import { create } from "zustand";

export type LoginField = "username" | "password";
export type LoginKeyboardMode = "lower" | "upper" | "symbols";
export type LoginRequestAction = "login" | "create" | "offline";
export type LoginKeyboardDirection = "up" | "down" | "left" | "right";

export interface LoginKeyDefinition {
  id: string;
  label: string;
  ariaLabel: string;
  kind: "character" | "mode" | "field" | "space" | "backspace" | "clear" | "done" | LoginRequestAction;
  value?: string;
  span?: number;
}

export interface LoginInputSnapshot {
  username: string;
  passwordLength: number;
  activeField: LoginField;
  selectedKeyId: string;
  keyboardMode: LoginKeyboardMode;
  busy: LoginRequestAction | null;
}

interface LoginRequest {
  id: number;
  action: LoginRequestAction;
}

interface LoginInputState {
  username: string;
  password: string;
  activeField: LoginField;
  selectedKeyId: string;
  keyboardMode: LoginKeyboardMode;
  busy: LoginRequestAction | null;
  request: LoginRequest | null;
  requestId: number;
  setUsername: (value: string) => void;
  setPassword: (value: string) => void;
  setActiveField: (field: LoginField) => void;
  selectKey: (keyId: string) => void;
  moveSelection: (direction: LoginKeyboardDirection) => void;
  pressKey: (keyId: string) => void;
  pressSelected: () => void;
  consumeRequest: (id: number) => void;
  setBusy: (busy: LoginRequestAction | null) => void;
  reset: () => void;
}

export const DEFAULT_LOGIN_KEY_ID = "char-1-0";

const characterLayouts: Record<LoginKeyboardMode, readonly (readonly string[])[]> = {
  lower: [
    ["1", "2", "3", "4", "5", "6", "7", "8", "9", "0"],
    ["q", "w", "e", "r", "t", "y", "u", "i", "o", "p"],
    ["a", "s", "d", "f", "g", "h", "j", "k", "l", "_"],
    ["z", "x", "c", "v", "b", "n", "m", ".", "-"],
  ],
  upper: [
    ["1", "2", "3", "4", "5", "6", "7", "8", "9", "0"],
    ["Q", "W", "E", "R", "T", "Y", "U", "I", "O", "P"],
    ["A", "S", "D", "F", "G", "H", "J", "K", "L", "_"],
    ["Z", "X", "C", "V", "B", "N", "M", ".", "-"],
  ],
  symbols: [
    ["1", "2", "3", "4", "5", "6", "7", "8", "9", "0"],
    ["!", "@", "#", "$", "%", "^", "&", "*", "(", ")"],
    ["{", "}", "[", "]", "<", ">", "=", "+", "/", "\\"],
    ["~", "`", ";", ":", "'", "\"", ",", ".", "?"],
  ],
};

function characterKey(value: string, row: number, column: number): LoginKeyDefinition {
  return {
    id: `char-${row}-${column}`,
    label: value,
    ariaLabel: value === " " ? "Space" : value,
    kind: "character",
    value,
  };
}

export function loginKeyboardRows(mode: LoginKeyboardMode): readonly (readonly LoginKeyDefinition[])[] {
  const rows = characterLayouts[mode];
  return [
    rows[0].map((value, column) => characterKey(value, 0, column)),
    rows[1].map((value, column) => characterKey(value, 1, column)),
    rows[2].map((value, column) => characterKey(value, 2, column)),
    [
      { id: "control-mode", label: mode === "lower" ? "⇧" : mode === "upper" ? "#+=" : "abc", ariaLabel: "Change keyboard mode", kind: "mode" },
      ...rows[3].map((value, column) => characterKey(value, 3, column + 1)),
    ],
    [
      { id: "control-field", label: "Field", ariaLabel: "Switch login field", kind: "field", span: 2 },
      { id: "control-space", label: "Space", ariaLabel: "Space", kind: "space", span: 3 },
      { id: "control-backspace", label: "⌫", ariaLabel: "Backspace", kind: "backspace", span: 2 },
      { id: "control-clear", label: "Clear", ariaLabel: "Clear active field", kind: "clear", span: 2 },
      { id: "control-done", label: "Done", ariaLabel: "Finish active field", kind: "done" },
    ],
    [
      { id: "action-login", label: "Enter world", ariaLabel: "Log in and enter world", kind: "login", span: 4 },
      { id: "action-create", label: "Create", ariaLabel: "Create account", kind: "create", span: 3 },
      { id: "action-offline", label: "Offline", ariaLabel: "Play offline", kind: "offline", span: 3 },
    ],
  ];
}

function keyPosition(rows: readonly (readonly LoginKeyDefinition[])[], keyId: string) {
  for (let rowIndex = 0; rowIndex < rows.length; rowIndex += 1) {
    let column = 0;
    for (let keyIndex = 0; keyIndex < rows[rowIndex].length; keyIndex += 1) {
      const key = rows[rowIndex][keyIndex];
      const span = key.span ?? 1;
      if (key.id === keyId) return { rowIndex, keyIndex, center: column + span / 2 };
      column += span;
    }
  }
  return null;
}

export function nextLoginKeyId(
  mode: LoginKeyboardMode,
  selectedKeyId: string,
  direction: LoginKeyboardDirection,
): string {
  const rows = loginKeyboardRows(mode);
  const position = keyPosition(rows, selectedKeyId) ?? keyPosition(rows, DEFAULT_LOGIN_KEY_ID)!;
  const row = rows[position.rowIndex];
  if (direction === "left" || direction === "right") {
    const delta = direction === "left" ? -1 : 1;
    return row[(position.keyIndex + delta + row.length) % row.length].id;
  }
  const rowDelta = direction === "up" ? -1 : 1;
  const targetRowIndex = (position.rowIndex + rowDelta + rows.length) % rows.length;
  const targetRow = rows[targetRowIndex];
  let column = 0;
  return targetRow.reduce((closest, key) => {
    const center = column + (key.span ?? 1) / 2;
    column += key.span ?? 1;
    return Math.abs(center - position.center) < Math.abs(closest.center - position.center)
      ? { id: key.id, center }
      : closest;
  }, { id: targetRow[0].id, center: (targetRow[0].span ?? 1) / 2 }).id;
}

function findLoginKey(mode: LoginKeyboardMode, keyId: string): LoginKeyDefinition | null {
  return loginKeyboardRows(mode).flat().find((key) => key.id === keyId) ?? null;
}

function nextMode(mode: LoginKeyboardMode): LoginKeyboardMode {
  if (mode === "lower") return "upper";
  if (mode === "upper") return "symbols";
  return "lower";
}

const initialState = {
  username: "",
  password: "",
  activeField: "username" as LoginField,
  selectedKeyId: DEFAULT_LOGIN_KEY_ID,
  keyboardMode: "lower" as LoginKeyboardMode,
  busy: null,
  request: null,
  requestId: 0,
};

export const useLoginInputStore = create<LoginInputState>((set, get) => ({
  ...initialState,
  setUsername: (username) => set({ username: username.slice(0, 20), activeField: "username" }),
  setPassword: (password) => set({ password: password.slice(0, 128), activeField: "password" }),
  setActiveField: (activeField) => set({ activeField }),
  selectKey: (selectedKeyId) => {
    if (findLoginKey(get().keyboardMode, selectedKeyId)) set({ selectedKeyId });
  },
  moveSelection: (direction) => set((state) => ({
    selectedKeyId: nextLoginKeyId(state.keyboardMode, state.selectedKeyId, direction),
  })),
  pressKey: (keyId) => {
    const state = get();
    const key = findLoginKey(state.keyboardMode, keyId);
    if (!key) return;
    set({ selectedKeyId: key.id });
    if (key.kind === "character" && key.value) {
      if (state.activeField === "username") {
        if (/^[A-Za-z0-9_]$/.test(key.value) && state.username.length < 20) set({ username: state.username + key.value });
      } else if (state.password.length < 128) set({ password: state.password + key.value });
      return;
    }
    if (key.kind === "mode") set({ keyboardMode: nextMode(state.keyboardMode) });
    else if (key.kind === "field") set({ activeField: state.activeField === "username" ? "password" : "username" });
    else if (key.kind === "space" && state.activeField === "password" && state.password.length < 128) set({ password: `${state.password} ` });
    else if (key.kind === "backspace") {
      if (state.activeField === "username") set({ username: state.username.slice(0, -1) });
      else set({ password: state.password.slice(0, -1) });
    } else if (key.kind === "clear") {
      if (state.activeField === "username") set({ username: "" });
      else set({ password: "" });
    } else if (key.kind === "done") {
      if (state.activeField === "username") set({ activeField: "password" });
      else set({ selectedKeyId: "action-login" });
    } else if (["login", "create", "offline"].includes(key.kind) && !state.busy) {
      const requestId = state.requestId + 1;
      set({ requestId, request: { id: requestId, action: key.kind as LoginRequestAction } });
    }
  },
  pressSelected: () => get().pressKey(get().selectedKeyId),
  consumeRequest: (id) => set((state) => state.request?.id === id ? { request: null } : {}),
  setBusy: (busy) => set({ busy }),
  reset: () => set(initialState),
}));

export function currentLoginInputSnapshot(): LoginInputSnapshot {
  const state = useLoginInputStore.getState();
  return {
    username: state.username,
    passwordLength: state.password.length,
    activeField: state.activeField,
    selectedKeyId: state.selectedKeyId,
    keyboardMode: state.keyboardMode,
    busy: state.busy,
  };
}