-lived opaque token to pass to CreateMessage.link_preview_token when
  // the user posts this preview.
  string preview_token = 2;
}