import { keyName, base } from 'w3c-keyname';
import { Plugin } from 'prosemirror-state';

// declare global: navigator

var mac = typeof navigator != "undefined" ? /Mac|iP(hone|[oa]d)/.test(navigator.platform) : false;

function normalizeKeyName(name) {
  var parts = name.split(/-(?!$)/), result = parts[parts.length - 1];
  if (result == "Space") { result = " "; }
  var alt, ctrl, shift, meta;
  for (var i = 0; i < parts.length - 1; i++) {
    var mod = parts[i];
    if (/^(cmd|meta|m)$/i.test(mod)) { meta = true; }
    else if (/^a(lt)?$/i.test(mod)) { alt = true; }
    else if (/^(c|ctrl|control)$/i.test(mod)) { ctrl = true; }
    else if (/^s(hift)?$/i.test(mod)) { shift = true; }
    else if (/^mod$/i.test(mod)) { if (mac) { meta = true; } else { ctrl = true; } }
    else { throw new Error("Unrecognized modifier name: " + mod) }
  }
  if (alt) { result = "Alt-" + result; }
  if (ctrl) { result = "Ctrl-" + result; }
  if (meta) { result = "Meta-" + result; }
  if (shift) { result = "Shift-" + result; }
  return result
}

function normalize(map) {
  var copy = Object.create(null);
  for (var prop in map) { copy[normalizeKeyName(prop)] = map[prop]; }
  return copy
}

function modifiers(name, event, shift) {
  if (event.altKey) { name = "Alt-" + name; }
  if (event.ctrlKey) { name = "Ctrl-" + name; }
  if (event.metaKey) { name = "Meta-" + name; }
  if (shift !== false && event.shiftKey) { name = "Shift-" + name; }
  return name
}

// :: (Object) → Plugin
// Create a keymap plugin for the given set of bindings.
//
// Bindings should map key names to [command](#commands)-style
// functions, which will be called with `(EditorState, dispatch,
// EditorView)` arguments, and should return true when they've handled
// the key. Note that the view argument isn't part of the command
// protocol, but can be used as an escape hatch if a binding needs to
// directly interact with the UI.
//
// Key names may be strings like `"Shift-Ctrl-Enter"`—a key
// identifier prefixed with zero or more modifiers. Key identifiers
// are based on the strings that can appear in
// [`KeyEvent.key`](https://developer.mozilla.org/en-US/docs/Web/API/KeyboardEvent/key).
// Use lowercase letters to refer to letter keys (or uppercase letters
// if you want shift to be held). You may use `"Space"` as an alias
// for the `" "` name.
//
// Modifiers can be given in any order. `Shift-` (or `s-`), `Alt-` (or
// `a-`), `Ctrl-` (or `c-` or `Control-`) and `Cmd-` (or `m-` or
// `Meta-`) are recognized. For characters that are created by holding
// shift, the `Shift-` prefix is implied, and should not be added
// explicitly.
//
// You can use `Mod-` as a shorthand for `Cmd-` on Mac and `Ctrl-` on
// other platforms.
//
// You can add multiple keymap plugins to an editor. The order in
// which they appear determines their precedence (the ones early in
// the array get to dispatch first).
function keymap(bindings) {
  return new Plugin({props: {handleKeyDown: keydownHandler(bindings)}})
}

// :: (Object) → (view: EditorView, event: dom.Event) → bool
// Given a set of bindings (using the same format as
// [`keymap`](#keymap.keymap)), return a [keydown
// handler](#view.EditorProps.handleKeyDown) that handles them.
function keydownHandler(bindings) {
  var map = normalize(bindings);
  return function(view, event) {
    var name = keyName(event), isChar = name.length == 1 && name != " ", baseName;
    var direct = map[modifiers(name, event, !isChar)];
    if (direct && direct(view.state, view.dispatch, view)) { return true }
    if (isChar && (event.shiftKey || event.altKey || event.metaKey || name.charCodeAt(0) > 127) &&
        (baseName = base[event.keyCode]) && baseName != name) {
      // Try falling back to the keyCode when there's a modifier
      // active or the character produced isn't ASCII, and our table
      // produces a different name from the the keyCode. See #668,
      // #1060
      var fromCode = map[modifiers(baseName, event, true)];
      if (fromCode && fromCode(view.state, view.dispatch, view)) { return true }
    } else if (isChar && event.shiftKey) {
      // Otherwise, if shift is active, also try the binding with the
      // Shift- prefix enabled. See #997
      var withShift = map[modifiers(name, event, true)];
      if (withShift && withShift(view.state, view.dispatch, view)) { return true }
    }
    return false
  }
}

export { keydownHandler, keymap };
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