package pow

import (
	"errors"
	"time"
)

// PoW package specific errors
var (
	ErrInvalidHMAC      = errors.New("challenge HMAC signature is invalid")
	ErrExpiredChallenge = errors.New("challenge has expired")
	ErrInvalidSolution  = errors.New("proof of work solution is invalid")
	ErrInvalidDifficulty = errors.New("difficulty level is invalid")
	ErrMalformedChallenge = errors.New("challenge format is malformed")
)

// Challenge represents a Proof of Work challenge with HMAC authentication
type Challenge struct {
	Timestamp  int64  `json:"timestamp"`
	Difficulty int    `json:"difficulty"`
	Resource   string `json:"resource"`
	Random     string `json:"random"`
	HMAC       string `json:"hmac"`
}

// Solution represents a client's solution to a PoW challenge
type Solution struct {
	Challenge Challenge `json:"challenge"`
	Nonce     string    `json:"nonce"`
}

// ChallengeRequest represents a request for a new challenge
type ChallengeRequest struct{}

// SolutionRequest represents a client's submission of a solved challenge
type SolutionRequest struct {
	Challenge Challenge `json:"challenge"`
	Nonce     string    `json:"nonce"`
}

// Config holds configuration for the PoW system
type Config struct {
	DefaultDifficulty     int           // Default difficulty in bits (e.g., 4)
	MaxDifficulty         int           // Maximum allowed difficulty (e.g., 10)
	MinDifficulty         int           // Minimum allowed difficulty (e.g., 3)
	ChallengeTTL          time.Duration // Time-to-live for challenges (e.g., 5 minutes)
	HMACSecret            []byte        // Secret key for HMAC signing
	Resource              string        // Resource identifier (e.g., "quotes")
	LoadAdjustmentBits    int           // Extra difficulty bits when server under load
	FailurePenaltyBits    int           // Extra difficulty bits per failure group
	MaxFailurePenaltyBits int           // Maximum failure penalty bits
}