/**
 * Closed rich-text AST for provider content (proposal §4.5 "rich content
 * contract"). Nothing outside these node types can be rendered: there is no
 * node that carries raw HTML, attributes, styles or arbitrary URLs.
 *
 * URL-bearing fields are only ever produced by `parseSafeHttpUrl` /
 * `toProxiedMediaUrl`, and the renderer re-validates them, so an AST that was
 * round-tripped through storage or the network cannot smuggle a bad scheme.
 */

export const RICH_TEXT_VERSION = 1 as const;

export type TextNode = { readonly type: "text"; readonly text: string };
export type LineBreakNode = { readonly type: "linebreak" };
/** Custom emoji / emote. `src` is always a media-proxy URL, never the origin URL. */
export type EmojiNode = { readonly type: "emoji"; readonly shortcode: string; readonly src: string };
export type LinkNode = {
  readonly type: "link";
  /** Absolute http(s) URL, credential-free. */
  readonly href: string;
  /** ASCII (punycode) host of `href`, shown to the operator next to the label. */
  readonly host: string;
  readonly children: readonly (TextNode | EmojiNode)[];
};
export type MentionNode = {
  readonly type: "mention";
  /** Handle without the leading "@", e.g. `alice` or `alice@example.social`. */
  readonly handle: string;
  readonly href?: string;
};
export type HashtagNode = {
  readonly type: "hashtag";
  /** Tag without the leading "#". */
  readonly tag: string;
  readonly href?: string;
};

export type InlineNode = TextNode | LineBreakNode | EmojiNode | LinkNode | MentionNode | HashtagNode;

export type ParagraphNode = { readonly type: "paragraph"; readonly children: readonly InlineNode[] };

export type RichTextDocument = {
  readonly type: "doc";
  readonly version: typeof RICH_TEXT_VERSION;
  readonly children: readonly ParagraphNode[];
  /** True when input exceeded a length/node/depth limit and was cut. */
  readonly truncated: boolean;
};

export type LinkPreview = {
  readonly type: "linkPreview";
  readonly href: string;
  readonly host: string;
  readonly title?: string;
  readonly description?: string;
  readonly siteName?: string;
  /** Media-proxy URL for the preview image. */
  readonly image?: string;
};