package com.tcm.training.admin.app.register.service;

import com.tcm.training.admin.app.register.entity.SysRegion;
import com.tcm.training.admin.app.register.mapper.SysRegionMapper;
import com.tcm.training.admin.app.register.vo.AppRegisterRegionDatasetVO;
import com.tcm.training.admin.app.register.vo.AppRegisterRegionOptionVO;
import com.tcm.training.admin.app.register.vo.AppRegisterRegionPickerOptionVO;
import lombok.Getter;
import lombok.NoArgsConstructor;
import lombok.Setter;
import org.springframework.stereotype.Service;

import java.util.ArrayList;
import java.util.Collections;
import java.util.LinkedHashMap;
import java.util.List;
import java.util.Map;

/**
 * APP 注册行政区划服务，负责三级联动查询与海诊通地区数据归一化。
 */
@Service
public class AppRegisterRegionService {

    private static final long ROOT_PARENT_ID = 0L;

    private final SysRegionMapper sysRegionMapper;

    /**
     * 注入行政区划查询 Mapper。
     */
    public AppRegisterRegionService(SysRegionMapper sysRegionMapper) {
        this.sysRegionMapper = sysRegionMapper;
    }

    /**
     * 按父级地区编码查询下一级行政区划。
     */
    public List<AppRegisterRegionOptionVO> listRegions(String parentCode) {
        Long parentId = resolveParentId(parentCode);
        if (parentId == null) {
            return Collections.emptyList();
        }
        List<SysRegion> regions = sysRegionMapper.selectByParentId(parentId);
        if (regions == null || regions.isEmpty()) {
            return Collections.emptyList();
        }
        List<AppRegisterRegionOptionVO> options = new ArrayList<AppRegisterRegionOptionVO>(regions.size());
        for (SysRegion region : regions) {
            options.add(toRegionOption(region));
        }
        return options;
    }

    /**
     * 构造兼容 APP 滚轮地区选择器的数据集。
     */
    public AppRegisterRegionDatasetVO buildRegionDataset() {
        List<SysRegion> regions = sysRegionMapper.selectAllOrdered();
        AppRegisterRegionDatasetVO dataset = new AppRegisterRegionDatasetVO();
        if (regions == null || regions.isEmpty()) {
            return dataset;
        }

        Map<Long, List<SysRegion>> childrenByParentId = new LinkedHashMap<Long, List<SysRegion>>();
        for (SysRegion region : regions) {
            Long parentId = region.getParentId() == null ? ROOT_PARENT_ID : region.getParentId();
            List<SysRegion> children = childrenByParentId.get(parentId);
            if (children == null) {
                children = new ArrayList<SysRegion>();
                childrenByParentId.put(parentId, children);
            }
            children.add(region);
        }

        List<SysRegion> provinces = childrenByParentId.get(ROOT_PARENT_ID);
        if (provinces == null || provinces.isEmpty()) {
            return dataset;
        }

        List<AppRegisterRegionPickerOptionVO> provinceOptions = new ArrayList<AppRegisterRegionPickerOptionVO>(provinces.size());
        List<List<AppRegisterRegionPickerOptionVO>> cityOptions = new ArrayList<List<AppRegisterRegionPickerOptionVO>>(provinces.size());
        List<List<List<AppRegisterRegionPickerOptionVO>>> areaOptions = new ArrayList<List<List<AppRegisterRegionPickerOptionVO>>>(provinces.size());

        for (SysRegion province : provinces) {
            provinceOptions.add(toPickerOption(province, 1));

            List<SysRegion> cities = childrenByParentId.get(province.getId());
            if (cities == null) {
                cities = Collections.emptyList();
            }
            List<AppRegisterRegionPickerOptionVO> currentCityOptions = new ArrayList<AppRegisterRegionPickerOptionVO>(cities.size());
            List<List<AppRegisterRegionPickerOptionVO>> currentAreaOptions = new ArrayList<List<AppRegisterRegionPickerOptionVO>>(cities.size());

            for (SysRegion city : cities) {
                currentCityOptions.add(toPickerOption(city, 2));

                List<SysRegion> districts = childrenByParentId.get(city.getId());
                if (districts == null) {
                    districts = Collections.emptyList();
                }
                List<AppRegisterRegionPickerOptionVO> currentDistrictOptions = new ArrayList<AppRegisterRegionPickerOptionVO>(districts.size());
                for (SysRegion district : districts) {
                    if (shouldHideInAppPicker(district)) {
                        continue;
                    }
                    currentDistrictOptions.add(toPickerOption(district, 3));
                }
                currentAreaOptions.add(currentDistrictOptions);
            }

            cityOptions.add(currentCityOptions);
            areaOptions.add(currentAreaOptions);
        }

        dataset.setProvinces(provinceOptions);
        dataset.setCities(cityOptions);
        dataset.setAreas(areaOptions);
        return dataset;
    }

    /**
     * APP 地区选择器不展示行政区划占位节点。
     */
    private boolean shouldHideInAppPicker(SysRegion region) {
        return region.getName() != null && region.getName().contains("市辖区");
    }

    /**
     * 将海诊通诊所地区编码或名称归一化为本地三级行政区划。
     */
    public RegionSelection resolveRegionSelection(String provinceCode,
                                                 String provinceName,
                                                 String cityCode,
                                                 String cityName,
                                                 String districtCode,
                                                 String districtName) {
        SysRegion province = resolveRegionByCode(provinceCode);
        SysRegion city = resolveRegionByCode(cityCode);
        SysRegion district = resolveRegionByCode(districtCode);

        if (district != null && city == null) {
            city = findRegionById(district.getParentId());
        }
        if (city != null && province == null) {
            province = findRegionById(city.getParentId());
        }

        province = resolveProvinceRegion(province, provinceName);
        city = resolveCityRegion(city, province, cityName);
        if (city != null && province == null) {
            province = findRegionById(city.getParentId());
        }
        district = resolveDistrictRegion(district, city, districtName);
        if (district != null && city == null) {
            city = findRegionById(district.getParentId());
        }
        if (city != null && province == null) {
            province = findRegionById(city.getParentId());
        }

        if (!isSameParent(city, province)) {
            city = null;
            district = null;
        }
        if (!isSameParent(district, city)) {
            district = null;
        }

        RegionSelection selection = new RegionSelection();
        if (province != null) {
            selection.setProvinceCode(province.getCode());
            selection.setProvinceName(province.getName());
        }
        if (city != null) {
            selection.setCityCode(city.getCode());
            selection.setCityName(city.getName());
        }
        if (district != null) {
            selection.setDistrictCode(district.getCode());
            selection.setDistrictName(district.getName());
        }
        return selection;
    }

    /**
     * 将实体转换为前端下拉选项。
     */
    private AppRegisterRegionOptionVO toRegionOption(SysRegion region) {
        AppRegisterRegionOptionVO option = new AppRegisterRegionOptionVO();
        option.setId(region.getId());
        option.setCode(region.getCode());
        option.setName(region.getName());
        option.setParentId(region.getParentId());
        option.setLevel(resolveRegionLevel(region.getCode()));
        return option;
    }

    /**
     * 将实体转换为滚轮选择器使用的标签和值。
     */
    private AppRegisterRegionPickerOptionVO toPickerOption(SysRegion region, int level) {
        AppRegisterRegionPickerOptionVO option = new AppRegisterRegionPickerOptionVO();
        option.setLabel(region.getName());
        option.setValue(resolvePickerValue(region.getCode(), level));
        return option;
    }

    /**
     * 将数据库 6 位行政区编码转换为前端滚轮选择器的分级编码。
     */
    private String resolvePickerValue(String code, int level) {
        if (code == null || code.trim().isEmpty()) {
            return "";
        }
        if (level == 1 && code.length() >= 2) {
            return code.substring(0, 2);
        }
        if (level == 2 && code.length() >= 4) {
            return code.substring(0, 4);
        }
        return code.length() >= 6 ? code.substring(0, 6) : code;
    }

    /**
     * 计算当前编码所属的行政区层级。
     */
    private Integer resolveRegionLevel(String code) {
        if (code == null || code.length() != 6) {
            return null;
        }
        if (code.endsWith("0000")) {
            return 1;
        }
        if (code.endsWith("00")) {
            return 2;
        }
        return 3;
    }

    /**
     * 将父级地区编码转换为父级 ID。
     */
    private Long resolveParentId(String parentCode) {
        String normalizedParentCode = trimToNull(parentCode);
        if (normalizedParentCode == null) {
            return ROOT_PARENT_ID;
        }
        SysRegion parent = sysRegionMapper.selectByCode(normalizedParentCode);
        return parent == null ? null : parent.getId();
    }

    /**
     * 优先按编码解析省份，编码缺失时再按名称匹配根节点。
     */
    private SysRegion resolveProvinceRegion(SysRegion province, String provinceName) {
        if (province != null) {
            return province;
        }
        return resolveRegionByName(ROOT_PARENT_ID, provinceName);
    }

    /**
     * 优先按编码解析城市，编码无效时回退到省份下的名称匹配。
     */
    private SysRegion resolveCityRegion(SysRegion city, SysRegion province, String cityName) {
        if (city != null && (province == null || isSameParent(city, province))) {
            return city;
        }
        if (province == null) {
            return null;
        }
        return resolveRegionByName(province.getId(), cityName);
    }

    /**
     * 优先按编码解析区县，编码无效时回退到城市下的名称匹配。
     */
    private SysRegion resolveDistrictRegion(SysRegion district, SysRegion city, String districtName) {
        if (district != null && (city == null || isSameParent(district, city))) {
            return district;
        }
        if (city == null) {
            return null;
        }
        return resolveRegionByName(city.getId(), districtName);
    }

    /**
     * 按编码查询行政区划，空值直接返回空。
     */
    private SysRegion resolveRegionByCode(String code) {
        String normalizedCode = trimToNull(code);
        if (normalizedCode == null) {
            return null;
        }
        return sysRegionMapper.selectByCode(normalizedCode);
    }

    /**
     * 在父节点下按名称精确匹配行政区划。
     */
    private SysRegion resolveRegionByName(Long parentId, String name) {
        String normalizedName = trimToNull(name);
        if (parentId == null || normalizedName == null) {
            return null;
        }
        return sysRegionMapper.selectByParentIdAndName(parentId, normalizedName);
    }

    /**
     * 按主键回查行政区划实体。
     */
    private SysRegion findRegionById(Long regionId) {
        if (regionId == null || regionId <= 0) {
            return null;
        }
        return sysRegionMapper.selectById(regionId);
    }

    /**
     * 判断子节点是否归属于指定父节点。
     */
    private boolean isSameParent(SysRegion child, SysRegion parent) {
        if (child == null || parent == null) {
            return true;
        }
        return parent.getId() != null && parent.getId().equals(child.getParentId());
    }

    /**
     * 将空白字符串统一转换为 null。
     */
    private String trimToNull(String value) {
        if (value == null) {
            return null;
        }
        String trimmed = value.trim();
        return trimmed.isEmpty() ? null : trimmed;
    }

    /**
     * 归一化后的三级行政区划结果。
     */
    @Getter
    @Setter
    @NoArgsConstructor
    public static class RegionSelection {

        private String provinceCode;

        private String provinceName;

        private String cityCode;

        private String cityName;

        private String districtCode;

        private String districtName;
    }
}