package secrets

import (
	"crypto/rand"
	"errors"
	"fmt"
	"math/big"
	"os"

	"github.com/wild-cloud/wild-central/internal/storage"
	"github.com/wild-cloud/wild-central/internal/tools"
	"gopkg.in/yaml.v3"
)

const (
	// DefaultSecretLength is 32 characters
	DefaultSecretLength = 32
	// Alphanumeric characters for secret generation
	alphanumeric = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789"
)

// Manager handles secret storage backed by a single YAML file.
type Manager struct {
	secretsPath string
	yq          *tools.YQ
}

// NewManager creates a new secrets manager bound to the given file path.
func NewManager(secretsPath string) *Manager {
	return &Manager{
		secretsPath: secretsPath,
		yq:          tools.NewYQ(),
	}
}

// GenerateSecret generates a cryptographically secure random alphanumeric string.
func GenerateSecret(length int) (string, error) {
	if length <= 0 {
		length = DefaultSecretLength
	}

	result := make([]byte, length)
	for i := range result {
		num, err := rand.Int(rand.Reader, big.NewInt(int64(len(alphanumeric))))
		if err != nil {
			return "", fmt.Errorf("generating random number: %w", err)
		}
		result[i] = alphanumeric[num.Int64()]
	}

	return string(result), nil
}

// GetSecret retrieves a secret value by dot-notation key.
func (m *Manager) GetSecret(key string) (string, error) {
	if !storage.FileExists(m.secretsPath) {
		return "", fmt.Errorf("secrets file not found: %s", m.secretsPath)
	}

	value, err := m.yq.Get(m.secretsPath, fmt.Sprintf(".%s", key))
	if err != nil {
		return "", fmt.Errorf("getting secret %s: %w", key, err)
	}

	if value == "" || value == "null" {
		return "", fmt.Errorf("secret not found: %s", key)
	}

	return value, nil
}

// SetSecret sets a secret value by dot-notation key.
func (m *Manager) SetSecret(key, value string) error {
	if !storage.FileExists(m.secretsPath) {
		return fmt.Errorf("secrets file not found: %s", m.secretsPath)
	}

	lockPath := m.secretsPath + ".lock"
	return storage.WithLock(lockPath, func() error {
		if err := m.yq.Set(m.secretsPath, fmt.Sprintf(".%s", key), value); err != nil {
			return err
		}
		return storage.EnsureFilePermissions(m.secretsPath, 0600)
	})
}

// DeleteSecret removes a secret by dot-notation key.
func (m *Manager) DeleteSecret(key string) error {
	if !storage.FileExists(m.secretsPath) {
		return fmt.Errorf("secrets file not found: %s", m.secretsPath)
	}

	lockPath := m.secretsPath + ".lock"
	return storage.WithLock(lockPath, func() error {
		if err := m.yq.Delete(m.secretsPath, fmt.Sprintf(".%s", key)); err != nil {
			return err
		}
		return storage.EnsureFilePermissions(m.secretsPath, 0600)
	})
}

// GetAll reads and returns the full secrets map.
func (m *Manager) GetAll() (map[string]any, error) {
	data, err := os.ReadFile(m.secretsPath)
	if err != nil {
		if errors.Is(err, os.ErrNotExist) {
			return map[string]any{}, nil
		}
		return nil, fmt.Errorf("reading secrets: %w", err)
	}

	var secretsMap map[string]any
	if err := yaml.Unmarshal(data, &secretsMap); err != nil {
		return nil, fmt.Errorf("parsing secrets: %w", err)
	}
	if secretsMap == nil {
		secretsMap = map[string]any{}
	}

	return secretsMap, nil
}

// MergeUpdate merges the provided key-value pairs into the existing secrets file.
func (m *Manager) MergeUpdate(updates map[string]any) error {
	lockPath := m.secretsPath + ".lock"
	return storage.WithLock(lockPath, func() error {
		existing, err := m.GetAll()
		if err != nil {
			return err
		}

		for key, value := range updates {
			existing[key] = value
		}

		yamlContent, err := yaml.Marshal(existing)
		if err != nil {
			return fmt.Errorf("marshaling secrets: %w", err)
		}

		return storage.WriteFile(m.secretsPath, yamlContent, 0600)
	})
}