feat: adds field visibility dropdown live component

lib/mv_web/live/member_live/index/field_selection.ex

@@ -0,0 +1,232 @@
+defmodule MvWeb.MemberLive.Index.FieldSelection do
+  @moduledoc """
+  Handles user-specific field selection persistence and URL parameter parsing.
+
+  This module manages:
+  - Reading/writing field selection from cookies (persistent storage)
+  - Reading/writing field selection from session (temporary storage)
+  - Parsing field selection from URL parameters
+  - Merging multiple sources with priority: URL > Session > Cookie
+
+  ## Data Format
+
+  Field selection is stored as a map:
+  ```elixir
+  %{
+    "first_name" => true,
+    "email" => true,
+    "street" => false,
+    "custom_field_abc-123" => true
+  }
+  ```
+
+  ## Cookie/Session Format
+
+  Stored as JSON string: `{"first_name":true,"email":true}`
+
+  ## URL Format
+
+  Comma-separated list: `?fields=first_name,email,custom_field_abc-123`
+  """
+
+  @cookie_name "member_field_selection"
+  @cookie_max_age 365 * 24 * 60 * 60
+  @session_key "member_field_selection"
+
+  @doc """
+  Reads field selection from session.
+
+  Returns a map of field names (strings) to boolean visibility values.
+  Returns empty map if no selection is stored.
+  """
+  @spec get_from_session(map()) :: %{String.t() => boolean()}
+  def get_from_session(session) when is_map(session) do
+    case Map.get(session, @session_key) do
+      nil -> %{}
+      json_string when is_binary(json_string) -> parse_json(json_string)
+      _ -> %{}
+    end
+  end
+
+  def get_from_session(_), do: %{}
+
+  @doc """
+  Saves field selection to session.
+
+  Converts the map to JSON string and stores it in the session.
+  """
+  @spec save_to_session(map(), %{String.t() => boolean()}) :: map()
+  def save_to_session(session, selection) when is_map(selection) do
+    json_string = Jason.encode!(selection)
+    Map.put(session, @session_key, json_string)
+  end
+
+  def save_to_session(session, _), do: session
+
+  @doc """
+  Reads field selection from cookie.
+
+  Returns a map of field names (strings) to boolean visibility values.
+  Returns empty map if no cookie is present.
+
+  Note: This function requires the connection to have cookies parsed.
+  In LiveView, cookies are typically accessed via get_connect_info.
+  """
+  @spec get_from_cookie(Plug.Conn.t()) :: %{String.t() => boolean()}
+  def get_from_cookie(conn) do
+    case Plug.Conn.get_req_header(conn, "cookie") do
+      nil ->
+        %{}
+
+      cookie_header ->
+        # Parse cookies manually from header
+        cookies = parse_cookie_header(cookie_header)
+
+        case Map.get(cookies, @cookie_name) do
+          nil -> %{}
+          json_string when is_binary(json_string) -> parse_json(json_string)
+          _ -> %{}
+        end
+    end
+  end
+
+  # Parses cookie header string into a map
+  defp parse_cookie_header(cookie_header) when is_binary(cookie_header) do
+    cookie_header
+    |> String.split(";")
+    |> Enum.map(&String.trim/1)
+    |> Enum.map(&String.split(&1, "=", parts: 2))
+    |> Enum.reduce(%{}, fn
+      [key, value], acc -> Map.put(acc, key, URI.decode(value))
+      [key], acc -> Map.put(acc, key, "")
+      _, acc -> acc
+    end)
+  end
+
+  defp parse_cookie_header(_), do: %{}
+
+  @doc """
+  Saves field selection to cookie.
+
+  Sets a persistent cookie with the field selection as JSON.
+  """
+  @spec save_to_cookie(Plug.Conn.t(), %{String.t() => boolean()}) :: Plug.Conn.t()
+  def save_to_cookie(conn, selection) when is_map(selection) do
+    json_string = Jason.encode!(selection)
+    secure = Application.get_env(:mv, :use_secure_cookies, false)
+
+    Plug.Conn.put_resp_cookie(conn, @cookie_name, json_string,
+      max_age: @cookie_max_age,
+      same_site: "Lax",
+      http_only: true,
+      secure: secure
+    )
+  end
+
+  def save_to_cookie(conn, _), do: conn
+
+  @doc """
+  Parses field selection from URL parameters.
+
+  Expects a comma-separated list of field names in the `fields` parameter.
+  All fields in the list are set to `true` (visible).
+
+  ## Examples
+
+      iex> parse_from_url(%{"fields" => "first_name,email"})
+      %{"first_name" => true, "email" => true}
+
+      iex> parse_from_url(%{"fields" => "custom_field_abc-123"})
+      %{"custom_field_abc-123" => true}
+
+      iex> parse_from_url(%{})
+      %{}
+  """
+  @spec parse_from_url(map()) :: %{String.t() => boolean()}
+  def parse_from_url(params) when is_map(params) do
+    case Map.get(params, "fields") do
+      nil -> %{}
+      "" -> %{}
+      fields_string when is_binary(fields_string) -> parse_fields_string(fields_string)
+      _ -> %{}
+    end
+  end
+
+  def parse_from_url(_), do: %{}
+
+  @doc """
+  Merges multiple field selection sources with priority.
+
+  Priority order (highest to lowest):
+  1. URL parameters
+  2. Session
+  3. Cookie
+
+  Later sources override earlier ones for the same field.
+
+  ## Examples
+
+      iex> merge_sources(%{"first_name" => true}, %{"email" => true}, %{"street" => true})
+      %{"first_name" => true, "email" => true, "street" => true}
+
+      iex> merge_sources(%{"first_name" => false}, %{"first_name" => true}, %{})
+      %{"first_name" => false}  # URL has priority
+  """
+  @spec merge_sources(
+          %{String.t() => boolean()},
+          %{String.t() => boolean()},
+          %{String.t() => boolean()}
+        ) :: %{String.t() => boolean()}
+  def merge_sources(url_selection, session_selection, cookie_selection) do
+    %{}
+    |> Map.merge(cookie_selection)
+    |> Map.merge(session_selection)
+    |> Map.merge(url_selection)
+  end
+
+  @doc """
+  Converts field selection map to URL parameter string.
+
+  Returns a comma-separated string of visible fields (where value is `true`).
+
+  ## Examples
+
+      iex> to_url_param(%{"first_name" => true, "email" => true, "street" => false})
+      "first_name,email"
+  """
+  @spec to_url_param(%{String.t() => boolean()}) :: String.t()
+  def to_url_param(selection) when is_map(selection) do
+    selection
+    |> Enum.filter(fn {_field, visible} -> visible end)
+    |> Enum.map(fn {field, _visible} -> field end)
+    |> Enum.join(",")
+  end
+
+  def to_url_param(_), do: ""
+
+  # Parses a JSON string into a map, handling errors gracefully
+  defp parse_json(json_string) when is_binary(json_string) do
+    case Jason.decode(json_string) do
+      {:ok, decoded} when is_map(decoded) ->
+        # Ensure all values are booleans
+        Enum.reduce(decoded, %{}, fn
+          {key, value} when is_boolean(value) -> {key, value}
+          {key, _value} -> {key, true}
+        end)
+
+      _ ->
+        %{}
+    end
+  end
+
+  defp parse_json(_), do: %{}
+
+  # Parses a comma-separated string of field names
+  defp parse_fields_string(fields_string) do
+    fields_string
+    |> String.split(",")
+    |> Enum.map(&String.trim/1)
+    |> Enum.filter(&(&1 != ""))
+    |> Enum.reduce(%{}, fn field, acc -> Map.put(acc, field, true) end)
+  end
+end