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. Prompts for machine-specific paths (`mob_dir`, `elixir_lib`) and writes them
       to `mob.exs` (gitignored) and `android/local.properties`
    2. Downloads and caches the pre-built OTP runtime tarballs for Android and iOS
    3. Writes the Mob logo as a placeholder app icon (if no icon exists yet)

  ## Options

    * `--no-icon`      — skip icon setup entirely
    * `--icon PATH`    — use a custom image instead of the Mob logo placeholder

  ## Icon output

    - `android/app/src/main/res/mipmap-*/ic_launcher.png`
    - `ios/Assets.xcassets/AppIcon.appiconset/icon_*.png` + `Contents.json`

  The Mob logo is written as a placeholder. Replace it any time:

      mix mob.icon                     # generate a custom icon
      mix mob.icon --source my_logo.png

  ## Under the hood

  `mix mob.install` does three things that would otherwise require manual steps:

  **1. Path configuration** — reads `mob.exs`, detects sensible defaults, prompts
  for missing values, and writes them back. Equivalent to:

      # mob.exs (gitignored, machine-specific)
      config :mob_dev,
        mob_dir: "/Users/me/code/mob"

  **2. OTP download** — fetches pre-built ERTS tarballs from GitHub Releases:

      # Roughly equivalent to:
      curl -L https://github.com/genericjam/mob/releases/download/<tag>/otp-android-arm64.tar.gz \
           -o ~/.mob_dev/otp-android-arm64.tar.gz

  **3. Placeholder icon** — writes the Mob logo to all platform icon sizes (pre-built PNGs,
  no system tools required). Run `mix mob.icon` afterwards to replace it with a custom icon.
  """

  @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
      setup_icon(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

    Run `mix mob.icon` to replace the placeholder icon with a custom one.
    """)
  end

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

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

    case MobDev.OtpDownloader.ensure_android("arm64-v8a") do
      {:ok, path} ->
        Mix.shell().info([:green, "* Android arm64 OTP: #{path}", :reset])

      {:error, reason} ->
        Mix.shell().error("Warning: Android arm64 OTP download failed: #{reason}")
    end

    case MobDev.OtpDownloader.ensure_android("armeabi-v7a") do
      {:ok, path} ->
        Mix.shell().info([:green, "* Android arm32 OTP: #{path}", :reset])

      {:error, reason} ->
        Mix.shell().error("Warning: Android arm32 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 ───────────────────────────────────────────────────────

  # elixir_lib is no longer prompted — it's always auto-detected from the running BEAM.
  @required_keys [:mob_dir]

  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 (is_binary(val) and 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])
    else
      # mob.exs already has all required paths (e.g. generated with --local).
      # Still sync local.properties if it has placeholder values.
      write_local_properties(project_dir, cfg)
    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.
  # Falls back to deps/mob for Hex installs.
  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
      _ ->
        deps_mob = Path.join(project_dir, "deps/mob")
        if File.dir?(deps_mob), do: deps_mob, 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])}
    """

    File.write!(path, content)
  end

  @doc false
  @spec write_local_properties(String.t(), keyword()) :: :ok | nil
  def 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("arm64-v8a")
        otp_dir_arm32 = MobDev.OtpDownloader.android_otp_dir("armeabi-v7a")

        new_content =
          content
          |> replace_prop("mob.otp_release", otp_dir)
          |> replace_prop("mob.otp_release_arm32", otp_dir_arm32)
          |> 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

  @doc false
  @spec replace_prop(String.t(), String.t(), String.t() | nil) :: String.t()
  def replace_prop(content, key, value) when not is_nil(value) do
    String.replace(content, ~r/^#{Regex.escape(key)}=.*$/m, "#{key}=#{value}")
  end

  def replace_prop(content, _key, nil), do: content

  # ── Icon setup ────────────────────────────────────────────────────────────────

  defp setup_icon(project_dir, nil) do
    placeholder =
      Path.join([
        project_dir,
        "android",
        "app",
        "src",
        "main",
        "res",
        "mipmap-mdpi",
        "ic_launcher.png"
      ])

    if File.exists?(placeholder) do
      Mix.shell().info([
        :cyan,
        "* icons already present — skipping (run `mix mob.icon` to replace)",
        :reset
      ])
    else
      Mix.shell().info("Writing Mob logo as placeholder icon...")
      MobDev.IconGenerator.use_mob_logo(project_dir)

      Mix.shell().info([
        :green,
        "* placeholder icons written (run `mix mob.icon` to customise)",
        :reset
      ])
    end
  end

  defp setup_icon(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