package com.yaoyuan.jiscuss.exception;

import com.yaoyuan.jiscuss.response.ApiResponse;
import com.yaoyuan.jiscuss.response.ResponseCode;
import jakarta.validation.ConstraintViolationException;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.http.HttpStatus;
import org.springframework.http.ResponseEntity;
import org.springframework.security.access.AccessDeniedException;
import org.springframework.web.bind.MethodArgumentNotValidException;
import org.springframework.web.bind.annotation.ExceptionHandler;
import org.springframework.web.bind.annotation.RestControllerAdvice;

import java.util.stream.Collectors;

/**
 * Global exception handler.
 *
 * <p>Catches {@link BaseException}, validation errors, and unexpected exceptions so they
 * are returned as structured JSON instead of Spring's default error page.
 */
@RestControllerAdvice
public class GlobalExceptionHandler {

    private static final Logger log = LoggerFactory.getLogger(GlobalExceptionHandler.class);

    /** Business logic exceptions (already typed with a ResponseCode). */
    @ExceptionHandler(BaseException.class)
    public ResponseEntity<ApiResponse<Void>> handleBaseException(BaseException ex) {
        log.warn("Business exception: code={}, msg={}", ex.getCode().getCode(), ex.getCode().getMsg());
        return ResponseEntity
                .status(HttpStatus.BAD_REQUEST)
                .body(ApiResponse.fail(ex.getCode()));
    }

    /** @Valid / @Validated failures on @RequestBody. */
    @ExceptionHandler(MethodArgumentNotValidException.class)
    public ResponseEntity<ApiResponse<Void>> handleValidationException(MethodArgumentNotValidException ex) {
        String message = ex.getBindingResult().getFieldErrors().stream()
                .map(fe -> fe.getField() + ": " + fe.getDefaultMessage())
                .collect(Collectors.joining("; "));
        log.warn("Validation failed: {}", message);
        return ResponseEntity
                .status(HttpStatus.BAD_REQUEST)
                .body(ApiResponse.error(message));
    }

    /** @Validated failures on @RequestParam / @PathVariable. */
    @ExceptionHandler(ConstraintViolationException.class)
    public ResponseEntity<ApiResponse<Void>> handleConstraintViolation(ConstraintViolationException ex) {
        String message = ex.getConstraintViolations().stream()
                .map(cv -> cv.getPropertyPath() + ": " + cv.getMessage())
                .collect(Collectors.joining("; "));
        log.warn("Constraint violation: {}", message);
        return ResponseEntity
                .status(HttpStatus.BAD_REQUEST)
                .body(ApiResponse.error(message));
    }

    /**
     * Spring Security access-denied exceptions re-thrown by method security.
     * Note: exceptions raised before method invocation are handled by {@code CustomAccessDeniedHandler}.
     */
    @ExceptionHandler(AccessDeniedException.class)
    public ResponseEntity<ApiResponse<Void>> handleAccessDenied(AccessDeniedException ex) {
        return ResponseEntity
                .status(HttpStatus.FORBIDDEN)
                .body(ApiResponse.error("没有权限访问该资源"));
    }

    /** Catch-all for any unhandled exception — never expose stack traces to clients. */
    @ExceptionHandler(Exception.class)
    public ResponseEntity<ApiResponse<Void>> handleGeneral(Exception ex) {
        log.error("Unexpected error", ex);
        return ResponseEntity
                .status(HttpStatus.INTERNAL_SERVER_ERROR)
                .body(ApiResponse.fail(ResponseCode.SERVICE_ERROR));
    }
}