Stirling-PDF/frontend/src/contexts/NavigationContext.tsx

import React, { createContext, useContext, useReducer, useCallback } from 'react';

/**
 * NavigationContext - Complete navigation management system
 * 
 * Handles navigation modes, navigation guards for unsaved changes,
 * and breadcrumb/history navigation. Separated from FileContext to 
 * maintain clear separation of concerns.
 */

// Navigation mode types
export type ModeType = 
  | 'viewer' 
  | 'pageEditor' 
  | 'fileEditor' 
  | 'merge' 
  | 'split' 
  | 'compress' 
  | 'ocr' 
  | 'convert' 
  | 'addPassword' 
  | 'changePermissions' 
  | 'sanitize';

// Navigation state
interface NavigationState {
  currentMode: ModeType;
  hasUnsavedChanges: boolean;
  pendingNavigation: (() => void) | null;
  showNavigationWarning: boolean;
}

// Navigation actions
type NavigationAction =
  | { type: 'SET_MODE'; payload: { mode: ModeType } }
  | { type: 'SET_UNSAVED_CHANGES'; payload: { hasChanges: boolean } }
  | { type: 'SET_PENDING_NAVIGATION'; payload: { navigationFn: (() => void) | null } }
  | { type: 'SHOW_NAVIGATION_WARNING'; payload: { show: boolean } };

// Navigation reducer
const navigationReducer = (state: NavigationState, action: NavigationAction): NavigationState => {
  switch (action.type) {
    case 'SET_MODE':
      return { ...state, currentMode: action.payload.mode };
    
    case 'SET_UNSAVED_CHANGES':
      return { ...state, hasUnsavedChanges: action.payload.hasChanges };
    
    case 'SET_PENDING_NAVIGATION':
      return { ...state, pendingNavigation: action.payload.navigationFn };
    
    case 'SHOW_NAVIGATION_WARNING':
      return { ...state, showNavigationWarning: action.payload.show };
    
    default:
      return state;
  }
};

// Initial state
const initialState: NavigationState = {
  currentMode: 'pageEditor',
  hasUnsavedChanges: false,
  pendingNavigation: null,
  showNavigationWarning: false
};

// Navigation context actions interface
export interface NavigationContextActions {
  setMode: (mode: ModeType) => void;
  setHasUnsavedChanges: (hasChanges: boolean) => void;
  showNavigationWarning: (show: boolean) => void;
  requestNavigation: (navigationFn: () => void) => void;
  confirmNavigation: () => void;
  cancelNavigation: () => void;
}

// Split context values
export interface NavigationContextStateValue {
  currentMode: ModeType;
  hasUnsavedChanges: boolean;
  pendingNavigation: (() => void) | null;
  showNavigationWarning: boolean;
}

export interface NavigationContextActionsValue {
  actions: NavigationContextActions;
}

// Create contexts
const NavigationStateContext = createContext<NavigationContextStateValue | undefined>(undefined);
const NavigationActionsContext = createContext<NavigationContextActionsValue | undefined>(undefined);

// Provider component
export const NavigationProvider: React.FC<{ children: React.ReactNode }> = ({ children }) => {
  const [state, dispatch] = useReducer(navigationReducer, initialState);

  const actions: NavigationContextActions = {
    setMode: useCallback((mode: ModeType) => {
      dispatch({ type: 'SET_MODE', payload: { mode } });
    }, []),

    setHasUnsavedChanges: useCallback((hasChanges: boolean) => {
      dispatch({ type: 'SET_UNSAVED_CHANGES', payload: { hasChanges } });
    }, []),

    showNavigationWarning: useCallback((show: boolean) => {
      dispatch({ type: 'SHOW_NAVIGATION_WARNING', payload: { show } });
    }, []),

    requestNavigation: useCallback((navigationFn: () => void) => {
      // If no unsaved changes, navigate immediately
      if (!state.hasUnsavedChanges) {
        navigationFn();
        return;
      }

      // Otherwise, store the navigation and show warning
      dispatch({ type: 'SET_PENDING_NAVIGATION', payload: { navigationFn } });
      dispatch({ type: 'SHOW_NAVIGATION_WARNING', payload: { show: true } });
    }, [state.hasUnsavedChanges]),

    confirmNavigation: useCallback(() => {
      // Execute pending navigation
      if (state.pendingNavigation) {
        state.pendingNavigation();
      }
      
      // Clear navigation state
      dispatch({ type: 'SET_PENDING_NAVIGATION', payload: { navigationFn: null } });
      dispatch({ type: 'SHOW_NAVIGATION_WARNING', payload: { show: false } });
    }, [state.pendingNavigation]),

    cancelNavigation: useCallback(() => {
      // Clear navigation without executing
      dispatch({ type: 'SET_PENDING_NAVIGATION', payload: { navigationFn: null } });
      dispatch({ type: 'SHOW_NAVIGATION_WARNING', payload: { show: false } });
    }, [])
  };

  const stateValue: NavigationContextStateValue = {
    currentMode: state.currentMode,
    hasUnsavedChanges: state.hasUnsavedChanges,
    pendingNavigation: state.pendingNavigation,
    showNavigationWarning: state.showNavigationWarning
  };

  const actionsValue: NavigationContextActionsValue = {
    actions
  };

  return (
    <NavigationStateContext.Provider value={stateValue}>
      <NavigationActionsContext.Provider value={actionsValue}>
        {children}
      </NavigationActionsContext.Provider>
    </NavigationStateContext.Provider>
  );
};

// Navigation hooks
export const useNavigationState = () => {
  const context = useContext(NavigationStateContext);
  if (context === undefined) {
    throw new Error('useNavigationState must be used within NavigationProvider');
  }
  return context;
};

export const useNavigationActions = () => {
  const context = useContext(NavigationActionsContext);
  if (context === undefined) {
    throw new Error('useNavigationActions must be used within NavigationProvider');
  }
  return context;
};

// Combined hook for convenience
export const useNavigation = () => {
  const state = useNavigationState();
  const { actions } = useNavigationActions();
  return { ...state, ...actions };
};

// Navigation guard hook (equivalent to old useFileNavigation)
export const useNavigationGuard = () => {
  const state = useNavigationState();
  const { actions } = useNavigationActions();
  
  return {
    pendingNavigation: state.pendingNavigation,
    showNavigationWarning: state.showNavigationWarning,
    hasUnsavedChanges: state.hasUnsavedChanges,
    requestNavigation: actions.requestNavigation,
    confirmNavigation: actions.confirmNavigation,
    cancelNavigation: actions.cancelNavigation,
    setHasUnsavedChanges: actions.setHasUnsavedChanges,
    setShowNavigationWarning: actions.showNavigationWarning
  };
};

// Utility functions for mode handling
export const isValidMode = (mode: string): mode is ModeType => {
  const validModes: ModeType[] = [
    'viewer', 'pageEditor', 'fileEditor', 'merge', 'split', 
    'compress', 'ocr', 'convert', 'addPassword', 'changePermissions', 'sanitize'
  ];
  return validModes.includes(mode as ModeType);
};

export const getDefaultMode = (): ModeType => 'pageEditor';

// TODO: This will be expanded for URL-based routing system
// - URL parsing utilities
// - Route definitions  
// - Navigation hooks with URL sync
// - History management
// - Breadcrumb restoration from URL params