defmodule PlausibleWeb.Api.StatsController do
  use PlausibleWeb, :controller
  use Plausible.Repo
  use Plug.ErrorHandler
  alias Plausible.Stats
  alias Plausible.Stats.{Query, Filters}

  def main_graph(conn, params) do
    site = conn.assigns[:site]
    query = Query.from(site.timezone, params) |> Filters.add_prefix()

    query =
      case query.filters["event:goal"] do
        nil -> Query.put_filter(query, "event:name", {:is, "pageview"})
        _ -> query
      end

    timeseries = Task.async(fn -> Stats.timeseries(site, query, ["visitors"]) end)
    {top_stats, sample_percent} = fetch_top_stats(site, query)

    timeseries_result = Task.await(timeseries)
    plot = Enum.map(timeseries_result, fn row -> row["visitors"] end)
    labels = Enum.map(timeseries_result, fn row -> row["date"] end)
    present_index = present_index_for(site, query, labels)

    json(conn, %{
      plot: plot,
      labels: labels,
      present_index: present_index,
      top_stats: top_stats,
      interval: query.interval,
      sample_percent: sample_percent
    })
  end

  defp present_index_for(site, query, dates) do
    case query.interval do
      "hour" ->
        current_date =
          Timex.now(site.timezone)
          |> Timex.format!("{YYYY}-{0M}-{0D} {h24}:00:00")

        Enum.find_index(dates, &(&1 == current_date))

      "date" ->
        current_date =
          Timex.now(site.timezone)
          |> Timex.to_date()

        Enum.find_index(dates, &(&1 == current_date))

      "month" ->
        current_date =
          Timex.now(site.timezone)
          |> Timex.to_date()
          |> Timex.beginning_of_month()

        Enum.find_index(dates, &(&1 == current_date))

      "minute" ->
        nil
    end
  end

  defp fetch_top_stats(site, %Query{period: "30m"} = query) do
    %{
      "visitors" => %{"value" => visitors},
      "pageviews" => %{"value" => pageviews}
    } = Stats.aggregate(site, query, ["visitors", "pageviews"])

    stats = [
      %{
        name: "Current visitors",
        value: Stats.current_visitors(site)
      },
      %{
        name: "Unique visitors (last 30 min)",
        value: visitors
      },
      %{
        name: "Pageviews (last 30 min)",
        value: pageviews
      }
    ]

    {stats, 100}
  end

  defp fetch_top_stats(site, %Query{filters: %{"event:goal" => _goal}} = query) do
    total_filter = Map.merge(query.filters, %{"event:goal" => nil})
    prev_query = Query.shift_back(query, site)

    %{
      "visitors" => %{"value" => unique_visitors}
    } = Stats.aggregate(site, %{query | filters: total_filter}, ["visitors"])

    %{
      "visitors" => %{"value" => prev_unique_visitors}
    } = Stats.aggregate(site, %{prev_query | filters: total_filter}, ["visitors"])

    %{
      "visitors" => %{"value" => converted_visitors},
      "events" => %{"value" => completions}
    } = Stats.aggregate(site, query, ["visitors", "events"])

    %{
      "visitors" => %{"value" => prev_converted_visitors},
      "events" => %{"value" => prev_completions}
    } = Stats.aggregate(site, prev_query, ["visitors", "events"])

    conversion_rate = calculate_cr(unique_visitors, converted_visitors)
    prev_conversion_rate = calculate_cr(prev_unique_visitors, prev_converted_visitors)

    stats = [
      %{
        name: "Unique visitors",
        value: unique_visitors,
        change: percent_change(prev_unique_visitors, unique_visitors)
      },
      %{
        name: "Unique conversions",
        value: converted_visitors,
        change: percent_change(prev_converted_visitors, converted_visitors)
      },
      %{
        name: "Total conversions",
        value: completions,
        change: percent_change(prev_completions, completions)
      },
      %{
        name: "Conversion rate",
        value: conversion_rate,
        change: percent_change(prev_conversion_rate, conversion_rate)
      }
    ]

    {stats, 100}
  end

  defp fetch_top_stats(site, query) do
    prev_query = Query.shift_back(query, site)

    metrics =
      if query.filters["event:page"] do
        ["visitors", "pageviews", "bounce_rate", "time_on_page", "sample_percent"]
      else
        ["visitors", "pageviews", "bounce_rate", "visit_duration", "sample_percent"]
      end

    current_results = Stats.aggregate(site, query, metrics)
    prev_results = Stats.aggregate(site, prev_query, metrics)

    stats =
      [
        top_stats_entry(current_results, prev_results, "Unique visitors", "visitors"),
        top_stats_entry(current_results, prev_results, "Total pageviews", "pageviews"),
        top_stats_entry(current_results, prev_results, "Bounce rate", "bounce_rate"),
        top_stats_entry(current_results, prev_results, "Visit duration", "visit_duration"),
        top_stats_entry(current_results, prev_results, "Time on page", "time_on_page")
      ]
      |> Enum.filter(& &1)

    {stats, current_results["sample_percent"]["value"]}
  end

  defp top_stats_entry(current_results, prev_results, name, key) do
    if current_results[key] do
      %{
        name: name,
        value: current_results[key]["value"],
        change: calculate_change(key, prev_results[key]["value"], current_results[key]["value"])
      }
    end
  end

  defp calculate_change("bounce_rate", old_count, new_count) do
    if old_count > 0, do: new_count - old_count
  end

  defp calculate_change(_metric, old_count, new_count) do
    percent_change(old_count, new_count)
  end

  defp percent_change(old_count, new_count) do
    cond do
      old_count == 0 and new_count > 0 ->
        100

      old_count == 0 and new_count == 0 ->
        0

      true ->
        round((new_count - old_count) / old_count * 100)
    end
  end

  def sources(conn, params) do
    site = conn.assigns[:site]

    query =
      Query.from(site.timezone, params)
      |> Filters.add_prefix()
      |> maybe_hide_noref("visit:source", params)

    pagination = parse_pagination(params)

    metrics =
      if params["detailed"], do: ["visitors", "bounce_rate", "visit_duration"], else: ["visitors"]

    res =
      Stats.breakdown(site, query, "visit:source", metrics, pagination)
      |> transform_keys(%{"source" => "name", "visitors" => "count"})

    json(conn, res)
  end

  def utm_mediums(conn, params) do
    site = conn.assigns[:site]

    query =
      Query.from(site.timezone, params)
      |> Filters.add_prefix()
      |> maybe_hide_noref("visit:utm_medium", params)

    pagination = parse_pagination(params)
    metrics = ["visitors", "bounce_rate", "visit_duration"]

    res =
      Stats.breakdown(site, query, "visit:utm_medium", metrics, pagination)
      |> transform_keys(%{"utm_medium" => "name", "visitors" => "count"})

    json(conn, res)
  end

  def utm_campaigns(conn, params) do
    site = conn.assigns[:site]

    query =
      Query.from(site.timezone, params)
      |> Filters.add_prefix()
      |> maybe_hide_noref("visit:utm_campaign", params)

    pagination = parse_pagination(params)
    metrics = ["visitors", "bounce_rate", "visit_duration"]

    res =
      Stats.breakdown(site, query, "visit:utm_campaign", metrics, pagination)
      |> transform_keys(%{"utm_campaign" => "name", "visitors" => "count"})

    json(conn, res)
  end

  def utm_sources(conn, params) do
    site = conn.assigns[:site]

    query =
      Query.from(site.timezone, params)
      |> Filters.add_prefix()
      |> maybe_hide_noref("visit:utm_source", params)

    pagination = parse_pagination(params)
    metrics = ["visitors", "bounce_rate", "visit_duration"]

    res =
      Stats.breakdown(site, query, "visit:utm_source", metrics, pagination)
      |> transform_keys(%{"utm_source" => "name", "visitors" => "count"})

    json(conn, res)
  end

  def referrer_drilldown(conn, %{"referrer" => "Google"} = params) do
    site = conn.assigns[:site] |> Repo.preload(:google_auth)
    query = Query.from(site.timezone, params)

    search_terms =
      if site.google_auth && site.google_auth.property && !query.filters["goal"] do
        google_api().fetch_stats(site, query, params["limit"] || 9)
      end

    %{"visitors" => %{"value" => total_visitors}} = Stats.aggregate(site, query, ["visitors"])

    case search_terms do
      nil ->
        user_id = get_session(conn, :current_user_id)
        is_admin = user_id && Plausible.Sites.has_admin_access?(user_id, site)
        json(conn, %{not_configured: true, is_admin: is_admin, total_visitors: total_visitors})

      {:ok, terms} ->
        json(conn, %{search_terms: terms, total_visitors: total_visitors})

      {:error, e} ->
        put_status(conn, 500)
        |> json(%{error: e})
    end
  end

  def referrer_drilldown(conn, %{"referrer" => referrer} = params) do
    site = conn.assigns[:site]

    query =
      Query.from(site.timezone, params)
      |> Query.put_filter("source", referrer)
      |> Filters.add_prefix()

    pagination = parse_pagination(params)

    metrics =
      if params["detailed"], do: ["visitors", "bounce_rate", "visit_duration"], else: ["visitors"]

    referrers =
      Stats.breakdown(site, query, "visit:referrer", metrics, pagination)
      |> transform_keys(%{"referrer" => "name", "visitors" => "count"})

    %{"visitors" => %{"value" => total_visitors}} = Stats.aggregate(site, query, ["visitors"])
    json(conn, %{referrers: referrers, total_visitors: total_visitors})
  end

  def pages(conn, params) do
    site = conn.assigns[:site]
    query = Query.from(site.timezone, params) |> Filters.add_prefix()

    query =
      case query.filters["event:goal"] do
        nil -> Query.put_filter(query, "event:name", {:is, "pageview"})
        _ -> query
      end

    metrics =
      if params["detailed"],
        do: ["visitors", "pageviews", "bounce_rate", "time_on_page"],
        else: ["visitors"]

    pagination = parse_pagination(params)

    pages =
      Stats.breakdown(site, query, "event:page", metrics, pagination)
      |> transform_keys(%{"page" => "name", "visitors" => "count"})

    json(conn, pages)
  end

  def entry_pages(conn, params) do
    site = conn.assigns[:site]
    query = Query.from(site.timezone, params) |> Filters.add_prefix()
    pagination = parse_pagination(params)
    metrics = ["visitors", "visits", "visit_duration"]

    entry_pages =
      Stats.breakdown(site, query, "visit:entry_page", metrics, pagination)
      |> transform_keys(%{"entry_page" => "name", "visits" => "entries", "visitors" => "count"})

    json(conn, entry_pages)
  end

  def exit_pages(conn, params) do
    site = conn.assigns[:site]
    query = Query.from(site.timezone, params) |> Filters.add_prefix()
    {limit, page} = parse_pagination(params)
    metrics = ["visitors", "visits"]

    exit_pages =
      Stats.breakdown(site, query, "visit:exit_page", metrics, {limit, page})
      |> transform_keys(%{"exit_page" => "name", "visits" => "exits", "visitors" => "count"})

    pages = Enum.map(exit_pages, & &1["name"])

    total_visits_query =
      Query.put_filter(query, "event:page", {:member, pages})
      |> Query.put_filter("event:goal", nil)
      |> Query.put_filter("event:name", {:is, "pageview"})
      |> Query.put_filter("visit:goal", query.filters["event:goal"])
      |> Query.put_filter("visit:page", query.filters["event:page"])

    total_pageviews =
      Stats.breakdown(site, total_visits_query, "event:page", ["pageviews"], {limit, 1})

    exit_pages =
      Enum.map(exit_pages, fn exit_page ->
        exit_rate =
          case Enum.find(total_pageviews, &(&1["page"] == exit_page["name"])) do
            %{"pageviews" => pageviews} ->
              Float.floor(exit_page["exits"] / pageviews * 100)

            nil ->
              nil
          end

        Map.put(exit_page, "exit_rate", exit_rate)
      end)

    json(conn, exit_pages)
  end

  def countries(conn, params) do
    site = conn.assigns[:site]
    query = Query.from(site.timezone, params) |> Filters.add_prefix()

    countries =
      Stats.breakdown(site, query, "visit:country", ["visitors"], {300, 1})
      |> transform_keys(%{"country" => "name", "visitors" => "count"})
      |> Enum.map(fn country ->
        alpha3 = Stats.CountryName.to_alpha3(country["name"])
        Map.put(country, "name", alpha3)
      end)
      |> add_percentages

    json(conn, countries)
  end

  def browsers(conn, params) do
    site = conn.assigns[:site]
    query = Query.from(site.timezone, params) |> Filters.add_prefix()
    pagination = parse_pagination(params)

    browsers =
      Stats.breakdown(site, query, "visit:browser", ["visitors"], pagination)
      |> transform_keys(%{"browser" => "name", "visitors" => "count"})
      |> add_percentages

    json(conn, browsers)
  end

  def browser_versions(conn, params) do
    site = conn.assigns[:site]
    query = Query.from(site.timezone, params) |> Filters.add_prefix()
    pagination = parse_pagination(params)

    versions =
      Stats.breakdown(site, query, "visit:browser_version", ["visitors"], pagination)
      |> transform_keys(%{"browser_version" => "name", "visitors" => "count"})
      |> add_percentages

    json(conn, versions)
  end

  def operating_systems(conn, params) do
    site = conn.assigns[:site]
    query = Query.from(site.timezone, params) |> Filters.add_prefix()
    pagination = parse_pagination(params)

    systems =
      Stats.breakdown(site, query, "visit:os", ["visitors"], pagination)
      |> transform_keys(%{"os" => "name", "visitors" => "count"})
      |> add_percentages

    json(conn, systems)
  end

  def operating_system_versions(conn, params) do
    site = conn.assigns[:site]
    query = Query.from(site.timezone, params) |> Filters.add_prefix()
    pagination = parse_pagination(params)

    versions =
      Stats.breakdown(site, query, "visit:os_version", ["visitors"], pagination)
      |> transform_keys(%{"os_version" => "name", "visitors" => "count"})
      |> add_percentages

    json(conn, versions)
  end

  def screen_sizes(conn, params) do
    site = conn.assigns[:site]
    query = Query.from(site.timezone, params) |> Filters.add_prefix()
    pagination = parse_pagination(params)

    sizes =
      Stats.breakdown(site, query, "visit:device", ["visitors"], pagination)
      |> transform_keys(%{"device" => "name", "visitors" => "count"})
      |> add_percentages

    json(conn, sizes)
  end

  defp calculate_cr(unique_visitors, converted_visitors) do
    if unique_visitors > 0,
      do: Float.round(converted_visitors / unique_visitors * 100, 1),
      else: 0.0
  end

  def conversions(conn, params) do
    site = conn.assigns[:site]
    query = Query.from(site.timezone, params) |> Filters.add_prefix()
    pagination = parse_pagination(params)

    total_filter = Map.merge(query.filters, %{"event:goal" => nil})

    %{"visitors" => %{"value" => total_visitors}} =
      Stats.aggregate(site, %{query | filters: total_filter}, ["visitors"])

    prop_names = Stats.props(site, query)

    conversions =
      Stats.breakdown(site, query, "event:goal", ["visitors", "events"], pagination)
      |> transform_keys(%{"goal" => "name", "visitors" => "count", "events" => "total_count"})
      |> Enum.map(fn goal ->
        goal
        |> Map.put(:prop_names, prop_names[goal["name"]])
        |> Map.put(:conversion_rate, calculate_cr(total_visitors, goal["count"]))
      end)

    json(conn, conversions)
  end

  def prop_breakdown(conn, params) do
    site = conn.assigns[:site]
    query = Query.from(site.timezone, params) |> Filters.add_prefix()
    pagination = parse_pagination(params)

    total_filter = Map.merge(query.filters, %{"event:goal" => nil})

    %{"visitors" => %{"value" => unique_visitors}} =
      Stats.aggregate(site, %{query | filters: total_filter}, ["visitors"])

    prop_name = "event:props:" <> params["prop_name"]

    props =
      Stats.breakdown(site, query, prop_name, ["visitors", "events"], pagination)
      |> transform_keys(%{
        params["prop_name"] => "name",
        "visitors" => "count",
        "events" => "total_count"
      })
      |> Enum.map(fn prop ->
        Map.put(prop, "conversion_rate", calculate_cr(unique_visitors, prop["count"]))
      end)

    json(conn, props)
  end

  def current_visitors(conn, _) do
    site = conn.assigns[:site]
    json(conn, Stats.current_visitors(site))
  end

  defp google_api(), do: Application.fetch_env!(:plausible, :google_api)

  def handle_errors(conn, %{kind: kind, reason: reason}) do
    json(conn, %{error: Exception.format_banner(kind, reason)})
  end

  def filter_suggestions(conn, params) do
    site = conn.assigns[:site]
    query = Query.from(site.timezone, params) |> Filters.add_prefix()

    json(conn, Stats.filter_suggestions(site, query, params["filter_name"], params["q"]))
  end

  defp transform_keys(results, keys_to_replace) do
    Enum.map(results, fn map ->
      Enum.map(map, fn {key, val} ->
        {Map.get(keys_to_replace, key, key), val}
      end)
      |> Enum.into(%{})
    end)
  end

  defp parse_pagination(params) do
    limit = if params["limit"], do: String.to_integer(params["limit"]), else: 9
    page = if params["page"], do: String.to_integer(params["page"]), else: 1
    {limit, page}
  end

  defp add_percentages(stat_list) do
    total = Enum.reduce(stat_list, 0, fn %{"count" => count}, total -> total + count end)

    Enum.map(stat_list, fn stat ->
      Map.put(stat, "percentage", round(stat["count"] / total * 100))
    end)
  end

  defp maybe_hide_noref(query, property, params) do
    cond do
      is_nil(query.filters[property]) and params["show_noref"] != "true" ->
        new_filters = Map.put(query.filters, property, {:is_not, "Direct / None"})
        %Query{query | filters: new_filters}

      true ->
        query
    end
  end
end