1 files changed, 91 insertions, 0 deletions

diff --git a/src/util/pagenation.ts b/src/util/pagenation.ts
new file mode 100644
index 0000000..15ee01b
--- /dev/null
+++ b/src/util/pagenation.ts
@@ -0,0 +1,91 @@
+export type PagenationProp = {
+  now: number,
+  max: number,
+  between: number,
+}
+export function createPagenation(prop: PagenationProp) {
+  if (prop.between < 0) {
+    throw new Error(`betweenは0以上にして下さい`);
+  }
+  if (prop.max < 0) {
+    throw new Error(`maxは0以上にして下さい`);
+  }
+  if (prop.now < 0) {
+    throw new Error(`nowは0以上にして下さい`);
+  }
+  if (prop.max < prop.now) {
+    throw new Error(`nowの値はmaxと同じか、より小さな値にして下さい. now:${prop.now} , max:${prop.max}`);
+  }
+  if (prop.max == 0) {
+    return [];
+  }
+  const MIN = 1;
+  // 左・中・右の3ブロックの変数を作成
+  const blockLeft = MIN;
+  let blockMiddle = [
+    ...Array.from({ length: prop.between }).map((_, index) => {
+      const i = prop.now - prop.between + index;
+      return i;
+    }),
+    prop.now,
+    ...Array.from({ length: prop.between }).map((_, index) => {
+      const i = prop.now + index + 1;
+      return i;
+    }),
+  ];
+  blockMiddle = blockMiddle.filter(i => {
+    if (i <= blockLeft) {
+      return false;
+    }
+    if (prop.max <= i) {
+      return false;
+    }
+    return true;
+  });
+  const blockRight = prop.max;
+  type A = { type: "back", key: string, link: number | null };
+  type B = { type: "next", key: string, link: number | null };
+  type C = { type: "sp", key: string, };
+  type D = { type: "num", key: string, link: number | null, num: number }
+  // 結合を作成
+  const pageIdList: (A | B | C | D)[] = [];
+  {
+    // 左戻る矢印
+    if (prop.now == MIN) {
+      pageIdList.push({ type: "back", key: "back", link: null });
+    } else {
+      pageIdList.push({ type: "back", key: "back", link: prop.now - 1 });
+    }
+    // 最初のページ
+    pageIdList.push({ type: "num", key: `p-${blockLeft}`, link: blockLeft, num: blockLeft });
+    let lastPageId = blockLeft;
+    // 左と中の間の…を入れるかどうか
+    if (0 < blockMiddle.length && lastPageId + 1 != blockMiddle[0]) {
+      pageIdList.push({ type: "sp", key: "sp-left" });
+    }
+    blockMiddle.forEach(m => {
+      pageIdList.push({ type: "num", key: `p-${m}`, link: m, num: m });
+      lastPageId = m;
+    });
+    if (0 < blockMiddle.length && lastPageId + 1 != blockRight) {
+      // 最後のページ
+      pageIdList.push({ type: "sp", key: "sp-right" });
+    }
+    if (lastPageId != blockRight) {
+      pageIdList.push({ type: "num", key: `p-${blockRight}`, link: blockRight, num: blockRight });
+      lastPageId = blockRight;
+    }
+    // 右矢印
+    if (prop.now == prop.max) {
+      pageIdList.push({ type: "next", key: "next", link: null });
+    } else {
+      pageIdList.push({ type: "next", key: "next", link: prop.now + 1 });
+    }
+    pageIdList.forEach(p => {
+      if ("link" in p && p.link == prop.now) {
+        p.link = null;
+      }
+    })
+  }
+  return pageIdList
+}
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