feat: Add get_record!/1,2

Author: jrogov

lib/file_cache.ex

@@ -137,6 +137,16 @@ defmodule FileCache do
     do_get!(validate_id!(id), validate_op_options!(opts))
   end
 
+  @doc """
+  Works as `get!/2`, but returns all data about cache file: path, expiration, etc.
+
+  Useful when it's required to set HTTP's Cache-Control header
+  or work with cache file manually (e.g. pass its path to external program)
+  """
+  def get_record!(id, opts \\ []) do
+    do_get_record!(validate_id!(id), validate_op_options!(opts))
+  end
+
   def exists?(id, opts) do
     id
     |> validate_id!()
@@ -186,9 +196,20 @@ defmodule FileCache do
   end
 
   defp do_get!(id, opts) do
-    case Perm.find(id, opts[:cache], opts) do
-      nil -> nil
-      path -> File.stream!(path)
+    with result when is_map(result) <- Perm.find(id, opts[:cache], opts) do
+      File.stream!(result.path)
+    end
+  end
+
+  def do_get_record!(id, opts) do
+    with result when is_map(result) <- Perm.find(id, opts[:cache], opts) do
+      %FileCache.Record{
+        id: result.id,
+        path: result.path,
+        expires_at: result.expires_at,
+        ttl: result.expires_at - Utils.system_time(),
+        stream: File.stream!(result.path)
+      }
     end
   end
 

lib/file_cache/perm.ex

@@ -25,8 +25,7 @@ defmodule FileCache.Perm do
     #
     # So for the time being, we are finding (and cleaning) *all* files with the suffix of `id`
 
-    result = find_all(id, cache_name, opts)[id]
-    result && result[:path]
+    find_all(id, cache_name, opts)[id]
   end
 
   def find_all(cache_name), do: find_all(cache_name, [])
@@ -40,9 +39,7 @@ defmodule FileCache.Perm do
     now = Utils.system_time()
     {sync_clean?, _opts} = Keyword.pop(opts, :sync_clean, false)
 
-    cache_name
-    |> wildcard(id)
-    |> Enum.reduce(%{}, fn path, acc ->
+    reduce_all(id, cache_name, %{}, fn path, acc ->
       with {:ok, this} <- parse_filepath(path, cache_name) do
         exp = this.expires_at
         last = Map.get(acc, this.id)
@@ -67,6 +64,12 @@ defmodule FileCache.Perm do
     end)
   end
 
+  def reduce_all(id, cache_name, acc, fun) do
+    cache_name
+    |> wildcard(id)
+    |> Enum.reduce(acc, fun)
+  end
+
   def delete(id, cache_name, _opts) do
     cache_name
     |> wildcard(id)

lib/file_cache/record.ex

@@ -0,0 +1,8 @@
+defmodule FileCache.Record do
+  @moduledoc """
+  Structure for FileCache record with cache id, content file's path, expiration timestamp, time-to-live and file stream,
+  as returned by common FileCache operations
+  """
+
+  defstruct [:id, :path, :expires_at, :ttl, :stream]
+end

test/file_cache_test.exs

@@ -117,6 +117,40 @@ defmodule FileCacheTest do
     end
   end
 
+  describe "get_record!" do
+    setup do
+      setup_cache(ttl: 60_000)
+    end
+
+    test "returns nil for missing key", c do
+      assert nil == FileCache.get_record!("not_exist", opts(c))
+    end
+
+    test "get complete record about cache file", c do
+      data = 1..10
+
+      start_timestamp = FileCache.Utils.system_time()
+      assert binary(data) == read!(FileCache.put!(binary(data), @key, opts(c)))
+
+      assert %FileCache.Record{
+               id: id,
+               path: path,
+               stream: stream,
+               expires_at: expires_at,
+               ttl: ttl
+             } = FileCache.get_record!(@key, opts(c))
+
+      assert @key == id
+      assert binary(data) == read!(stream)
+      assert binary(data) == read!(File.stream!(path))
+
+      assert 59_000 <= ttl and ttl < 61_000
+
+      test_ttl = expires_at - start_timestamp
+      assert 59_000 <= test_ttl and test_ttl < 61_000
+    end
+  end
+
   describe "execute!" do
     setup do
       setup_cache()