Add ability to handle args in GraphQL resolvers

lib/absinthe_demo/database.ex

@@ -1,30 +1,42 @@
 defmodule AbsintheDemo.Database do
-  import Ecto.Query, only: [from: 2]
+  import Ecto.Query, only: [from: 2, from: 1]
   alias AbsintheDemo.{Author, Post, Category, Repo}
 
-  # Posts
-
-  def all_posts() do
-    Repo.all(Post)
+  def gen_all(query) do
+    query |> Repo.all()
   end
 
+  # Posts
+
   def get_post(id) do
     Repo.get(Post, id)
   end
 
-  def get_posts_of_author(author_id) do
-    from(c in Post, preload: :author, where: c.author_id == ^author_id)
-    |> Repo.all()
+  def query_all_posts(args) do
+    from(p in Post)
+    |> apply_post_args(args)
   end
 
-  def get_posts_of_category(category_id) do
-    from(p in Post,
-      join: pc in "posts_categories",
-      on: pc.category_id == ^category_id and pc.post_id == p.id
-    )
-    |> Repo.all()
+  defp apply_post_args(query, %{author_id: author_id} = args) do
+    query = from(p in query, where: p.author_id == ^author_id)
+
+    apply_post_args(query, Map.delete(args, :author_id))
+  end
+
+  defp apply_post_args(query, %{categories: categories} = args) do
+    query = from(p in query, join: c in assoc(p, :categories), where: c.name in ^categories)
+
+    apply_post_args(query, Map.delete(args, :categories))
   end
 
+  defp apply_post_args(query, %{title: title} = args) do
+    query = from(p in query, where: ilike(p.title, ^"%#{title}%"))
+
+    apply_post_args(query, Map.delete(args, :title))
+  end
+
+  defp apply_post_args(query, %{}), do: query
+
   # Authors
 
   def all_authors() do

lib/absinthe_demo_web/data_source.ex

@@ -1,8 +1,15 @@
 defmodule AbsintheDemo.DataSource do
+  import Ecto.Query, only: [from: 2]
+  alias AbsintheDemo.{Post, Database}
+
   def data() do
     Dataloader.Ecto.new(AbsintheDemo.Repo, query: &query/2)
   end
 
+  def query(Post, params) do
+    Database.query_all_posts(params)
+  end
+
   def query(queryable, _params) do
     queryable
   end

lib/absinthe_demo_web/graphql/resolvers.ex

@@ -1,8 +1,8 @@
 defmodule AbsintheDemoWeb.GraphQL.Resolvers do
   alias AbsintheDemo.Database
 
-  def list_posts(_parent, _args, resolution) do
-    {:ok, Database.all_posts()}
+  def list_posts(_parent, args, resolution) do
+    {:ok, Database.query_all_posts(args) |> Database.gen_all()}
   end
 
   def list_authors(_parent, _args, _resolution) do

lib/absinthe_demo_web/graphql/schema.ex

@@ -20,6 +20,8 @@ defmodule AbsintheDemoWeb.GraphQL.Schema do
   query do
     @desc "Get all posts"
     field :posts, list_of(:post) do
+      arg(:categories, list_of(:string))
+      arg(:title, :string)
       resolve(&Resolvers.list_posts/3)
     end
 

lib/absinthe_demo_web/graphql/typedefs.ex

@@ -12,21 +12,32 @@ defmodule AbsintheDemoWeb.GraphQL.Typedefs do
 
     field :author, :author, resolve: dataloader(:blog_context)
 
-    field :categories, list_of(:category), resolve: dataloader(:blog_context)
+    field :categories, list_of(:category) do
+      # post_id arg is implied
+      resolve(dataloader(:blog_context))
+    end
   end
 
   object :author do
     field :id, :id
     field :name, :string
-    field :profile_picture_link, :string
+    field :profile_pic_link, :string
 
-    field :posts, list_of(:post), resolve: dataloader(:blog_context)
+    field :posts, list_of(:post) do
+      # author_id arg is implied
+      arg(:categories, list_of(:string))
+      resolve(dataloader(:blog_context))
+    end
   end
 
   object :category do
     field :id, :id
     field :name, :string
 
-    field :posts, list_of(:post), resolve: dataloader(:blog_context)
+    field :posts, list_of(:post) do
+      arg(:categories, list_of(:string))
+      arg(:author_id, :id)
+      resolve(dataloader(:blog_context))
+    end
   end
 end