first implementation

backend/src/main/java/com/aiteacher/config/AiConfig.java

@@ -0,0 +1,21 @@
+package com.aiteacher.config;
+
+import com.fasterxml.jackson.databind.ObjectMapper;
+import org.springframework.ai.chat.client.ChatClient;
+import org.springframework.ai.chat.model.ChatModel;
+import org.springframework.context.annotation.Bean;
+import org.springframework.context.annotation.Configuration;
+
+@Configuration
+public class AiConfig {
+
+    @Bean
+    public ObjectMapper objectMapper() {
+        return new ObjectMapper();
+    }
+
+    @Bean
+    public ChatClient chatClient(ChatModel chatModel) {
+        return ChatClient.builder(chatModel).build();
+    }
+}

backend/src/main/java/com/aiteacher/config/GlobalExceptionHandler.java

@@ -0,0 +1,56 @@
+package com.aiteacher.config;
+
+import com.aiteacher.book.NoKnowledgeSourceException;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+import org.springframework.http.HttpStatus;
+import org.springframework.http.ResponseEntity;
+import org.springframework.web.bind.annotation.ExceptionHandler;
+import org.springframework.web.bind.annotation.RestControllerAdvice;
+import org.springframework.web.multipart.MaxUploadSizeExceededException;
+
+import java.util.Map;
+import java.util.NoSuchElementException;
+
+@RestControllerAdvice
+public class GlobalExceptionHandler {
+
+    private static final Logger log = LoggerFactory.getLogger(GlobalExceptionHandler.class);
+
+    @ExceptionHandler(NoKnowledgeSourceException.class)
+    public ResponseEntity<Map<String, String>> handleNoKnowledgeSource(NoKnowledgeSourceException ex) {
+        return ResponseEntity.status(HttpStatus.SERVICE_UNAVAILABLE)
+            .body(Map.of("error", ex.getMessage()));
+    }
+
+    @ExceptionHandler(NoSuchElementException.class)
+    public ResponseEntity<Map<String, String>> handleNotFound(NoSuchElementException ex) {
+        return ResponseEntity.status(HttpStatus.NOT_FOUND)
+            .body(Map.of("error", ex.getMessage()));
+    }
+
+    @ExceptionHandler(IllegalArgumentException.class)
+    public ResponseEntity<Map<String, String>> handleBadRequest(IllegalArgumentException ex) {
+        return ResponseEntity.status(HttpStatus.BAD_REQUEST)
+            .body(Map.of("error", ex.getMessage()));
+    }
+
+    @ExceptionHandler(IllegalStateException.class)
+    public ResponseEntity<Map<String, String>> handleConflict(IllegalStateException ex) {
+        return ResponseEntity.status(HttpStatus.CONFLICT)
+            .body(Map.of("error", ex.getMessage()));
+    }
+
+    @ExceptionHandler(MaxUploadSizeExceededException.class)
+    public ResponseEntity<Map<String, String>> handleMaxUploadSize(MaxUploadSizeExceededException ex) {
+        return ResponseEntity.status(HttpStatus.PAYLOAD_TOO_LARGE)
+            .body(Map.of("error", "File exceeds maximum size of 100 MB."));
+    }
+
+    @ExceptionHandler(Exception.class)
+    public ResponseEntity<Map<String, String>> handleGeneric(Exception ex) {
+        log.error("Unhandled exception", ex);
+        return ResponseEntity.status(HttpStatus.INTERNAL_SERVER_ERROR)
+            .body(Map.of("error", "An unexpected error occurred."));
+    }
+}

backend/src/main/java/com/aiteacher/config/SecurityConfig.java

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+package com.aiteacher.config;
+
+import org.springframework.beans.factory.annotation.Value;
+import org.springframework.context.annotation.Bean;
+import org.springframework.context.annotation.Configuration;
+import org.springframework.security.config.Customizer;
+import org.springframework.security.config.annotation.web.builders.HttpSecurity;
+import org.springframework.security.config.annotation.web.configuration.EnableWebSecurity;
+import org.springframework.security.config.annotation.web.configurers.AbstractHttpConfigurer;
+import org.springframework.security.core.userdetails.User;
+import org.springframework.security.core.userdetails.UserDetails;
+import org.springframework.security.core.userdetails.UserDetailsService;
+import org.springframework.security.provisioning.InMemoryUserDetailsManager;
+import org.springframework.security.web.SecurityFilterChain;
+
+@Configuration
+@EnableWebSecurity
+public class SecurityConfig {
+
+    @Bean
+    public SecurityFilterChain filterChain(HttpSecurity http) throws Exception {
+        http
+            .authorizeHttpRequests(auth -> auth.anyRequest().authenticated())
+            .httpBasic(Customizer.withDefaults())
+            .csrf(AbstractHttpConfigurer::disable);
+        return http.build();
+    }
+
+    @Bean
+    public UserDetailsService userDetailsService(
+            @Value("${app.auth.password}") String password) {
+        UserDetails user = User.builder()
+            .username("neurosurgeon")
+            .password("{noop}" + password)
+            .roles("USER")
+            .build();
+        return new InMemoryUserDetailsManager(user);
+    }
+}