export type NearbyPointDisplayMode = 'default' | 'replace' | 'expand';

export type NearbyPointAutoRule = {
  distanceThresholdMeters: number;
  replaceAtZoom: number;
  expandAtZoom: number;
  expandOffsetPx: number;
  angleStepDeg: number;
  minGroupSize: number;
};

export type NearbyPointLayoutRule = {
  ringSize: number;
  fanAngleForTwoDeg: number;
  fanAngleForFourDeg: number;
  fanAngleForManyDeg: number;
  ringGapPx: number;
  ringGapFactor: number;
};

export type NearbyPointDensityDisplayRule = {
  minDensityValue: number;
  minZoom: number;
};

export type NearbyPointConfig = {
  autoRule: NearbyPointAutoRule;
  layoutRule: NearbyPointLayoutRule;
  densityDisplayRules: NearbyPointDensityDisplayRule[];
};

export type NearbyPointRuntimeMeta = {
  groupId: string;
  displayName: string;
  groupSize: number;
  priority: number;
  showZoomMin: number | null;
  showZoomMax: number | null;
  replaceAtZoom: number;
  expandAtZoom: number;
  expandOffsetPx: number;
  expandAngleDeg: number;
  displayMode: NearbyPointDisplayMode;
};

// 备注：近邻点统一调参入口。
// 当前参数偏向“更容易成组、稍早进入替换与展开、展开位移更明显”，
// 方便抽吸效果在常用浏览层级更早被感知。
export const DEFAULT_NEARBY_POINT_AUTO_RULE: NearbyPointAutoRule = {
  distanceThresholdMeters: 9000,
  replaceAtZoom: 10.5,
  expandAtZoom: 12.2,
  expandOffsetPx: 48,
  angleStepDeg: 55,
  minGroupSize: 2
};

// 备注：展开布局统一调参入口。这里控制单圈数量、扇形角度和外圈扩散节奏。
export const DEFAULT_NEARBY_POINT_LAYOUT_RULE: NearbyPointLayoutRule = {
  ringSize: 5,
  fanAngleForTwoDeg: 110,
  fanAngleForFourDeg: 150,
  fanAngleForManyDeg: 180,
  ringGapPx: 22,
  ringGapFactor: 0.85
};

// 备注：密度分档显示规则。distance 越大表示越稀疏，越早参与显示候选。
export const DEFAULT_NEARBY_POINT_DENSITY_DISPLAY_RULES: NearbyPointDensityDisplayRule[] =
  [
    {
      minDensityValue: 1500000,
      minZoom: 0
    },
    {
      minDensityValue: 800000,
      minZoom: 6.1
    },
    {
      minDensityValue: 400000,
      minZoom: 8.1
    },
    {
      minDensityValue: 50000,
      minZoom: 10.6
    },
    {
      minDensityValue: 0,
      minZoom: 12.2
    }
  ];

export const DEFAULT_NEARBY_POINT_CONFIG: NearbyPointConfig = {
  autoRule: DEFAULT_NEARBY_POINT_AUTO_RULE,
  layoutRule: DEFAULT_NEARBY_POINT_LAYOUT_RULE,
  densityDisplayRules: DEFAULT_NEARBY_POINT_DENSITY_DISPLAY_RULES
};

export const getNearbyPointConfig = (): NearbyPointConfig => {
  return DEFAULT_NEARBY_POINT_CONFIG;
};

export const getNearbyPointAutoRule = (): NearbyPointAutoRule => {
  return getNearbyPointConfig().autoRule;
};

export const getNearbyPointLayoutRule = (): NearbyPointLayoutRule => {
  return getNearbyPointConfig().layoutRule;
};

export const getNearbyPointDensityDisplayRules =
  (): NearbyPointDensityDisplayRule[] => {
    return getNearbyPointConfig().densityDisplayRules;
  };

type GroupCandidate = {
  index: number;
  point: Record<string, any>;
  lon: number;
  lat: number;
  layerKey: string;
};

const normalizeText = (value: unknown): string => {
  return String(value ?? '')
    .trim()
    .replace(/[()（）]/g, '')
    .toLowerCase();
};

const toFiniteNumber = (value: unknown): number | null => {
  if (value === '' || value === null || value === undefined) {
    return null;
  }
  const numericValue = Number(value);
  return Number.isFinite(numericValue) ? numericValue : null;
};

const haversineDistanceMeters = (
  lon1: number,
  lat1: number,
  lon2: number,
  lat2: number
): number => {
  const toRad = (degree: number) => (degree * Math.PI) / 180;
  const earthRadius = 6371000;
  const dLat = toRad(lat2 - lat1);
  const dLon = toRad(lon2 - lon1);
  const lat1Rad = toRad(lat1);
  const lat2Rad = toRad(lat2);

  const a =
    Math.sin(dLat / 2) * Math.sin(dLat / 2) +
    Math.cos(lat1Rad) *
      Math.cos(lat2Rad) *
      Math.sin(dLon / 2) *
      Math.sin(dLon / 2);
  const c = 2 * Math.atan2(Math.sqrt(a), Math.sqrt(1 - a));
  return earthRadius * c;
};

const clearNearbyPointRuntimeMeta = (point: Record<string, any>) => {
  delete point._nearbyRule;
  delete point._nearbyGroupId;
  delete point._nearbyDisplayName;
  delete point._nearbyGroupSize;
  delete point._nearbyPriority;
  delete point._nearbyShowZoomMin;
  delete point._nearbyShowZoomMax;
  delete point._nearbyReplaceAtZoom;
  delete point._nearbyExpandAtZoom;
  delete point._nearbyExpandOffsetPx;
  delete point._nearbyExpandAngleDeg;
  delete point._nearbyDisplayMode;
  delete point._nearbyIsPrimary;
};

const getPointDisplayName = (point: Record<string, any>): string => {
  return (
    point.titleName || point.stnm || point.ennm || point.stcd || point._id || ''
  );
};

const getPointStableIdentity = (
  point: Record<string, any>,
  index: number
): string => {
  return normalizeText(
    point.stcd ||
      point._id ||
      point.titleName ||
      point.stnm ||
      point.ennm ||
      `point_${index}`
  );
};

const getGroupSortKey = (candidate: GroupCandidate): string => {
  return [
    getPointStableIdentity(candidate.point, candidate.index),
    normalizeText(candidate.point.layerKey),
    String(candidate.index).padStart(6, '0')
  ].join('|');
};

const compareGroupCandidates = (
  left: GroupCandidate,
  right: GroupCandidate
): number => {
  const leftDensityValue = toFiniteNumber(left.point.distance);
  const rightDensityValue = toFiniteNumber(right.point.distance);

  if (
    leftDensityValue !== null &&
    rightDensityValue !== null &&
    leftDensityValue !== rightDensityValue
  ) {
    return rightDensityValue - leftDensityValue;
  }

  if (leftDensityValue !== null || rightDensityValue !== null) {
    return leftDensityValue !== null ? -1 : 1;
  }

  return getGroupSortKey(left).localeCompare(getGroupSortKey(right));
};

const buildRuntimeMeta = (
  groupId: string,
  groupSize: number,
  priority: number,
  displayName: string,
  rule: NearbyPointAutoRule
): NearbyPointRuntimeMeta => {
  const displayMode: NearbyPointDisplayMode =
    priority === 1 ? 'default' : priority === 2 ? 'replace' : 'expand';

  return {
    groupId,
    displayName,
    groupSize,
    priority,
    showZoomMin: priority === 1 ? null : rule.replaceAtZoom,
    showZoomMax: null,
    replaceAtZoom: rule.replaceAtZoom,
    expandAtZoom: rule.expandAtZoom,
    expandOffsetPx: rule.expandOffsetPx,
    expandAngleDeg: priority === 1 ? 0 : (priority - 2) * rule.angleStepDeg,
    displayMode
  };
};

const buildGroupCandidates = (
  points: Record<string, any>[] = []
): GroupCandidate[] => {
  const candidates: GroupCandidate[] = [];

  points.forEach((point, index) => {
    const lon = toFiniteNumber(point.lgtd);
    const lat = toFiniteNumber(point.lttd);
    if (lon === null || lat === null) {
      clearNearbyPointRuntimeMeta(point);
      return;
    }
    if (Math.abs(lon) > 180 || Math.abs(lat) > 90) {
      clearNearbyPointRuntimeMeta(point);
      return;
    }

    candidates.push({
      index,
      point,
      lon,
      lat,
      layerKey: String(point.layerKey || '')
    });
  });

  return candidates;
};

const buildLayerScopedNearbyGroups = (
  candidates: GroupCandidate[],
  rule: NearbyPointAutoRule
): GroupCandidate[][] => {
  const layerScopedCandidates = new Map<string, GroupCandidate[]>();

  candidates.forEach(candidate => {
    const layerKey = candidate.layerKey || '__empty_layer__';
    const layerItems = layerScopedCandidates.get(layerKey) || [];
    layerItems.push(candidate);
    layerScopedCandidates.set(layerKey, layerItems);
  });

  const result: GroupCandidate[][] = [];

  layerScopedCandidates.forEach(layerItems => {
    const sortedCandidates = [...layerItems].sort(compareGroupCandidates);
    const consumedIndexes = new Set<number>();

    sortedCandidates.forEach((seedCandidate, seedIndex) => {
      if (consumedIndexes.has(seedIndex)) {
        return;
      }

      const groupItems: GroupCandidate[] = [seedCandidate];
      const groupIndexes = [seedIndex];

      for (
        let candidateIndex = seedIndex + 1;
        candidateIndex < sortedCandidates.length;
        candidateIndex += 1
      ) {
        if (consumedIndexes.has(candidateIndex)) {
          continue;
        }

        const currentCandidate = sortedCandidates[candidateIndex];
        const distanceMeters = haversineDistanceMeters(
          seedCandidate.lon,
          seedCandidate.lat,
          currentCandidate.lon,
          currentCandidate.lat
        );

        if (distanceMeters <= rule.distanceThresholdMeters) {
          groupItems.push(currentCandidate);
          groupIndexes.push(candidateIndex);
        }
      }

      if (groupItems.length >= rule.minGroupSize) {
        groupIndexes.forEach(index => consumedIndexes.add(index));
        result.push(groupItems);
      }
    });
  });

  return result;
};

// 备注：统一按空间距离自动识别近邻点组，不按名称或点类型分规则。
export const attachNearbyPointRuntimeMeta = (
  points: Record<string, any>[] = [],
  rule: NearbyPointAutoRule = getNearbyPointAutoRule()
): Record<string, any>[] => {
  if (!Array.isArray(points) || points.length === 0) {
    return [];
  }

  points.forEach(point => clearNearbyPointRuntimeMeta(point));

  const candidates = buildGroupCandidates(points);
  if (candidates.length < rule.minGroupSize) {
    return points;
  }
  const groupedCandidates = buildLayerScopedNearbyGroups(candidates, rule);

  let groupSeed = 0;
  groupedCandidates.forEach(groupItems => {
    if (groupItems.length < rule.minGroupSize) {
      return;
    }

    const sortedItems = [...groupItems].sort(compareGroupCandidates);
    groupSeed += 1;
    const groupId = `nearby-group-${groupSeed}`;

    sortedItems.forEach((candidate, orderIndex) => {
      const priority = orderIndex + 1;
      const runtimeMeta = buildRuntimeMeta(
        groupId,
        sortedItems.length,
        priority,
        getPointDisplayName(candidate.point),
        rule
      );

      candidate.point._nearbyRule = runtimeMeta;
      candidate.point._nearbyGroupId = runtimeMeta.groupId;
      candidate.point._nearbyDisplayName = runtimeMeta.displayName;
      candidate.point._nearbyGroupSize = runtimeMeta.groupSize;
      candidate.point._nearbyPriority = runtimeMeta.priority;
      candidate.point._nearbyShowZoomMin = runtimeMeta.showZoomMin;
      candidate.point._nearbyShowZoomMax = runtimeMeta.showZoomMax;
      candidate.point._nearbyReplaceAtZoom = runtimeMeta.replaceAtZoom;
      candidate.point._nearbyExpandAtZoom = runtimeMeta.expandAtZoom;
      candidate.point._nearbyExpandOffsetPx = runtimeMeta.expandOffsetPx;
      candidate.point._nearbyExpandAngleDeg = runtimeMeta.expandAngleDeg;
      candidate.point._nearbyDisplayMode = runtimeMeta.displayMode;
      candidate.point._nearbyIsPrimary = runtimeMeta.priority === 1;
    });
  });

  return points;
};