let LazyResult = require('./lazy-result')

/**
 * Contains plugins to process CSS. Create one `Processor` instance,
 * initialize its plugins, and then use that instance on numerous CSS files.
 *
 * @example
 * const processor = postcss([autoprefixer, precss])
 * processor.process(css1).then(result => console.log(result.css))
 * processor.process(css2).then(result => console.log(result.css))
 */
class Processor {
  /**
   * @param {Array.<Plugin|pluginFunction>|Processor} plugins PostCSS plugins.
   *        See {@link Processor#use} for plugin format.
   */
  constructor (plugins = []) {
    /**
     * Current PostCSS version.
     *
     * @type {string}
     *
     * @example
     * if (result.processor.version.split('.')[0] !== '6') {
     *   throw new Error('This plugin works only with PostCSS 6')
     * }
     */
    this.version = '7.0.32'
    /**
     * Plugins added to this processor.
     *
     * @type {pluginFunction[]}
     *
     * @example
     * const processor = postcss([autoprefixer, precss])
     * processor.plugins.length //=> 2
     */
    this.plugins = this.normalize(plugins)
  }

  /**
   * Adds a plugin to be used as a CSS processor.
   *
   * PostCSS plugin can be in 4 formats:
   * * A plugin created by {@link postcss.plugin} method.
   * * A function. PostCSS will pass the function a @{link Root}
   *   as the first argument and current {@link Result} instance
   *   as the second.
   * * An object with a `postcss` method. PostCSS will use that method
   *   as described in #2.
   * * Another {@link Processor} instance. PostCSS will copy plugins
   *   from that instance into this one.
   *
   * Plugins can also be added by passing them as arguments when creating
   * a `postcss` instance (see [`postcss(plugins)`]).
   *
   * Asynchronous plugins should return a `Promise` instance.
   *
   * @param {Plugin|pluginFunction|Processor} plugin PostCSS plugin
   *                                                 or {@link Processor}
   *                                                 with plugins.
   *
   * @example
   * const processor = postcss()
   *   .use(autoprefixer)
   *   .use(precss)
   *
   * @return {Processes} Current processor to make methods chain.
   */
  use (plugin) {
    this.plugins = this.plugins.concat(this.normalize([plugin]))
    return this
  }

  /**
   * Parses source CSS and returns a {@link LazyResult} Promise proxy.
   * Because some plugins can be asynchronous it doesn’t make
   * any transformations. Transformations will be applied
   * in the {@link LazyResult} methods.
   *
   * @param {string|toString|Result} css String with input CSS or any object
   *                                     with a `toString()` method,
   *                                     like a Buffer. Optionally, send
   *                                     a {@link Result} instance
   *                                     and the processor will take
   *                                     the {@link Root} from it.
   * @param {processOptions} [opts]      Options.
   *
   * @return {LazyResult} Promise proxy.
   *
   * @example
   * processor.process(css, { from: 'a.css', to: 'a.out.css' })
   *   .then(result => {
   *      console.log(result.css)
   *   })
   */
  process (css, opts = { }) {
    if (this.plugins.length === 0 && opts.parser === opts.stringifier) {
      if (process.env.NODE_ENV !== 'production') {
        if (typeof console !== 'undefined' && console.warn) {
          console.warn(
            'You did not set any plugins, parser, or stringifier. ' +
            'Right now, PostCSS does nothing. Pick plugins for your case ' +
            'on https://www.postcss.parts/ and use them in postcss.config.js.'
          )
        }
      }
    }
    return new LazyResult(this, css, opts)
  }

  normalize (plugins) {
    let normalized = []
    for (let i of plugins) {
      if (i.postcss) i = i.postcss

      if (typeof i === 'object' && Array.isArray(i.plugins)) {
        normalized = normalized.concat(i.plugins)
      } else if (typeof i === 'function') {
        normalized.push(i)
      } else if (typeof i === 'object' && (i.parse || i.stringify)) {
        if (process.env.NODE_ENV !== 'production') {
          throw new Error(
            'PostCSS syntaxes cannot be used as plugins. Instead, please use ' +
            'one of the syntax/parser/stringifier options as outlined ' +
            'in your PostCSS runner documentation.'
          )
        }
      } else {
        throw new Error(i + ' is not a PostCSS plugin')
      }
    }
    return normalized
  }
}

module.exports = Processor

/**
 * @callback builder
 * @param {string} part          Part of generated CSS connected to this node.
 * @param {Node}   node          AST node.
 * @param {"start"|"end"} [type] Node’s part type.
 */

/**
 * @callback parser
 *
 * @param {string|toString} css   String with input CSS or any object
 *                                with toString() method, like a Buffer.
 * @param {processOptions} [opts] Options with only `from` and `map` keys.
 *
 * @return {Root} PostCSS AST
 */

/**
 * @callback stringifier
 *
 * @param {Node} node       Start node for stringifing. Usually {@link Root}.
 * @param {builder} builder Function to concatenate CSS from node’s parts
 *                          or generate string and source map.
 *
 * @return {void}
 */

/**
 * @typedef {object} syntax
 * @property {parser} parse          Function to generate AST by string.
 * @property {stringifier} stringify Function to generate string by AST.
 */

/**
 * @typedef {object} toString
 * @property {function} toString
 */

/**
 * @callback pluginFunction
 * @param {Root} root     Parsed input CSS.
 * @param {Result} result Result to set warnings or check other plugins.
 */

/**
 * @typedef {object} Plugin
 * @property {function} postcss PostCSS plugin function.
 */

/**
 * @typedef {object} processOptions
 * @property {string} from             The path of the CSS source file.
 *                                     You should always set `from`,
 *                                     because it is used in source map
 *                                     generation and syntax error messages.
 * @property {string} to               The path where you’ll put the output
 *                                     CSS file. You should always set `to`
 *                                     to generate correct source maps.
 * @property {parser} parser           Function to generate AST by string.
 * @property {stringifier} stringifier Class to generate string by AST.
 * @property {syntax} syntax           Object with `parse` and `stringify`.
 * @property {object} map              Source map options.
 * @property {boolean} map.inline                    Does source map should
 *                                                   be embedded in the output
 *                                                   CSS as a base64-encoded
 *                                                   comment.
 * @property {string|object|false|function} map.prev Source map content
 *                                                   from a previous
 *                                                   processing step
 *                                                   (for example, Sass).
 *                                                   PostCSS will try to find
 *                                                   previous map automatically,
 *                                                   so you could disable it by
 *                                                   `false` value.
 * @property {boolean} map.sourcesContent            Does PostCSS should set
 *                                                   the origin content to map.
 * @property {string|false} map.annotation           Does PostCSS should set
 *                                                   annotation comment to map.
 * @property {string} map.from                       Override `from` in map’s
 *                                                   sources`.
 */