r3bl-ts-utils/src/tui-node-keyboard/keypress-builder-readline.ts

The `r3bl-ts-utils` package is a set of useful TypeScript functions and classes that can be used in Node.js and browser environments. They are inspired by Kotlin stdlib, and Rust to write code as expressions rather than statements, colorized text, powerfu

/*
 * Copyright (c) 2022 R3BL LLC. All rights reserved.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 *
 */

import { _also } from "../lang-utils/kotlin-lang-utils"
import { _callIfTruthy, _callIfTruthyWithReturn } from "../lang-utils/expression-lang-utils"
import { Keypress } from "./keypress"
import {
  KeyCreator,
  ModifierKey,
  modifierKeysPropertyNames,
  SpecialKey,
} from "./keypress-constants"
import { keyCodeMap, keyNameMap, keySequenceMap, ReadlineKey } from "./readline-config"

export const createFromKeypress = (
  nullableKey?: ReadlineKey,
  nullableInput?: string
): Readonly<Keypress> => {
  // Is it a special key (w/ or w/out modifiers)?
  const specialKey = tryToFindSpecialKeyInMap(nullableKey)
  if (specialKey) return specialKey

  // Is it a regular key w/ modifiers?
  const regularKeyWithModifiers = tryToCreateRegularKeyWithModifiers(nullableKey)
  if (regularKeyWithModifiers) return regularKeyWithModifiers

  // Must be just a regular key.
  return createRegularKey(nullableKey, nullableInput)
}

/**
 * First search key.code, then key.name, and finally key.sequence.
 */
const tryToFindSpecialKeyInMap = (key: ReadlineKey | undefined): Readonly<Keypress> | undefined => {
  if (!key) return undefined

  let nullableReturnValue: Keypress | undefined = undefined

  // Check key.code first.
  if (key.code)
    for (const [partialSequence, keyPressFn] of keyCodeMap.entries()) {
      if (key.code.includes(partialSequence)) {
        nullableReturnValue = keyPressFn()
        break
      }
    }

  // Check key.name second (if key.code not matched).
  if (!nullableReturnValue && key.name)
    _callIfTruthy(keyNameMap.get(key.name), (fun) => (nullableReturnValue = fun()))

  // Check key.sequence third (if key.code & key.name not matched).
  if (!nullableReturnValue && key.sequence)
    for (const [partialSequence, keyPressFn] of keySequenceMap.entries()) {
      if (key.sequence.includes(partialSequence)) {
        nullableReturnValue = keyPressFn()
        break
      }
    }

  // Check for modifiers to be set.
  return _callIfTruthyWithReturn(
    nullableReturnValue,
    (returnValue) => _also(returnValue, () => applyModifierKeysTo(key, returnValue._key)),
    () => undefined
  )
}

const tryToCreateRegularKeyWithModifiers = (
  key: ReadlineKey | undefined
): Readonly<Keypress> | undefined => {
  if (!key) return undefined

  // Special handling for ctrl and meta -> "input" is undefined but "key.name" has the input.
  // No special handling needed for shift.
  if (key.ctrl || key.meta) return createRegularKey(key, key.name)
  else return undefined
}

const createRegularKey = (
  nullableKey: ReadlineKey | undefined,
  nullableInput: string | undefined
): Readonly<Keypress> => {
  const newKey: SpecialKey & ModifierKey = _also(KeyCreator.emptyKey, (emptyKey) =>
    _callIfTruthy(nullableKey, (key) => applyModifierKeysTo(key, emptyKey))
  )
  const inputCopy: string | undefined = nullableInput ? nullableInput.slice() : undefined
  return Keypress.buildImmutable(newKey, inputCopy)
}

/**
 * @param {ReadlineKey} source Get shift, meta, ctrl information from this
 * @param {Keypress} target Apply the information to this
 * @return {Keypress} modified target
 */
const applyModifierKeysTo = (
  source: ReadlineKey,
  target: (SpecialKey & ModifierKey) | undefined
): void => {
  for (const propertyName of modifierKeysPropertyNames)
    if (source[propertyName] && target) target[propertyName] = Boolean(source[propertyName])
}