import { ParserError } from "../util/errors.js";
import type { FileInfo } from "../types/index.js";
import type { Plugin } from "../types/index.js";

export default {
  /**
   * The order that this parser will run, in relation to other parsers.
   */
  order: 100,

  /**
   * Whether to allow "empty" files. This includes zero-byte files, as well as empty JSON objects.
   */
  allowEmpty: true,

  /**
   * Determines whether this parser can parse a given file reference.
   * Parsers that match will be tried, in order, until one successfully parses the file.
   * Parsers that don't match will be skipped, UNLESS none of the parsers match, in which case
   * every parser will be tried.
   */
  canParse: ".json",

  /**
   * Allow JSON files with byte order marks (BOM)
   */
  allowBOM: true,

  /**
   * Parses the given file as JSON
   */
  async parse(file: FileInfo): Promise<unknown> {
    let data = file.data;
    if (Buffer.isBuffer(data)) {
      data = data.toString();
    }

    if (typeof data === "string") {
      if (data.trim().length === 0) {
        return; // This mirrors the YAML behavior
      }

      if (this.allowBOM && data.charCodeAt(0) === 0xfeff) {
        data = data.slice(1);
      }

      try {
        return JSON.parse(data);
      } catch (e: any) {
        throw new ParserError(e.message, file.url);
      }
    } else {
      // data is already a JavaScript value (object, array, number, null, NaN, etc.)
      return data as object;
    }
  },
} as Plugin;