import {base, keyName} from "w3c-keyname"
import {Plugin, Command} from "prosemirror-state"
import {EditorView} from "prosemirror-view"

const mac = typeof navigator != "undefined" && /Mac|iP(hone|[oa]d)/.test(navigator.platform)
const windows = typeof navigator != "undefined" && /Win/.test(navigator.platform)

function normalizeKeyName(name: string) {
  let parts = name.split(/-(?!$)/), result = parts[parts.length - 1]
  if (result == "Space") result = " "
  let alt, ctrl, shift, meta
  for (let i = 0; i < parts.length - 1; i++) {
    let mod = parts[i]
    if (/^(cmd|meta|m)$/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: {[key: string]: Command}) {
  let copy: {[key: string]: Command} = Object.create(null)
  for (let prop in map) copy[normalizeKeyName(prop)] = map[prop]
  return copy
}

function modifiers(name: string, event: KeyboardEvent, shift = true) {
  if (event.altKey) name = "Alt-" + name
  if (event.ctrlKey) name = "Ctrl-" + name
  if (event.metaKey) name = "Meta-" + name
  if (shift && event.shiftKey) name = "Shift-" + name
  return name
}

/// 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).
export function keymap(bindings: {[key: string]: Command}): Plugin {
  return new Plugin({props: {handleKeyDown: keydownHandler(bindings)}})
}

/// Given a set of bindings (using the same format as
/// [`keymap`](#keymap.keymap)), return a [keydown
/// handler](#view.EditorProps.handleKeyDown) that handles them.
export function keydownHandler(bindings: {[key: string]: Command}): (view: EditorView, event: KeyboardEvent) => boolean {
  let map = normalize(bindings)
  return function(view, event) {
    let name = keyName(event), baseName, direct = map[modifiers(name, event)]
    if (direct && direct(view.state, view.dispatch, view)) return true
    // A character key
    if (name.length == 1 && name != " ") {
      if (event.shiftKey) {
        // In case the name was already modified by shift, try looking
        // it up without its shift modifier
        let noShift = map[modifiers(name, event, false)]
        if (noShift && noShift(view.state, view.dispatch, view)) return true
      }
      if ((event.altKey || event.metaKey || event.ctrlKey) &&
          // Ctrl-Alt may be used for AltGr on Windows
          !(windows && event.ctrlKey && event.altKey) &&
          (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, #1529.
        let fromCode = map[modifiers(baseName, event)]
        if (fromCode && fromCode(view.state, view.dispatch, view)) return true
      }
    }
    return false
  }
}
