defmodule DaProductApp.Merchants.Merchant do
  @moduledoc """
  Unified merchant entity supporting both NPCI specification and partner management.
  
  Merchants are enrolled by partners and contain both NPCI-required fields
  and partner-specific business information for international payments.
  """
  use Ecto.Schema
  import Ecto.Changeset

  alias DaProductApp.Merchants.MerchantInvoice
  alias DaProductApp.Partners.Partner
  alias DaProductApp.Transactions.Transaction

  schema "merchants" do
    # NPCI Required Fields (from UPI specification)
    field :mid, :string                   # Merchant ID (NPCI standard)
    field :tid, :string                   # Terminal ID
    field :sid, :string                   # Store ID
    field :sub_code, :string              # Sub merchant code
    field :merchant_type, :string         # SMALL, MEDIUM, LARGE
    field :merchant_genre, :string        # RETAIL, ONLINE
    field :onboarding_type, :string       # AGGREGATOR, DIRECT, BANK
    field :inst_code, :string             # Institution code
    field :country_code, :string          # Country code (SG, AE, US, IN)
    field :network_inst_id, :string       # Network institution ID
    
    # Business Identity Fields (from international migration)
    field :merchant_code, :string         # Internal unique identifier
    field :brand_name, :string            # Public brand name
    field :legal_name, :string            # Legal registered name
    field :franchise_name, :string        # Franchise name if applicable
    field :ownership_type, :string        # PRIVATE, PUBLIC, PARTNERSHIP
    
    # UPI & Payment Fields (from international migration)
    field :merchant_vpa, :string          # UPI VPA (e.g., merchant@partner)
    field :business_type, :string         # RETAIL, ECOMMERCE, SERVICES
    field :business_category, :string     # MCC code category
    field :static_qr_code, :string        # Static QR for merchant
    
    # Transaction Controls (from international migration)
    field :qr_enabled, :boolean, default: true
    field :dynamic_qr_enabled, :boolean, default: false
    field :max_transaction_limit, :decimal
    field :daily_transaction_limit, :decimal
    
    # International Support (new fields)
    field :corridor, :string              # SINGAPORE, UAE, USA
    field :local_currency, :string        # SGD, AED, USD, INR
    field :fx_markup_rate, :decimal       # Partner's FX markup percentage
    
    # Settlement Details (from international migration + new)
    field :settlement_frequency, :string, default: "T+1"  # T+0, T+1, WEEKLY
    field :settlement_account_intl, :string    # From international migration
    field :settlement_account_number, :string  # New field
    field :settlement_account_ifsc, :string    # New field
    field :settlement_account_type, :string, default: "CURRENT"  # New field
    field :settlement_bank_country, :string    # New field
    
    # Contact Information (from international migration)
    field :contact_person, :string
    field :contact_email, :string
    field :contact_phone, :string
    field :address, :string
    field :city, :string
    field :state, :string
    field :pincode, :string
    
    # Compliance & KYC (from international migration + new)
    field :gstin, :string                 # GST identification number
    field :pan, :string                   # PAN card number
    field :regulatory_license, :string    # New field
    field :compliance_status, :string, default: "PENDING"  # New field
    field :risk_category, :string, default: "MEDIUM"       # New field
    
    # Status & Tracking (from international migration + new)
    field :intl_status, :string, default: "ACTIVE"  # From international migration
    field :status, :string, default: "ACTIVE"       # New field (will replace intl_status)
    field :onboarded_at, :utc_datetime
    field :last_transaction_at, :utc_datetime
    field :partner_managed, :boolean, default: true  # New field
    
    # Relationships
    belongs_to :partner, Partner, type: :binary_id
    has_many :invoices, MerchantInvoice
    has_many :transactions, Transaction
    
    timestamps(type: :utc_datetime)
  end

  @required ~w(mid tid)a
  @optional ~w(
    sid sub_code merchant_type merchant_genre onboarding_type inst_code 
    brand_name legal_name franchise_name ownership_type country_code network_inst_id
    merchant_code merchant_vpa business_type business_category static_qr_code
    qr_enabled dynamic_qr_enabled max_transaction_limit daily_transaction_limit
    corridor local_currency fx_markup_rate settlement_frequency settlement_account_intl
    settlement_account_number settlement_account_ifsc settlement_account_type settlement_bank_country
    contact_person contact_email contact_phone address city state pincode
    gstin pan regulatory_license compliance_status risk_category intl_status status
    onboarded_at last_transaction_at partner_managed partner_id
  )a

  def changeset(struct, attrs) do
    struct
    |> cast(attrs, @required ++ @optional)
    |> validate_required(@required)
    |> validate_merchant_fields()
    |> validate_business_fields()
    |> validate_international_fields()
    |> validate_contact_fields()
    |> unique_constraint([:mid, :tid])
    |> unique_constraint(:merchant_code)
    |> unique_constraint(:merchant_vpa)
  end

  # Validation helper functions
  defp validate_merchant_fields(changeset) do
    changeset
    |> validate_format(:mid, ~r/^[A-Za-z0-9]{6,15}$/, message: "MID must be 6-15 alphanumeric characters")
    |> validate_format(:tid, ~r/^[A-Za-z0-9]{1,8}$/, message: "TID must be 1-8 alphanumeric characters")
    |> validate_format(:merchant_code, ~r/^[A-Za-z0-9_]{4,20}$/, message: "Merchant code must be 4-20 characters")
  end

  defp validate_business_fields(changeset) do
    changeset
    |> validate_inclusion(:merchant_type, ["SMALL", "MEDIUM", "LARGE"])
    |> validate_inclusion(:merchant_genre, ["RETAIL", "ONLINE"])
    |> validate_inclusion(:onboarding_type, ["AGGREGATOR", "DIRECT", "BANK"])
    |> validate_inclusion(:business_type, ["RETAIL", "ECOMMERCE", "SERVICES"])
    |> validate_inclusion(:ownership_type, ["PRIVATE", "PUBLIC", "PARTNERSHIP"])
    |> validate_format(:merchant_vpa, ~r/^[\w\.-]+@[\w\.-]+$/, message: "Invalid VPA format")
    |> validate_length(:brand_name, min: 2, max: 99)
    |> validate_length(:legal_name, max: 99)
  end

  defp validate_international_fields(changeset) do
    changeset
    |> validate_inclusion(:corridor, ["SINGAPORE", "UAE", "USA", "DOMESTIC"])
    |> validate_inclusion(:local_currency, ["SGD", "AED", "USD", "INR"])
    |> validate_inclusion(:country_code, ["SG", "AE", "US", "IN"])
    |> validate_number(:fx_markup_rate, greater_than_or_equal_to: 0, less_than_or_equal_to: 10)
    |> validate_inclusion(:settlement_frequency, ["T+0", "T+1", "WEEKLY"])
    |> validate_inclusion(:settlement_account_type, ["CURRENT", "SAVINGS"])
  end

  defp validate_contact_fields(changeset) do
    changeset
    |> validate_format(:contact_email, ~r/@/, message: "Invalid email format")
    |> validate_format(:contact_phone, ~r/^\+?[\d\-\s\(\)]{7,15}$/, message: "Invalid phone format")
    |> validate_length(:pincode, is: 6)
    |> validate_inclusion(:compliance_status, ["PENDING", "VERIFIED", "REJECTED"])
    |> validate_inclusion(:risk_category, ["LOW", "MEDIUM", "HIGH"])
    |> validate_inclusion(:status, ["ACTIVE", "SUSPENDED", "INACTIVE"])
    |> validate_inclusion(:intl_status, ["ACTIVE", "SUSPENDED", "INACTIVE"])
  end

  # Helper functions for business logic
  def active?(merchant), do: (merchant.status || merchant.intl_status) == "ACTIVE"
  def international?(merchant), do: merchant.corridor && merchant.corridor != "DOMESTIC"
  def qr_enabled?(merchant), do: merchant.qr_enabled and active?(merchant)
  def can_process_amount?(merchant, amount) do
    active?(merchant) and 
    (is_nil(merchant.max_transaction_limit) or 
     Decimal.compare(amount, merchant.max_transaction_limit) != :gt)
  end
end