defmodule Polymarket.Activity do
  @moduledoc """
  Pure normalization and join helpers for Polymarket activity data.

  This module operates on plain maps. It does not fetch from the Data API
  or the CLOB; the caller pipes raw activity events (typically from
  `Polymarket.Data.get_activity/2`) and CLOB fills (from
  `PolymarketClob.API.Account.get_trades/3`) into these helpers.

  All input keys are looked up in **both** camelCase string form (the
  shape Polymarket's Data API returns) and snake_case string form (the
  shape the CLOB and several internal callers use). Atom keys are also
  accepted as a convenience for in-Elixir construction.

  ## Match semantics

  `cost_for_order/3`, `revenue_for_order/3`, and `redemption_for_market/2`
  **sum** USDC sizes across every matching event. This is a deliberate
  divergence from the bot's `extract_activity_cost/3` which returns the
  first match: GTC orders that partially fill across multiple takers
  produce multiple activity rows, and summing is the correct total.

  All three return `nil` when no event matches, distinguishing
  "no activity yet" from "events that summed to 0". The bot uses `0.0`
  for the same case; the SDK chose `nil` to keep "missing data" and
  "actual zero" semantically separate.

  ## Activity ↔ fills join

  Polymarket's `/activity` endpoint identifies each TRADE by
  `transactionHash`, not `orderHash`. To find the activity row for a
  given CLOB order id, we resolve `tx_hash` from the fills list first
  and then match against `activity.transactionHash`. When no fills list
  is available, `cost_for_order/3` and `revenue_for_order/3` fall back
  to a best-effort match against legacy `orderHash` / `taker_order_id`
  fields. Pass an empty list `[]` for fills if all you have is the order
  id and you want the fallback path.
  """

  alias Polymarket.Activity.Event

  @type raw_event :: map()
  @type raw_fill :: map()
  @type order_id :: String.t()
  @type condition_id :: String.t()

  # ── Normalization ──

  @doc """
  Normalizes a list of raw `/activity` event maps into typed
  `Polymarket.Activity.Event` structs.

  Unknown event types are still emitted with `type: :unknown` and the
  full raw map preserved under `:raw`, so a caller iterating over a
  large activity feed never loses events it did not anticipate.
  """
  @spec normalize([raw_event()]) :: [Event.t()]
  def normalize(events) when is_list(events) do
    Enum.map(events, &normalize_one/1)
  end

  defp normalize_one(event) when is_map(event) do
    %Event{
      type: parse_type(field(event, "type")),
      side: parse_side(field(event, "side")),
      tx_hash: field(event, "transactionHash") || field(event, "transaction_hash"),
      condition_id: field(event, "conditionId") || field(event, "condition_id"),
      token_id: field(event, "asset") || field(event, "token_id"),
      usdc_size: parse_float(field(event, "usdcSize") || field(event, "usdc_size")),
      shares: parse_float(field(event, "size")),
      price: parse_float(field(event, "price")),
      timestamp: parse_integer(field(event, "timestamp")),
      raw: event
    }
  end

  # ── Cost / revenue / redemption ──

  @doc """
  Sums fee-inclusive USDC cost across every TRADE BUY event matching
  `order_id`. Returns `nil` when no event matches.

  Activity is matched to an order id by:

    1. Finding fills whose `order_id` or `taker_order_id` equals the
       requested `order_id` and collecting their `tx_hash`/`transaction_hash`.
    2. Selecting activity events whose `transactionHash` is in that set
       AND whose `type == "TRADE"` AND `side == "BUY"`.

  When step 1 yields nothing (e.g. caller did not supply fills), a
  fallback matches activity rows directly by `orderHash` or
  `taker_order_id` equal to `order_id`. The fallback is best-effort
  only — Polymarket has historically populated `transactionHash` more
  reliably than `orderHash` on `/activity`.
  """
  @spec cost_for_order([raw_event()], order_id(), [raw_fill()]) :: float() | nil
  def cost_for_order(activities, order_id, fills)
      when is_list(activities) and is_binary(order_id) and is_list(fills) do
    sum_usdc_for_trade(activities, order_id, fills, "BUY")
  end

  @doc """
  Sums fee-inclusive USDC revenue across every TRADE SELL event
  matching `order_id`. Returns `nil` when no event matches.

  Same join semantics as `cost_for_order/3`.
  """
  @spec revenue_for_order([raw_event()], order_id(), [raw_fill()]) :: float() | nil
  def revenue_for_order(activities, order_id, fills)
      when is_list(activities) and is_binary(order_id) and is_list(fills) do
    sum_usdc_for_trade(activities, order_id, fills, "SELL")
  end

  @doc """
  Sums REDEEM payouts for `condition_id`. Returns `nil` when no event
  matches.

  Activity rows are matched directly on `conditionId` / `condition_id`;
  no fills join is needed because REDEEM events do not carry a CLOB
  order id.
  """
  @spec redemption_for_market([raw_event()], condition_id()) :: float() | nil
  def redemption_for_market(activities, condition_id)
      when is_list(activities) and is_binary(condition_id) do
    matches =
      for event <- activities,
          field(event, "type") == "REDEEM",
          field(event, "conditionId") == condition_id or
            field(event, "condition_id") == condition_id do
        parse_float(field(event, "usdcSize") || field(event, "usdc_size")) || 0.0
      end

    sum_or_nil(matches)
  end

  # ── Private ──

  defp sum_usdc_for_trade(activities, order_id, fills, expected_side) do
    tx_hashes = tx_hashes_for_order(fills, order_id)

    matches =
      if tx_hashes != [] do
        for event <- activities,
            field(event, "type") == "TRADE",
            field(event, "side") == expected_side,
            event_tx_hash = field(event, "transactionHash") || field(event, "transaction_hash"),
            event_tx_hash in tx_hashes do
          parse_float(field(event, "usdcSize") || field(event, "usdc_size")) || 0.0
        end
      else
        # Legacy fallback for callers without a fills list. Match activity
        # rows by `orderHash` / `taker_order_id` directly. Best-effort:
        # Polymarket's /activity does not always populate orderHash.
        for event <- activities,
            field(event, "type") == "TRADE",
            field(event, "side") == expected_side,
            field(event, "orderHash") == order_id or
              field(event, "order_hash") == order_id or
              field(event, "taker_order_id") == order_id do
          parse_float(field(event, "usdcSize") || field(event, "usdc_size")) || 0.0
        end
      end

    sum_or_nil(matches)
  end

  defp tx_hashes_for_order(fills, order_id) do
    Enum.flat_map(fills, fn fill ->
      if field(fill, "order_id") == order_id or
           field(fill, "taker_order_id") == order_id or
           field(fill, "orderID") == order_id do
        case field(fill, "tx_hash") || field(fill, "transaction_hash") ||
               field(fill, "transactionHash") do
          nil -> []
          hash -> [hash]
        end
      else
        []
      end
    end)
  end

  defp sum_or_nil([]), do: nil
  defp sum_or_nil(values), do: Enum.sum(values)

  defp parse_type("TRADE"), do: :trade
  defp parse_type("REDEEM"), do: :redeem
  defp parse_type(_), do: :unknown

  defp parse_side("BUY"), do: :buy
  defp parse_side("SELL"), do: :sell
  defp parse_side(_), do: nil

  defp parse_float(value) when is_float(value), do: value
  defp parse_float(value) when is_integer(value), do: value * 1.0

  # Binary inputs must parse to a number with no trailing characters.
  # `Float.parse("12abc")` returns `{12.0, "abc"}`,
  # which the lenient `{n, _}` pattern would accept as 12.0. That would
  # silently turn a partial numeric string into a confident 12.0
  # contribution to a P&L sum. Require empty rest so partial parses
  # surface as `nil` and the caller can distinguish "missing data" from
  # "real value." Mirrors the strictness already used in `parse_integer/1`.
  defp parse_float(value) when is_binary(value) do
    case Float.parse(value) do
      {n, ""} -> n
      _ -> nil
    end
  end

  defp parse_float(_), do: nil

  defp parse_integer(value) when is_integer(value), do: value

  defp parse_integer(value) when is_binary(value) do
    case Integer.parse(value) do
      {n, ""} -> n
      _ -> nil
    end
  end

  defp parse_integer(_), do: nil

  # Defensive map accessor: tries the string key first (the shape every
  # production caller currently uses), then the corresponding atom key
  # for in-Elixir test fixtures.
  defp field(map, key) when is_map(map) and is_binary(key) do
    case Map.fetch(map, key) do
      {:ok, value} ->
        value

      :error ->
        atom_key = safe_existing_atom(key)
        if atom_key, do: Map.get(map, atom_key), else: nil
    end
  end

  defp field(_, _), do: nil

  defp safe_existing_atom(key) do
    String.to_existing_atom(key)
  rescue
    ArgumentError -> nil
  end
end