defmodule DaProductApp.Adapters.SandboxPartner do
  @moduledoc """
  Sandbox UPI International partner returning simulated responses.
  
  Simulates an international partner in Singapore corridor:
  - Receives SGD after PSP converts INR → SGD
  - Credits local merchant in SGD
  - Handles FX-aware QR generation and transactions
  """
  @behaviour DaProductApp.Adapters.InternationalPartnerBehaviour

  @impl true
  def credit_merchant(params) do
    # Simulate crediting international merchant in local currency
    # PSP has already received INR from NPCI and converted to SGD
    {:ok, %{
      code: "CS", 
      payload: %{
        partner_status: "PENDING",
        partner_txn_id: "SGP_#{:rand.uniform(999999)}",
        local_amount: params.base_amount,
        local_currency: params.base_currency,
        inr_equivalent: params.inr_amount,
        fx_rate_applied: params.fx_rate,
        merchant_account_credited: true,
        settlement_status: "PROCESSING"
      }
    }}
  end

  @impl true
  def check_transaction_status(params) do
    # Simulate checking status with international partner
    {:ok, %{
      code: "CS", 
      payload: %{
        partner_status: "SUCCESS",
        settlement_status: "COMPLETED", 
        merchant_balance_updated: true,
        local_amount_settled: params.base_amount,
        partner_txn_id: params.partner_txn_id
      }
    }}
  end

  @impl true
  def reverse_payment(params) do
    # Simulate reversing payment from international merchant
    # Return foreign currency back to PSP for INR reversal to customer
    {:ok, %{
      code: "00", 
      payload: %{
        partner_status: "REVERSED",
        settlement_status: "REVERSED",
        reversal_completed: true,
        foreign_amount_reversed: params.base_amount,
        inr_reversal_required: params.inr_amount
      }
    }}
  end

  @impl true  
  def generate_dynamic_qr_with_fx(params) do
    # Simulate generating international QR with FX details embedded
    # This would be called by merchant via partner's system
    base_amount = params.base_amount || simulate_fx_conversion(params.inr_amount)
    
    # Build UPI International QR string with FX parameters
    qr_data = build_international_qr(%{
      merchant_vpa: params.merchant_vpa,
      merchant_name: params.merchant_name,
      base_amount: base_amount,
      base_currency: "SGD",
      fx_rate: params.fx_rate || "0.0165",
      markup: params.markup || "2.50",
      inr_amount: params.inr_amount
    })
    
    {:ok, %{
      code: "00",
      payload: %{
        qr_code: qr_data,
        qr_image_url: "https://api.qrserver.com/v1/create-qr-code/?data=#{URI.encode(qr_data)}",
        expires_at: DateTime.add(DateTime.utc_now(), 15, :minute),
        fx_details: %{
          base_amount: base_amount,
          base_currency: "SGD",
          fx_rate: params.fx_rate || "0.0165",
          markup_rate: params.markup || "2.50",
          inr_equivalent: params.inr_amount
        },
        corridor: "SINGAPORE",
        partner_ref: "QR_#{:rand.uniform(999999)}"
      }
    }}
  end

  @impl true
  def validate_fx_rates(_params) do
    # Simulate FX rate validation for the corridor
    {:ok, %{
      code: "00",
      payload: %{
        rates_valid: true,
        current_rate: "0.0165",
        markup_rate: "2.50",
        rate_expires_at: DateTime.add(DateTime.utc_now(), 5, :minute),
        corridor: "SINGAPORE"
      }
    }}
  end

  @impl true
  def get_corridor_info() do
    %{
      currency: "SGD",
      country: "Singapore", 
      corridor_code: "SGP",
      supported_features: ["dynamic_qr", "fx_conversion", "real_time_settlement"]
    }
  end

  # Private helper functions
  defp simulate_fx_conversion(inr_amount) when is_binary(inr_amount) do
    {inr_float, _} = Float.parse(inr_amount)
    simulate_fx_conversion(inr_float)
  end

  defp simulate_fx_conversion(inr_amount) when is_number(inr_amount) do
    # Simulate INR to SGD conversion: 1 INR = 0.0165 SGD + 2.5% markup
    sgd_rate = 0.0165
    markup = 0.025
    base_sgd = inr_amount * sgd_rate
    sgd_with_markup = base_sgd * (1 + markup)
    Float.round(sgd_with_markup, 2)
  end

  defp build_international_qr(fx_details) do
    # Build UPI International QR with embedded FX parameters per UPI spec
    base_qr = "upi://pay?pa=#{fx_details.merchant_vpa}&pn=#{URI.encode(fx_details.merchant_name)}"
    
    fx_params = [
      "am=#{fx_details.base_amount}",        # Base amount in local currency
      "cu=#{fx_details.base_currency}",      # Base currency (SGD/USD/AED)
      "fx=#{fx_details.fx_rate}",            # FX rate
      "mkup=#{fx_details.markup}",           # Markup percentage  
      "inr=#{fx_details.inr_amount}",        # INR equivalent for customer
      "mode=17",                             # UPI International mode
      "purpose=10"                           # International merchant payment
    ]
    
    "#{base_qr}&#{Enum.join(fx_params, "&")}"
  end
end