package storage

import (
	"fmt"
	"time"

	"github.com/golang-jwt/jwt/v5"
	"github.com/openaccounting/oa-server/core/util/id"
)

// TokenService handles JWT token generation and validation for file access
type TokenService struct {
	signingKey []byte
}

// NewTokenService creates a new token service with a signing key
func NewTokenService(signingKey string) *TokenService {
	if signingKey == "" {
		// Generate a random signing key if none provided
		// In production, this should be a consistent secret from config
		signingKey = id.String(id.New())
	}
	
	return &TokenService{
		signingKey: []byte(signingKey),
	}
}

// FileClaims represents the JWT claims for file access
type FileClaims struct {
	FilePath string `json:"file_path"`
	UserID   string `json:"user_id,omitempty"`
	OrgID    string `json:"org_id,omitempty"`
	jwt.RegisteredClaims
}

// GenerateFileToken creates a JWT token for accessing a specific file
func (ts *TokenService) GenerateFileToken(filePath string, userID, orgID string, expiry time.Duration) (string, error) {
	now := time.Now()
	claims := FileClaims{
		FilePath: filePath,
		UserID:   userID,
		OrgID:    orgID,
		RegisteredClaims: jwt.RegisteredClaims{
			ExpiresAt: jwt.NewNumericDate(now.Add(expiry)),
			IssuedAt:  jwt.NewNumericDate(now),
			NotBefore: jwt.NewNumericDate(now),
			Issuer:    "openaccounting-server",
			Subject:   "file-access",
			ID:        id.String(id.New()),
		},
	}

	token := jwt.NewWithClaims(jwt.SigningMethodHS256, claims)
	tokenString, err := token.SignedString(ts.signingKey)
	if err != nil {
		return "", fmt.Errorf("failed to sign token: %w", err)
	}

	return tokenString, nil
}

// ValidateFileToken validates a JWT token and returns the file claims
func (ts *TokenService) ValidateFileToken(tokenString string) (*FileClaims, error) {
	token, err := jwt.ParseWithClaims(tokenString, &FileClaims{}, func(token *jwt.Token) (interface{}, error) {
		// Verify the signing method
		if _, ok := token.Method.(*jwt.SigningMethodHMAC); !ok {
			return nil, fmt.Errorf("unexpected signing method: %v", token.Header["alg"])
		}
		return ts.signingKey, nil
	})

	if err != nil {
		return nil, fmt.Errorf("failed to parse token: %w", err)
	}

	claims, ok := token.Claims.(*FileClaims)
	if !ok || !token.Valid {
		return nil, fmt.Errorf("invalid token claims")
	}

	return claims, nil
}