/*
Secrets Store — Encrypted secrets management for Volt containers.

Secrets are stored AGE-encrypted on disk and can be injected into containers
at runtime as environment variables or file mounts.

Storage:
  - Secrets directory: /etc/volt/secrets/
  - Each secret: /etc/volt/secrets/<name>.age (AGE-encrypted)
  - Metadata: /etc/volt/secrets/metadata.json (secret names + injection configs)

Encryption:
  - Uses the node's CDN AGE key for encryption/decryption
  - Secrets are encrypted at rest — only decrypted at injection time

Copyright (c) Armored Gates LLC. All rights reserved.
*/
package secrets

import (
	"encoding/json"
	"fmt"
	"os"
	"path/filepath"
	"sort"
	"strings"
	"time"

	"github.com/armoredgate/volt/pkg/encryption"
)

// ── Constants ────────────────────────────────────────────────────────────────

const (
	// SecretsDir is the directory where encrypted secrets are stored.
	SecretsDir = "/etc/volt/secrets"

	// MetadataFile stores secret names and injection configurations.
	MetadataFile = "/etc/volt/secrets/metadata.json"
)

// ── Types ────────────────────────────────────────────────────────────────────

// SecretMetadata tracks a secret's metadata (not its value).
type SecretMetadata struct {
	Name      string    `json:"name"`
	CreatedAt time.Time `json:"created_at"`
	UpdatedAt time.Time `json:"updated_at"`
	Size      int       `json:"size"` // plaintext size in bytes
}

// SecretInjection defines how a secret is injected into a container.
type SecretInjection struct {
	SecretName    string `json:"secret_name"`
	ContainerName string `json:"container_name"`
	Mode          string `json:"mode"` // "env" or "file"
	EnvVar        string `json:"env_var,omitempty"`   // for mode=env
	FilePath      string `json:"file_path,omitempty"` // for mode=file
}

// secretsMetadataFile is the on-disk metadata format.
type secretsMetadataFile struct {
	Secrets    []SecretMetadata  `json:"secrets"`
	Injections []SecretInjection `json:"injections"`
}

// Store manages encrypted secrets.
type Store struct {
	dir string
}

// ── Constructor ──────────────────────────────────────────────────────────────

// NewStore creates a new secrets store at the default location.
func NewStore() *Store {
	return &Store{dir: SecretsDir}
}

// NewStoreAt creates a secrets store at a custom location (for testing).
func NewStoreAt(dir string) *Store {
	return &Store{dir: dir}
}

// ── Secret CRUD ──────────────────────────────────────────────────────────────

// Create stores a new secret (or updates an existing one).
// The value is encrypted using the node's AGE key before storage.
func (s *Store) Create(name string, value []byte) error {
	if err := validateSecretName(name); err != nil {
		return err
	}

	if err := os.MkdirAll(s.dir, 0700); err != nil {
		return fmt.Errorf("create secrets dir: %w", err)
	}

	// Get encryption recipients
	recipients, err := encryption.BuildRecipients()
	if err != nil {
		return fmt.Errorf("secret create: encryption keys not initialized. Run: volt security keys init")
	}

	// Encrypt the value
	ciphertext, err := encryption.Encrypt(value, recipients)
	if err != nil {
		return fmt.Errorf("secret create %s: encrypt: %w", name, err)
	}

	// Write encrypted file
	secretPath := filepath.Join(s.dir, name+".age")
	if err := os.WriteFile(secretPath, ciphertext, 0600); err != nil {
		return fmt.Errorf("secret create %s: write: %w", name, err)
	}

	// Update metadata
	return s.updateMetadata(name, len(value))
}

// Get retrieves and decrypts a secret value.
func (s *Store) Get(name string) ([]byte, error) {
	secretPath := filepath.Join(s.dir, name+".age")
	ciphertext, err := os.ReadFile(secretPath)
	if err != nil {
		if os.IsNotExist(err) {
			return nil, fmt.Errorf("secret %q not found", name)
		}
		return nil, fmt.Errorf("secret get %s: %w", name, err)
	}

	plaintext, err := encryption.Decrypt(ciphertext, encryption.CDNIdentityPath())
	if err != nil {
		return nil, fmt.Errorf("secret get %s: decrypt: %w", name, err)
	}

	return plaintext, nil
}

// Delete removes a secret and its metadata.
func (s *Store) Delete(name string) error {
	secretPath := filepath.Join(s.dir, name+".age")
	if err := os.Remove(secretPath); err != nil {
		if os.IsNotExist(err) {
			return fmt.Errorf("secret %q not found", name)
		}
		return fmt.Errorf("secret delete %s: %w", name, err)
	}

	// Remove from metadata
	return s.removeFromMetadata(name)
}

// List returns metadata for all stored secrets.
func (s *Store) List() ([]SecretMetadata, error) {
	md, err := s.loadMetadata()
	if err != nil {
		// No metadata file = no secrets
		return nil, nil
	}
	return md.Secrets, nil
}

// Exists checks if a secret with the given name exists.
func (s *Store) Exists(name string) bool {
	secretPath := filepath.Join(s.dir, name+".age")
	_, err := os.Stat(secretPath)
	return err == nil
}

// ── Injection ────────────────────────────────────────────────────────────────

// AddInjection configures a secret to be injected into a container.
func (s *Store) AddInjection(injection SecretInjection) error {
	if !s.Exists(injection.SecretName) {
		return fmt.Errorf("secret %q not found", injection.SecretName)
	}

	md, err := s.loadMetadata()
	if err != nil {
		md = &secretsMetadataFile{}
	}

	// Check for duplicate injection
	for _, existing := range md.Injections {
		if existing.SecretName == injection.SecretName &&
			existing.ContainerName == injection.ContainerName &&
			existing.EnvVar == injection.EnvVar &&
			existing.FilePath == injection.FilePath {
			return nil // Already configured
		}
	}

	md.Injections = append(md.Injections, injection)
	return s.saveMetadata(md)
}

// GetInjections returns all injection configurations for a container.
func (s *Store) GetInjections(containerName string) ([]SecretInjection, error) {
	md, err := s.loadMetadata()
	if err != nil {
		return nil, nil
	}

	var injections []SecretInjection
	for _, inj := range md.Injections {
		if inj.ContainerName == containerName {
			injections = append(injections, inj)
		}
	}
	return injections, nil
}

// ResolveInjections decrypts and returns all secret values for a container's
// configured injections. Returns a map of env_var/file_path → decrypted value.
func (s *Store) ResolveInjections(containerName string) (envVars map[string]string, files map[string][]byte, err error) {
	injections, err := s.GetInjections(containerName)
	if err != nil {
		return nil, nil, err
	}

	envVars = make(map[string]string)
	files = make(map[string][]byte)

	for _, inj := range injections {
		value, err := s.Get(inj.SecretName)
		if err != nil {
			return nil, nil, fmt.Errorf("resolve injection %s for %s: %w",
				inj.SecretName, containerName, err)
		}

		switch inj.Mode {
		case "env":
			envVars[inj.EnvVar] = string(value)
		case "file":
			files[inj.FilePath] = value
		}
	}

	return envVars, files, nil
}

// RemoveInjection removes a specific injection configuration.
func (s *Store) RemoveInjection(secretName, containerName string) error {
	md, err := s.loadMetadata()
	if err != nil {
		return nil
	}

	var filtered []SecretInjection
	for _, inj := range md.Injections {
		if !(inj.SecretName == secretName && inj.ContainerName == containerName) {
			filtered = append(filtered, inj)
		}
	}

	md.Injections = filtered
	return s.saveMetadata(md)
}

// ── Metadata ─────────────────────────────────────────────────────────────────

func (s *Store) loadMetadata() (*secretsMetadataFile, error) {
	mdPath := filepath.Join(s.dir, "metadata.json")
	data, err := os.ReadFile(mdPath)
	if err != nil {
		return nil, err
	}

	var md secretsMetadataFile
	if err := json.Unmarshal(data, &md); err != nil {
		return nil, fmt.Errorf("parse secrets metadata: %w", err)
	}

	return &md, nil
}

func (s *Store) saveMetadata(md *secretsMetadataFile) error {
	data, err := json.MarshalIndent(md, "", "  ")
	if err != nil {
		return fmt.Errorf("marshal secrets metadata: %w", err)
	}

	mdPath := filepath.Join(s.dir, "metadata.json")
	return os.WriteFile(mdPath, data, 0600)
}

func (s *Store) updateMetadata(name string, plainSize int) error {
	md, err := s.loadMetadata()
	if err != nil {
		md = &secretsMetadataFile{}
	}

	now := time.Now()
	found := false
	for i := range md.Secrets {
		if md.Secrets[i].Name == name {
			md.Secrets[i].UpdatedAt = now
			md.Secrets[i].Size = plainSize
			found = true
			break
		}
	}

	if !found {
		md.Secrets = append(md.Secrets, SecretMetadata{
			Name:      name,
			CreatedAt: now,
			UpdatedAt: now,
			Size:      plainSize,
		})
	}

	// Sort by name
	sort.Slice(md.Secrets, func(i, j int) bool {
		return md.Secrets[i].Name < md.Secrets[j].Name
	})

	return s.saveMetadata(md)
}

func (s *Store) removeFromMetadata(name string) error {
	md, err := s.loadMetadata()
	if err != nil {
		return nil // No metadata to clean up
	}

	// Remove secret entry
	var filtered []SecretMetadata
	for _, sec := range md.Secrets {
		if sec.Name != name {
			filtered = append(filtered, sec)
		}
	}
	md.Secrets = filtered

	// Remove all injections for this secret
	var filteredInj []SecretInjection
	for _, inj := range md.Injections {
		if inj.SecretName != name {
			filteredInj = append(filteredInj, inj)
		}
	}
	md.Injections = filteredInj

	return s.saveMetadata(md)
}

// ── Validation ───────────────────────────────────────────────────────────────

func validateSecretName(name string) error {
	if name == "" {
		return fmt.Errorf("secret name cannot be empty")
	}
	if len(name) > 253 {
		return fmt.Errorf("secret name too long (max 253 characters)")
	}

	// Must be lowercase alphanumeric with hyphens/dots/underscores
	for _, c := range name {
		if !((c >= 'a' && c <= 'z') || (c >= '0' && c <= '9') || c == '-' || c == '.' || c == '_') {
			return fmt.Errorf("secret name %q contains invalid character %q (allowed: a-z, 0-9, -, ., _)", name, string(c))
		}
	}

	if strings.HasPrefix(name, ".") || strings.HasPrefix(name, "-") {
		return fmt.Errorf("secret name cannot start with '.' or '-'")
	}

	return nil
}