From f8f1ec623f718144b5fd74e60e9407cb758b4d26 Mon Sep 17 00:00:00 2001
From: Mitchell Hanberg <mitch@mitchellhanberg.com>
Date: Fri, 10 Jul 2020 12:32:51 -0400
Subject: [PATCH] Plugin architecture for parsers

---
 lib/temple.ex        | 261 +-----------------------------
 lib/temple/parser.ex | 375 +++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 378 insertions(+), 258 deletions(-)
 create mode 100644 lib/temple/parser.ex

diff --git a/lib/temple.ex b/lib/temple.ex
index 6a09900..74be0a3 100644
--- a/lib/temple.ex
+++ b/lib/temple.ex
@@ -122,266 +122,11 @@ defmodule Temple do
     end
   end
 
-  defmodule Private do
-    @moduledoc false
-    @aliases Application.get_env(:temple, :aliases, [])
-
-    @nonvoid_elements ~w[
-    head title style script
-    noscript template
-    body section nav article aside h1 h2 h3 h4 h5 h6
-    header footer address main
-    p pre blockquote ol ul li dl dt dd figure figcaption div
-    a em strong small s cite q dfn abbr data time code var samp kbd
-    sub sup i b u mark ruby rt rp bdi bdo span
-    ins del
-    iframe object video audio canvas
-    map
-    table caption colgroup tbody thead tfoot tr td th
-    form fieldset legend label button select datalist optgroup
-    option textarea output progress meter
-    details summary menuitem menu
-    html
-  ]a
-
-    @nonvoid_elements_aliases Enum.map(@nonvoid_elements, fn el ->
-                                Keyword.get(@aliases, el, el)
-                              end)
-    @nonvoid_elements_lookup Enum.map(@nonvoid_elements, fn el ->
-                               {Keyword.get(@aliases, el, el), el}
-                             end)
-
-    @void_elements ~w[
-    meta link base
-    area br col embed hr img input keygen param source track wbr
-  ]a
-
-    @void_elements_aliases Enum.map(@void_elements, fn el -> Keyword.get(@aliases, el, el) end)
-    @void_elements_lookup Enum.map(@void_elements, fn el ->
-                            {Keyword.get(@aliases, el, el), el}
-                          end)
-
-    def snake_to_kebab(stringable),
-      do:
-        stringable |> to_string() |> String.replace_trailing("_", "") |> String.replace("_", "-")
-
-    def kebab_to_snake(stringable),
-      do: stringable |> to_string() |> String.replace("-", "_")
-
-    def compile_attrs([]), do: ""
-
-    def compile_attrs([attrs]) when is_list(attrs) do
-      compile_attrs(attrs)
-    end
-
-    def compile_attrs(attrs) do
-      for {name, value} <- attrs, into: "" do
-        name = snake_to_kebab(name)
-
-        case value do
-          {_, _, _} = macro ->
-            " " <> name <> "=\"<%= " <> Macro.to_string(macro) <> " %>\""
-
-          value ->
-            " " <> name <> "=\"" <> to_string(value) <> "\""
-        end
-      end
-    end
-
-    def split_args(nil), do: {[], []}
-
-    def split_args(args) do
-      {do_and_else, args} =
-        args
-        |> Enum.split_with(fn
-          arg when is_list(arg) ->
-            (Keyword.keys(arg) -- [:do, :else]) |> Enum.count() == 0
-
-          _ ->
-            false
-        end)
-
-      {List.flatten(do_and_else), args}
-    end
-
-    def split_on_fn([{:fn, _, _} = func | rest], {args, _, args2}) do
-      split_on_fn(rest, {args, func, args2})
-    end
-
-    def split_on_fn([arg | rest], {args, nil, args2}) do
-      split_on_fn(rest, {[arg | args], nil, args2})
-    end
-
-    def split_on_fn([arg | rest], {args, func, args2}) do
-      split_on_fn(rest, {args, func, [arg | args2]})
-    end
-
-    def split_on_fn([], {args, func, args2}) do
-      {Enum.reverse(args), func, Enum.reverse(args2)}
-    end
-
-    def pop_compact?([]), do: {false, []}
-    def pop_compact?([args]) when is_list(args), do: pop_compact?(args)
-
-    def pop_compact?(args) do
-      Keyword.pop(args, :compact, false)
-    end
-
-    def traverse(buffer, {:__block__, _meta, block}) do
-      traverse(buffer, block)
-    end
-
-    def traverse(buffer, {name, meta, args} = macro) do
-      {do_and_else, args} =
-        args
-        |> split_args()
-
-      includes_fn? = args |> Enum.any?(fn x -> match?({:fn, _, _}, x) end)
-
-      case name do
-        {:., _, [{:__aliases__, _, [:Temple]}, name]} when name in @nonvoid_elements_aliases ->
-          {do_and_else, args} =
-            case args do
-              [args] ->
-                {do_value, args} = Keyword.pop(args, :do)
-
-                do_and_else = Keyword.put_new(do_and_else, :do, do_value)
-
-                {do_and_else, args}
-
-              _ ->
-                {do_and_else, args}
-            end
-
-          name = @nonvoid_elements_lookup[name]
-
-          {compact?, args} = pop_compact?(args)
-
-          Buffer.put(buffer, "<#{name}#{compile_attrs(args)}>")
-          unless compact?, do: Buffer.put(buffer, "\n")
-          traverse(buffer, do_and_else[:do])
-          if compact?, do: Buffer.remove_new_line(buffer)
-          Buffer.put(buffer, "</#{name}>")
-          Buffer.put(buffer, "\n")
-
-        {:., _, [{:__aliases__, _, [:Temple]}, name]} when name in @void_elements_aliases ->
-          name = @void_elements_lookup[name]
-
-          Buffer.put(buffer, "<#{name}#{compile_attrs(args)}>")
-          Buffer.put(buffer, "\n")
-
-        name when name in @nonvoid_elements_aliases ->
-          {do_and_else, args} =
-            case args do
-              [args] ->
-                {do_value, args} = Keyword.pop(args, :do)
-
-                do_and_else = Keyword.put_new(do_and_else, :do, do_value)
-
-                {do_and_else, args}
-
-              _ ->
-                {do_and_else, args}
-            end
-
-          name = @nonvoid_elements_lookup[name]
-
-          {compact?, args} = pop_compact?(args)
-
-          Buffer.put(buffer, "<#{name}#{compile_attrs(args)}>")
-          unless compact?, do: Buffer.put(buffer, "\n")
-          traverse(buffer, do_and_else[:do])
-          if compact?, do: Buffer.remove_new_line(buffer)
-          Buffer.put(buffer, "</#{name}>")
-          Buffer.put(buffer, "\n")
-
-        name when name in @void_elements_aliases ->
-          name = @void_elements_lookup[name]
-
-          Buffer.put(buffer, "<#{name}#{compile_attrs(args)}>")
-          Buffer.put(buffer, "\n")
-
-        name when includes_fn? ->
-          {args, func_arg, args2} = split_on_fn(args, {[], nil, []})
-
-          {func, _, [{arrow, _, [[{arg, _, _}], block]}]} = func_arg
-
-          Buffer.put(
-            buffer,
-            "<%= " <>
-              to_string(name) <>
-              " " <>
-              (Enum.map(args, &Macro.to_string(&1)) |> Enum.join(", ")) <>
-              ", " <>
-              to_string(func) <> " " <> to_string(arg) <> " " <> to_string(arrow) <> " %>"
-          )
-
-          Buffer.put(buffer, "\n")
-
-          traverse(buffer, block)
-
-          if Enum.any?(args2) do
-            Buffer.put(
-              buffer,
-              "<% end, " <>
-                (Enum.map(args2, fn arg -> Macro.to_string(arg) end)
-                 |> Enum.join(", ")) <> " %>"
-            )
-
-            Buffer.put(buffer, "\n")
-          else
-            Buffer.put(buffer, "<% end %>")
-            Buffer.put(buffer, "\n")
-          end
-
-        name when name in [:for, :if, :unless] ->
-          Buffer.put(buffer, "<%= " <> Macro.to_string({name, meta, args}) <> " do %>")
-          Buffer.put(buffer, "\n")
-
-          traverse(buffer, do_and_else[:do])
-
-          if Keyword.has_key?(do_and_else, :else) do
-            Buffer.put(buffer, "<% else %>")
-            Buffer.put(buffer, "\n")
-            traverse(buffer, do_and_else[:else])
-          end
-
-          Buffer.put(buffer, "<% end %>")
-          Buffer.put(buffer, "\n")
-
-        name when name in [:=] ->
-          Buffer.put(buffer, "<% " <> Macro.to_string(macro) <> " %>")
-          Buffer.put(buffer, "\n")
-          traverse(buffer, do_and_else[:do])
-
-        _ ->
-          Buffer.put(buffer, "<%= " <> Macro.to_string(macro) <> " %>")
-          Buffer.put(buffer, "\n")
-          traverse(buffer, do_and_else[:do])
-      end
-    end
-
-    def traverse(buffer, [first | rest]) do
-      traverse(buffer, first)
-
-      traverse(buffer, rest)
-    end
-
-    def traverse(buffer, text) when is_binary(text) do
-      Buffer.put(buffer, text)
-      Buffer.put(buffer, "\n")
-    end
-
-    def traverse(_buffer, arg) when arg in [nil, []] do
-      nil
-    end
-  end
-
   defmacro temple([do: block] = _block) do
     {:ok, buffer} = Buffer.start_link()
 
     buffer
-    |> Temple.Private.traverse(block)
+    |> Temple.Parser.Private.traverse(block)
 
     markup = Buffer.get(buffer)
 
@@ -399,7 +144,7 @@ defmodule Temple do
       {:ok, buffer} = Buffer.start_link()
 
       buffer
-      |> Temple.Private.traverse(unquote(block))
+      |> Temple.Parser.Private.traverse(unquote(block))
 
       markup = Buffer.get(buffer)
 
@@ -413,7 +158,7 @@ defmodule Temple do
     {:ok, buffer} = Buffer.start_link()
 
     buffer
-    |> Temple.Private.traverse(block)
+    |> Temple.Parser.Private.traverse(block)
 
     markup = Buffer.get(buffer)
 
diff --git a/lib/temple/parser.ex b/lib/temple/parser.ex
new file mode 100644
index 0000000..6fac4b9
--- /dev/null
+++ b/lib/temple/parser.ex
@@ -0,0 +1,375 @@
+defmodule Temple.Parser do
+  alias Temple.Buffer
+
+  @aliases Application.get_env(:temple, :aliases, [])
+
+  @nonvoid_elements ~w[
+    head title style script
+    noscript template
+    body section nav article aside h1 h2 h3 h4 h5 h6
+    header footer address main
+    p pre blockquote ol ul li dl dt dd figure figcaption div
+    a em strong small s cite q dfn abbr data time code var samp kbd
+    sub sup i b u mark ruby rt rp bdi bdo span
+    ins del
+    iframe object video audio canvas
+    map
+    table caption colgroup tbody thead tfoot tr td th
+    form fieldset legend label button select datalist optgroup
+    option textarea output progress meter
+    details summary menuitem menu
+    html
+  ]a
+
+  @nonvoid_elements_aliases Enum.map(@nonvoid_elements, fn el ->
+                              Keyword.get(@aliases, el, el)
+                            end)
+  @nonvoid_elements_lookup Enum.map(@nonvoid_elements, fn el ->
+                             {Keyword.get(@aliases, el, el), el}
+                           end)
+
+  @void_elements ~w[
+    meta link base
+    area br col embed hr img input keygen param source track wbr
+  ]a
+
+  @void_elements_aliases Enum.map(@void_elements, fn el -> Keyword.get(@aliases, el, el) end)
+  @void_elements_lookup Enum.map(@void_elements, fn el ->
+                          {Keyword.get(@aliases, el, el), el}
+                        end)
+
+  defmodule Private do
+    @moduledoc false
+
+    def snake_to_kebab(stringable),
+      do:
+        stringable |> to_string() |> String.replace_trailing("_", "") |> String.replace("_", "-")
+
+    def kebab_to_snake(stringable),
+      do: stringable |> to_string() |> String.replace("-", "_")
+
+    def compile_attrs([]), do: ""
+
+    def compile_attrs([attrs]) when is_list(attrs) do
+      compile_attrs(attrs)
+    end
+
+    def compile_attrs(attrs) do
+      for {name, value} <- attrs, into: "" do
+        name = snake_to_kebab(name)
+
+        case value do
+          {_, _, _} = macro ->
+            " " <> name <> "=\"<%= " <> Macro.to_string(macro) <> " %>\""
+
+          value ->
+            " " <> name <> "=\"" <> to_string(value) <> "\""
+        end
+      end
+    end
+
+    def split_args(nil), do: {[], []}
+
+    def split_args(args) do
+      {do_and_else, args} =
+        args
+        |> Enum.split_with(fn
+          arg when is_list(arg) ->
+            (Keyword.keys(arg) -- [:do, :else]) |> Enum.count() == 0
+
+          _ ->
+            false
+        end)
+
+      {List.flatten(do_and_else), args}
+    end
+
+    def split_on_fn([{:fn, _, _} = func | rest], {args, _, args2}) do
+      split_on_fn(rest, {args, func, args2})
+    end
+
+    def split_on_fn([arg | rest], {args, nil, args2}) do
+      split_on_fn(rest, {[arg | args], nil, args2})
+    end
+
+    def split_on_fn([arg | rest], {args, func, args2}) do
+      split_on_fn(rest, {args, func, [arg | args2]})
+    end
+
+    def split_on_fn([], {args, func, args2}) do
+      {Enum.reverse(args), func, Enum.reverse(args2)}
+    end
+
+    def pop_compact?([]), do: {false, []}
+    def pop_compact?([args]) when is_list(args), do: pop_compact?(args)
+
+    def pop_compact?(args) do
+      Keyword.pop(args, :compact, false)
+    end
+
+    def traverse(buffer, {:__block__, _meta, block}) do
+      traverse(buffer, block)
+    end
+
+    def traverse(buffer, {_name, _meta, _args} = macro) do
+      Temple.Parser.parsers()
+      |> Enum.reduce_while(nil, fn parser, _ ->
+        if parser.applicable?.(macro) do
+          parser.parse.(macro, buffer)
+          {:halt, nil}
+        else
+          {:cont, nil}
+        end
+      end)
+    end
+
+    def traverse(buffer, [first | rest]) do
+      traverse(buffer, first)
+
+      traverse(buffer, rest)
+    end
+
+    def traverse(buffer, text) when is_binary(text) do
+      Buffer.put(buffer, text)
+      Buffer.put(buffer, "\n")
+    end
+
+    def traverse(_buffer, arg) when arg in [nil, []] do
+      nil
+    end
+  end
+
+  def parsers(),
+    do: [
+      %{
+        name: :temple_namespace_nonvoid,
+        applicable?: fn {name, _meta, _args} ->
+          try do
+            {:., _, [{:__aliases__, _, [:Temple]}, name]} = name
+            name in @nonvoid_elements_aliases
+          rescue
+            MatchError ->
+              false
+          end
+        end,
+        parse: fn {name, _meta, args}, buffer ->
+          import Temple.Parser.Private
+          {:., _, [{:__aliases__, _, [:Temple]}, name]} = name
+
+          {do_and_else, args} =
+            args
+            |> split_args()
+
+          {do_and_else, args} =
+            case args do
+              [args] ->
+                {do_value, args} = Keyword.pop(args, :do)
+
+                do_and_else = Keyword.put_new(do_and_else, :do, do_value)
+
+                {do_and_else, args}
+
+              _ ->
+                {do_and_else, args}
+            end
+
+          name = @nonvoid_elements_lookup[name]
+
+          {compact?, args} = pop_compact?(args)
+
+          Buffer.put(buffer, "<#{name}#{compile_attrs(args)}>")
+          unless compact?, do: Buffer.put(buffer, "\n")
+          traverse(buffer, do_and_else[:do])
+          if compact?, do: Buffer.remove_new_line(buffer)
+          Buffer.put(buffer, "</#{name}>")
+          Buffer.put(buffer, "\n")
+        end
+      },
+      %{
+        name: :temple_namespace_void,
+        applicable?: fn {name, _meta, _args} ->
+          try do
+            {:., _, [{:__aliases__, _, [:Temple]}, name]} = name
+            name in @void_elements_aliases
+          rescue
+            MatchError ->
+              false
+          end
+        end,
+        parse: fn {name, _, args}, buffer ->
+          import Temple.Parser.Private
+          {:., _, [{:__aliases__, _, [:Temple]}, name]} = name
+
+          {_do_and_else, args} =
+            args
+            |> split_args()
+
+          name = @void_elements_lookup[name]
+
+          Buffer.put(buffer, "<#{name}#{compile_attrs(args)}>")
+          Buffer.put(buffer, "\n")
+        end
+      },
+      %{
+        name: :nonvoid_elements_aliases,
+        applicable?: fn {name, _, _} ->
+          name in @nonvoid_elements_aliases
+        end,
+        parse: fn {name, _, args}, buffer ->
+          import Temple.Parser.Private
+
+          {do_and_else, args} =
+            args
+            |> split_args()
+
+          {do_and_else, args} =
+            case args do
+              [args] ->
+                {do_value, args} = Keyword.pop(args, :do)
+
+                do_and_else = Keyword.put_new(do_and_else, :do, do_value)
+
+                {do_and_else, args}
+
+              _ ->
+                {do_and_else, args}
+            end
+
+          name = @nonvoid_elements_lookup[name]
+
+          {compact?, args} = pop_compact?(args)
+
+          Buffer.put(buffer, "<#{name}#{compile_attrs(args)}>")
+          unless compact?, do: Buffer.put(buffer, "\n")
+          traverse(buffer, do_and_else[:do])
+          if compact?, do: Buffer.remove_new_line(buffer)
+          Buffer.put(buffer, "</#{name}>")
+          Buffer.put(buffer, "\n")
+        end
+      },
+      %{
+        name: :void_elements_aliases,
+        applicable?: fn {name, _, _} ->
+          name in @void_elements_aliases
+        end,
+        parse: fn {name, _, args}, buffer ->
+          import Temple.Parser.Private
+
+          {_do_and_else, args} =
+            args
+            |> split_args()
+
+          name = @void_elements_lookup[name]
+
+          Buffer.put(buffer, "<#{name}#{compile_attrs(args)}>")
+          Buffer.put(buffer, "\n")
+        end
+      },
+      %{
+        name: :anonymous_functions,
+        applicable?: fn {_, _, args} ->
+          import Temple.Parser.Private, only: [split_args: 1]
+
+          args |> split_args() |> elem(1) |> Enum.any?(fn x -> match?({:fn, _, _}, x) end)
+        end,
+        parse: fn {name, _, args}, buffer ->
+          import Temple.Parser.Private
+
+          {_do_and_else, args} =
+            args
+            |> split_args()
+
+          {args, func_arg, args2} = split_on_fn(args, {[], nil, []})
+
+          {func, _, [{arrow, _, [[{arg, _, _}], block]}]} = func_arg
+
+          Buffer.put(
+            buffer,
+            "<%= " <>
+              to_string(name) <>
+              " " <>
+              (Enum.map(args, &Macro.to_string(&1)) |> Enum.join(", ")) <>
+              ", " <>
+              to_string(func) <> " " <> to_string(arg) <> " " <> to_string(arrow) <> " %>"
+          )
+
+          Buffer.put(buffer, "\n")
+
+          traverse(buffer, block)
+
+          if Enum.any?(args2) do
+            Buffer.put(
+              buffer,
+              "<% end, " <>
+                (Enum.map(args2, fn arg -> Macro.to_string(arg) end)
+                 |> Enum.join(", ")) <> " %>"
+            )
+
+            Buffer.put(buffer, "\n")
+          else
+            Buffer.put(buffer, "<% end %>")
+            Buffer.put(buffer, "\n")
+          end
+        end
+      },
+      %{
+        name: :for_if_unless,
+        applicable?: fn {name, _, _} ->
+          name in [:for, :if, :unless]
+        end,
+        parse: fn {name, meta, args}, buffer ->
+          import Temple.Parser.Private
+
+          {do_and_else, args} =
+            args
+            |> split_args()
+
+          Buffer.put(buffer, "<%= " <> Macro.to_string({name, meta, args}) <> " do %>")
+          Buffer.put(buffer, "\n")
+
+          traverse(buffer, do_and_else[:do])
+
+          if Keyword.has_key?(do_and_else, :else) do
+            Buffer.put(buffer, "<% else %>")
+            Buffer.put(buffer, "\n")
+            traverse(buffer, do_and_else[:else])
+          end
+
+          Buffer.put(buffer, "<% end %>")
+          Buffer.put(buffer, "\n")
+        end
+      },
+      %{
+        name: :match,
+        applicable?: fn {name, _, _} ->
+          name in [:=]
+        end,
+        parse: fn {_, _, args} = macro, buffer ->
+          import Temple.Parser.Private
+
+          {do_and_else, _args} =
+            args
+            |> split_args()
+
+          Buffer.put(buffer, "<% " <> Macro.to_string(macro) <> " %>")
+          Buffer.put(buffer, "\n")
+          traverse(buffer, do_and_else[:do])
+        end
+      },
+      %{
+        name: :default,
+        applicable?: fn _ -> true end,
+        parse: fn {_, _, args} = macro, buffer ->
+          import Temple.Parser.Private
+
+          {do_and_else, _args} =
+            args
+            |> split_args()
+
+          Buffer.put(buffer, "<%= " <> Macro.to_string(macro) <> " %>")
+          Buffer.put(buffer, "\n")
+          traverse(buffer, do_and_else[:do])
+        end
+      }
+    ]
+end