package ect

import (
	"os"
	"strconv"
	"time"
)

// Env names for production configuration. All optional; zero values use defaults.
const (
	EnvIATMaxAgeMinutes   = "ECT_IAT_MAX_AGE_MINUTES"   // max age of iat (default 15)
	EnvIATMaxFutureSec    = "ECT_IAT_MAX_FUTURE_SEC"    // max iat in future / clock skew (default 30)
	EnvDefaultExpiryMin   = "ECT_DEFAULT_EXPIRY_MIN"    // default token expiry when exp is zero (default 10)
	EnvJTIReplayCacheSize = "ECT_JTI_REPLAY_CACHE_SIZE" // max JTIs to remember for replay check (0 = disabled)
	EnvJTIReplayTTLMin    = "ECT_JTI_REPLAY_TTL_MIN"    // TTL for JTI cache entries (default 60)
)

// Config holds production-friendly settings loaded from environment.
type Config struct {
	IATMaxAge      time.Duration
	IATMaxFuture   time.Duration
	DefaultExpiry  time.Duration
	JTIReplaySize  int           // 0 = no replay cache
	JTIReplayTTL   time.Duration
}

// DefaultConfig returns in-process defaults (no env).
func DefaultConfig() Config {
	return Config{
		IATMaxAge:     15 * time.Minute,
		IATMaxFuture:  30 * time.Second,
		DefaultExpiry: 10 * time.Minute,
		JTIReplayTTL:  60 * time.Minute,
	}
}

// LoadConfigFromEnv returns Config with values from environment where set.
func LoadConfigFromEnv() Config {
	c := DefaultConfig()
	if v := os.Getenv(EnvIATMaxAgeMinutes); v != "" {
		if n, err := strconv.Atoi(v); err == nil && n > 0 {
			c.IATMaxAge = time.Duration(n) * time.Minute
		}
	}
	if v := os.Getenv(EnvIATMaxFutureSec); v != "" {
		if n, err := strconv.Atoi(v); err == nil && n >= 0 {
			c.IATMaxFuture = time.Duration(n) * time.Second
		}
	}
	if v := os.Getenv(EnvDefaultExpiryMin); v != "" {
		if n, err := strconv.Atoi(v); err == nil && n > 0 {
			c.DefaultExpiry = time.Duration(n) * time.Minute
		}
	}
	if v := os.Getenv(EnvJTIReplayCacheSize); v != "" {
		if n, err := strconv.Atoi(v); err == nil && n >= 0 {
			c.JTIReplaySize = n
		}
	}
	if v := os.Getenv(EnvJTIReplayTTLMin); v != "" {
		if n, err := strconv.Atoi(v); err == nil && n > 0 {
			c.JTIReplayTTL = time.Duration(n) * time.Minute
		}
	}
	return c
}

// CreateOptions returns CreateOptions from this config.
func (c Config) CreateOptions(keyID string) CreateOptions {
	return CreateOptions{
		KeyID:         keyID,
		IATMaxAge:     c.IATMaxAge,
		DefaultExpiry: c.DefaultExpiry,
	}
}

// VerifyOptions returns VerifyOptions from this config (VerifierID, ResolveKey, Store must be set by caller).
func (c Config) VerifyOptions() VerifyOptions {
	opts := DefaultVerifyOptions()
	opts.IATMaxAge = c.IATMaxAge
	opts.IATMaxFuture = c.IATMaxFuture
	opts.DAG = DefaultDAGConfig()
	return opts
}