class Provider::BinancePublic < Provider
  include SecurityConcept, RateLimitable
  extend SslConfigurable

  Error = Class.new(Provider::Error)
  InvalidSecurityPriceError = Class.new(Error)
  RateLimitError = Class.new(Error)

  MIN_REQUEST_INTERVAL = 0.1

  # Binance's official ISO 10383 operating MIC (assigned Jan 2026, country AE).
  # Crypto is not tied to a national jurisdiction, so we intentionally do NOT
  # propagate the ISO-assigned country code to search results — the resolver
  # treats a nil candidate country as a wildcard, letting any family resolve
  # a Binance pick regardless of their own country.
  BINANCE_MIC = "BNCX".freeze

  # Quote assets we expose in search results. Order = preference when multiple
  # quote variants exist for the same base asset. USDT is Binance's dominant
  # dollar quote and is surfaced to users as USD. GBP is absent because
  # Binance has zero GBP trading pairs today; GBP-family users fall back to
  # USDT->USD via the app's FX conversion, same as HUF/CZK/PLN users.
  SUPPORTED_QUOTES = %w[USDT EUR JPY BRL TRY].freeze

  # Binance quote asset -> user-facing currency & ticker suffix.
  QUOTE_TO_CURRENCY = {
    "USDT" => "USD",
    "EUR"  => "EUR",
    "JPY"  => "JPY",
    "BRL"  => "BRL",
    "TRY"  => "TRY"
  }.freeze

  KLINE_MAX_LIMIT = 1000
  MS_PER_DAY = 24 * 60 * 60 * 1000
  SEARCH_LIMIT = 25

  # USD-pegged stablecoins. Binance has no self-pair (USDTUSDT is invalid) and
  # the few stablecoin/USDT pairs that do exist (USDCUSDT, etc.) hover at ~1.0
  # with sub-cent noise — synthesizing a flat 1.0 USD price is both accurate
  # enough and avoids surfacing transient depeg ticks from market data.
  USD_STABLECOINS = %w[USDT USDC BUSD DAI FDUSD TUSD USDP PYUSD].freeze

  # Symbol prefix applied by holdings processors (CoinStats, Coinbase, Kraken,
  # Binance, SimpleFIN, Lunchflow) to distinguish crypto from stock tickers.
  CRYPTO_PREFIX = "CRYPTO:".freeze

  def initialize
    # No API key required — public market data only.
  end

  def healthy?
    with_provider_response do
      client.get("#{base_url}/api/v3/ping")
      true
    end
  end

  def usage
    with_provider_response do
      UsageData.new(used: nil, limit: nil, utilization: nil, plan: "Free (no key required)")
    end
  end

  # ================================
  #           Securities
  # ================================

  def search_securities(symbol, country_code: nil, exchange_operating_mic: nil)
    with_provider_response do
      query = symbol.to_s.strip.upcase.delete_prefix(CRYPTO_PREFIX)
      next [] if query.empty?

      if USD_STABLECOINS.include?(query)
        next [ stablecoin_search_result(query) ]
      end

      symbols = exchange_info_symbols

      matches = symbols.select do |s|
        base   = s["baseAsset"].to_s.upcase
        quote  = s["quoteAsset"].to_s.upcase
        symbol = s["symbol"].to_s.upcase

        next false unless SUPPORTED_QUOTES.include?(quote)

        # Match on either the base asset (so "BTC" surfaces every BTC pair) or
        # the full Binance pair symbol (so users pasting their own portfolio
        # ticker like "BTCEUR" or "BTCUSD" — which prefixes Binance's raw
        # "BTCUSDT" — also hit a result).
        base.include?(query) || symbol == query || symbol.start_with?(query)
      end

      ranked = matches.sort_by do |s|
        base   = s["baseAsset"].to_s.upcase
        quote  = s["quoteAsset"].to_s.upcase
        symbol = s["symbol"].to_s.upcase
        quote_index = SUPPORTED_QUOTES.index(quote) || 99

        relevance = if symbol == query
          0 # exact full-ticker match — highest priority
        elsif symbol.start_with?(query)
          1 # ticker prefix match (e.g. "BTCUSD" against "BTCUSDT")
        elsif base == query
          2 # exact base-asset match (e.g. "BTC")
        elsif base.start_with?(query)
          3
        else
          4
        end

        [ relevance, quote_index, base ]
      end

      ranked.first(SEARCH_LIMIT).map do |s|
        base = s["baseAsset"].to_s.upcase
        quote = s["quoteAsset"].to_s.upcase
        display_currency = QUOTE_TO_CURRENCY[quote]

        Security.new(
          symbol: "#{base}#{display_currency}",
          name: base,
          # Brandfetch /crypto/{base} URL — unknown coins (rare) will 400 and
          # render as a broken img in the dropdown; same tradeoff as stocks
          # with obscure tickers. `::Security` reaches the AR model —
          # unqualified `Security` here resolves to the Data value-object
          # from SecurityConcept.
          logo_url: ::Security.brandfetch_crypto_url(base),
          exchange_operating_mic: BINANCE_MIC,
          country_code: nil,
          currency: display_currency
        )
      end
    end
  end

  def fetch_security_info(symbol:, exchange_operating_mic:)
    with_provider_response do
      parsed = parse_ticker(symbol)
      raise Error, "Unsupported Binance ticker: #{symbol}" if parsed.nil?

      # logo_url is intentionally nil — crypto logos are set at save time by
      # Security#generate_logo_url_from_brandfetch via the /crypto/{base}
      # route, not returned from this provider.
      links = parsed[:binance_pair] ? "https://www.binance.com/en/trade/#{parsed[:binance_pair]}" : nil

      SecurityInfo.new(
        symbol: symbol,
        name: parsed[:base],
        links: links,
        logo_url: nil,
        description: nil,
        kind: "crypto",
        exchange_operating_mic: exchange_operating_mic
      )
    end
  end

  def fetch_security_price(symbol:, exchange_operating_mic:, date:)
    with_provider_response do
      historical = fetch_security_prices(
        symbol: symbol,
        exchange_operating_mic: exchange_operating_mic,
        start_date: date,
        end_date: date
      )

      raise historical.error if historical.error.present?
      raise InvalidSecurityPriceError, "No price found for #{symbol} on #{date}" if historical.data.blank?

      historical.data.first
    end
  end

  def fetch_security_prices(symbol:, exchange_operating_mic:, start_date:, end_date:)
    with_provider_response do
      parsed = parse_ticker(symbol)
      raise InvalidSecurityPriceError, "Unsupported Binance ticker: #{symbol}" if parsed.nil?

      if parsed[:stablecoin]
        next stablecoin_prices(symbol, parsed, start_date, end_date, exchange_operating_mic)
      end

      binance_pair = parsed[:binance_pair]
      display_currency = parsed[:display_currency]
      prices = []
      cursor = start_date
      seen_data = false

      while cursor <= end_date
        window_end = [ cursor + (KLINE_MAX_LIMIT - 1).days, end_date ].min

        throttle_request
        response = client.get("#{base_url}/api/v3/klines") do |req|
          req.params["symbol"]    = binance_pair
          req.params["interval"]  = "1d"
          req.params["startTime"] = date_to_ms(cursor)
          req.params["endTime"]   = date_to_ms(window_end) + MS_PER_DAY - 1
          req.params["limit"]     = KLINE_MAX_LIMIT
        end

        batch = JSON.parse(response.body)

        if batch.empty?
          # Empty window. Two cases:
          #   1. cursor is before the pair's listing date — keep advancing
          #      until we hit the first window containing valid klines.
          #      Critical for long-range imports (e.g. account sync from a
          #      trade start date that predates the Binance listing).
          #   2. We have already collected prices and this window is past
          #      the end of available history — stop to avoid wasted calls
          #      on delisted pairs.
          break if seen_data
        else
          seen_data = true
          batch.each do |row|
            open_time_ms = row[0].to_i
            close_price  = row[4].to_f
            next if close_price <= 0

            prices << Price.new(
              symbol: symbol,
              date: Time.at(open_time_ms / 1000).utc.to_date,
              price: close_price,
              currency: display_currency,
              exchange_operating_mic: exchange_operating_mic
            )
          end
        end

        # Note: we intentionally do NOT break on a short (non-empty) batch.
        # A window that straddles the pair's listing date legitimately returns
        # fewer than KLINE_MAX_LIMIT rows while there is still valid data in
        # subsequent windows.
        cursor = window_end + 1.day
      end

      prices
    end
  end

  private
    # Synthetic search hit for a USD-pegged stablecoin. Binance has no self-pair
    # (USDTUSDT etc. don't exist), so we manufacture a result instead of letting
    # the resolver fall back to an offline CRYPTO:* row. The downstream price
    # path short-circuits via parse_ticker -> stablecoin_prices.
    def stablecoin_search_result(base)
      Security.new(
        symbol: "#{base}USD",
        name: base,
        logo_url: ::Security.brandfetch_crypto_url(base),
        exchange_operating_mic: BINANCE_MIC,
        country_code: nil,
        currency: "USD"
      )
    end

    # Synthesize flat 1.0 USD prices for USD-pegged stablecoins across the
    # requested range. Avoids a Binance round-trip (there is no self-pair like
    # USDTUSDT) and produces stable values for portfolio aggregation.
    def stablecoin_prices(symbol, parsed, start_date, end_date, exchange_operating_mic)
      (start_date..end_date).map do |date|
        Price.new(
          symbol: symbol,
          date: date,
          price: 1.0,
          currency: parsed[:display_currency],
          exchange_operating_mic: exchange_operating_mic
        )
      end
    end

    def base_url
      ENV["BINANCE_PUBLIC_URL"] || "https://data-api.binance.vision"
    end

    def client
      @client ||= Faraday.new(url: base_url, ssl: self.class.faraday_ssl_options) do |faraday|
        # Explicit timeouts so a hanging Binance endpoint can't stall a Sidekiq
        # worker or Puma thread indefinitely. Values are deliberately generous
        # enough for a full 1000-row klines response but capped to bound the
        # worst-case retry chain (3 attempts * 20s + backoff ~= 65s).
        faraday.options.open_timeout = 5
        faraday.options.timeout      = 20

        faraday.request(:retry, {
          max: 3,
          interval: 0.5,
          interval_randomness: 0.5,
          backoff_factor: 2,
          exceptions: Faraday::Retry::Middleware::DEFAULT_EXCEPTIONS + [ Faraday::ConnectionFailed ]
        })

        faraday.request :json
        faraday.response :raise_error
        faraday.headers["Accept"] = "application/json"
      end
    end

    # Maps a user-visible ticker to the Binance pair symbol, base asset, and
    # display currency. Accepts:
    #   - "BTCUSD"/"ETHEUR" — fiat suffix from search_securities output
    #   - "CRYPTO:BTCUSD" — prefixed form stored by holdings processors
    #   - "CRYPTO:SOL"/"SOL" — bare base asset; defaults to the USDT pair (USD)
    #   - "CRYPTO:USDT"/"USDT" — USD-pegged stablecoin; binance_pair is nil and
    #     callers short-circuit to a synthetic 1.0 USD price
    # Returns nil only when the input is empty after stripping the prefix.
    def parse_ticker(ticker)
      raw = ticker.to_s.upcase
      prefixed = raw.start_with?(CRYPTO_PREFIX)
      ticker_up = raw.delete_prefix(CRYPTO_PREFIX)
      return nil if ticker_up.empty?

      if USD_STABLECOINS.include?(ticker_up)
        return { binance_pair: nil, base: ticker_up, display_currency: "USD", stablecoin: true }
      end

      SUPPORTED_QUOTES.each do |quote|
        display_currency = QUOTE_TO_CURRENCY[quote]
        next unless ticker_up.end_with?(display_currency)

        base = ticker_up.delete_suffix(display_currency)
        next if base.empty?

        # "{stablecoin}USD" form (e.g. "USDTUSD" produced by search_securities)
        # routes to synthetic 1.0 USD pricing — there is no Binance self-pair.
        if display_currency == "USD" && USD_STABLECOINS.include?(base)
          return { binance_pair: nil, base: base, display_currency: "USD", stablecoin: true }
        end

        return { binance_pair: "#{base}#{quote}", base: base, display_currency: display_currency }
      end

      # No fiat suffix matched. Only treat the input as a bare base asset when
      # it arrived with the CRYPTO: prefix from a holdings processor — that
      # tells us it really is a single coin symbol (SOL, TRUMP, KAITO), not a
      # malformed pair like "BTCBNB" or "BTCGBP" that we want to reject.
      return nil unless prefixed

      { binance_pair: "#{ticker_up}USDT", base: ticker_up, display_currency: "USD" }
    end

    # Cached for 24h — exchangeInfo returns the full symbol universe (thousands
    # of rows, weight 10) and rarely changes.
    def exchange_info_symbols
      Rails.cache.fetch("binance_public:exchange_info", expires_in: 24.hours) do
        throttle_request
        response = client.get("#{base_url}/api/v3/exchangeInfo")
        parsed = JSON.parse(response.body)
        (parsed["symbols"] || []).select { |s| s["status"] == "TRADING" }
      end
    end

    def date_to_ms(date)
      Time.utc(date.year, date.month, date.day).to_i * 1000
    end

    # Preserve BinancePublic::Error subclasses (e.g. InvalidSecurityPriceError)
    # through with_provider_response. The inherited RateLimitable transformer
    # only preserves RateLimitError and would otherwise downcast our custom
    # errors to the generic Error class.
    def default_error_transformer(error)
      return error if error.is_a?(self.class::Error)
      super
    end
end