package com.example.hrlab.audit;

import com.example.hrlab.common.Correlation;
import com.example.hrlab.common.JsonUtils;
import com.example.hrlab.security.SecurityUtils;
import jakarta.servlet.http.HttpServletRequest;
import java.nio.charset.StandardCharsets;
import java.security.MessageDigest;
import java.time.Clock;
import java.time.OffsetDateTime;
import java.util.HexFormat;
import java.util.Map;
import org.springframework.jdbc.core.JdbcTemplate;
import org.springframework.stereotype.Service;
import org.springframework.web.context.request.RequestContextHolder;
import org.springframework.web.context.request.ServletRequestAttributes;

@Service
public class AuditService {
    private final JdbcTemplate jdbcTemplate;
    private final Clock clock;

    public AuditService(JdbcTemplate jdbcTemplate, Clock clock) {
        this.jdbcTemplate = jdbcTemplate;
        this.clock = clock;
    }

    public void record(String action, String entityType, Object entityId, Object before, Object after) {
        String beforeJson = JsonUtils.toJson(before == null ? Map.of() : before);
        String afterJson = JsonUtils.toJson(after == null ? Map.of() : after);
        String prevHash = jdbcTemplate.query("SELECT record_hash FROM audit_logs ORDER BY id DESC LIMIT 1",
                rs -> rs.next() ? rs.getString(1) : null);
        OffsetDateTime occurredAt = OffsetDateTime.now(clock);
        String correlationId = Correlation.currentId();
        String recordHash = hash(prevHash, action, entityType, String.valueOf(entityId), beforeJson, afterJson, correlationId, occurredAt.toString());
        RequestInfo requestInfo = requestInfo();
        jdbcTemplate.update("""
                INSERT INTO audit_logs(actor_user_id, action, entity_type, entity_id, before_json, after_json,
                    ip_addr, user_agent, correlation_id, prev_hash, record_hash, occurred_at)
                VALUES (?, ?, ?, ?, ?::jsonb, ?::jsonb, ?, ?, ?, ?, ?, ?)
                """, SecurityUtils.currentUserIdOrNull(), action, entityType, entityId == null ? null : String.valueOf(entityId),
                beforeJson, afterJson, requestInfo.ip(), requestInfo.userAgent(), correlationId, prevHash, recordHash, occurredAt);
    }

    public String hash(String prevHash, String action, String entityType, String entityId, String beforeJson,
                       String afterJson, String correlationId, String occurredAt) {
        try {
            MessageDigest digest = MessageDigest.getInstance("SHA-256");
            String material = String.join("|",
                    prevHash == null ? "" : prevHash,
                    action,
                    entityType,
                    entityId == null ? "" : entityId,
                    beforeJson,
                    afterJson,
                    correlationId,
                    occurredAt);
            return HexFormat.of().formatHex(digest.digest(material.getBytes(StandardCharsets.UTF_8)));
        } catch (Exception ex) {
            throw new IllegalStateException("审计哈希计算失败", ex);
        }
    }

    private RequestInfo requestInfo() {
        if (RequestContextHolder.getRequestAttributes() instanceof ServletRequestAttributes attrs) {
            HttpServletRequest request = attrs.getRequest();
            String ip = request.getHeader("X-Forwarded-For");
            if (ip == null || ip.isBlank()) {
                ip = request.getRemoteAddr();
            }
            return new RequestInfo(ip, request.getHeader("User-Agent"));
        }
        return new RequestInfo(null, null);
    }

    private record RequestInfo(String ip, String userAgent) {
    }
}