package sts

import (
	"context"
	"fmt"
	"time"

	"github.com/seaweedfs/seaweedfs/weed/iam/providers"
)

// STSService provides Security Token Service functionality
type STSService struct {
	config       *STSConfig
	initialized  bool
	providers    map[string]providers.IdentityProvider
	sessionStore SessionStore
}

// STSConfig holds STS service configuration
type STSConfig struct {
	// TokenDuration is the default duration for issued tokens
	TokenDuration time.Duration `json:"tokenDuration"`
	
	// MaxSessionLength is the maximum duration for any session
	MaxSessionLength time.Duration `json:"maxSessionLength"`
	
	// Issuer is the STS issuer identifier
	Issuer string `json:"issuer"`
	
	// SigningKey is used to sign session tokens
	SigningKey []byte `json:"signingKey"`
	
	// SessionStore configuration
	SessionStoreType string                 `json:"sessionStoreType"` // memory, filer, redis
	SessionStoreConfig map[string]interface{} `json:"sessionStoreConfig,omitempty"`
}

// AssumeRoleWithWebIdentityRequest represents a request to assume role with web identity
type AssumeRoleWithWebIdentityRequest struct {
	// RoleArn is the ARN of the role to assume
	RoleArn string `json:"RoleArn"`
	
	// WebIdentityToken is the OIDC token from the identity provider
	WebIdentityToken string `json:"WebIdentityToken"`
	
	// RoleSessionName is a name for the assumed role session
	RoleSessionName string `json:"RoleSessionName"`
	
	// DurationSeconds is the duration of the role session (optional)
	DurationSeconds *int64 `json:"DurationSeconds,omitempty"`
	
	// Policy is an optional session policy (optional)
	Policy *string `json:"Policy,omitempty"`
}

// AssumeRoleWithCredentialsRequest represents a request to assume role with username/password
type AssumeRoleWithCredentialsRequest struct {
	// RoleArn is the ARN of the role to assume
	RoleArn string `json:"RoleArn"`
	
	// Username is the username for authentication
	Username string `json:"Username"`
	
	// Password is the password for authentication
	Password string `json:"Password"`
	
	// RoleSessionName is a name for the assumed role session
	RoleSessionName string `json:"RoleSessionName"`
	
	// ProviderName is the name of the identity provider to use
	ProviderName string `json:"ProviderName"`
	
	// DurationSeconds is the duration of the role session (optional)
	DurationSeconds *int64 `json:"DurationSeconds,omitempty"`
}

// AssumeRoleResponse represents the response from assume role operations
type AssumeRoleResponse struct {
	// Credentials contains the temporary security credentials
	Credentials *Credentials `json:"Credentials"`
	
	// AssumedRoleUser contains information about the assumed role user
	AssumedRoleUser *AssumedRoleUser `json:"AssumedRoleUser"`
	
	// PackedPolicySize is the percentage of max policy size used (AWS compatibility)
	PackedPolicySize *int64 `json:"PackedPolicySize,omitempty"`
}

// Credentials represents temporary security credentials
type Credentials struct {
	// AccessKeyId is the access key ID
	AccessKeyId string `json:"AccessKeyId"`
	
	// SecretAccessKey is the secret access key
	SecretAccessKey string `json:"SecretAccessKey"`
	
	// SessionToken is the session token
	SessionToken string `json:"SessionToken"`
	
	// Expiration is when the credentials expire
	Expiration time.Time `json:"Expiration"`
}

// AssumedRoleUser contains information about the assumed role user
type AssumedRoleUser struct {
	// AssumedRoleId is the unique identifier of the assumed role
	AssumedRoleId string `json:"AssumedRoleId"`
	
	// Arn is the ARN of the assumed role user
	Arn string `json:"Arn"`
	
	// Subject is the subject identifier from the identity provider
	Subject string `json:"Subject,omitempty"`
}

// SessionInfo represents information about an active session
type SessionInfo struct {
	// SessionId is the unique identifier for the session
	SessionId string `json:"sessionId"`
	
	// SessionName is the name of the role session
	SessionName string `json:"sessionName"`
	
	// RoleArn is the ARN of the assumed role
	RoleArn string `json:"roleArn"`
	
	// Subject is the subject identifier from the identity provider
	Subject string `json:"subject"`
	
	// Provider is the identity provider used
	Provider string `json:"provider"`
	
	// CreatedAt is when the session was created
	CreatedAt time.Time `json:"createdAt"`
	
	// ExpiresAt is when the session expires
	ExpiresAt time.Time `json:"expiresAt"`
	
	// Credentials are the temporary credentials for this session
	Credentials *Credentials `json:"credentials"`
}

// SessionStore defines the interface for storing session information
type SessionStore interface {
	// StoreSession stores session information
	StoreSession(ctx context.Context, sessionId string, session *SessionInfo) error
	
	// GetSession retrieves session information
	GetSession(ctx context.Context, sessionId string) (*SessionInfo, error)
	
	// RevokeSession revokes a session
	RevokeSession(ctx context.Context, sessionId string) error
	
	// CleanupExpiredSessions removes expired sessions
	CleanupExpiredSessions(ctx context.Context) error
}

// NewSTSService creates a new STS service
func NewSTSService() *STSService {
	return &STSService{
		providers: make(map[string]providers.IdentityProvider),
	}
}

// Initialize initializes the STS service with configuration
func (s *STSService) Initialize(config *STSConfig) error {
	if config == nil {
		return fmt.Errorf("config cannot be nil")
	}
	
	if err := s.validateConfig(config); err != nil {
		return fmt.Errorf("invalid STS configuration: %w", err)
	}
	
	s.config = config
	
	// Initialize session store
	sessionStore, err := s.createSessionStore(config)
	if err != nil {
		return fmt.Errorf("failed to initialize session store: %w", err)
	}
	s.sessionStore = sessionStore
	
	s.initialized = true
	return nil
}

// validateConfig validates the STS configuration
func (s *STSService) validateConfig(config *STSConfig) error {
	if config.TokenDuration <= 0 {
		return fmt.Errorf("token duration must be positive")
	}
	
	if config.MaxSessionLength <= 0 {
		return fmt.Errorf("max session length must be positive")
	}
	
	if config.Issuer == "" {
		return fmt.Errorf("issuer is required")
	}
	
	if len(config.SigningKey) < 16 {
		return fmt.Errorf("signing key must be at least 16 bytes")
	}
	
	return nil
}

// createSessionStore creates a session store based on configuration
func (s *STSService) createSessionStore(config *STSConfig) (SessionStore, error) {
	switch config.SessionStoreType {
	case "", "memory":
		return NewMemorySessionStore(), nil
	case "filer":
		return NewFilerSessionStore(config.SessionStoreConfig)
	default:
		return nil, fmt.Errorf("unsupported session store type: %s", config.SessionStoreType)
	}
}

// IsInitialized returns whether the service is initialized
func (s *STSService) IsInitialized() bool {
	return s.initialized
}

// RegisterProvider registers an identity provider
func (s *STSService) RegisterProvider(provider providers.IdentityProvider) error {
	if provider == nil {
		return fmt.Errorf("provider cannot be nil")
	}
	
	name := provider.Name()
	if name == "" {
		return fmt.Errorf("provider name cannot be empty")
	}
	
	s.providers[name] = provider
	return nil
}

// AssumeRoleWithWebIdentity assumes a role using a web identity token (OIDC)
func (s *STSService) AssumeRoleWithWebIdentity(ctx context.Context, request *AssumeRoleWithWebIdentityRequest) (*AssumeRoleResponse, error) {
	if !s.initialized {
		return nil, fmt.Errorf("STS service not initialized")
	}
	
	if request == nil {
		return nil, fmt.Errorf("request cannot be nil")
	}
	
	// TODO: Implement AssumeRoleWithWebIdentity
	// 1. Validate the web identity token with appropriate provider
	// 2. Check if the role exists and can be assumed
	// 3. Generate temporary credentials
	// 4. Create and store session information
	// 5. Return response with credentials
	
	return nil, fmt.Errorf("AssumeRoleWithWebIdentity not implemented yet")
}

// AssumeRoleWithCredentials assumes a role using username/password credentials
func (s *STSService) AssumeRoleWithCredentials(ctx context.Context, request *AssumeRoleWithCredentialsRequest) (*AssumeRoleResponse, error) {
	if !s.initialized {
		return nil, fmt.Errorf("STS service not initialized")
	}
	
	if request == nil {
		return nil, fmt.Errorf("request cannot be nil")
	}
	
	// TODO: Implement AssumeRoleWithCredentials
	// 1. Validate credentials with the specified provider
	// 2. Check if the role exists and can be assumed
	// 3. Generate temporary credentials
	// 4. Create and store session information
	// 5. Return response with credentials
	
	return nil, fmt.Errorf("AssumeRoleWithCredentials not implemented yet")
}

// ValidateSessionToken validates a session token and returns session information
func (s *STSService) ValidateSessionToken(ctx context.Context, sessionToken string) (*SessionInfo, error) {
	if !s.initialized {
		return nil, fmt.Errorf("STS service not initialized")
	}
	
	if sessionToken == "" {
		return nil, fmt.Errorf("session token cannot be empty")
	}
	
	// TODO: Implement session token validation
	// 1. Parse and verify the session token
	// 2. Extract session ID from token
	// 3. Retrieve session from store
	// 4. Validate expiration and other claims
	// 5. Return session information
	
	return nil, fmt.Errorf("session token validation not implemented yet")
}

// RevokeSession revokes an active session
func (s *STSService) RevokeSession(ctx context.Context, sessionToken string) error {
	if !s.initialized {
		return fmt.Errorf("STS service not initialized")
	}
	
	if sessionToken == "" {
		return fmt.Errorf("session token cannot be empty")
	}
	
	// TODO: Implement session revocation
	// 1. Parse session token to extract session ID
	// 2. Remove session from store
	// 3. Add token to revocation list
	
	return fmt.Errorf("session revocation not implemented yet")
}