defmodule Firebird.Phoenix.Scaffold do
  @moduledoc """
  Generates a complete Phoenix WASM application scaffold.

  Creates a ready-to-run project that uses Firebird's WASM-accelerated
  Phoenix components for HTTP request handling.

  ## Generated Structure

      my_app/
      ├── lib/
      │   ├── my_app/
      │   │   ├── application.ex    # OTP Application with Phoenix WASM supervisor
      │   │   ├── router.ex         # Route definitions using RouterDSL
      │   │   ├── controllers/
      │   │   │   ├── page_controller.ex
      │   │   │   └── user_controller.ex
      │   │   └── templates/
      │   │       ├── layout.html.eex
      │   │       └── page/
      │   │           └── index.html.eex
      │   └── my_app.ex             # Main module
      ├── test/
      │   ├── test_helper.exs
      │   └── my_app/
      │       └── router_test.exs
      ├── config/
      │   └── config.exs
      └── mix.exs
  """

  @doc """
  Generate a Phoenix WASM application scaffold.

  ## Parameters

  - `app_name` - Application name (e.g., "my_app")
  - `opts` - Options:
    - `:path` - Output directory (default: current dir + app_name)
    - `:module` - Module name (default: camelized app_name)

  ## Returns

  - `{:ok, path}` - Scaffold generated at path
  - `{:error, reason}` - Generation failed
  """
  @spec generate(String.t(), keyword()) :: {:ok, String.t()} | {:error, term()}
  def generate(app_name, opts \\ []) do
    module_name = Keyword.get(opts, :module, Macro.camelize(app_name))
    base_path = Keyword.get(opts, :path, Path.join(File.cwd!(), app_name))

    files = [
      {"mix.exs", mix_exs(app_name, module_name)},
      {"lib/#{app_name}.ex", main_module(module_name)},
      {"lib/#{app_name}/application.ex", application(module_name)},
      {"lib/#{app_name}/router.ex", router(module_name)},
      {"lib/#{app_name}/controllers/page_controller.ex", page_controller(module_name)},
      {"lib/#{app_name}/controllers/user_controller.ex", user_controller(module_name)},
      {"lib/#{app_name}/templates/layout.html.eex", layout_template()},
      {"lib/#{app_name}/templates/page/index.html.eex", page_index_template()},
      {"test/test_helper.exs", test_helper()},
      {"test/#{app_name}/router_test.exs", router_test(module_name)},
      {"config/config.exs", config(app_name)},
      {"README.md", readme(app_name, module_name)}
    ]

    Enum.each(files, fn {rel_path, content} ->
      full_path = Path.join(base_path, rel_path)
      File.mkdir_p!(Path.dirname(full_path))
      File.write!(full_path, content)
    end)

    {:ok, base_path}
  end

  defp mix_exs(app_name, module_name) do
    """
    defmodule #{module_name}.MixProject do
      use Mix.Project

      def project do
        [
          app: :#{app_name},
          version: "0.1.0",
          elixir: "~> 1.14",
          start_permanent: Mix.env() == :prod,
          deps: deps()
        ]
      end

      def application do
        [
          extra_applications: [:logger],
          mod: {#{module_name}.Application, []}
        ]
      end

      defp deps do
        [
          {:firebird, "~> 0.1.0"},
          {:jason, "~> 1.4"}
        ]
      end
    end
    """
  end

  defp main_module(module_name) do
    """
    defmodule #{module_name} do
      @moduledoc \"\"\"
      #{module_name} - A Phoenix WASM application powered by Firebird.
      \"\"\"
    end
    """
  end

  defp application(module_name) do
    """
    defmodule #{module_name}.Application do
      use Application

      @impl true
      def start(_type, _args) do
        children = [
          {Firebird.Phoenix.Application, name: :phoenix_wasm}
        ]

        opts = [strategy: :one_for_one, name: #{module_name}.Supervisor]
        Supervisor.start_link(children, opts)
      end
    end
    """
  end

  defp router(module_name) do
    """
    defmodule #{module_name}.Router do
      use Firebird.Phoenix.RouterDSL

      pipeline :browser do
        plug "put_secure_headers"
        plug "accept:text/html"
      end

      pipeline :api do
        plug "accept:application/json"
        plug "cors:*"
      end

      scope "/" do
        get "/", "PageController.index"
        get "/about", "PageController.about"
      end

      scope "/api", :api do
        resources "/users", "UserController"
      end

      @doc \"\"\"
      Define action handlers for route dispatch.
      \"\"\"
      def actions do
        %{
          "PageController.index" => {200, "text/html", "<h1>Welcome to #{module_name}</h1>"},
          "PageController.about" => {200, "text/html", "<h1>About</h1>"},
          "UserController.index" => {200, "application/json", "[]"},
          "UserController.show" => {200, "application/json", ~s({"id":"{{id}}"})},
          "UserController.create" => {201, "application/json", ~s({"status":"created"})},
          "UserController.update" => {200, "application/json", ~s({"id":"{{id}}","status":"updated"})},
          "UserController.delete" => {204, "text/plain", ""}
        }
      end

      @doc \"\"\"
      Handle a request using the WASM router and endpoint.
      \"\"\"
      def handle_request(method, path) do
        Firebird.Phoenix.Application.process_request(:phoenix_wasm,
          method: method,
          path: path,
          routes: routes(),
          actions: actions()
        )
      end
    end
    """
  end

  defp page_controller(module_name) do
    """
    defmodule #{module_name}.PageController do
      @moduledoc "Handles page requests."

      def index(_params) do
        {200, "text/html", "<h1>Welcome to #{module_name}!</h1>"}
      end

      def about(_params) do
        {200, "text/html", "<h1>About #{module_name}</h1><p>Powered by Firebird WASM</p>"}
      end
    end
    """
  end

  defp user_controller(module_name) do
    """
    defmodule #{module_name}.UserController do
      @moduledoc "Handles user API requests."

      def index(_params) do
        {200, "application/json", ~s([{"id":"1","name":"Alice"},{"id":"2","name":"Bob"}])}
      end

      def show(%{"id" => id}) do
        {200, "application/json", ~s({"id":"#{"\#{id}"}","name":"User #{"\#{id}}"}"})}
      end

      def create(_params) do
        {201, "application/json", ~s({"status":"created"})}
      end

      def update(%{"id" => id}) do
        {200, "application/json", ~s({"id":"#{"\#{id}"}","status":"updated"})}
      end

      def delete(_params) do
        {204, "text/plain", ""}
      end
    end
    """
  end

  defp layout_template do
    """
    <!DOCTYPE html>
    <html>
    <head>
      <meta charset="utf-8">
      <title><%= @title %></title>
    </head>
    <body>
      <nav>
        <a href="/">Home</a>
        <a href="/about">About</a>
      </nav>
      <main>
        <%= @inner_content %>
      </main>
    </body>
    </html>
    """
  end

  defp page_index_template do
    """
    <h1>Welcome!</h1>
    <p>This application is powered by Firebird Phoenix WASM.</p>
    <p>All request processing uses WebAssembly modules for:</p>
    <ul>
      <li>Route matching</li>
      <li>Template rendering</li>
      <li>Request parsing</li>
      <li>Response building</li>
    </ul>
    """
  end

  defp test_helper do
    """
    ExUnit.start()
    """
  end

  defp router_test(module_name) do
    """
    defmodule #{module_name}.RouterTest do
      use ExUnit.Case
      import Firebird.Phoenix.Testing

      test "routes are defined" do
        routes = #{module_name}.Router.routes()
        assert length(routes) > 0
      end

      test "pipelines are defined" do
        pipelines = #{module_name}.Router.pipelines()
        assert Map.has_key?(pipelines, :browser)
        assert Map.has_key?(pipelines, :api)
      end

      test "actions are defined" do
        actions = #{module_name}.Router.actions()
        assert Map.has_key?(actions, "PageController.index")
        assert Map.has_key?(actions, "UserController.show")
      end
    end
    """
  end

  defp config(app_name) do
    """
    import Config

    config :#{app_name},
      phoenix_wasm: [
        components: [:router, :template, :plug, :endpoint, :json]
      ]

    config :logger, level: :info
    """
  end

  defp readme(_app_name, module_name) do
    """
    # #{module_name}

    A Phoenix WASM application powered by [Firebird](https://github.com/hdresearch/firebird).

    ## Getting Started

    ```bash
    mix deps.get
    mix test
    ```

    ## Architecture

    This application uses Firebird's WASM-accelerated Phoenix components:

    - **Router** (`#{module_name}.Router`) - Route definitions using Firebird DSL
    - **Endpoint** - WASM-based request lifecycle processing
    - **Controllers** - Action handlers for each route
    - **Templates** - EEx templates compiled to WASM-compatible format

    ## API Routes

    | Method | Path | Handler |
    |--------|------|---------|
    #{Enum.map_join(["GET /", "GET /about", "GET /api/users", "GET /api/users/:id", "POST /api/users", "PUT /api/users/:id", "DELETE /api/users/:id"], "\n", fn route ->
      [method, path] = String.split(route, " ", parts: 2)
      "| #{method} | #{path} | Auto-dispatched |"
    end)}

    ## Usage

    ```elixir
    # Handle a request
    {:ok, resp} = #{module_name}.Router.handle_request("GET", "/api/users/42")
    resp.status  # => 200
    resp.body    # => {"id":"42"}
    ```
    """
  end
end