### Installation

Source: https://github.com/apache/casbin-nest-authz/blob/master/README.md

Command to install the nest-authz package.

```bash
$ npm install --save nest-authz
```

--------------------------------

### Module Registration Example 1

Source: https://github.com/apache/casbin-nest-authz/blob/master/README.md

Example of registering AuthZModule with model and policy paths, including custom user and resource context functions.

```typescript
import {
  AuthZModule,
  AuthPossession
} from 'nest-authz';
import { TypeOrmModule } from '@nestjs/typeorm';

@Module({
  imports: [
    AuthZModule.register({
      model: 'model.conf',
      policy: TypeORMAdapter.newAdapter({
        type: 'mysql',
        host: 'localhost',
        port: 3306,
        username: 'root',
        password: 'password',
        database: 'nestdb'
      }),
      userFromContext: (ctx) => {
        const request = ctx.switchToHttp().getRequest();
        return request.user && request.user.username;
      },
      resourceFromContext: (ctx, perm) => {
        const request = ctx.switchToHttp().getRequest();
        return { type: perm.resource, id: request.id };
      }
    }),
  ],
  controllers: [AppController],
  providers: [AppService]
})
```

--------------------------------

### Module Registration Example 2 (Preferred)

Source: https://github.com/apache/casbin-nest-authz/blob/master/README.md

Example of registering AuthZModule using an enforcerProvider, preferred for its flexibility, with custom user context function.

```typescript
import {
  AuthZModule,
  AUTHZ_ENFORCER
} from 'nest-authz';
import { TypeOrmModule } from '@nestjs/typeorm';
import { ConfigModule, ConfigService } from './config.module';
import * as casbin from 'casbin';

@Module({
  imports: [
    ConfigModule,
    AuthZModule.register({
      imports: [ConfigModule],
      enforcerProvider: {
        provide: AUTHZ_ENFORCER,
        useFactory: async (configSrv: ConfigService) => {
          const config = await configSrv.getAuthConfig();
          return casbin.newEnforcer(config.model, config.policy);
        },
        inject: [ConfigService],
      },
      userFromContext: (ctx) => {
        const request = ctx.switchToHttp().getRequest();
        return request.user && {
          username: request.user.username, 
          isAdmin: request.user.isAdmin 
        };
      }
    }),
  ],
  controllers: [AppController],
  providers: [AppService]
})
```

--------------------------------

### Using AuthZRBACService

Source: https://github.com/apache/casbin-nest-authz/blob/master/README.md

Example demonstrating how to inject and use AuthZRBACService to check user permissions for a specific action.

```typescript
import {
  Controller,
  Get,
  UnauthorizedException,
  Req
} from '@nestjs/common';
import {
  AuthZGuard,
  AuthZRBACService,
  AuthActionVerb,
  AuthPossession,
  UsePermissions
} from 'nest-authz';

@Controller()
export class AppController {
  constructor(private readonly rbacSrv: AuthZRBACService) {}

  @Get('users')
  async findAllUsers(@Req() request: Request) {
    let username = request.user['username'];
    // If there is a policy  `p, root, user, read:any` in policy.csv
    // then user `root` can do this operation

    // Using string literals for simplicity.
    const isPermitted = await this.rbacSrv.hasPermissionForUser(username, "user", "read:any");
    if (!isPermitted) {
      throw new UnauthorizedException(
        'You are not authorized to read users list'
      );
    }
    // A user can not reach this point if he/she is not granted for permission read users
    // ...
  }
}
```

--------------------------------

### Using @UsePermissions Decorator with resourceFromContext

Source: https://github.com/apache/casbin-nest-authz/blob/master/README.md

Example of using 'resourceFromContext' to dynamically determine the resource based on the request context.

```typescript
@UsePermissions({
  action: AuthActionVerb.READ,
  resource: 'User',
  resourceFromContext: (ctx, perm) => {
    const req = ctx.switchToHttp().getRequest();
    return { type: perm.resource, id: req.id };
  }
})
async userById(id: string) {}

```

--------------------------------

### Using AuthZService for In-Method Permission Checks

Source: https://github.com/apache/casbin-nest-authz/blob/master/README.md

Example of injecting and using AuthZService within a controller method to perform permission checks.

```typescript
import { Controller, Get, UnauthorizedException, Req } from '@nestjs/common';
import {
  AuthZGuard,
  AuthZService,
  AuthActionVerb,
  AuthPossession,
  UsePermissions
} from 'nest-authz';

@Controller()
export class AppController {
  constructor(private readonly authzSrv: AuthZService) {}

  @Get('users')
  async findAllUsers(@Req() request: Request) {
    let username = request.user['username'];
    // If there is a policy  `p, root, user, read:any` in policy.csv
    // then user `root` can do this operation

    // Using string literals for simplicity.
    const isPermitted = await this.authzSrv.hasPermissionForUser(username, "user", "read:any");
    if (!isPermitted) {
      throw new UnauthorizedException(
        'You are not authorized to read users list'
      );
    }
    // A user can not reach this point if he/she is not granted for permission read users
    // ...
  }
}

```

--------------------------------

### Using @UsePermissions Decorator with Basic Permissions

Source: https://github.com/apache/casbin-nest-authz/blob/master/README.md

Example of applying the @UsePermissions decorator to a NestJS route to enforce read permissions on 'USER' resource.

```typescript
  @Get('users')
  @UseGuards(AuthZGuard)
  @UsePermissions({
    action: AuthActionVerb.READ,
    resource: 'USER',
    possession: AuthPossession.ANY
  })
  async findAllUsers() {}

```

--------------------------------

### Using @UsePermissions Decorator with Multiple Permissions

Source: https://github.com/apache/casbin-nest-authz/blob/master/README.md

Shows how to apply multiple permission checks to a single route, requiring all to be satisfied.

```typescript
@UsePermissions({
  action: AuthActionVerb.READ,
  resource: 'USER_ADDRESS',
  possession: AuthPossession.ANY
}, {
  action; AuthActionVerb.READ,
  resource: 'USER_ROLES',
  possession: AuthPossession.ANY
})

```

--------------------------------

### Using @UsePermissions Decorator with Object Resource

Source: https://github.com/apache/casbin-nest-authz/blob/master/README.md

Demonstrates using an object for the 'resource' property in @UsePermissions to support ABAC models.

```typescript
@UsePermissions({
  action: AuthActionVerb.READ,
  resource: {type: 'User', operation: 'single'},
  possession: AuthPossession.ANY
})
async userById(id: string) {}

@UsePermissions({
  action: AuthActionVerb.READ,
  resource: {type: 'User', operation: 'batch'},
  possession: AuthPossession.ANY
})
async findAllUsers() {}

```

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