defmodule Channels.Webhook do
  @moduledoc """
  Delivers notifications to an HTTP webhook endpoint.

  POSTs a JSON body to the configured URL whenever a notification fires.
  An optional bearer token can be set for endpoint authentication.

  ## Params

    * `:url`    — the endpoint URL to POST to (required)
    * `:secret` — sent as `Authorization: Bearer <secret>` (optional)

  ## Payload shape

  ```json
  {
    "monitor_id":        "my-http-check",
    "monitor_name":      "My HTTP Check",
    "status":            "down",
    "previous_status":   "up",
    "occurred_at":       "2026-05-30T12:00:00Z",
    "node":              "raven@indigo",
    "instance_id":       "inst-1",
    "alert_started_at":  "2026-05-30T11:46:00Z",
    "duration_down_s":   840
  }
  ```

  `node`, `instance_id`, `alert_started_at`, and `duration_down_s` are
  `null` whenever the firing handler didn't have that information — always
  present in the payload, never omitted.

  A 2xx response is considered successful. Any other status code or
  connection error is returned as `{:error, reason}`.
  """

  use CodeNameRaven.Channel, category: :webhook

  alias CodeNameRaven.Channel.Notification

  @impl true
  def display_name, do: "Webhook"

  @impl true
  def params_template, do: %{url: "https://", secret: nil}

  @impl true
  def params_schema do
    [
      url: [type: :string, required: true],
      secret: [type: :string]
    ]
  end

  @impl true
  def deliver(%Notification{} = n, %{url: url} = params) when is_binary(url) and url != "" do
    payload = %{
      monitor_id: n.monitor_id,
      monitor_name: n.monitor_name,
      status: to_string(n.status),
      previous_status: n.previous_status && to_string(n.previous_status),
      occurred_at: DateTime.to_iso8601(n.occurred_at),
      node: n.node && to_string(n.node),
      instance_id: n.instance_id,
      alert_started_at: n.alert_started_at && DateTime.to_iso8601(n.alert_started_at),
      duration_down_s: Notification.duration_down(n)
    }

    headers =
      [{"content-type", "application/json"}] ++
        if(params[:secret], do: [{"authorization", "Bearer #{params[:secret]}"}], else: [])

    case CodeNameRaven.Protocol.Http.request(:post, url, body: Jason.encode!(payload), headers: headers) do
      {:ok, %{status: status}} when status in 200..299 -> :ok
      {:ok, %{status: status}} -> {:error, "HTTP #{status}"}
      {:error, reason} -> {:error, to_string(reason)}
    end
  end

  def deliver(_notification, _params), do: {:error, "url is required"}
end