package com.baiyue.common.web;

import com.baiyue.common.core.api.ApiResponse;
import com.baiyue.common.core.api.ResultCode;
import com.baiyue.common.core.exception.BizException;
import jakarta.servlet.http.HttpServletRequest;
import jakarta.validation.ConstraintViolationException;
import io.micrometer.core.instrument.MeterRegistry;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.http.ResponseEntity;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.security.access.AccessDeniedException;
import org.springframework.security.core.AuthenticationException;
import org.springframework.validation.BindException;
import org.springframework.validation.FieldError;
import org.springframework.http.converter.HttpMessageNotReadableException;
import org.springframework.dao.CannotAcquireLockException;
import org.springframework.web.bind.MethodArgumentNotValidException;
import org.springframework.web.bind.MissingRequestHeaderException;
import org.springframework.web.bind.MissingServletRequestParameterException;
import org.springframework.web.method.annotation.MethodArgumentTypeMismatchException;
import org.springframework.web.bind.annotation.ExceptionHandler;
import org.springframework.web.bind.annotation.RestControllerAdvice;
import org.springframework.web.servlet.resource.NoResourceFoundException;
import org.springframework.web.server.ResponseStatusException;
import org.springframework.web.multipart.MaxUploadSizeExceededException;
import org.springframework.web.multipart.support.MissingServletRequestPartException;

import java.util.LinkedHashMap;
import java.util.Map;

/**
 * Servlet Web 全局异常处理器，将业务异常、参数校验异常和系统异常转换为统一 API 响应。
 */
@RestControllerAdvice
public class GlobalExceptionHandler {
    private static final Logger log = LoggerFactory.getLogger(GlobalExceptionHandler.class);

    @Autowired(required = false)
    private MeterRegistry meterRegistry;

    @ExceptionHandler(BizException.class)
    public ResponseEntity<ApiResponse<Void>> handleBusiness(BizException exception, HttpServletRequest request) {
        return failure(exception.getResultCode(), exception.getMessage(), request);
    }

    @ExceptionHandler(MethodArgumentNotValidException.class)
    public ResponseEntity<ApiResponse<Map<String, String>>> handleValidation(
            MethodArgumentNotValidException exception, HttpServletRequest request) {
        return validationResponse(fieldErrors(exception.getBindingResult().getFieldErrors()), request);
    }

    @ExceptionHandler(BindException.class)
    public ResponseEntity<ApiResponse<Map<String, String>>> handleBinding(
            BindException exception, HttpServletRequest request) {
        return validationResponse(fieldErrors(exception.getBindingResult().getFieldErrors()), request);
    }

    @ExceptionHandler(ConstraintViolationException.class)
    public ResponseEntity<ApiResponse<Map<String, String>>> handleConstraint(
            ConstraintViolationException exception, HttpServletRequest request) {
        Map<String, String> errors = new LinkedHashMap<>();
        exception.getConstraintViolations().forEach(violation ->
                errors.put(violation.getPropertyPath().toString(), violation.getMessage()));
        return validationResponse(errors, request);
    }

    @ExceptionHandler({HttpMessageNotReadableException.class, MissingRequestHeaderException.class,
            MissingServletRequestParameterException.class, MissingServletRequestPartException.class,
            MethodArgumentTypeMismatchException.class})
    public ResponseEntity<ApiResponse<Void>> handleBadRequest(Exception exception, HttpServletRequest request) {
        return failure(ResultCode.BAD_REQUEST, ResultCode.BAD_REQUEST.message(), request);
    }

    @ExceptionHandler(AuthenticationException.class)
    public ResponseEntity<ApiResponse<Void>> handleAuthentication(
            AuthenticationException exception, HttpServletRequest request) {
        return failure(ResultCode.UNAUTHORIZED, ResultCode.UNAUTHORIZED.message(), request);
    }

    @ExceptionHandler(AccessDeniedException.class)
    public ResponseEntity<ApiResponse<Void>> handleAccessDenied(
            AccessDeniedException exception, HttpServletRequest request) {
        return failure(ResultCode.FORBIDDEN, ResultCode.FORBIDDEN.message(), request);
    }

    @ExceptionHandler(ResponseStatusException.class)
    public ResponseEntity<ApiResponse<Void>> handleResponseStatus(
            ResponseStatusException exception, HttpServletRequest request) {
        ResultCode code = resultCode(exception.getStatusCode().value());
        String message = exception.getReason() == null || exception.getReason().isBlank()
                ? code.message() : exception.getReason();
        return failure(code, message, request);
    }

    @ExceptionHandler(NoResourceFoundException.class)
    public ResponseEntity<ApiResponse<Void>> handleNoResourceFound(
            NoResourceFoundException exception, HttpServletRequest request) {
        return failure(ResultCode.NOT_FOUND, ResultCode.NOT_FOUND.message(), request);
    }

    @ExceptionHandler(CannotAcquireLockException.class)
    public ResponseEntity<ApiResponse<Void>> handleCannotAcquireLock(
            CannotAcquireLockException exception, HttpServletRequest request) {
        log.warn("Database lock acquisition conflict requestId={} traceId={}",
                CorrelationContext.requestId(request), CorrelationContext.traceId(request));
        return failure(ResultCode.CONFLICT, "资源正在处理中，请稍后重试", request);
    }

    @ExceptionHandler(MaxUploadSizeExceededException.class)
    public ResponseEntity<ApiResponse<Void>> handleMaxUploadSize(
            MaxUploadSizeExceededException exception, HttpServletRequest request) {
        long maxBytes = exception.getMaxUploadSize();
        String message = maxBytes > 0
                ? "上传文件不能超过" + Math.max(1, (maxBytes + 1024 * 1024 - 1) / (1024 * 1024)) + "MB"
                : "上传文件超过服务允许大小";
        return failure(ResultCode.BAD_REQUEST, message, request);
    }

    @ExceptionHandler(Exception.class)
    public ResponseEntity<ApiResponse<Void>> handleUnexpected(Exception exception, HttpServletRequest request) {
        log.error("Unhandled request failure requestId={} traceId={}",
                CorrelationContext.requestId(request), CorrelationContext.traceId(request), exception);
        return failure(ResultCode.INTERNAL_ERROR, ResultCode.INTERNAL_ERROR.message(), request);
    }

    private Map<String, String> fieldErrors(Iterable<FieldError> fieldErrors) {
        Map<String, String> errors = new LinkedHashMap<>();
        fieldErrors.forEach(error -> errors.putIfAbsent(error.getField(), error.getDefaultMessage()));
        return errors;
    }

    private ResponseEntity<ApiResponse<Map<String, String>>> validationResponse(
            Map<String, String> errors, HttpServletRequest request) {
        ResultCode code = ResultCode.VALIDATION_FAILED;
        ApiResponse<Map<String, String>> body = ApiResponse.of(code, validationMessage(errors), errors,
                CorrelationContext.requestId(request), CorrelationContext.traceId(request));
        recordFailure(code);
        return ResponseEntity.ok(body);
    }

    private String validationMessage(Map<String, String> errors) {
        if (errors.isEmpty()) {
            return ResultCode.VALIDATION_FAILED.message();
        }
        return errors.entrySet().stream()
                .map(entry -> entry.getKey() + ": " + entry.getValue())
                .collect(java.util.stream.Collectors.joining("；"));
    }

    private ResponseEntity<ApiResponse<Void>> failure(ResultCode code, String message,
                                                       HttpServletRequest request) {
        ApiResponse<Void> body = ApiResponse.failure(code, message,
                CorrelationContext.requestId(request), CorrelationContext.traceId(request));
        recordFailure(code);
        return ResponseEntity.ok(body);
    }

    private void recordFailure(ResultCode code) {
        if (meterRegistry != null) {
            meterRegistry.counter("baiyue.api.business.failures", "code", code.code()).increment();
        }
    }

    private ResultCode resultCode(int status) {
        return switch (status) {
            case 400 -> ResultCode.BAD_REQUEST;
            case 401 -> ResultCode.UNAUTHORIZED;
            case 403 -> ResultCode.FORBIDDEN;
            case 404 -> ResultCode.NOT_FOUND;
            case 409 -> ResultCode.CONFLICT;
            case 422 -> ResultCode.VALIDATION_FAILED;
            case 429 -> ResultCode.TOO_MANY_REQUESTS;
            case 503 -> ResultCode.SERVICE_UNAVAILABLE;
            default -> ResultCode.INTERNAL_ERROR;
        };
    }
}