#45 差分 API 作成

backend/Gemfile

@@ -57,3 +57,5 @@ gem "image_processing", "~> 1.14"
 gem "nokogiri", "~> 1.18"
 
 gem 'gollum'
+
+gem 'diff-lcs'

backend/Gemfile.lock

@@ -88,6 +88,7 @@ GEM
     connection_pool (2.5.3)
     crass (1.0.6)
     date (3.4.1)
+    diff-lcs (1.6.2)
     dotenv (3.1.8)
     drb (2.2.1)
     ed25519 (1.4.0)
@@ -412,6 +413,7 @@ PLATFORMS
 DEPENDENCIES
   bootsnap
   brakeman
+  diff-lcs
   gollum
   image_processing (~> 1.14)
   jwt

backend/app/controllers/wiki_pages_controller.rb

@@ -7,10 +7,51 @@ class WikiPagesController < ApplicationController
   end
 
   def show_by_title
-    wiki_page = WikiPage.find_by(title: params[:title])
+    title = params[:title]
+    version = params[:version].presence
+
+    wiki_page = WikiPage.find_by(title:)
     return head :not_found unless wiki_page
 
-    render json: wiki_page.as_json.merge(body: wiki_page.body)
+    wiki_page.sha = version
+
+    body = wiki_page.body
+    sha = wiki_page.sha
+    pred = wiki_page.pred
+    succ = wiki_page.succ
+    render json: wiki_page.as_json.merge(body:, sha:, pred:, succ:)
+  end
+
+  def diff
+    id = params[:id]
+    from = params[:from]
+    to = params[:to].presence
+    return head :bad_request if id.blank? || from.blank?
+
+    wiki_page_from = WikiPage.find(id)
+    wiki_page_to = wiki_page_from.clone
+    wiki_page_from.sha = from
+    wiki_page_to.sha = to
+
+    diffs = Diff::LCS.sdiff(wiki_page_from.body, wiki_page_to.body)
+    diff_json = diffs.map { |change|
+        case change.action
+        when ?=
+          { type: 'context', content: change.old_element }
+        when ?|
+          [{ type: 'removed', content: change.old_element },
+           { type: 'added', content: change.new_element }]
+        when ?+
+          { type: 'added', content: change.new_element }
+        when ?-
+          { type: 'removed', content: change.old_element }
+        end }.flatten.compact
+
+    render json: { wiki_page_id:  wiki_page_from.id,
+                   title:         wiki_page_from.title,
+                   older_sha:     wiki_page_from.sha,
+                   newer_sha:     wiki_page_to.sha,
+                   diff:          diff_json }
   end
 
   def create
@@ -57,8 +98,12 @@ class WikiPagesController < ApplicationController
 
     render json: log.map { |commit|
         wiki_page = WikiPage.find(commit.message.split(' ')[1].to_i)
+        wiki_page.sha = commit.id
         user = User.find(commit.author.name.to_i)
-        { sha:          commit.id,
+        { sha:          wiki_page.sha,
+          pred:         wiki_page.pred,
+          succ:         wiki_page.succ,
+
           wiki_page:    wiki_page && { id: wiki_page.id, title: wiki_page.title },
           user:         user && { id: user.id, name: user.name },
           change_type:  commit.message.split(' ')[0].downcase[0...(-1)],

backend/app/models/wiki_page.rb

@@ -8,9 +8,36 @@ class WikiPage < ApplicationRecord
 
   validates :title, presence: true, length: { maximum: 255 }, uniqueness: true
 
+  def sha= val
+    if val.present?
+      @sha = val
+      @page = wiki.page("#{ id }.md", @sha)
+    else
+      @page = wiki.page("#{ id }.md")
+      @sha = @page.versions.first.id
+    end
+    vers = @page.versions
+    idx = vers.find_index { |ver| ver.id == @sha }
+    @pred = vers[idx + 1]&.id
+    @succ = idx.positive? ? vers[idx - 1].id : nil
+    @sha
+  end
+
+  def sha
+    @sha
+  end
+
+  def pred
+    @pred
+  end
+
+  def succ
+    @succ
+  end
+
   def body
-    page = wiki.page("#{ id }.md")
-    page&.raw_data
+    sha = nil unless @page
+    @page&.raw_data&.force_encoding('UTF-8')
   end
 
   def set_body content, user:

backend/config/routes.rb

@@ -7,6 +7,7 @@ Rails.application.routes.draw do
   get 'wiki/title/:title', to: 'wiki_pages#show_by_title'
   get 'wiki/search', to: 'wiki_pages#search'
   get 'wiki/changes', to: 'wiki_pages#changes'
+  get 'wiki/:id/diff', to: 'wiki_pages#diff'
   get 'wiki/:id', to: 'wiki_pages#show'
   post 'wiki', to: 'wiki_pages#create'
   put 'wiki/:id', to: 'wiki_pages#update'