export type JsonLine = {
  path: string;
  depth: number;
  key?: string;
  kind: "open" | "close" | "value";
  text: string;
  tone?: "string" | "number" | "boolean" | "null";
  foldable?: boolean;
  expanded?: boolean;
};

/** Pretty JSON lines retain separators and paths, including after collapsing branches. */
export function jsonLines(value: unknown, collapsed: ReadonlySet<string> = new Set()): JsonLine[] {
  const lines: JsonLine[] = [];
  function visit(current: unknown, path: string, depth: number, key: string | undefined, last: boolean) {
    const comma = last ? "" : ",";
    if (current !== null && typeof current === "object") {
      const array = Array.isArray(current);
      const entries: [string, unknown][] = array
        ? current.map((item, index) => [String(index), item])
        : Object.entries(current);
      const open = array ? "[" : "{";
      const close = array ? "]" : "}";
      if (entries.length === 0) {
        lines.push({ path, depth, key, kind: "value", text: `${open}${close}${comma}` });
      } else if (collapsed.has(path)) {
        lines.push({ path, depth, key, kind: "open", text: `${open}…${close}${comma}`, foldable: true, expanded: false });
      } else {
        lines.push({ path, depth, key, kind: "open", text: open, foldable: true, expanded: true });
        entries.forEach(([childKey, childValue], index) => {
          visit(childValue, `${path}/${childKey.replace(/~/g, "~0").replace(/\//g, "~1")}`, depth + 1, array ? undefined : childKey, index === entries.length - 1);
        });
        lines.push({ path, depth, kind: "close", text: `${close}${comma}` });
      }
      return;
    }
    const tone = current === null ? "null" : typeof current as "string" | "number" | "boolean";
    lines.push({ path, depth, key, kind: "value", tone, text: `${JSON.stringify(current)}${comma}` });
  }
  visit(value, "$", 0, undefined, true);
  return lines;
}