defmodule Phx.Live.Head do
@moduledoc """
Provides commands for manipulating the HTML Head of Phoenix Live View applications
while minimizing data over the wire.
The available command actions support a variety of utility operations useful for
HTML Head manipulation. Such as setting or removing tag attributes and
adding or removing CSS classes for vector (SVG) favicons.
> #### Note {: .info}
> This lib is not meant to be used directly. Have a look at `Phx.Live.Favicon`
> and `Phx.Live.Metadata`. Those libs provide a cleaner syntax and specific
> documentation for their intended usage.
## Query
The query is used by the the Javascript client to select HTML elements
using `document.querySelectorAll(query)`.
## Actions
### Nodes / Elements
* `snap` - Takes a snapshot of all selected nodes.
* `restore` - Restores a saved snapshot.
* `dynamic` - Set the value of a `{placeholder}`.
### Attributes
The actions are applied to an attribute in all selected HTML elements.
Supported actions on the "class" attribute:
* `set` - Set class name(s).
* `add` - Add to list of class names.
* `remove` - Remove from list of class names.
* `toggle` - Toggle class name.
* `initial` - Reset attribute to it's intial value.
Supported actions on other attributes:
* `set` - Set value of attribute.
* `initial` - Reset attribute to it's intial value.
* `snap` - Take a snapshot of all selected nodes.
* `restore` - Restore attributes using a saved snapshot
## Dynamic attributes / placeholders
To use a dynamic value for an attribute, the element must have an additional
`data-dynamic-[attribute]` attribute with a value containing a named
placeholder. For example: `{sub}`.
**Example**
```html
<!-- data-dynamic-href is set -->
<!-- {sub} is used in it's value -->
<link rel='icon' href="default_fav.png" data-dynamic-href="favs/{sub}/fav-16x16.png">
```
When an event is pushed with `target = "link[rel*=icon]"`, `action = :dynamic`, `attr = "sub"`, and
`value = "new_message"` the result will look like:
```html
<link rel='icon' href="favs/new_message/fav-16x16.png" [...]>
```
"""
import Phoenix.LiveView, only: [push_event: 3]
alias Phoenix.LiveView.Socket
alias Phoenix.LiveView.Utils
@initial "i"
@snap "b"
@restore "r"
@all "*"
@type action :: :add | :dynamic | :initial | :remove | :set | :toggle | :snap | :restore
@type query :: String.t()
@type attr :: String.t() | atom()
@type value :: String.t() | atom() | integer()
@type name :: String.t() | atom()
@type change :: [...]
@doc """
Reset all `attributes` of elements matching `query` to their initial value.
"""
@spec reset(Socket.t(), query) :: Socket.t()
def reset(socket, query) do
query = maybe_min_query(query)
push_or_merge_head_event(socket, query, [@initial, @all, @initial])
end
@doc """
Reset an `attribute` of elements matching `query` to it's initial value.
"""
@spec reset(Socket.t(), query, attr) :: Socket.t()
def reset(socket, query, attr), do: push(socket, query, :initial, attr, @initial)
@doc """
Create a snapshot named `name` of an `attribute` from all favicon link element
"""
@spec snap(Socket.t(), query, name, attr) :: Socket.t()
def snap(socket, query, name, attr \\ @all) do
query = maybe_min_query(query)
push_or_merge_head_event(socket, query, [@snap, attr, name])
end
@doc """
Restore an `attribute` from snapshot with named `name`.
"""
@spec restore(Socket.t(), query, name, attr) :: Socket.t()
def restore(socket, query, name, attr \\ @all) do
query = maybe_min_query(query)
push_or_merge_head_event(socket, query, [@restore, attr, name])
end
@doc """
Pushes `action` to apply on `attribute` of elements matching `query`. See [Actions](#module-actions) for available actions.
"""
@spec push(Socket.t(), query, action, attr, value | nil) :: Socket.t()
def push(socket, query, action, attr, value \\ nil)
when not (action != :remove and is_nil(value)) do
query = maybe_min_query(query)
action = min_action(action)
attr = maybe_min_attr(attr)
push_or_merge_head_event(socket, query, [action, attr, value])
end
@spec maybe_min_attr(attr) :: String.t()
defp maybe_min_attr("class"), do: "c"
defp maybe_min_attr("class-name"), do: "c"
defp maybe_min_attr("href"), do: "h"
defp maybe_min_attr(other) when is_binary(other), do: other
defp maybe_min_attr(other) when is_atom(other), do: other |> to_string() |> maybe_min_attr()
@spec maybe_min_query(query) :: String.t()
defp maybe_min_query("link[rel*='icon']"), do: "f"
defp maybe_min_query(other) when is_binary(other), do: other
@spec min_action(action) :: :a | :d | :i | :x | :s | :t
defp min_action(:dynamic), do: :d
defp min_action(:set), do: :s
defp min_action(:remove), do: :x
defp min_action(:add), do: :a
defp min_action(:toggle), do: :t
defp min_action(:initial), do: :i
@spec push_or_merge_head_event(Socket.t(), query, change) :: Socket.t()
defp push_or_merge_head_event(%Socket{} = socket, query, change)
when is_binary(query) and (is_list(change) or change === @initial) do
# use an accumulator to signal if head events were merged so
# the list only has to be traversed once.
{events, merged?} =
socket
|> Utils.get_push_events()
|> Enum.map_reduce(false, fn
["hd", %{c: changes}], _ ->
{["hd", %{c: push_or_merge_head_change(changes, query, change)}], true}
other, merged? ->
{other, merged?}
end)
# we either simply push a new event to the stack when their were no merged
# head events or we replace the whole list of events with our mapped variant
# including merged head events
if merged? do
put_in(socket.private.__changed__.push_events, events)
else
push_event(socket, "hd", %{c: [[query, [change]]]})
end
end
# no previous changes
defp push_or_merge_head_change([[] = rest], query, change), do: new_bucket(query, rest, change)
# query matches query of last set of changes
defp push_or_merge_head_change([[q, changes] | rest], q, [@initial, attr, _] = change) do
changes = split_and_override_attr(changes, attr, [@snap])
prepend_to_bucket(q, changes, change, rest)
end
defp push_or_merge_head_change([[q, changes] | rest], q, [@snap, _, _] = change) do
prepend_to_bucket(q, changes, change, rest)
end
defp push_or_merge_head_change([[q, changes] | rest], q, [@restore, attr, _] = change) do
changes = split_and_override_attr(changes, attr, [@snap])
prepend_to_bucket(q, changes, change, rest)
end
defp push_or_merge_head_change([[q, changes] | rest], q, [_, attr, _] = change) do
changes = split_and_override_attr(changes, attr, [@snap, @initial, @restore])
prepend_to_bucket(q, changes, change, rest)
end
# query does not match query of last set of changes
defp push_or_merge_head_change(rest, query, change), do: new_bucket(query, rest, change)
defp split_and_override_attr(changes, attr, splitters) do
{overridable, to_keep} =
Enum.split_while(changes, fn [action, _a, _v] -> action not in splitters end)
if attr == @all do
to_keep
else
Enum.reject(overridable, &match?([_, ^attr, _], &1)) ++ to_keep
end
end
defp new_bucket(query, rest, change), do: [[query, [change]] | rest]
defp prepend_to_bucket(query, changes, change, rest), do: [[query, [change | changes]] | rest]
def pub_push_or_merge_head_change, do: &push_or_merge_head_change/3
end
