defmodule Mix.Tasks.Devcon4.Install do
  @shortdoc "Set up devcontainer in your project"

  @moduledoc """
  Sets up devcontainer files in your project.

      mix devcon4.install

  The generated files follow the open [Dev Containers](https://containers.dev/)
  specification. To build and run the container, you need Docker and either the
  [devcontainer CLI](https://github.com/devcontainers/cli) (`npm install -g @devcontainers/cli`),
  VS Code with the Dev Containers extension, or any compatible tool.

  ## What it does

    * Creates `.devcontainer/devcontainer.json` with container settings,
      volumes, and firewall initialization
    * Creates `.devcontainer/Dockerfile` with Elixir, Node.js, and
      development tools
    * Creates `.devcontainer/init-firewall.sh` with a restrictive outbound
      firewall (GitHub, Hex.pm only by default)

  ## Options

    * `--elixir-version` - Elixir version for the base image (default: detected from `mix.exs`)
    * `--erlang-version` - Erlang/OTP version for the base image (default: detected from runtime)
    * `--ubuntu-version` - Ubuntu release codename (default: `noble`)
    * `--ubuntu-date-tag` - Ubuntu image date tag (default: `20260217`)
    * `--timezone` - Default timezone fallback (default: `America/Sao_Paulo`)
    * `--add` - Add an optional package (repeatable). See available packages below.
    * `--no-firewall` - Skip firewall setup (no init-firewall.sh, no NET_ADMIN capability)
    * `--force` - Overwrite existing files without prompting

  ## Available packages

  #{Devcon4.available_packages() |> Enum.map_join("\n", fn {name, cfg} -> "    * `#{name}` - #{cfg["description"]}" end)}

  ## Examples

      # Install with defaults (no optional packages)
      mix devcon4.install

      # Install with Claude Code
      mix devcon4.install --add claude

      # Install with custom versions and Claude Code
      mix devcon4.install --add claude --elixir-version 1.17.0
  """

  use Mix.Task

  @switches [
    elixir_version: :string,
    erlang_version: :string,
    ubuntu_version: :string,
    ubuntu_date_tag: :string,
    timezone: :string,
    add: [:string, :keep],
    no_firewall: :boolean,
    force: :boolean
  ]

  @defaults [
    ubuntu_version: "noble",
    ubuntu_date_tag: "20260217",
    timezone: "America/Sao_Paulo",
    no_firewall: false,
    force: false
  ]

  @impl Mix.Task
  def run(argv) do
    {opts, _args} = OptionParser.parse!(argv, strict: @switches)

    defaults =
      @defaults
      |> Keyword.put(:elixir_version, detect_elixir_version())
      |> Keyword.put(:erlang_version, detect_erlang_version())

    opts = Keyword.merge(defaults, opts)

    app_name = detect_app_name()
    project_name = humanize(app_name)
    volume_prefix = String.replace(app_name, "_", "-")

    add_names = Keyword.get_values(opts, :add)
    packages = Devcon4.load_packages(add_names)
    firewall = not opts[:no_firewall]

    File.mkdir_p!(".devcontainer")

    create_from_template(
      "devcontainer.json.eex",
      ".devcontainer/devcontainer.json",
      [
        project_name: project_name,
        volume_prefix: volume_prefix,
        timezone: opts[:timezone],
        firewall: firewall,
        extra_build_args: extract_build_args(packages),
        extra_mounts: extract_mounts(packages, volume_prefix),
        extra_env: extract_env(packages)
      ],
      opts[:force]
    )

    create_from_template(
      "Dockerfile.eex",
      ".devcontainer/Dockerfile",
      [
        elixir_version: opts[:elixir_version],
        erlang_version: opts[:erlang_version],
        ubuntu_version: opts[:ubuntu_version],
        ubuntu_date_tag: opts[:ubuntu_date_tag],
        firewall: firewall,
        package_args: extract_package_args(packages),
        package_dirs: extract_package_dirs(packages),
        package_installs: extract_package_installs(packages)
      ],
      opts[:force]
    )

    if firewall do
      create_from_template(
        "init-firewall.sh.eex",
        ".devcontainer/init-firewall.sh",
        [
          extra_domains: extract_domains(packages)
        ],
        opts[:force]
      )

      # Make firewall script executable
      File.chmod!(".devcontainer/init-firewall.sh", 0o755)
    end

    added_label =
      case add_names do
        [] -> ""
        names -> " (with #{Enum.join(names, ", ")})"
      end

    Mix.shell().info("""

    Devcontainer files installed in .devcontainer/#{added_label}

    Prerequisites:
      - Docker (or compatible runtime)
      - devcontainer CLI: npm install -g @devcontainers/cli
        (or use VS Code with the Dev Containers extension)

    To start the container:

        # Via CLI
        devcontainer up --workspace-folder .
        devcontainer exec --workspace-folder . bash

        # Via VS Code
        Ctrl+Shift+P -> "Dev Containers: Reopen in Container"

    To customize, edit the generated files directly:
      - Add firewall domains in .devcontainer/init-firewall.sh
      - Add system packages in .devcontainer/Dockerfile
      - Change container settings in .devcontainer/devcontainer.json
    """)
  end

  # -- Package extraction helpers --

  defp extract_package_args(packages) do
    Enum.flat_map(packages, fn {_name, pkg} ->
      (get_in(pkg, ["dockerfile", "args"]) || %{}) |> Enum.to_list()
    end)
  end

  defp extract_package_dirs(packages) do
    Enum.flat_map(packages, fn {_name, pkg} ->
      get_in(pkg, ["dockerfile", "dirs"]) || []
    end)
  end

  defp extract_package_installs(packages) do
    Enum.flat_map(packages, fn {_name, pkg} ->
      desc = pkg["description"]
      cmds = get_in(pkg, ["dockerfile", "run"]) || []
      if cmds != [], do: [{desc, cmds}], else: []
    end)
  end

  defp extract_build_args(packages) do
    Enum.flat_map(packages, fn {_name, pkg} ->
      (get_in(pkg, ["devcontainer", "build_args"]) || %{}) |> Enum.to_list()
    end)
  end

  defp extract_mounts(packages, volume_prefix) do
    Enum.flat_map(packages, fn {_name, pkg} ->
      (get_in(pkg, ["devcontainer", "mounts"]) || [])
      |> Enum.map(&String.replace(&1, "{volume_prefix}", volume_prefix))
    end)
  end

  defp extract_env(packages) do
    Enum.flat_map(packages, fn {_name, pkg} ->
      (get_in(pkg, ["devcontainer", "container_env"]) || %{}) |> Enum.to_list()
    end)
  end

  defp extract_domains(packages) do
    Enum.flat_map(packages, fn {_name, pkg} ->
      get_in(pkg, ["firewall", "domains"]) || []
    end)
  end

  # -- File helpers --

  defp create_from_template(template_name, target, assigns, force) do
    template = Devcon4.template_path(template_name)
    content = EEx.eval_file(template, assigns: assigns)
    write_file(target, content, force)
  end

  defp write_file(target, content, force) do
    if File.exists?(target) and not force do
      Mix.shell().info("* skipping #{target} (already exists, use --force to overwrite)")
    else
      action = if File.exists?(target), do: "overwriting", else: "creating"
      Mix.shell().info("* #{action} #{target}")
      File.write!(target, content)
    end
  end

  defp detect_app_name do
    config = Mix.Project.config()
    config[:app] |> to_string()
  end

  defp detect_elixir_version do
    System.version()
  end

  defp detect_erlang_version do
    otp_release = :erlang.system_info(:otp_release) |> to_string()
    otp_version_file = Path.join([:code.root_dir(), "releases", otp_release, "OTP_VERSION"])

    case File.read(otp_version_file) do
      {:ok, content} ->
        content |> String.trim() |> String.split(".") |> Enum.take(3) |> Enum.join(".")

      _ ->
        otp_release <> ".0.0"
    end
  end

  defp humanize(name) do
    name
    |> String.replace("_", " ")
    |> String.split()
    |> Enum.map_join(" ", &String.capitalize/1)
  end
end