import {
  createContext,
  useCallback,
  useContext,
  useMemo,
  useRef,
  useState,
  type ReactNode,
} from "react";

export interface CommandPaletteItem {
  key: string;
  label: string;
  hint?: string;
}

export interface RuntimeCommand {
  id: string;
  title: string;
  hint?: string;
  section?: string;
  keybinds?: string[];
  disabled?: boolean;
  visible?: boolean;
  run: () => void | Promise<void>;
}

interface RegisteredCommand extends RuntimeCommand {
  order: number;
  registrationId: number;
}

export interface CommandRegistry {
  commands: RuntimeCommand[];
  registerCommand: (command: RuntimeCommand) => () => void;
  registerCommands: (commands: RuntimeCommand[]) => () => void;
  unregisterCommand: (id: string) => void;
  clearCommands: () => void;
  runCommand: (id: string) => Promise<boolean>;
  runKeybinding: (binding: string) => Promise<boolean>;
}

interface CommandRegistryContextValue extends CommandRegistry {}

const CommandRegistryContext = createContext<CommandRegistryContextValue | null>(null);

export interface CommandRegistryProviderProps {
  children: ReactNode;
  initialCommands?: RuntimeCommand[];
}

export function normalizeBinding(binding: string): string {
  return binding.trim().toLowerCase();
}

function isCommandVisible(command: RuntimeCommand): boolean {
  return command.visible !== false;
}

export function commandToPaletteItem(command: RuntimeCommand): CommandPaletteItem {
  const keybindHint =
    command.keybinds && command.keybinds.length > 0
      ? command.keybinds.map(normalizeBinding).join(", ")
      : null;
  const hint =
    [command.section, command.hint, keybindHint].filter(Boolean).join(" · ") || undefined;

  return {
    key: command.id,
    label: command.title,
    hint,
  };
}

export function shouldCleanupRegisteredCommand(
  entry: { id: string; registrationId: number },
  commandId: string,
  registrationId: number,
): boolean {
  return entry.id === commandId && entry.registrationId === registrationId;
}

export function CommandRegistryProvider({
  children,
  initialCommands = [],
}: CommandRegistryProviderProps) {
  const orderCounterRef = useRef(0);
  const registrationCounterRef = useRef(0);
  const toRegistered = useCallback(
    (command: RuntimeCommand, registrationId: number): RegisteredCommand => ({
      ...command,
      order: orderCounterRef.current++,
      registrationId,
    }),
    [],
  );

  const [commands, setCommands] = useState<RegisteredCommand[]>(() =>
    initialCommands.map((command) => toRegistered(command, registrationCounterRef.current++)),
  );
  const commandMapRef = useRef<Map<string, RegisteredCommand>>(new Map());
  commandMapRef.current = new Map(commands.map((command) => [command.id, command]));

  const registerCommand = useCallback(
    (command: RuntimeCommand) => {
      const registrationId = registrationCounterRef.current++;
      setCommands((prev) => {
        const existingIndex = prev.findIndex((entry) => entry.id === command.id);
        if (existingIndex < 0) {
          return [...prev, toRegistered(command, registrationId)];
        }

        const existing = prev[existingIndex];
        if (!existing) return prev;
        const next = [...prev];
        next[existingIndex] = {
          ...existing,
          ...command,
          order: existing.order,
          registrationId,
        };
        return next;
      });

      return () => {
        setCommands((prev) =>
          prev.filter(
            (entry) => !shouldCleanupRegisteredCommand(entry, command.id, registrationId),
          ),
        );
      };
    },
    [toRegistered],
  );

  const registerCommands = useCallback(
    (nextCommands: RuntimeCommand[]) => {
      const unregisterHandlers = nextCommands.map((command) => registerCommand(command));
      return () => {
        for (const unregister of unregisterHandlers) unregister();
      };
    },
    [registerCommand],
  );

  const unregisterCommand = useCallback((id: string) => {
    setCommands((prev) => prev.filter((entry) => entry.id !== id));
  }, []);

  const clearCommands = useCallback(() => {
    setCommands([]);
  }, []);

  const runCommand = useCallback(async (id: string): Promise<boolean> => {
    const command = commandMapRef.current.get(id);
    if (!command || command.disabled || !isCommandVisible(command)) {
      return false;
    }

    await command.run();
    return true;
  }, []);

  const runKeybinding = useCallback(async (binding: string): Promise<boolean> => {
    const normalized = normalizeBinding(binding);
    if (!normalized) return false;

    const ordered = [...commandMapRef.current.values()].sort(
      (left, right) => left.order - right.order,
    );
    for (const command of ordered) {
      if (command.disabled || !isCommandVisible(command)) {
        continue;
      }

      const bindings = command.keybinds?.map(normalizeBinding) ?? [];
      if (!bindings.includes(normalized)) {
        continue;
      }

      await command.run();
      return true;
    }

    return false;
  }, []);

  const value = useMemo<CommandRegistryContextValue>(
    () => ({
      commands: [...commands]
        .sort((left, right) => left.order - right.order)
        .map((command) => ({
          id: command.id,
          title: command.title,
          hint: command.hint,
          section: command.section,
          keybinds: command.keybinds,
          disabled: command.disabled,
          visible: command.visible,
          run: command.run,
        })),
      registerCommand,
      registerCommands,
      unregisterCommand,
      clearCommands,
      runCommand,
      runKeybinding,
    }),
    [
      clearCommands,
      commands,
      registerCommand,
      registerCommands,
      runCommand,
      runKeybinding,
      unregisterCommand,
    ],
  );

  return (
    <CommandRegistryContext.Provider value={value}>{children}</CommandRegistryContext.Provider>
  );
}

export function useCommandRegistry(): CommandRegistry {
  const context = useContext(CommandRegistryContext);
  if (!context) {
    throw new Error(
      "Command registry is not available. Wrap your app in <CommandRegistryProvider>.",
    );
  }
  return context;
}

export function useCommandRegistryItems(): CommandPaletteItem[] {
  const registry = useCommandRegistry();
  return useMemo(
    () =>
      registry.commands
        .filter((command) => !command.disabled && isCommandVisible(command))
        .map(commandToPaletteItem),
    [registry.commands],
  );
}