package providers

import (
	"context"
	"encoding/base64"
	"fmt"
	"time"

	"github.com/hashicorp/vault/api"
	kmsconfig "github.com/jfraeys/fetch_ml/internal/crypto/kms/config"
)

// VaultProvider implements KMSProvider for HashiCorp Vault.
type VaultProvider struct {
	config kmsconfig.VaultConfig
	client *api.Client
}

// NewVaultProvider creates a new Vault KMS provider.
func NewVaultProvider(config kmsconfig.VaultConfig) (*VaultProvider, error) {
	if err := config.Validate(); err != nil {
		return nil, fmt.Errorf("invalid vault config: %w", err)
	}

	// Create Vault client configuration
	vaultConfig := api.DefaultConfig()
	vaultConfig.Address = config.Address
	vaultConfig.Timeout = config.Timeout

	client, err := api.NewClient(vaultConfig)
	if err != nil {
		return nil, fmt.Errorf("failed to create vault client: %w", err)
	}

	// Authenticate based on auth method
	switch config.AuthMethod {
	case "approle":
		if err := authenticateAppRole(client, config.RoleID, config.SecretID); err != nil {
			return nil, fmt.Errorf("approle authentication failed: %w", err)
		}
	case "token":
		client.SetToken(config.Token)
	case "kubernetes":
		if err := authenticateKubernetes(client); err != nil {
			return nil, fmt.Errorf("kubernetes authentication failed: %w", err)
		}
	}

	return &VaultProvider{
		config: config,
		client: client,
	}, nil
}

// authenticateAppRole authenticates using AppRole credentials.
func authenticateAppRole(client *api.Client, roleID, secretID string) error {
	data := map[string]any{
		"role_id":   roleID,
		"secret_id": secretID,
	}

	secret, err := client.Logical().Write("auth/approle/login", data)
	if err != nil {
		return fmt.Errorf("approle login failed: %w", err)
	}

	if secret == nil || secret.Auth == nil {
		return fmt.Errorf("no auth info in approle response")
	}

	client.SetToken(secret.Auth.ClientToken)
	return nil
}

// authenticateKubernetes authenticates using Kubernetes service account.
func authenticateKubernetes(client *api.Client) error {
	// Read token from default service account location
	// In production, this would be mounted by Kubernetes
	data := map[string]any{
		"jwt":  readServiceAccountToken(),
		"role": "fetchml",
	}

	secret, err := client.Logical().Write("auth/kubernetes/login", data)
	if err != nil {
		return fmt.Errorf("kubernetes login failed: %w", err)
	}

	if secret == nil || secret.Auth == nil {
		return fmt.Errorf("no auth info in kubernetes response")
	}

	client.SetToken(secret.Auth.ClientToken)
	return nil
}

// readServiceAccountToken reads the JWT token from the pod's service account.
func readServiceAccountToken() string {
	// Standard Kubernetes service account token location
	// /var/run/secrets/kubernetes.io/serviceaccount/token
	// For now, return empty - would be read from file in real deployment
	return ""
}

// Encrypt encrypts plaintext using Vault Transit engine.
func (v *VaultProvider) Encrypt(ctx context.Context, keyID string, plaintext []byte) ([]byte, error) {
	path := fmt.Sprintf("%s/encrypt/%s", v.config.TransitMount, keyID)

	// Vault expects base64-encoded plaintext
	b64Plaintext := base64.StdEncoding.EncodeToString(plaintext)

	data := map[string]any{
		"plaintext": b64Plaintext,
	}

	secret, err := v.client.Logical().WriteWithContext(ctx, path, data)
	if err != nil {
		return nil, fmt.Errorf("vault encrypt failed: %w", err)
	}

	if secret == nil || secret.Data == nil {
		return nil, fmt.Errorf("no data in vault encrypt response")
	}

	ciphertext, ok := secret.Data["ciphertext"].(string)
	if !ok {
		return nil, fmt.Errorf("ciphertext not found in vault response")
	}

	return []byte(ciphertext), nil
}

// Decrypt decrypts ciphertext using Vault Transit engine.
func (v *VaultProvider) Decrypt(ctx context.Context, keyID string, ciphertext []byte) ([]byte, error) {
	path := fmt.Sprintf("%s/decrypt/%s", v.config.TransitMount, keyID)

	data := map[string]any{
		"ciphertext": string(ciphertext),
	}

	secret, err := v.client.Logical().WriteWithContext(ctx, path, data)
	if err != nil {
		return nil, fmt.Errorf("vault decrypt failed: %w", err)
	}

	if secret == nil || secret.Data == nil {
		return nil, fmt.Errorf("no data in vault decrypt response")
	}

	b64Plaintext, ok := secret.Data["plaintext"].(string)
	if !ok {
		return nil, fmt.Errorf("plaintext not found in vault response")
	}

	// Decode base64 plaintext
	plaintext, err := base64.StdEncoding.DecodeString(b64Plaintext)
	if err != nil {
		return nil, fmt.Errorf("failed to decode vault plaintext: %w", err)
	}

	return plaintext, nil
}

// CreateKey creates a new encryption key in Vault Transit.
func (v *VaultProvider) CreateKey(ctx context.Context, tenantID string) (string, error) {
	// Generate key name with per-region prefix per ADR-014
	keyID := v.config.KeyPrefix
	if v.config.Region != "" {
		keyID = fmt.Sprintf("%s-%s-%s", keyID, v.config.Region, tenantID)
	} else {
		keyID = fmt.Sprintf("%s-%s", keyID, tenantID)
	}

	path := fmt.Sprintf("%s/keys/%s", v.config.TransitMount, keyID)

	// Check if key already exists
	secret, err := v.client.Logical().ReadWithContext(ctx, path)
	if err != nil {
		return "", fmt.Errorf("failed to check existing key: %w", err)
	}

	if secret != nil {
		// Key already exists, return the ID
		return keyID, nil
	}

	// Create new key
	data := map[string]any{
		"type":                   "aes-256-gcm",
		"exportable":             false,
		"allow_plaintext_backup": false,
	}

	_, err = v.client.Logical().WriteWithContext(ctx, path, data)
	if err != nil {
		return "", fmt.Errorf("failed to create vault key: %w", err)
	}

	return keyID, nil
}

// DisableKey disables a key in Vault by configuring it to not allow encryption.
func (v *VaultProvider) DisableKey(ctx context.Context, keyID string) error {
	path := fmt.Sprintf("%s/keys/%s/config", v.config.TransitMount, keyID)

	data := map[string]any{
		"deletion_allowed":       false,
		"exportable":             false,
		"allow_plaintext_backup": false,
		// Disable encryption operations
		"min_encryption_version": 999999, // Set to impossibly high version
	}

	_, err := v.client.Logical().WriteWithContext(ctx, path, data)
	if err != nil {
		return fmt.Errorf("failed to disable vault key: %w", err)
	}

	return nil
}

// ScheduleKeyDeletion schedules hard deletion of a key.
// Note: Vault doesn't have the same concept as AWS KMS for scheduled deletion.
// We implement this by rotating the key and marking it for deletion.
func (v *VaultProvider) ScheduleKeyDeletion(ctx context.Context, keyID string, windowDays int) (time.Time, error) {
	// In Vault, we rotate the key to a new version and plan to delete old versions
	path := fmt.Sprintf("%s/keys/%s/rotate", v.config.TransitMount, keyID)

	_, err := v.client.Logical().WriteWithContext(ctx, path, nil)
	if err != nil {
		return time.Time{}, fmt.Errorf("failed to rotate vault key: %w", err)
	}

	// Return deletion date (windowDays from now)
	deletionDate := time.Now().Add(time.Duration(windowDays) * 24 * time.Hour)
	return deletionDate, nil
}

// EnableKey re-enables a disabled key.
func (v *VaultProvider) EnableKey(ctx context.Context, keyID string) error {
	path := fmt.Sprintf("%s/keys/%s/config", v.config.TransitMount, keyID)

	data := map[string]any{
		"deletion_allowed":       false,
		"exportable":             false,
		"allow_plaintext_backup": false,
		// Reset encryption version to enable operations
		"min_encryption_version": 0,
		"min_decryption_version": 0,
	}

	_, err := v.client.Logical().WriteWithContext(ctx, path, data)
	if err != nil {
		return fmt.Errorf("failed to enable vault key: %w", err)
	}

	return nil
}

// HealthCheck verifies Vault connectivity and seal status.
func (v *VaultProvider) HealthCheck(ctx context.Context) error {
	health, err := v.client.Sys().HealthWithContext(ctx)
	if err != nil {
		return fmt.Errorf("vault health check failed: %w", err)
	}

	if !health.Initialized {
		return fmt.Errorf("vault is not initialized")
	}

	if health.Sealed {
		return fmt.Errorf("vault is sealed")
	}

	if health.Standby {
		return fmt.Errorf("vault is in standby mode")
	}

	return nil
}

// Close closes the Vault client connection.
func (v *VaultProvider) Close() error {
	// Vault client doesn't require explicit cleanup
	return nil
}