includes_loader.ts

import { posix } from "../deps/path.ts";
import { Exception } from "./errors.ts";

import type { Data, Formats, Reader } from "../core.ts";

export interface Options {
  /** The reader instance used to read the files */
  reader: Reader;

  /** The default _includes directory */
  includes: string;

  /** The registered file formats */
  formats: Formats;
}

/**
 * Class to load _includes files.
 */
export default class IncludesLoader {
  /** The filesystem reader */
  reader: Reader;

  /** Default _includes path */
  includes: string;

  /** List of extensions to load files and the loader used */
  formats: Formats;

  constructor(options: Options) {
    this.reader = options.reader;
    this.formats = options.formats;
    this.includes = options.includes;
  }

  async load(path: string, from?: string): Promise<[string, Data] | undefined> {
    const entry = this.formats.search(path);

    if (!entry) {
      return;
    }

    const [, format] = entry;

    if (!format.pageLoader) {
      return;
    }

    let finalPath: string;

    if (path.startsWith(".")) {
      if (!from) {
        throw new Exception(`Cannot load "${path}" without a base path`, {
          path,
        });
      }

      finalPath = posix.join("/", posix.dirname(from), path);
    } else {
      finalPath = posix.join("/", format.includesPath || this.includes, path);
    }

    return [
      finalPath,
      await this.reader.read(finalPath, format.pageLoader),
    ];
  }
}