Feat/blog post filter (#250)

lib/pescarte/blog/blog.ex

@@ -0,0 +1,61 @@
+defmodule Pescarte.Blog do
+  @moduledoc """
+  O contexto Blog é responsável por gerenciar as operações relacionadas a postagens e tags.
+  """
+  import Ecto.Query
+  alias Pescarte.Blog.Post
+  alias Pescarte.Database.Repo
+
+  @type filters :: %{
+          optional(:title) => String.t(),
+          optional(:start_date) => NaiveDateTime.t(),
+          optional(:end_date) => NaiveDateTime.t(),
+          optional(:tags) => list(Tag.t()),
+          optional(:page) => non_neg_integer(),
+          optional(:page_size) => pos_integer()
+        }
+
+  @spec list_posts_with_filter(filters()) :: {:ok, list(Post.t())} | {:error, term()}
+  def list_posts_with_filter(filters \\ %{}) do
+    Post
+    |> apply_post_search_filter(filters)
+    |> apply_post_date_filter(filters)
+    |> apply_post_tag_filter(filters)
+    |> apply_order_by()
+    |> apply_pagination(filters)
+    |> Repo.replica().all()
+  end
+
+  defp apply_post_search_filter(query, %{title: search_term}) do
+    from(p in query, where: ilike(p.titulo, ^"%#{search_term}%"))
+  end
+
+  defp apply_post_search_filter(query, _), do: query
+
+  defp apply_post_date_filter(query, %{start_date: start_date, end_date: end_date}) do
+    from p in query, where: p.published_at >= ^start_date and p.published_at <= ^end_date
+  end
+
+  defp apply_post_date_filter(query, _), do: query
+
+  defp apply_post_tag_filter(query, %{tags: tags}) when is_list(tags) do
+    from p in query,
+      join: t in assoc(p, :blog_tags),
+      where: t.nome in ^tags,
+      group_by: p.id,
+      having: count(t.id) == ^length(tags)
+  end
+
+  defp apply_post_tag_filter(query, _), do: query
+
+  defp apply_order_by(query) do
+    from p in query, order_by: [desc: p.published_at]
+  end
+
+  defp apply_pagination(query, %{page: page, page_size: page_size}) do
+    offset = (page - 1) * page_size
+    from p in query, limit: ^page_size, offset: ^offset
+  end
+
+  defp apply_pagination(query, _), do: from(p in query, limit: 10, offset: 0)
+end