backend/app/controllers/posts_controller.rb

@@ -8,8 +8,11 @@ class PostsController < ApplicationController
     limit = params[:limit].presence&.to_i
     cursor = params[:cursor].presence
 
-    q = filtered_posts.order(created_at: :desc)
-    q = q.where('posts.created_at < ?', Time.iso8601(cursor)) if cursor
+    created_at = ('COALESCE(posts.original_created_before - INTERVAL 1 SECOND,' +
+                  'posts.original_created_from,' +
+                  'posts.created_at)')
+    q = filtered_posts.order(Arel.sql("#{ created_at } DESC"))
+    q = q.where("#{ created_at } < ?", Time.iso8601(cursor)) if cursor
 
     posts = limit ? q.limit(limit + 1) : q
 
@@ -20,14 +23,14 @@ class PostsController < ApplicationController
     end
 
     render json: { posts: posts.map { |post|
-      post.as_json(include: { tags: { only: [:id, :name, :category, :post_count] } }).tap { |json|
+      post.as_json(include: { tags: { only: [:id, :name, :category, :post_count] } }).tap do |json|
         json['thumbnail'] =
             if post.thumbnail.attached?
               rails_storage_proxy_url(post.thumbnail, only_path: false)
             else
               nil
             end
-      }
+      end
     }, next_cursor: }
   end
 
@@ -39,7 +42,7 @@ class PostsController < ApplicationController
 
     render json: (post
                   .as_json(include: { tags: { only: [:id, :name, :category, :post_count] } })
-                  .merge(viewed: viewed))
+                  .merge(viewed:))
   end
 
   # GET /posts/1
@@ -60,14 +63,17 @@ class PostsController < ApplicationController
     return head :forbidden unless current_user.member?
 
     # TODO: URL が正規のものがチェック，不正ならエラー
-    # TODO: title、URL は必須にする．
+    # TODO: URL は必須にする（タイトルは省略可）．
     # TODO: サイトに応じて thumbnail_base 設定
     title = params[:title]
     url = params[:url]
     thumbnail = params[:thumbnail]
     tag_names = params[:tags].to_s.split(' ')
+    original_created_from = params[:original_created_from]
+    original_created_before = params[:original_created_before]
 
-    post = Post.new(title:, url:, thumbnail_base: '', uploaded_user: current_user)
+    post = Post.new(title:, url:, thumbnail_base: '', uploaded_user: current_user,
+                    original_created_from:, original_created_before:)
     post.thumbnail.attach(thumbnail)
     if post.save
       post.resized_thumbnail!
@@ -100,10 +106,12 @@ class PostsController < ApplicationController
 
     title = params[:title]
     tag_names = params[:tags].to_s.split(' ')
+    original_created_from = params[:original_created_from]
+    original_created_before = params[:original_created_before]
 
     post = Post.find(params[:id].to_i)
     tags = post.tags.where(category: 'nico').to_a + Tag.normalise_tags(tag_names)
-    if post.update(title:, tags:)
+    if post.update(title:, tags:, original_created_from:, original_created_before:)
       render json: post.as_json(include: { tags: { only: [:id, :name, :category, :post_count] } }),
              status: :ok
     else

backend/app/models/post.rb

@@ -15,6 +15,8 @@ class Post < ApplicationRecord
            foreign_key: :target_post_id
   has_one_attached :thumbnail
 
+  validate :validate_original_created_range
+
   def as_json options = { }
     super(options).merge({ thumbnail: thumbnail.attached? ?
                                       Rails.application.routes.url_helpers.rails_blob_url(
@@ -49,4 +51,20 @@ class Post < ApplicationRecord
                      filename:      'resized_thumbnail.jpg',
                      content_type:  'image/jpeg')
   end
+
+  private
+
+  def validate_original_created_range
+    f = original_created_from
+    b = original_created_before
+    return if f.blank? || b.blank?
+
+    f = Time.zone.parse(f) if String === f
+    b = Time.zone.parse(b) if String === b
+    return if !(f) || !(b)
+
+    if f >= b
+      errors.add :original_created_before, 'オリジナルの作成日時の順番がをかしぃです．'
+    end
+  end
 end

backend/db/migrate/20250909075500_add_original_created_at_to_posts.rb

@@ -0,0 +1,6 @@
+class AddOriginalCreatedAtToPosts < ActiveRecord::Migration[8.0]
+  def change
+    add_column :posts, :original_created_from, :datetime, after: :created_at
+    add_column :posts, :original_created_before, :datetime, after: :original_created_from
+  end
+end

backend/db/schema.rb

@@ -10,7 +10,7 @@
 #
 # It's strongly recommended that you check this file into your version control system.
 
-ActiveRecord::Schema[8.0].define(version: 2025_07_29_210600) do
+ActiveRecord::Schema[8.0].define(version: 2025_09_09_075500) do
   create_table "active_storage_attachments", charset: "utf8mb4", collation: "utf8mb4_0900_ai_ci", force: :cascade do |t|
     t.string "name", null: false
     t.string "record_type", null: false
@@ -83,6 +83,8 @@ ActiveRecord::Schema[8.0].define(version: 2025_07_29_210600) do
     t.bigint "parent_id"
     t.bigint "uploaded_user_id"
     t.datetime "created_at", null: false
+    t.datetime "original_created_from"
+    t.datetime "original_created_before"
     t.datetime "updated_at", null: false
     t.index ["parent_id"], name: "index_posts_on_parent_id"
     t.index ["uploaded_user_id"], name: "index_posts_on_uploaded_user_id"

frontend/src/components/PostEditForm.tsx

@@ -3,6 +3,7 @@ import toCamel from 'camelcase-keys'
 import { useState } from 'react'
 
 import PostFormTagsArea from '@/components/PostFormTagsArea'
+import DateTimeField from '@/components/common/DateTimeField'
 import Label from '@/components/common/Label'
 import { Button } from '@/components/ui/button'
 import { API_BASE_URL } from '@/config'
@@ -16,6 +17,10 @@ type Props = { post:    Post
 
 
 export default (({ post, onSave }: Props) => {
+  const [originalCreatedBefore, setOriginalCreatedBefore] =
+      useState<string | null> (post.originalCreatedBefore)
+  const [originalCreatedFrom, setOriginalCreatedFrom] =
+      useState<string | null> (post.originalCreatedFrom)
   const [title, setTitle] = useState (post.title)
   const [tags, setTags] = useState<string> (post.tags
 					    .filter (t => t.category !== 'nico')
@@ -23,13 +28,19 @@ export default (({ post, onSave }: Props) => {
 					    .join (' '))
 
   const handleSubmit = async () => {
-    const res = await axios.put (`${ API_BASE_URL }/posts/${ post.id }`, { title, tags },
+    const res = await axios.put (
+	`${ API_BASE_URL }/posts/${ post.id }`,
+	{ title, tags,
+	  original_created_from: originalCreatedFrom,
+	  original_created_before: originalCreatedBefore },
 	{ headers: { 'Content-Type':     'multipart/form-data',
 		     'X-Transfer-Code':  localStorage.getItem ('user_code') ?? '' } })
     const data = toCamel (res.data as any, { deep: true }) as Post
     onSave ({ ...post,
 	      title:                  data.title,
-	      tags:   data.tags } as Post)
+	      tags:                   data.tags,
+	      originalCreatedFrom:    data.originalCreatedFrom,
+	      originalCreatedBefore:  data.originalCreatedBefore } as Post)
   }
 
   return (
@@ -40,12 +51,29 @@ export default (({ post, onSave }: Props) => {
 	  <input type="text"
 		 className="w-full border rounded p-2"
 		 value={title}
-		 onChange={e => setTitle (e.target.value)}/>
+		 onChange={ev => setTitle (ev.target.value)}/>
 	</div>
 
 	{/* タグ */}
 	<PostFormTagsArea tags={tags} setTags={setTags}/>
 
+	{/* オリジナルの作成日時 */}
+	<div>
+	  <Label>オリジナルの作成日時</Label>
+	  <div className="my-1">
+	    <DateTimeField
+		value={originalCreatedFrom ?? undefined}
+		onChange={setOriginalCreatedFrom}/>
+	    以降
+	  </div>
+	  <div className="my-1">
+	    <DateTimeField
+		value={originalCreatedBefore ?? undefined}
+		onChange={setOriginalCreatedBefore}/>
+	    より前
+	  </div>
+	</div>
+
 	{/* 送信 */}
 	<Button onClick={handleSubmit}
 		className="px-4 py-2 bg-blue-600 text-white rounded disabled:bg-gray-400">

frontend/src/components/common/DateTimeField.tsx

@@ -0,0 +1,43 @@
+import { useEffect, useState } from 'react'
+
+import type { FC } from 'react'
+
+
+const pad = (n: number) => n.toString ().padStart (2, '0')
+
+
+const toDateTimeLocalValue = (d: Date) => {
+  const y = d.getFullYear ()
+  const m = pad (d.getMonth () + 1)
+  const day = pad (d.getDate ())
+  const h = pad (d.getHours ())
+  const min = pad (d.getMinutes ())
+  const s = pad (d.getSeconds ())
+  return `${ y }-${ m }-${ day }T${ h }:${ min }:${ s }`
+}
+
+
+type Props = {
+    value?:     string
+    onChange?:  (isoUTC: string | null) => void }
+
+
+export default (({ value, onChange }: Props) => {
+  const [local, setLocal] = useState ('')
+
+  useEffect (() => {
+    setLocal (value ? toDateTimeLocalValue (new Date (value)) : '')
+  }, [value])
+
+  return (
+      <input
+	  className="border rounded p-2"
+	  type="datetime-local"
+	  step={1}
+	  value={local}
+	  onChange={ev => {
+	    const v = ev.target.value
+	    setLocal (v)
+	    onChange?.(v ? (new Date (v)).toISOString () : null)
+	  }}/>)
+}) satisfies FC<Props>

frontend/src/pages/posts/PostNewPage.tsx

@@ -4,6 +4,7 @@ import { Helmet } from 'react-helmet-async'
 import { useNavigate } from 'react-router-dom'
 
 import PostFormTagsArea from '@/components/PostFormTagsArea'
+import DateTimeField from '@/components/common/DateTimeField'
 import Form from '@/components/common/Form'
 import Label from '@/components/common/Label'
 import PageTitle from '@/components/common/PageTitle'
@@ -26,15 +27,17 @@ export default (({ user }: Props) => {
 
   const navigate = useNavigate ()
 
+  const [originalCreatedBefore, setOriginalCreatedBefore] = useState<string | null> (null)
+  const [originalCreatedFrom, setOriginalCreatedFrom] = useState<string | null> (null)
+  const [tags, setTags] = useState ('')
+  const [thumbnailAutoFlg, setThumbnailAutoFlg] = useState (true)
+  const [thumbnailFile, setThumbnailFile] = useState<File | null> (null)
+  const [thumbnailLoading, setThumbnailLoading] = useState (false)
+  const [thumbnailPreview, setThumbnailPreview] = useState<string> ('')
   const [title, setTitle] = useState ('')
   const [titleAutoFlg, setTitleAutoFlg] = useState (true)
   const [titleLoading, setTitleLoading] = useState (false)
   const [url, setURL] = useState ('')
-  const [thumbnailFile, setThumbnailFile] = useState<File | null> (null)
-  const [thumbnailPreview, setThumbnailPreview] = useState<string> ('')
-  const [thumbnailAutoFlg, setThumbnailAutoFlg] = useState (true)
-  const [thumbnailLoading, setThumbnailLoading] = useState (false)
-  const [tags, setTags] = useState ('')
 
   const previousURLRef = useRef ('')
 
@@ -45,6 +48,10 @@ export default (({ user }: Props) => {
     formData.append ('tags', tags)
     if (thumbnailFile)
       formData.append ('thumbnail', thumbnailFile)
+    if (originalCreatedFrom)
+      formData.append ('original_created_from', originalCreatedFrom)
+    if (originalCreatedBefore)
+      formData.append ('original_created_before', originalCreatedBefore)
 
     try
     {
@@ -122,7 +129,7 @@ export default (({ user }: Props) => {
 	  {/* URL */}
 	  <div>
 	    <Label>URL</Label>
-	    <input type="text"
+	    <input type="url"
 		   placeholder="例：https://www.nicovideo.jp/watch/..."
 		   value={url}
 		   onChange={e => setURL (e.target.value)}
@@ -181,6 +188,23 @@ export default (({ user }: Props) => {
 	  {/* タグ */}
 	  <PostFormTagsArea tags={tags} setTags={setTags}/>
 
+	  {/* オリジナルの作成日時 */}
+	  <div>
+	    <Label>オリジナルの作成日時</Label>
+	    <div className="my-1">
+	      <DateTimeField
+		  value={originalCreatedFrom ?? undefined}
+		  onChange={setOriginalCreatedFrom}/>
+	      以降
+	    </div>
+	    <div className="my-1">
+	      <DateTimeField
+		  value={originalCreatedBefore ?? undefined}
+		  onChange={setOriginalCreatedBefore}/>
+	      より前
+	    </div>
+	  </div>
+
 	  {/* 送信 */}
 	  <Button onClick={handleSubmit}
 		  className="px-4 py-2 bg-blue-600 text-white rounded disabled:bg-gray-400"

frontend/src/types.ts

@@ -24,7 +24,10 @@ export type Post = {
     thumbnailBase:          string
     tags:                   Tag[]
     viewed:                 boolean
-    related:        Post[] }
+    related:                Post[]
+    createdAt:              string
+    originalCreatedFrom:    string | null
+    originalCreatedBefore:  string | null }
 
 export type SubMenuItem = {
     component:  React.ReactNode