"use strict";

const db = require("../db/knex");

let RBushClass = null;
let tree = null;
let dirty = true;
let buildPromise = null;
let generation = 0;

function numberOrNull(value) {
  if (value === null || value === undefined || value === "") {
    return null;
  }

  const n = Number(value);
  return Number.isFinite(n) ? n : null;
}

function makeIndexItem(row) {
  const minLat = numberOrNull(row.min_latitude);
  const maxLat = numberOrNull(row.max_latitude);
  const minLon = numberOrNull(row.min_longitude);
  const maxLon = numberOrNull(row.max_longitude);

  // Usa il bounding box quando tutti e quattro i limiti sono presenti.
  if (
    minLat !== null &&
    maxLat !== null &&
    minLon !== null &&
    maxLon !== null &&
    minLat >= -90 &&
    maxLat <= 90 &&
    minLat <= maxLat &&
    minLon >= -180 &&
    maxLon <= 180 &&
    minLon <= maxLon
  ) {
    return {
      minX: minLon,
      minY: minLat,
      maxX: maxLon,
      maxY: maxLat,
      id: String(row.id),
    };
  }

  // Fallback per attività prive di bounding box completo.
  const lat = numberOrNull(row.center_latitude);
  const lon = numberOrNull(row.center_longitude);

  if (
    lat === null ||
    lon === null ||
    lat < -90 ||
    lat > 90 ||
    lon < -180 ||
    lon > 180
  ) {
    return null;
  }

  return {
    minX: lon,
    minY: lat,
    maxX: lon,
    maxY: lat,
    id: String(row.id),
  };
}

async function loadRBush() {
  if (!RBushClass) {
    const module = await import("rbush");
    RBushClass = module.default;
  }

  return RBushClass;
}

async function ensureIndex() {
  if (!dirty && tree) {
    return tree;
  }

  if (buildPromise) {
    await buildPromise;

    if (!dirty && tree) {
      return tree;
    }
  }

  const buildGeneration = generation;

  buildPromise = (async () => {
    const RBush = await loadRBush();

    const rows = await db("activities").select(
      "id",
      "min_latitude",
      "max_latitude",
      "min_longitude",
      "max_longitude",
      "center_latitude",
      "center_longitude"
    );

    const items = [];

    for (const row of rows) {
      const item = makeIndexItem(row);
      if (item) items.push(item);
    }

    const nextTree = new RBush();
    nextTree.load(items);

    // Non pubblicare un indice costruito mentre era in corso
    // un'invalidazione dovuta a una modifica dei dati.
    if (buildGeneration === generation) {
      tree = nextTree;
      dirty = false;
    }
  })();

  try {
    await buildPromise;
  } finally {
    buildPromise = null;
  }

  if (dirty || !tree) {
    return ensureIndex();
  }

  return tree;
}

function invalidateActivitySpatialIndex() {
  generation += 1;
  dirty = true;
}

function searchBoxes(treeInstance, west, east, south, north) {
  const boxes =
    west <= east
      ? [{ minX: west, maxX: east, minY: south, maxY: north }]
      : [
          { minX: west, maxX: 180, minY: south, maxY: north },
          { minX: -180, maxX: east, minY: south, maxY: north },
        ];

  const found = new Map();

  for (const box of boxes) {
    for (const item of treeInstance.search(box)) {
      found.set(item.id, item);
    }
  }

  return [...found.keys()];
}

async function searchActivitiesInBounds({
  west,
  east,
  south,
  north,
  readableSources,
  includeDeleted = false,
  limit = 1500,
}) {
  const index = await ensureIndex();

  const ids = searchBoxes(index, west, east, south, north);

  if (!ids.length || !readableSources.length) {
    return { items: [], truncated: false };
  }

  const rowsById = new Map();
  const batchSize = 400;

  // Blocchi piccoli per evitare di superare il limite dei parametri SQLite.
  for (let i = 0; i < ids.length; i += batchSize) {
    const batch = ids.slice(i, i + batchSize);

    let query = db("activities")
      .whereIn("id", batch)
      .whereIn("user", readableSources);

    if (!includeDeleted) {
      query = query.whereNull("deleted_at");
    }

    const rows = await query.select("*");

    for (const row of rows) {
      rowsById.set(String(row.id), row);
    }
  }

  // Mantiene un ordine deterministico rispetto ai candidati RBush.
  const matching = [];

  for (const id of ids) {
    const row = rowsById.get(id);

    if (row) {
      matching.push(row);

      if (matching.length > limit) {
        break;
      }
    }
  }

  return {
    items: matching.slice(0, limit),
    truncated: matching.length > limit,
  };
}

module.exports = {
  searchActivitiesInBounds,
  invalidateActivitySpatialIndex,
};