defmodule Mix.Tasks.Mob.Install do
  use Mix.Task

  @shortdoc "First-run setup for a new Mob project"

  @moduledoc """
  Runs first-time setup for a Mob project generated by `mix mob.new`.

  Must be run from inside the project directory (the one containing `mix.exs`).

      mix mob.install [--no-icon] [--icon PATH]

  ## What it does

    1. Generates app icons (random robot avatar, or a provided source image)

  ## Options

    * `--no-icon`      — skip icon generation
    * `--icon PATH`    — use an existing image instead of generating a random robot

  ## Icon output

    - `android/app/src/main/res/mipmap-*/ic_launcher.png`
    - `ios/Assets.xcassets/AppIcon.appiconset/icon_*.png` + `Contents.json`
    - `icon_source.png` (1024×1024 master, when generating)

  Run at any time to regenerate icons:

      mix mob.install --no-icon        # skip icons, re-run other setup steps
      mix mob.icon                     # icon only, any time after install
  """

  @switches [no_icon: :boolean, icon: :string]

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

    project_dir = File.cwd!()

    unless File.exists?(Path.join(project_dir, "mix.exs")) do
      Mix.raise("No mix.exs found. Run mix mob.install from your project root.")
    end

    configure_paths(project_dir)
    download_otp()

    unless opts[:no_icon] do
      generate_icons(project_dir, opts[:icon])
    end

    Mix.shell().info("""

    Mob project ready!

        mix mob.deploy --native   # first deploy: build APK + iOS app, install + push BEAMs
        mix mob.deploy            # fast push + restart (day-to-day)
        mix mob.watch             # auto-push changes while developing
        mix mob.connect           # connect IEx to running device nodes
    """)
  end

  # ── OTP download ─────────────────────────────────────────────────────────────

  defp download_otp do
    Mix.shell().info("Ensuring OTP releases are cached...")

    case MobDev.OtpDownloader.ensure_android() do
      {:ok, path}      -> Mix.shell().info([:green, "* Android OTP: #{path}", :reset])
      {:error, reason} -> Mix.shell().error("Warning: Android OTP download failed: #{reason}")
    end

    if match?({:unix, :darwin}, :os.type()) do
      case MobDev.OtpDownloader.ensure_ios_sim() do
        {:ok, path}      -> Mix.shell().info([:green, "* iOS OTP: #{path}", :reset])
        {:error, reason} -> Mix.shell().error("Warning: iOS OTP download failed: #{reason}")
      end
    end
  end

  # ── Path configuration ───────────────────────────────────────────────────────

  @required_keys [:mob_dir, :elixir_lib]

  defp configure_paths(project_dir) do
    mob_exs = Path.join(project_dir, "mob.exs")

    cfg =
      if File.exists?(mob_exs) do
        Config.Reader.read!(mob_exs) |> Keyword.get(:mob_dev, [])
      else
        []
      end

    missing = Enum.filter(@required_keys, fn key ->
      val = cfg[key]
      is_nil(val) or String.contains?(val, "/path/to/")
    end)

    if missing != [] do
      defaults = detect_defaults(project_dir)

      Mix.shell().info("""

      Configure your local build paths in mob.exs.
      These are machine-specific and gitignored.
      Press Enter to accept a detected value [ ], or type a new path.
      """)

      updates =
        Enum.map(missing, fn key ->
          {key, prompt_path(key, defaults[key])}
        end)

      new_cfg = Keyword.merge(cfg, updates)
      write_mob_exs(mob_exs, new_cfg)
      write_local_properties(project_dir, new_cfg)

      Mix.shell().info([:green, "* mob.exs configured", :reset])
    end
  end

  defp detect_defaults(project_dir) do
    %{
      elixir_lib: detect_elixir_lib(),
      mob_dir:    detect_mob_dir(project_dir)
    }
  end

  # We're running inside Elixir — :code.lib_dir(:elixir) is always available.
  defp detect_elixir_lib do
    :code.lib_dir(:elixir) |> to_string() |> Path.dirname()
  end

  # Read the {:mob, path: "..."} dep from mix.exs and resolve it.
  defp detect_mob_dir(project_dir) do
    mix_exs = Path.join(project_dir, "mix.exs")
    with {:ok, content} <- File.read(mix_exs),
         [_, rel] <- Regex.run(~r/\{:mob,\s+path:\s+"([^"]+)"/, content) do
      Path.expand(rel, project_dir)
    else
      _ -> nil
    end
  end

  defp prompt_path(key, detected) do
    label = prompt_label(key)
    if detected do
      input = Mix.shell().prompt("  #{label} [#{detected}]:") |> String.trim()
      if input == "", do: detected, else: input
    else
      Mix.shell().prompt("  #{label}:") |> String.trim()
    end
  end

  defp prompt_label(:mob_dir),    do: "mob library path"
  defp prompt_label(:elixir_lib), do: "Elixir lib path"

  defp write_mob_exs(path, cfg) do
    content = """
    import Config

    config :mob_dev,
      mob_dir:    #{inspect(cfg[:mob_dir])},
      elixir_lib: #{inspect(cfg[:elixir_lib])}
    """

    File.write!(path, content)
  end

  defp write_local_properties(project_dir, cfg) do
    props = Path.join(project_dir, "android/local.properties")

    if File.exists?(props) do
      content = File.read!(props)

      if String.contains?(content, "/path/to/") do
        otp_dir = MobDev.OtpDownloader.android_otp_dir()

        new_content =
          content
          |> replace_prop("mob.otp_release", otp_dir)
          |> replace_prop("mob.mob_dir",     cfg[:mob_dir])

        File.write!(props, new_content)
        Mix.shell().info([:green, "* android/local.properties configured", :reset])
      end
    end
  end

  defp replace_prop(content, key, value) when not is_nil(value) do
    String.replace(content, ~r/^#{Regex.escape(key)}=.*$/m, "#{key}=#{value}")
  end
  defp replace_prop(content, _key, nil), do: content

  # ── Icon generation ───────────────────────────────────────────────────────────

  defp generate_icons(project_dir, nil) do
    Mix.shell().info("Generating app icon (random robot)...")
    MobDev.IconGenerator.generate_random(project_dir)
    Mix.shell().info([:green, "* icons written", :reset])
  end

  defp generate_icons(project_dir, source) do
    unless File.exists?(source) do
      Mix.raise("Source file not found: #{source}")
    end
    Mix.shell().info("Generating app icon from #{source}...")
    MobDev.IconGenerator.generate_from_source(source, project_dir)
    Mix.shell().info([:green, "* icons written", :reset])
  end
end