/**
 * @typedef {import('unist').Node} Node
 * @typedef {import('vfile').VFileCompatible} VFileCompatible
 * @typedef {import('vfile').VFileValue} VFileValue
 * @typedef {import('..').Processor} Processor
 * @typedef {import('..').Plugin} Plugin
 * @typedef {import('..').Preset} Preset
 * @typedef {import('..').Pluggable} Pluggable
 * @typedef {import('..').PluggableList} PluggableList
 * @typedef {import('..').Transformer} Transformer
 * @typedef {import('..').Parser} Parser
 * @typedef {import('..').Compiler} Compiler
 * @typedef {import('..').RunCallback} RunCallback
 * @typedef {import('..').ProcessCallback} ProcessCallback
 *
 * @typedef Context
 * @property {Node} tree
 * @property {VFile} file
 */

import {bail} from 'bail'
import isBuffer from 'is-buffer'
import extend from 'extend'
import isPlainObj from 'is-plain-obj'
import {trough} from 'trough'
import {VFile} from 'vfile'

// Expose a frozen processor.
export const unified = base().freeze()

const own = {}.hasOwnProperty

// Function to create the first processor.
/**
 * @returns {Processor}
 */
function base() {
  const transformers = trough()
  /** @type {Processor['attachers']} */
  const attachers = []
  /** @type {Record<string, unknown>} */
  let namespace = {}
  /** @type {boolean|undefined} */
  let frozen
  let freezeIndex = -1

  // Data management.
  // @ts-expect-error: overloads are handled.
  processor.data = data
  processor.Parser = undefined
  processor.Compiler = undefined

  // Lock.
  processor.freeze = freeze

  // Plugins.
  processor.attachers = attachers
  // @ts-expect-error: overloads are handled.
  processor.use = use

  // API.
  processor.parse = parse
  processor.stringify = stringify
  // @ts-expect-error: overloads are handled.
  processor.run = run
  processor.runSync = runSync
  // @ts-expect-error: overloads are handled.
  processor.process = process
  processor.processSync = processSync

  // Expose.
  return processor

  // Create a new processor based on the processor in the current scope.
  /** @type {Processor} */
  function processor() {
    const destination = base()
    let index = -1

    while (++index < attachers.length) {
      destination.use(...attachers[index])
    }

    destination.data(extend(true, {}, namespace))

    return destination
  }

  /**
   * @param {string|Record<string, unknown>} [key]
   * @param {unknown} [value]
   * @returns {unknown}
   */
  function data(key, value) {
    if (typeof key === 'string') {
      // Set `key`.
      if (arguments.length === 2) {
        assertUnfrozen('data', frozen)
        namespace[key] = value
        return processor
      }

      // Get `key`.
      return (own.call(namespace, key) && namespace[key]) || null
    }

    // Set space.
    if (key) {
      assertUnfrozen('data', frozen)
      namespace = key
      return processor
    }

    // Get space.
    return namespace
  }

  /** @type {Processor['freeze']} */
  function freeze() {
    if (frozen) {
      return processor
    }

    while (++freezeIndex < attachers.length) {
      const [attacher, ...options] = attachers[freezeIndex]

      if (options[0] === false) {
        continue
      }

      if (options[0] === true) {
        options[0] = undefined
      }

      /** @type {Transformer|void} */
      const transformer = attacher.call(processor, ...options)

      if (typeof transformer === 'function') {
        transformers.use(transformer)
      }
    }

    frozen = true
    freezeIndex = Number.POSITIVE_INFINITY

    return processor
  }

  /**
   * @param {Pluggable|null|undefined} [value]
   * @param {...unknown} options
   * @returns {Processor}
   */
  function use(value, ...options) {
    /** @type {Record<string, unknown>|undefined} */
    let settings

    assertUnfrozen('use', frozen)

    if (value === null || value === undefined) {
      // Empty.
    } else if (typeof value === 'function') {
      addPlugin(value, ...options)
    } else if (typeof value === 'object') {
      if (Array.isArray(value)) {
        addList(value)
      } else {
        addPreset(value)
      }
    } else {
      throw new TypeError('Expected usable value, not `' + value + '`')
    }

    if (settings) {
      namespace.settings = Object.assign(namespace.settings || {}, settings)
    }

    return processor

    /**
     * @param {import('..').Pluggable<unknown[]>} value
     * @returns {void}
     */
    function add(value) {
      if (typeof value === 'function') {
        addPlugin(value)
      } else if (typeof value === 'object') {
        if (Array.isArray(value)) {
          const [plugin, ...options] = value
          addPlugin(plugin, ...options)
        } else {
          addPreset(value)
        }
      } else {
        throw new TypeError('Expected usable value, not `' + value + '`')
      }
    }

    /**
     * @param {Preset} result
     * @returns {void}
     */
    function addPreset(result) {
      addList(result.plugins)

      if (result.settings) {
        settings = Object.assign(settings || {}, result.settings)
      }
    }

    /**
     * @param {PluggableList|null|undefined} [plugins]
     * @returns {void}
     */
    function addList(plugins) {
      let index = -1

      if (plugins === null || plugins === undefined) {
        // Empty.
      } else if (Array.isArray(plugins)) {
        while (++index < plugins.length) {
          const thing = plugins[index]
          add(thing)
        }
      } else {
        throw new TypeError('Expected a list of plugins, not `' + plugins + '`')
      }
    }

    /**
     * @param {Plugin} plugin
     * @param {...unknown} [value]
     * @returns {void}
     */
    function addPlugin(plugin, value) {
      let index = -1
      /** @type {Processor['attachers'][number]|undefined} */
      let entry

      while (++index < attachers.length) {
        if (attachers[index][0] === plugin) {
          entry = attachers[index]
          break
        }
      }

      if (entry) {
        if (isPlainObj(entry[1]) && isPlainObj(value)) {
          value = extend(true, entry[1], value)
        }

        entry[1] = value
      } else {
        // @ts-expect-error: fine.
        attachers.push([...arguments])
      }
    }
  }

  /** @type {Processor['parse']} */
  function parse(doc) {
    processor.freeze()
    const file = vfile(doc)
    const Parser = processor.Parser
    assertParser('parse', Parser)

    if (newable(Parser, 'parse')) {
      // @ts-expect-error: `newable` checks this.
      return new Parser(String(file), file).parse()
    }

    // @ts-expect-error: `newable` checks this.
    return Parser(String(file), file) // eslint-disable-line new-cap
  }

  /** @type {Processor['stringify']} */
  function stringify(node, doc) {
    processor.freeze()
    const file = vfile(doc)
    const Compiler = processor.Compiler
    assertCompiler('stringify', Compiler)
    assertNode(node)

    if (newable(Compiler, 'compile')) {
      // @ts-expect-error: `newable` checks this.
      return new Compiler(node, file).compile()
    }

    // @ts-expect-error: `newable` checks this.
    return Compiler(node, file) // eslint-disable-line new-cap
  }

  /**
   * @param {Node} node
   * @param {VFileCompatible|RunCallback} [doc]
   * @param {RunCallback} [callback]
   * @returns {Promise<Node>|void}
   */
  function run(node, doc, callback) {
    assertNode(node)
    processor.freeze()

    if (!callback && typeof doc === 'function') {
      callback = doc
      doc = undefined
    }

    if (!callback) {
      return new Promise(executor)
    }

    executor(null, callback)

    /**
     * @param {null|((node: Node) => void)} resolve
     * @param {(error: Error) => void} reject
     * @returns {void}
     */
    function executor(resolve, reject) {
      // @ts-expect-error: `doc` can’t be a callback anymore, we checked.
      transformers.run(node, vfile(doc), done)

      /**
       * @param {Error|null} error
       * @param {Node} tree
       * @param {VFile} file
       * @returns {void}
       */
      function done(error, tree, file) {
        tree = tree || node
        if (error) {
          reject(error)
        } else if (resolve) {
          resolve(tree)
        } else {
          // @ts-expect-error: `callback` is defined if `resolve` is not.
          callback(null, tree, file)
        }
      }
    }
  }

  /** @type {Processor['runSync']} */
  function runSync(node, file) {
    /** @type {Node|undefined} */
    let result
    /** @type {boolean|undefined} */
    let complete

    processor.run(node, file, done)

    assertDone('runSync', 'run', complete)

    // @ts-expect-error: we either bailed on an error or have a tree.
    return result

    /**
     * @param {Error|null} [error]
     * @param {Node} [tree]
     * @returns {void}
     */
    function done(error, tree) {
      bail(error)
      result = tree
      complete = true
    }
  }

  /**
   * @param {VFileCompatible} doc
   * @param {ProcessCallback} [callback]
   * @returns {Promise<VFile>|undefined}
   */
  function process(doc, callback) {
    processor.freeze()
    assertParser('process', processor.Parser)
    assertCompiler('process', processor.Compiler)

    if (!callback) {
      return new Promise(executor)
    }

    executor(null, callback)

    /**
     * @param {null|((file: VFile) => void)} resolve
     * @param {(error?: Error|null|undefined) => void} reject
     * @returns {void}
     */
    function executor(resolve, reject) {
      const file = vfile(doc)

      processor.run(processor.parse(file), file, (error, tree, file) => {
        if (error || !tree || !file) {
          done(error)
        } else {
          /** @type {unknown} */
          const result = processor.stringify(tree, file)

          if (result === undefined || result === null) {
            // Empty.
          } else if (looksLikeAVFileValue(result)) {
            file.value = result
          } else {
            file.result = result
          }

          done(error, file)
        }
      })

      /**
       * @param {Error|null|undefined} [error]
       * @param {VFile|undefined} [file]
       * @returns {void}
       */
      function done(error, file) {
        if (error || !file) {
          reject(error)
        } else if (resolve) {
          resolve(file)
        } else {
          // @ts-expect-error: `callback` is defined if `resolve` is not.
          callback(null, file)
        }
      }
    }
  }

  /** @type {Processor['processSync']} */
  function processSync(doc) {
    /** @type {boolean|undefined} */
    let complete

    processor.freeze()
    assertParser('processSync', processor.Parser)
    assertCompiler('processSync', processor.Compiler)

    const file = vfile(doc)

    processor.process(file, done)

    assertDone('processSync', 'process', complete)

    return file

    /**
     * @param {Error|null|undefined} [error]
     * @returns {void}
     */
    function done(error) {
      complete = true
      bail(error)
    }
  }
}

/**
 * Check if `value` is a constructor.
 *
 * @param {unknown} value
 * @param {string} name
 * @returns {boolean}
 */
function newable(value, name) {
  return (
    typeof value === 'function' &&
    // Prototypes do exist.
    // type-coverage:ignore-next-line
    value.prototype &&
    // A function with keys in its prototype is probably a constructor.
    // Classes’ prototype methods are not enumerable, so we check if some value
    // exists in the prototype.
    // type-coverage:ignore-next-line
    (keys(value.prototype) || name in value.prototype)
  )
}

/**
 * Check if `value` is an object with keys.
 *
 * @param {Record<string, unknown>} value
 * @returns {boolean}
 */
function keys(value) {
  /** @type {string} */
  let key

  for (key in value) {
    if (own.call(value, key)) {
      return true
    }
  }

  return false
}

/**
 * Assert a parser is available.
 *
 * @param {string} name
 * @param {unknown} value
 * @returns {asserts value is Parser}
 */
function assertParser(name, value) {
  if (typeof value !== 'function') {
    throw new TypeError('Cannot `' + name + '` without `Parser`')
  }
}

/**
 * Assert a compiler is available.
 *
 * @param {string} name
 * @param {unknown} value
 * @returns {asserts value is Compiler}
 */
function assertCompiler(name, value) {
  if (typeof value !== 'function') {
    throw new TypeError('Cannot `' + name + '` without `Compiler`')
  }
}

/**
 * Assert the processor is not frozen.
 *
 * @param {string} name
 * @param {unknown} frozen
 * @returns {asserts frozen is false}
 */
function assertUnfrozen(name, frozen) {
  if (frozen) {
    throw new Error(
      'Cannot call `' +
        name +
        '` on a frozen processor.\nCreate a new processor first, by calling it: use `processor()` instead of `processor`.'
    )
  }
}

/**
 * Assert `node` is a unist node.
 *
 * @param {unknown} node
 * @returns {asserts node is Node}
 */
function assertNode(node) {
  // `isPlainObj` unfortunately uses `any` instead of `unknown`.
  // type-coverage:ignore-next-line
  if (!isPlainObj(node) || typeof node.type !== 'string') {
    throw new TypeError('Expected node, got `' + node + '`')
    // Fine.
  }
}

/**
 * Assert that `complete` is `true`.
 *
 * @param {string} name
 * @param {string} asyncName
 * @param {unknown} complete
 * @returns {asserts complete is true}
 */
function assertDone(name, asyncName, complete) {
  if (!complete) {
    throw new Error(
      '`' + name + '` finished async. Use `' + asyncName + '` instead'
    )
  }
}

/**
 * @param {VFileCompatible} [value]
 * @returns {VFile}
 */
function vfile(value) {
  return looksLikeAVFile(value) ? value : new VFile(value)
}

/**
 * @param {VFileCompatible} [value]
 * @returns {value is VFile}
 */
function looksLikeAVFile(value) {
  return Boolean(
    value &&
      typeof value === 'object' &&
      'message' in value &&
      'messages' in value
  )
}

/**
 * @param {unknown} [value]
 * @returns {value is VFileValue}
 */
function looksLikeAVFileValue(value) {
  return typeof value === 'string' || isBuffer(value)
}