defmodule ArcadiaCloud.DigitalOcean.Client do
  @moduledoc """
  Thin Req wrapper over the DigitalOcean v2 API.

  Token resolution: per-purpose, looked up via `ArcadiaCloud.DigitalOcean.Tokens`.
  Phase 0/1: env var `DO_API_TOKEN`. Phase 2: from the secrets vault.

  Paginated list endpoints stream all pages by default.
  """

  alias ArcadiaCloud.DigitalOcean.Tokens

  @base "https://api.digitalocean.com/v2"
  @page_size 100

  # ---- public ---------------------------------------------------------------

  def list_droplets(opts \\ []), do: list_paginated("/droplets", "droplets", opts)
  def list_projects(opts \\ []), do: list_paginated("/projects", "projects", opts)
  def list_domains(opts \\ []), do: list_paginated("/domains", "domains", opts)
  def list_volumes(opts \\ []), do: list_paginated("/volumes", "volumes", opts)
  def list_floating_ips(opts \\ []), do: list_paginated("/floating_ips", "floating_ips", opts)
  def list_snapshots(opts \\ []), do: list_paginated("/snapshots", "snapshots", opts)
  def list_firewalls(opts \\ []), do: list_paginated("/firewalls", "firewalls", opts)
  def list_load_balancers(opts \\ []), do: list_paginated("/load_balancers", "load_balancers", opts)

  def list_droplet_backups(droplet_id, opts \\ []) do
    list_paginated("/droplets/#{droplet_id}/backups", "backups", opts)
  end

  def list_droplet_snapshots(droplet_id, opts \\ []) do
    list_paginated("/droplets/#{droplet_id}/snapshots", "snapshots", opts)
  end

  # ---- write actions --------------------------------------------------------

  @doc """
  Request a snapshot of a droplet. Returns {:ok, action} — the snapshot
  is created asynchronously; poll `get_droplet_action/3` until the action
  status is "completed".
  """
  def create_droplet_snapshot(droplet_id, snapshot_name, opts \\ []) do
    case request(:post, "/droplets/#{droplet_id}/actions",
           body: %{type: "snapshot", name: snapshot_name},
           purpose: opts[:purpose] || "provisioning"
         ) do
      {:ok, %{"action" => action}} -> {:ok, action}
      other -> other
    end
  end

  def get_droplet_action(droplet_id, action_id, opts \\ []) do
    case request(:get, "/droplets/#{droplet_id}/actions/#{action_id}",
           purpose: opts[:purpose] || "provisioning"
         ) do
      {:ok, %{"action" => action}} -> {:ok, action}
      other -> other
    end
  end

  def delete_snapshot(snapshot_id, opts \\ []) do
    request(:delete, "/snapshots/#{snapshot_id}", purpose: opts[:purpose] || "provisioning")
  end

  # ---- billing --------------------------------------------------------------

  def get_balance(opts \\ []) do
    request(:get, "/customers/my/balance", purpose: opts[:purpose] || "billing")
  end

  def list_billing_history(opts \\ []) do
    list_paginated("/customers/my/billing_history", "billing_history",
      Keyword.put(opts, :purpose, opts[:purpose] || "billing"))
  end

  def get_invoice_summary(invoice_uuid, opts \\ []) do
    request(:get, "/customers/my/invoices/#{invoice_uuid}/summary",
      purpose: opts[:purpose] || "billing")
  end

  @doc """
  Fetch the CSV body for an invoice. Returns {:ok, csv_string} | {:error, _}.
  """
  def fetch_invoice_csv(invoice_uuid, opts \\ []) do
    purpose = opts[:purpose] || "billing"

    with {:ok, token} <- Tokens.fetch(purpose) do
      case Req.request(
             method: :get,
             url: @base <> "/customers/my/invoices/#{invoice_uuid}/csv",
             headers: [
               {"authorization", "Bearer " <> token},
               {"accept", "text/csv"}
             ],
             retry: :transient,
             max_retries: 3,
             decode_body: false
           ) do
        {:ok, %Req.Response{status: 200, body: body}} when is_binary(body) ->
          {:ok, body}

        {:ok, %Req.Response{status: status, body: body}} ->
          {:error, {:http, status, body}}

        {:error, e} ->
          {:error, {:transport, e}}
      end
    end
  end

  def create_project(name, purpose, description \\ "", opts \\ []) do
    body = %{
      name: name,
      purpose: purpose,
      description: description,
      environment: "Development"
    }

    request(:post, "/projects", body: body, purpose: opts[:purpose] || "provisioning")
    |> case do
      {:ok, %{"project" => project}} -> {:ok, project}
      other -> other
    end
  end

  def list_project_resources(project_id, opts \\ []) do
    list_paginated("/projects/#{project_id}/resources", "resources", opts)
  end

  def assign_to_project(project_id, urns, opts \\ []) when is_list(urns) do
    request(:post, "/projects/#{project_id}/resources",
      body: %{resources: urns},
      purpose: opts[:purpose] || "provisioning"
    )
  end

  # ---- core -----------------------------------------------------------------

  defp list_paginated(path, root_key, opts) do
    purpose = opts[:purpose] || "sync_full"
    do_paginate(path, root_key, purpose, [], 1)
  end

  defp do_paginate(path, root_key, purpose, acc, page) do
    params = [page: page, per_page: @page_size]

    case request(:get, path, params: params, purpose: purpose) do
      {:ok, %{} = body} ->
        items = Map.get(body, root_key, [])
        new_acc = acc ++ items

        if has_next?(body) do
          do_paginate(path, root_key, purpose, new_acc, page + 1)
        else
          {:ok, new_acc}
        end

      err ->
        err
    end
  end

  defp has_next?(%{"links" => %{"pages" => %{"next" => _}}}), do: true
  defp has_next?(_), do: false

  defp request(method, path, opts) do
    purpose = Keyword.fetch!(opts, :purpose)

    with {:ok, token} <- Tokens.fetch(purpose) do
      req_opts =
        [
          method: method,
          url: @base <> path,
          headers: [{"authorization", "Bearer " <> token}],
          retry: :transient,
          max_retries: 3
        ]
        |> maybe_put(:params, opts[:params])
        |> maybe_put(:json, opts[:body])

      case Req.request(req_opts) do
        {:ok, %Req.Response{status: status, body: body}} when status in 200..299 ->
          {:ok, body}

        {:ok, %Req.Response{status: status, body: body}} ->
          {:error, {:http, status, body}}

        {:error, exception} ->
          {:error, {:transport, exception}}
      end
    end
  end

  defp maybe_put(opts, _key, nil), do: opts
  defp maybe_put(opts, key, value), do: Keyword.put(opts, key, value)
end