defmodule Integrations.Http do
  @moduledoc """
  HTTP endpoint monitor.

  Checks that a URL responds within an acceptable time and with an expected
  HTTP status code. Uses `Mint` for requests to collect connection phases
  (DNS, TCP, SSL handshakes, TTFB, and download times) and peer certificates.

  Collection only — see `Integrations.Http.Display` (same package) for the
  dashboard panel. `Display.BundledDefault` auto-hooks it whenever this
  monitor starts, same as a single-module package would; a release without
  `raven_web` simply never compiles the display half and runs this monitor
  headless.

  ## Params

    * `:url`             — The URL to check. Required.
    * `:method`          — The HTTP method (e.g., :get, :post). Defaults to :get.
    * `:timeout_ms`      — Request timeout in milliseconds. Defaults to `10_000`.
    * `:tls_verify`      — Whether to verify TLS certificate chain. Defaults to true.
    * `:headers`         — Custom headers to send.
    * `:body`            — Request body to send.
    * `:follow_redirects`— Whether to follow 3xx redirects. Defaults to false.
    * `:assertions`      — List of assertion maps to evaluate.

  ## Example config

      %CodeNameRaven.Monitor.Config{
        id:          "example-web",
        name:        "Example Website",
        module:      Integrations.Http,
        params:      %{url: "https://example.com"},
        interval_ms: 60_000,
        enabled:     true,
        tags:        ["web", "external"]
      }
  """

  use CodeNameRaven.Monitor

  @default_timeout_ms 10_000
  @high_latency_ms    3_000

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

  @impl true
  def params_schema do
    [
      url:                    [type: :string, required: true, doc: "URL to check"],
      method:                 [type: {:in, [:get, :post, :put, :patch, :delete, :head]}, default: :get],
      timeout_ms:             [type: :non_neg_integer, default: 10_000],
      tls_verify:             [type: :boolean, default: true],
      headers:                [type: {:list, :any}, default: [], doc: "List of %{name: _, value: _} maps"],
      assertions:             [type: {:list, :any}, default: [], doc: "List of assertion maps"],
      body:                   [type: :string, required: false, doc: "Request body"],
      follow_redirects:       [type: :any, default: false]
    ]
  end


  @impl true
  def target_uri(%{url: url}) when is_binary(url), do: {:ok, url}
  def target_uri(_params), do: :none

  @impl true
  def collect(%{url: _} = params, state) do
    method = Map.get(params, :method, :get)
    url = params.url
    timeout_ms = Map.get(params, :timeout_ms, @default_timeout_ms)
    tls_verify = Map.get(params, :tls_verify, true)
    headers = Map.get(params, :headers, [])
    body = Map.get(params, :body, nil)
    follow_redirects = Map.get(params, :follow_redirects, false)

    opts = [
      timeout_ms: timeout_ms,
      tls_verify: tls_verify,
      headers: headers,
      body: body,
      follow_redirects: follow_redirects
    ]

    case CodeNameRaven.Protocol.Http.request(method, url, opts) do
      {:ok, raw_result} ->
        cert_expiry_days =
          if raw_result.cert_expiry_at do
            diff_seconds = DateTime.diff(raw_result.cert_expiry_at, DateTime.utc_now())
            max(0, div(diff_seconds, 86400))
          else
            nil
          end

        mapped_raw = %{
          status_code:      raw_result.status,
          latency_ms:       raw_result.timing.total_ms,
          body:             raw_result.body,
          headers:          raw_result.headers,
          cert_expiry_days: cert_expiry_days,
          timing: %{
            dns_ms:      raw_result.timing.dns_ms,
            tcp_ms:      raw_result.timing.tcp_ms,
            ssl_ms:      raw_result.timing.ssl_ms,
            ttfb_ms:     raw_result.timing.ttfb_ms,
            download_ms: raw_result.timing.download_ms
          },
          redirects: raw_result.redirects
        }

        # Parse and evaluate assertions inline
        alias CodeNameRaven.Monitor.Assertion
        assertions = Assertion.parse(params[:assertions] || [])
        {assertion_status, failures} = Assertion.evaluate_all(assertions, mapped_raw)

        result = Map.merge(mapped_raw, %{
          assertions:         assertions,
          assertion_status:   assertion_status,
          assertion_failures:  failures
        })

        {:ok, result, state}

      {:error, reason} ->
        {:error, format_error(reason), state}
    end
  end
  def collect(params, state),
    do: {:error, "missing required param :url — got: #{inspect(params)}", state}

  @impl true
  def healthy?(%{assertions: [_ | _], assertion_status: status}), do: status
  def healthy?(%{status_code: code, latency_ms: latency} = result) do
    # Fallback if no assertions configured
    expected = Map.get(result, :expected_status, 200)
    cond do
      not status_matches?(code, expected) -> :down
      latency >= @high_latency_ms         -> :degraded
      true                                -> :up
    end
  end

  @impl true
  def metrics(result) do
    %{
      latency_ms:       result[:latency_ms],
      status_code:      result[:status_code],
      cert_expiry_days: result[:cert_expiry_days],
      dns_ms:           result[:timing][:dns_ms],
      tcp_ms:           result[:timing][:tcp_ms],
      ssl_ms:           result[:timing][:ssl_ms],
      ttfb_ms:          result[:timing][:ttfb_ms],
      download_ms:      result[:timing][:download_ms],
      redirects:        result[:redirects]
    }
    |> Enum.reject(fn {_k, v} -> is_nil(v) end)
    |> Map.new()
  end

  # ---------------------------------------------------------------------------
  # Private helpers
  # ---------------------------------------------------------------------------

  defp status_matches?(code, expected) when is_integer(expected),
    do: code == expected
  defp status_matches?(code, %Range{} = range),
    do: code in range
  defp status_matches?(code, expected) when is_list(expected),
    do: code in expected

  defp format_error(%{reason: reason}), do: inspect(reason)
  defp format_error(reason) when is_atom(reason), do: to_string(reason)
  defp format_error(reason), do: inspect(reason)
end