import type { Tins, Tri } from "@maplat/transform";
import type { PropertyTriKey } from "@maplat/transform";

type BiDirectionKey = "forw" | "bakw";
type TinsBD = { [key in BiDirectionKey]?: Tins };
export type SearchTris = { [key in BiDirectionKey]: Tri };
export type SearchIndex = { [key: string]: SearchTris[] };

/**
 * 三角形のインデックスキーを計算する
 * 三つの頂点のインデックスから、ソートされたキー配列を生成
 *
 * @param tri インデックスキーを計算する三角形
 * @returns ソートされたキー配列
 */
function calcSearchKeys(tri: Tri): string[] {
  const vtx = (["a", "b", "c"] as PropertyTriKey[]).map(
    (key) => tri.properties![key].index,
  );
  return [
    [0, 1],
    [0, 2],
    [1, 2],
    [0, 1, 2],
  ]
    .map((set) =>
      set
        .map((i) => vtx[i])
        .sort()
        .join("-")
    )
    .sort();
}

/**
 * 検索インデックスに三角形を追加する
 *
 * @param searchIndex 検索インデックス
 * @param tris 追加する三角形ペア
 * @param tins （オプション）追加先の三角形群
 * @throws キーの不一致エラー
 */
function insertSearchIndex(
  searchIndex: SearchIndex,
  tris: SearchTris,
  tins?: TinsBD,
) {
  const keys = calcSearchKeys(tris.forw);
  const bakKeys = calcSearchKeys(tris.bakw);
  if (JSON.stringify(keys) != JSON.stringify(bakKeys)) {
    throw `${JSON.stringify(tris, null, 2)}\n${
      JSON.stringify(
        keys,
      )
    }\n${JSON.stringify(bakKeys)}`;
  }
  for (let i = 0; i < keys.length; i++) {
    const key = keys[i];
    if (!searchIndex[key]) searchIndex[key] = [];
    searchIndex[key].push(tris);
  }
  if (tins) {
    tins.forw!.features.push(tris.forw);
    tins.bakw!.features.push(tris.bakw);
  }
}

function removeSearchIndex(
  searchIndex: SearchIndex,
  tris: SearchTris,
  tins?: TinsBD,
) {
  const keys = calcSearchKeys(tris.forw);
  const bakKeys = calcSearchKeys(tris.bakw);
  if (JSON.stringify(keys) != JSON.stringify(bakKeys)) {
    throw `${JSON.stringify(tris, null, 2)}\n${JSON.stringify(keys)}\n${
      JSON.stringify(bakKeys)
    }`;
  }

  keys.forEach((key) => {
    const current = searchIndex[key];
    if (!current) return;
    const filtered = current.filter((item) => item !== tris);
    if (filtered.length === 0) {
      delete searchIndex[key];
    } else {
      searchIndex[key] = filtered;
    }
  });

  if (tins) {
    const removeFeature = (collection?: Tins, target?: Tri) => {
      if (!collection || !target) return;
      collection.features = collection.features.filter((tri) => tri !== target);
    };
    removeFeature(tins.forw, tris.forw);
    removeFeature(tins.bakw, tris.bakw);
  }
}

export { calcSearchKeys, insertSearchIndex, removeSearchIndex };