import type {
  Unstable_DirectiveFormatter,
  Unstable_DirectiveSegment,
} from "../types/directive";
import type { Unstable_TriggerItem } from "../types/trigger";

const DIRECTIVE_RE =
  /:([\w-]{1,64})\[([^\]\n]{1,1024})\](?:\{name=([^}\n]{1,1024})\})?/gu;

/**
 * Default directive formatter using the `:type[label]{name=id}` syntax.
 *
 * When `id` equals `label`, the `{name=…}` attribute is omitted for brevity.
 */
export const unstable_defaultDirectiveFormatter: Unstable_DirectiveFormatter = {
  serialize(item: Unstable_TriggerItem): string {
    const attrs = item.id !== item.label ? `{name=${item.id}}` : "";
    return `:${item.type}[${item.label}]${attrs}`;
  },

  parse(text: string): Unstable_DirectiveSegment[] {
    const segments: Unstable_DirectiveSegment[] = [];
    let lastIndex = 0;

    for (const match of text.matchAll(DIRECTIVE_RE)) {
      if (match.index > lastIndex) {
        segments.push({
          kind: "text",
          text: text.slice(lastIndex, match.index),
        });
      }
      const label = match[2]!;
      segments.push({
        kind: "mention",
        type: match[1]!,
        label,
        id: match[3] ?? label,
      });
      lastIndex = match.index + match[0].length;
    }

    if (lastIndex < text.length) {
      segments.push({ kind: "text", text: text.slice(lastIndex) });
    }

    return segments;
  },
};