/**
 * Utility functions for GeoJSON data handling.
 * @module
 */

import type { ImportableGeoJSON, ReadOsmDataTypes } from "./types.ts";

/**
 * Parse GeoJSON from various input formats.
 *
 * Supports multiple input types for flexibility:
 * - **string**: JSON string to parse
 * - **ReadableStream**: Streaming JSON data
 * - **ArrayBuffer/SharedArrayBuffer**: Binary data to decode and parse
 * - **Object**: Already-parsed FeatureCollection (passed through)
 *
 * @param data - GeoJSON data in any supported format.
 * @returns Parsed GeoJSON FeatureCollection.
 * @throws If data is null or an unsupported type.
 *
 * @example
 * ```ts
 * // From string
 * const geojson = await readDataAsGeoJSON('{"type":"FeatureCollection","features":[]}')
 *
 * // From fetch response
 * const response = await fetch('/data.geojson')
 * const geojson = await readDataAsGeoJSON(response.body!)
 * ```
 */
export async function readDataAsGeoJSON(data: ReadOsmDataTypes): Promise<ImportableGeoJSON> {
  if (data == null) throw new Error("Data is null");
  if (typeof data === "string") return JSON.parse(data) as ImportableGeoJSON;

  if (data instanceof ReadableStream) {
    const reader = data.pipeThrough(new TextDecoderStream()).getReader();
    let result = "";
    while (true) {
      const { done, value } = await reader.read();
      if (done) break;
      if (value !== undefined) result += value;
    }
    return JSON.parse(result) as ImportableGeoJSON;
  }
  if (data instanceof ArrayBuffer || data instanceof SharedArrayBuffer) {
    const decoder = new TextDecoder();
    const text = decoder.decode(new Uint8Array(data));
    return JSON.parse(text) as ImportableGeoJSON;
  }
  if (typeof data === "object" && "type" in data && "features" in data) {
    return data as ImportableGeoJSON;
  }
  throw new Error(
    "Invalid data type. Accepts string, ReadableStream, ArrayBufferLike, or GeoJSON FeatureCollection.",
  );
}