package payments

import (
	"errors"
	"fmt"
)

// Valid payment types
var validPaymentTypes = map[string]bool{
	"deposit": true,
	"full":    true,
	"tip":     true,
	"balance": true,
	"partial": true,
}

// ValidateAmount checks that amount is greater than 0 and has valid precision (max 2 decimal places when in pence)
func ValidateAmount(amount int64) error {
	if amount <= 0 {
		return errors.New("amount must be greater than 0")
	}
	if amount > 1_000_000 { // £10,000 in pence
		return errors.New("amount exceeds maximum (£10,000)")
	}
	return nil
}

// ValidatePartialAmount checks that the partial amount doesn't exceed the remaining balance
func ValidatePartialAmount(amountPence int64, remainingPence int64) error {
	if amountPence > remainingPence {
		return fmt.Errorf("partial amount (£%.2f) exceeds remaining balance (£%.2f)",
			float64(amountPence)/100, float64(remainingPence)/100)
	}
	if amountPence <= 0 {
		return errors.New("amount must be greater than 0")
	}
	return nil
}

// ValidatePaymentType checks that payment type is valid
func ValidatePaymentType(pt string) error {
	if !validPaymentTypes[pt] {
		return errors.New("invalid payment type")
	}
	return nil
}

// ValidateRefundReason checks that refund reason is not empty
func ValidateRefundReason(reason string) error {
	if reason == "" {
		return errors.New("refund reason is required")
	}
	return nil
}

// ValidateCardInfo checks that exactly one of cardID or newCardToken is provided,
// non-nil, and non-empty.
func ValidateCardInfo(cardID, newCardToken *string) error {
	hasCardID := cardID != nil && *cardID != ""
	hasToken := newCardToken != nil && *newCardToken != ""
	if hasCardID && hasToken {
		return errors.New("provide either card_id or new_card_token, not both")
	}
	if !hasCardID && !hasToken {
		return errors.New("either card_id or new_card_token is required")
	}
	return nil
}

// ValidateVerificationToken checks that a Square 3DS/SCA verification token is
// non-empty when present and within a sane length. Square's tokens are short
// opaque strings; the bound guards against absurd/malformed payloads before
// the token is forwarded to Square's API.
func ValidateVerificationToken(token *string) error {
	if token == nil || *token == "" {
		return nil
	}
	if len(*token) > 512 {
		return errors.New("verification_token is too long")
	}
	return nil
}