index.d.ts

// TypeScript Version: 3.4

import {Node} from 'unist'
import {VFile, VFileContents, VFileOptions} from 'vfile'
import vfile = require('vfile')

declare namespace unified {
  /**
   * Processor allows plugins, parsers, and compilers to be chained together to transform content.
   *
   * @typeParam P Processor settings. Useful when packaging unified with a preset parser and compiler.
   */
  interface Processor<P = Settings> {
    /**
     * Clone current processor
     *
     * @returns New unfrozen processor which is configured to function the same as its ancestor. But when the descendant processor is configured in the future it does not affect the ancestral processor.
     */
    (): Processor<P>

    /**
     * Configure the processor to use a plugin and optionally configure that plugin with options.
     *
     * @param plugin unified plugin
     * @param settings Configuration for plugin
     * @typeParam S Plugin settings
     * @returns The processor on which use is invoked
     */
    use<S extends any[] = [Settings?]>(
      plugin: Plugin<S, P>,
      ...settings: S
    ): Processor<P>

    /**
     * Configure the processor with a preset to use
     *
     * @param preset `Object` with an plugins (set to list), and/or an optional settings object
     */
    use<S extends any[] = [Settings?]>(preset: Preset<S, P>): Processor<P>

    /**
     * Configure using a tuple of plugin and setting(s)
     *
     * @param pluginTuple pairs, plugin and settings in an array
     * @typeParam S Plugin settings
     */
    use<S extends any[] = [Settings?]>(
      pluginTuple: PluginTuple<S, P>
    ): Processor<P>

    /**
     * A list of plugins and presets to be applied to processor
     *
     * @param list List of plugins, presets, and pairs
     */
    use(list: PluggableList<P>): Processor<P>

    /**
     * Configuration passed to a frozen processor
     *
     * @param processorSettings Settings passed to processor
     */
    use(processorSettings: ProcessorSettings<P>): Processor<P>

    /**
     * Parse text to a syntax tree.
     *
     * @param file VFile or anything which can be given to vfile()
     * @returns Syntax tree representation of input.
     */
    parse(file: VFileCompatible): Node

    /**
     * Function handling the parsing of text to a syntax tree.
     * Used in the parse phase in the process and invoked with a `string` and `VFile` representation of the document to parse.
     *
     * `Parser` can be a normal function in which case it must return a `Node`: the syntax tree representation of the given file.
     *
     * `Parser` can also be a constructor function (a function with keys in its `prototype`) in which case it’s invoked with `new`. Instances must have a parse method which is invoked without arguments and must return a `Node`.
     */
    Parser: ParserConstructor | ParserFunction

    /**
     * Compile a syntax tree to text.
     *
     * @param node
     * @param file `VFile` or anything which can be given to `vfile()`
     * @returns String representation of the syntax tree file
     */
    stringify(node: Node, file?: VFileCompatible): string

    /**
     * Function handling the compilation of syntax tree to a text.
     * Used in the stringify phase in the process and invoked with a `Node` and `VFile` representation of the document to stringify.
     *
     * `Compiler` can be a normal function in which case it must return a `string`: the text representation of the given syntax tree.
     *
     * `Compiler` can also be a constructor function (a function with keys in its `prototype`) in which case it’s invoked with `new`.
     * Instances must have a `compile` method which is invoked without arguments and must return a `string`.
     */
    Compiler: CompilerConstructor | CompilerFunction

    /**
     * Transform a syntax tree by applying plugins to it.
     *
     * @param node Node to transform
     * @returns `Promise` if `done` is not given. Rejected with an error, or resolved with the resulting syntax tree.
     */
    run(node: Node): Promise<Node>

    /**
     * Transform a syntax tree by applying plugins to it.
     *
     * @param node Node to transform
     * @param file `VFile` or anything which can be given to `vfile()`
     * @returns `Promise` if `done` is not given. Rejected with an error, or resolved with the resulting syntax tree.
     */
    run(node: Node, file: VFileCompatible): Promise<Node>

    /**
     * Transform a syntax tree by applying plugins to it.
     *
     * @param node Node to transform
     * @param done Invoked when transformation is complete.
     */
    run(node: Node, done: RunCallback): void

    /**
     * Transform a syntax tree by applying plugins to it.
     *
     * @param node Node to transform
     * @param file `VFile` or anything which can be given to `vfile()`
     * @param done Invoked when transformation is complete.
     */
    run(node: Node, file: VFileCompatible, done: RunCallback): void

    /**
     * Transform a syntax tree by applying plugins to it.
     *
     * If asynchronous plugins are configured an error is thrown.
     *
     * @param node Node to transform
     * @param file `VFile` or anything which can be given to `vfile()`
     * @returns The given syntax tree.
     */
    runSync(node: Node, file?: VFileCompatible): Node

    /**
     * Process the given representation of a file as configured on the processor. The process invokes `parse`, `run`, and `stringify` internally.
     * @param file `VFile` or anything which can be given to `vfile()`
     * @returns `Promise` if `done` is not given.
     * Rejected with an error or resolved with the resulting file.
     */
    process(file: VFileCompatible): Promise<VFile>

    /**
     * Process the given representation of a file as configured on the processor. The process invokes `parse`, `run`, and `stringify` internally.
     * @param file `VFile` or anything which can be given to `vfile()`
     * @param done Invoked when the process is complete. Invoked with a fatal error, if any, and the VFile.
     */
    process(file: VFileCompatible, done: ProcessCallback): void

    /**
     * Process the given representation of a file as configured on the processor. The process invokes `parse`, `run`, and `stringify` internally.
     *
     * If asynchronous plugins are configured an error is thrown.
     *
     * @param file `VFile` or anything which can be given to `vfile()`
     * @returns Virtual file with modified contents.
     */
    processSync(file: VFileCompatible): VFile

    /**
     * Get or set information in an in-memory key-value store accessible to all phases of the process.
     * An example is a list of HTML elements which are self-closing, which is needed when parsing, transforming, and compiling HTML.
     *
     * @returns key-value store object
     */
    data(): {[key: string]: unknown}

    /**
     * @param key Identifier
     * @returns If getting, the value at key
     */
    data(key: string): unknown

    /**
     * @param value Value to set. Omit if getting key
     * @returns If setting, the processor on which data is invoked
     */
    data(key: string, value: any): Processor<P>

    /**
     * Freeze a processor. Frozen processors are meant to be extended and not to be configured or processed directly.
     *
     * Once a processor is frozen it cannot be unfrozen. New processors functioning just like it can be created by invoking the processor.
     *
     * It’s possible to freeze processors explicitly, by calling `.freeze()`, but `.parse()`, `.run()`, `.stringify()`, and `.process()` call `.freeze()` to freeze a processor too.
     *
     * @returns The processor on which freeze is invoked.
     */
    freeze(): Processor<P>
  }

  /**
   * A Plugin (Attacher) is the thing passed to `use`.
   * It configures the processor and in turn can receive options.
   *
   * Attachers can configure processors, such as by interacting with parsers and compilers, linking them to other processors, or by specifying how the syntax tree is handled.
   *
   * @this Processor context object is set to the invoked on processor.
   * @param settings Configuration
   * @typeParam S Plugin settings
   * @typeParam P Processor settings
   * @returns Optional Transformer.
   */
  type Plugin<S extends any[] = [Settings?], P = Settings> = Attacher<S, P>

  /**
   * Configuration passed to a Plugin or Processor
   */
  type Settings = {
    [key: string]: unknown
  }

  /**
   * Presets provide a potentially sharable way to configure processors.
   * They can contain multiple plugins and optionally settings as well.
   *
   * @typeParam P Processor settings
   */
  interface Preset<S = Settings, P = Settings> {
    plugins: PluggableList<P>
    settings?: Settings
  }

  /**
   * Settings can be passed directly to the processor
   *
   * @typeParam P Settings applied to a processor. Useful when packaging unified with a preset parser and compiler.
   */
  interface ProcessorSettings<P = Settings> {
    settings: P
  }

  /**
   * A pairing of a plugin with its settings
   *
   * @typeParam S Plugin settings
   * @typeParam P Processor settings
   */
  type PluginTuple<S extends any[] = [Settings?], P = Settings> = [
    Plugin<S, P>,
    /**
     * NOTE: ideally this would be S instead of any[]
     * As of TypeScript 3.5.2 generic tuples cannot be spread
     * See: https://github.com/microsoft/TypeScript/issues/26113
     */
    ...any[]
  ]

  /**
   * A union of the different ways to add plugins to unified
   *
   * @typeParam S Plugin settings
   * @typeParam P Processor settings
   */
  type Pluggable<S extends any[] = [Settings?], P = Settings> =
    | Plugin<S, P>
    | Preset<S, P>
    | PluginTuple<S, P>

  /**
   * A list of plugins and presets
   *
   * @typeParam P Processor settings
   */
  type PluggableList<P = Settings> = Array<Pluggable<[any?], P>>

  /**
   * An attacher is the thing passed to `use`.
   * It configures the processor and in turn can receive options.
   *
   * Attachers can configure processors, such as by interacting with parsers and compilers, linking them to other processors, or by specifying how the syntax tree is handled.
   *
   * @this Processor context object is set to the invoked on processor.
   * @param settings Configuration
   * @typeParam S Plugin settings
   * @typeParam P Processor settings
   * @returns Optional Transformer.
   */
  interface Attacher<S extends any[] = [Settings?], P = Settings> {
    (this: Processor<P>, ...settings: S): Transformer | void
  }

  /**
   * Transformers modify the syntax tree or metadata of a file. A transformer is a function which is invoked each time a file is passed through the transform phase.
   * If an error occurs (either because it’s thrown, returned, rejected, or passed to `next`), the process stops.
   *
   * The transformation process in unified is handled by `trough`, see it’s documentation for the exact semantics of transformers.
   *
   * @param node Node or tree to be transformed
   * @param file File associated with node or tree
   * @param next If the signature of a transformer includes `next` (third argument), the function may finish asynchronous, and must invoke `next()`.
   * @returns
   * - `Error` — Can be returned to stop the process
   * - `Node` — Can be returned and results in further transformations and `stringify`s to be performed on the new tree
   * - `Promise` — If a promise is returned, the function is asynchronous, and must be resolved (optionally with a `Node`) or rejected (optionally with an `Error`)
   */
  interface Transformer {
    (
      node: Node,
      file: VFile,
      next?: (error: Error | null, tree: Node, file: VFile) => {}
    ): Error | Node | Promise<Node>
  }

  /**
   * Transform file contents into an AST
   */
  interface Parser {
    /**
     * Transform file contents into an AST
     *
     * @returns Parsed AST node/tree
     */
    parse(): Node
  }

  /**
   * A constructor function (a function with keys in its `prototype`) or class that implements a
   * `parse` method.
   */
  interface ParserConstructor {
    /**
     * Creates a Parser
     *
     * @param text Text to transform into AST node(s)
     * @param file File associated with text
     */
    new (text: string, file: VFile): Parser
  }

  /**
   * Transform file contents into an AST
   *
   * @param text Text to transform into AST node(s)
   * @param file File associated with text
   * @returns Parsed AST node/tree
   */
  type ParserFunction = (text: string, file: VFile) => Node

  /**
   * Transform an AST node/tree into text
   */
  interface Compiler {
    /**
     * Transform an AST node/tree into text
     *
     * @returns Compiled text
     */
    compile(): string
  }

  /**
   * A constructor function (a function with keys in its `prototype`) or class that implements a
   * `compile` method.
   */
  interface CompilerConstructor {
    /**
     * Creates a Compiler
     *
     * @param node Node/tree to be stringified
     * @param file File associated with node
     */
    new (node: Node, file: VFile): Compiler
  }

  /**
   * Transform an AST node/tree into text
   *
   * @param node Node/tree to be stringified
   * @param file File associated with node
   * @returns Compiled text
   */
  type CompilerFunction = (node: Node, file: VFile) => string

  /**
   * Access results from transforms
   *
   * @param error Error if any occurred
   * @param node Transformed AST tree/node
   * @param vfile File associated with node
   */
  type RunCallback = (error: Error | null, node: Node, file: VFile) => void

  /**
   * Access results from transforms
   *
   * @param error Error if any occurred
   * @param vfile File with updated content
   */
  type ProcessCallback = (error: Error | null, file: VFile) => void

  /**
   * A union of the VFile types unified supports
   */
  type VFileCompatible = VFile | VFileOptions | VFileContents
}

/**
 * Unified processor allows plugins, parsers, and compilers to be chained together to transform content.
 *
 * @typeParam P Processor settings. Useful when packaging unified with a preset parser and compiler.
 */
declare function unified<P = unified.Settings>(): unified.Processor<P>
export = unified