package currency

import (
	"time"
)

// Config holds configuration for the currency converter
type Config struct {
	APIKey     string
	CacheTTL   time.Duration
	APITimeout time.Duration
}

// Converter interface defines currency conversion operations
type Converter interface {
	// Convert converts an amount from one currency to another
	Convert(amount float64, from, to string) (float64, error)

	// GetRate returns the exchange rate between two currencies
	GetRate(from, to string) (float64, error)
}

// exchangeRateResponse represents the API response from exchangerate-api.com
type exchangeRateResponse struct {
	Result             string             `json:"result"`
	Documentation      string             `json:"documentation"`
	TermsOfUse         string             `json:"terms_of_use"`
	TimeLastUpdateUnix int64              `json:"time_last_update_unix"`
	TimeLastUpdateUTC  string             `json:"time_last_update_utc"`
	TimeNextUpdateUnix int64              `json:"time_next_update_unix"`
	TimeNextUpdateUTC  string             `json:"time_next_update_utc"`
	BaseCode           string             `json:"base_code"`
	ConversionRates    map[string]float64 `json:"conversion_rates"`
}

// cachedRates stores exchange rates with metadata
type cachedRates struct {
	rates      map[string]float64
	baseCode   string
	fetchedAt  time.Time
	validUntil time.Time
}

// client interface for fetching exchange rates
type client interface {
	// fetchRates fetches current exchange rates for a base currency
	fetchRates(baseCurrency string) (*exchangeRateResponse, error)
}

// cache interface for storing exchange rates
type cache interface {
	// get retrieves cached rates for a base currency
	get(baseCurrency string) (*cachedRates, bool)

	// set stores rates for a base currency with TTL
	set(baseCurrency string, rates *cachedRates)

	// clear removes all cached rates
	clear()
}