translator.ts

import { NodeHtmlMarkdownOptions } from './options';
import { NodeMetadata, NodeMetadataMap, Visitor } from './visitor';
import { ElementNode } from './nodes';


/* ****************************************************************************************************************** */
// region: Types
/* ****************************************************************************************************************** */

export type TranslatorConfigFactory = {
  (ctx: TranslatorContext): TranslatorConfig
  base?: TranslatorConfig
}

export type TranslatorConfigObject = { [tags: string]: TranslatorConfig | TranslatorConfigFactory }

export type TranslatorContext = Partial<NodeMetadata> & {
  node: ElementNode
  options: NodeHtmlMarkdownOptions
  parent?: ElementNode
  nodeMetadata: NodeMetadataMap
  visitor: Visitor
  base?: TranslatorConfig
}

export interface TranslatorConfig {
  /**
   * Preceeds content, follows surroundingNewLines
   */
  prefix?: string

  /**
   * Follows content, preceeds surroundingNewLines
   */
  postfix?: string

  /**
   * Set fixed output content
   */
  content?: string

  /**
   * Post-process content after inner nodes have been rendered.
   * Returning undefined will cause the content to not be updated
   */
  postprocess?: (ctx: TranslatorContext & { content: string }) => string | PostProcessResult

  /**
   * If false, no child elements will be scanned
   * @default true
   */
  recurse?: boolean

  /**
   * Adds newline before and after (true, false, or number of newlines to add per side)
   * @default false
   */
  surroundingNewlines?: boolean | number

  /**
   * Ignore node entirely
   */
  ignore?: boolean

  /**
   * Do not escape content
   */
  noEscape?: boolean

  /**
   * If first character matches end of the last written data, add a space
   * @example
   * // old text: **abc**
   * // new text: **def**
   * // becomes: **abc** **def**
   */
  spaceIfRepeatingChar?: boolean

  /**
   * Ensure translator is always visited, even if element is empty
   * Note: For speed, trees are optimized beforehand to only visit elements which have child nodes or text content.
   * In some cases, however, you may want to create or alter a translator to be triggered even if the element is empty.
   * (If using a TranslatorConfigFactory, this value is always treated as true)
   */
  preserveIfEmpty?: boolean

  /**
   * Keep whitespace as it is
   */
  preserveWhitespace?: boolean

  /**
   * Custom translator collection to use for child HTML nodes
   */
  childTranslators?: TranslatorCollection
}

export enum PostProcessResult {
  NoChange,
  RemoveNode
}

// endregion


/* ****************************************************************************************************************** */
// region: TranslatorCollection
/* ****************************************************************************************************************** */

export class TranslatorCollection {
  /**
   * @internal
   */
  [tagName: string]: any

  get size() { return Object.keys(this).length }

  /**
   * Add / update translator config for one or more element tags
   */
  set(keys: string, config: TranslatorConfig | TranslatorConfigFactory, /* @internal */ preserveBase?: boolean) {
    keys.split(',').forEach(el => {
      el = el.toUpperCase();

      let res = config;
      if (preserveBase) {
        const base = this[el];
        if (isTranslatorConfig(base))
          res = !isTranslatorConfig(config)
                ? Object.assign((...args: any[]) => (<Function>config).apply(void 0, args), { base })
                : { ...base, ...config };
      }

      this[el] = res;
    });
  }

  /**
   * Get translator config for element tag
   */
  get(key: string): TranslatorConfig | TranslatorConfigFactory {
    return this[key.toUpperCase()] as any;
  }

  /**
   * Returns array of entries
   */
  entries(): [ elementName: string, config: TranslatorConfig | TranslatorConfigFactory ][] {
    return Object.entries(this);
  }

  /**
   * Remove translator config for one or more element tags
   */
  remove(keys: string): void {
    keys.split(',').forEach(el => delete this[el.toUpperCase()]);
  }
}

// endregion


/* ****************************************************************************************************************** */
// region: Utilities
/* ****************************************************************************************************************** */

/**
 * Only use to narrow union of types where only TranslatorConfig has JS type 'object'
 */
export const isTranslatorConfig = (v: any): v is TranslatorConfig => typeof v === 'object';

export function createTranslatorContext(
  visitor: Visitor,
  node: ElementNode,
  metadata?: NodeMetadata,
  base?: TranslatorConfig
): TranslatorContext
{
  const { instance, nodeMetadata, } = visitor;
  return {
    node,
    options: instance.options,
    parent: <ElementNode>node.parentNode,
    nodeMetadata,
    visitor,
    base,
    ...metadata
  };
}

// endregion