package ssh

import (
	"context"
	"errors"
	"fmt"
	"io"
	"log"
	"net"
	"os"
	"path/filepath"
	"strings"
	"sync"
	"time"

	"git.totmin.ru/en2zmax/forge-toolkit/configreload"
	"golang.org/x/crypto/ssh"
)

// Manager manages multiple SSH connections for a single session.
type Manager struct {
	connections map[string]*Client
	primary     string
	keyManager  *KeyManager

	// policy - текущая (закэшированная) per-agent политика подключений.
	// nil = политика не настроена: ad-hoc режим как раньше (без ограничений).
	policy *Policy
	// policyLoader - live-reload политики из <FORGE_TENANT_CONFIG>/ssh.json
	// (см. configreload). nil, если FORGE_TENANT_CONFIG не задан (легаси) или
	// задана статическая политика через SetPolicy (тесты).
	policyLoader *configreload.Loader[*Policy]

	mu             sync.RWMutex
	aliasLocks     map[string]*sync.Mutex
	reconnectFails map[string]time.Time // alias -> last failed reconnect time
	dockerCache    map[string]*bool     // alias -> docker available (nil = unknown)
}

// NewManager creates a new SSH connection manager. Если задан
// FORGE_TENANT_CONFIG/ssh.json - политика подхватывается через live-reload
// (configreload по контент-хэшу): правки ssh.json применяются к следующему
// Connect без рестарта.
func NewManager(keyPath string) *Manager {
	mgr := &Manager{
		connections:    make(map[string]*Client),
		keyManager:     NewKeyManager(keyPath),
		aliasLocks:     make(map[string]*sync.Mutex),
		reconnectFails: make(map[string]time.Time),
		dockerCache:    make(map[string]*bool),
	}

	if err := mgr.keyManager.EnsureKey(); err != nil {
		log.Printf("manager: key setup warning: %v", err)
	}

	if path, ok := PolicyPathFromEnv(); ok {
		mgr.policyLoader = configreload.New(path, parsePolicy)
	}

	return mgr
}

// SetPolicy задаёт per-agent политику подключений вручную (тесты).
// Отключает live-reload (loader == nil), чтобы тесты были детерминированы.
func (m *Manager) SetPolicy(p *Policy) {
	_ = p.normalize()
	m.policy = p
	m.policyLoader = nil
}

// currentPolicy возвращает актуальную политику, перечитав её при изменении
// содержимого ssh.json (live-reload). Нет loader'а → статическая policy.
// Ошибки: ErrNotFound → (nil, err) (нет политики = ad-hoc без ограничений);
// парсинг-ошибка → (lastGood, err) (сохраняем рабочую, но сообщаем).
func (m *Manager) currentPolicy() (*Policy, error) {
	if m.policyLoader == nil {
		return m.policy, nil
	}
	return m.policyLoader.Get()
}

// getAliasLock returns a per-alias lock.
func (m *Manager) getAliasLock(alias string) *sync.Mutex {
	m.mu.Lock()
	defer m.mu.Unlock()

	if lock, ok := m.aliasLocks[alias]; ok {
		return lock
	}

	lock := &sync.Mutex{}
	m.aliasLocks[alias] = lock
	return lock
}

// generateAlias creates a unique alias and reserves it.
func (m *Manager) generateAlias(username, host string) string {
	base := fmt.Sprintf("%s@%s", username, host)

	m.mu.Lock()
	defer m.mu.Unlock()

	if _, exists := m.connections[base]; !exists {
		m.connections[base] = nil // Reserve
		return base
	}

	for i := 2; i < 100; i++ {
		candidate := fmt.Sprintf("%s-%d", base, i)
		if _, exists := m.connections[candidate]; !exists {
			m.connections[candidate] = nil // Reserve
			return candidate
		}
	}

	// Fallback (might collide but highly unlikely to fill 100 slots)
	final := fmt.Sprintf("%s-%d", base, 100)
	m.connections[final] = nil
	return final
}

// ConnectOptions contains options for SSH connection.
type ConnectOptions struct {
	Host           string
	Port           int
	Username       string
	Password       string
	PrivateKeyPath string
	Alias          string
	Via            string
	// Target is an optional destination host routed through a PAM gateway
	// (SafeInspect). When set, the gateway receives "Username@Target" and
	// TargetPassword is used as the second authentication stage.
	Target         string
	TargetPassword string
	// Profile - имя профиля из ssh.json (см. policy.go). Если задан, креды
	// (Host/Username/Port/Key/Via/Target) берутся из политики, а не от
	// модели. Модель выбирает только имя; адрес и ключ задаёт оператор.
	Profile string
}

// Connect establishes an SSH connection and returns the alias. Применяет
// per-agent политику (см. policy.go): профиль резолвит креды, а host
// обязан пройти allowlist. Модель не может подключиться вне разрешённого.
func (m *Manager) Connect(ctx context.Context, opts ConnectOptions) (alias string, err error) {
	if opts.Port == 0 {
		opts.Port = 22
	}

	// Live-reload политики: перечитываем ssh.json по контент-хэшу.
	// ErrNotFound → нет политики (ad-hoc без ограничений). Парсинг-ошибка →
	// last-good (если был) + предупреждение; без last-good — fail-closed.
	pol, perr := m.currentPolicy()
	if perr != nil {
		if !errors.Is(perr, configreload.ErrNotFound) && pol == nil {
			return "", fmt.Errorf("ssh: per-agent policy unavailable: %w", perr)
		}
		log.Printf("ssh: policy warning: %v", perr)
	}

	// Резолв профиля: платформа объявляет креды, модель выбирает по имени.
	if opts.Profile != "" {
		if pol == nil {
			return "", errors.New("ssh: profile requested but no per-agent policy configured")
		}
		pr, ok := pol.Resolve(opts.Profile)
		if !ok {
			return "", fmt.Errorf("ssh: profile %q not found in policy", opts.Profile)
		}
		opts.Host = pr.Host
		opts.Username = pr.Username
		if pr.Port != 0 {
			opts.Port = pr.Port
		}
		if opts.PrivateKeyPath == "" {
			opts.PrivateKeyPath = pr.KeyPath
		}
		if opts.Via == "" {
			opts.Via = pr.Via
		}
		if opts.Target == "" {
			opts.Target = pr.Target
			if opts.TargetPassword == "" {
				opts.TargetPassword = pr.TargetPass
			}
		}
	}

	// Креды обязательны (профиль дал их, либо модель прислала host+username).
	if opts.Host == "" || opts.Username == "" {
		return "", errors.New("ssh: host and username are required")
	}

	// Allowlist: вне списка - deny (fail-closed). Пустой список = allow all.
	if pol != nil && !pol.Allow(opts.Host) {
		return "", fmt.Errorf("ssh: host %q is not in allowed_hosts of per-agent policy", opts.Host)
	}

	// Default key: если ни профиль, ни вызов не задали ключ - берём
	// DefaultKeyPath политики, иначе "" (системный ключ KeyManager).
	if pol != nil && opts.PrivateKeyPath == "" {
		opts.PrivateKeyPath = pol.DefaultKeyPath
	}

	var reserved bool
	if opts.Alias == "" {
		// Include the PAM target (if any) so distinct targets routed through
		// the same gateway get distinct auto-generated aliases.
		aliasBase := opts.Username
		if opts.Target != "" {
			aliasBase = opts.Username + "@" + opts.Target
		}
		opts.Alias = m.generateAlias(aliasBase, opts.Host)
		reserved = true
	}

	if opts.Via == opts.Alias {
		return "", errors.New("'via' cannot be the same as 'alias'")
	}

	m.mu.Lock()
	existing, exists := m.connections[opts.Alias]
	if exists {
		if existing != nil {
			m.mu.Unlock()
			if existing.creds.Host == opts.Host && existing.creds.Username == opts.Username && existing.creds.Target == opts.Target {
				return opts.Alias, nil
			}
			return "", fmt.Errorf("alias '%s' already exists for %s@%s", opts.Alias, existing.creds.Username, existing.creds.Host)
		}
		// Existing is nil (reserved)
		if !reserved {
			m.mu.Unlock()
			return "", fmt.Errorf("alias '%s' is currently connecting/reserved", opts.Alias)
		}
		// It's our reservation, proceed
	} else {
		// New explicit alias
		m.connections[opts.Alias] = nil // Reserve
	}
	m.mu.Unlock()

	// Defer cleanup of reservation on error
	defer func() {
		if err != nil {
			m.mu.Lock()
			// Only remove if it's still nil (failed to connect)
			if c, ok := m.connections[opts.Alias]; ok && c == nil {
				delete(m.connections, opts.Alias)
			}
			m.mu.Unlock()
		}
	}()

	creds := Credentials{
		Host:           opts.Host,
		Port:           opts.Port,
		Username:       opts.Username,
		Password:       opts.Password,
		Via:            opts.Via,
		Target:         opts.Target,
		TargetPassword: opts.TargetPassword,
	}

	if opts.PrivateKeyPath != "" {
		keyBytes, err := os.ReadFile(opts.PrivateKeyPath)
		if err != nil {
			return "", fmt.Errorf("failed to read private key: %w", err)
		}
		signer, err := ssh.ParsePrivateKey(keyBytes)
		if err != nil {
			return "", fmt.Errorf("failed to parse private key: %w", err)
		}
		creds.PrivateKey = signer
	} else if opts.Password == "" {
		signer, err := m.keyManager.LoadPrivateKey()
		if err != nil {
			return "", fmt.Errorf("no auth provided and system key unavailable: %w", err)
		}
		creds.PrivateKey = signer
		log.Printf("ssh: using system key for %s", opts.Alias)
	}

	var jumpClient *Client
	if opts.Via != "" {
		m.mu.RLock()
		jumpClient = m.connections[opts.Via]
		m.mu.RUnlock()
		if jumpClient == nil {
			return "", fmt.Errorf("jump host '%s' not connected", opts.Via)
		}
	}

	client, err := NewClient(ctx, opts.Alias, creds, jumpClient)
	if err != nil {
		return "", err
	}

	m.mu.Lock()
	m.connections[opts.Alias] = client
	if m.primary == "" {
		m.primary = opts.Alias
	}
	m.mu.Unlock()

	return opts.Alias, nil
}

// Disconnect closes one or all connections.
func (m *Manager) Disconnect(alias string) (string, error) {
	m.mu.Lock()
	defer m.mu.Unlock()

	if alias == "" {
		count := 0
		for a, client := range m.connections {
			if client != nil {
				client.Close()
				count++
			}
			delete(m.connections, a)
			delete(m.aliasLocks, a)
			delete(m.reconnectFails, a)
			delete(m.dockerCache, a)
		}
		m.primary = ""
		return fmt.Sprintf("Disconnected all (%d) connections", count), nil
	}

	client, ok := m.connections[alias]
	if !ok {
		return "", fmt.Errorf("no connection with alias '%s'", alias)
	}

	if client != nil {
		client.Close()
	}
	delete(m.connections, alias)
	delete(m.aliasLocks, alias)
	delete(m.reconnectFails, alias)
	delete(m.dockerCache, alias)

	if m.primary == alias {
		m.primary = ""
		for a, c := range m.connections {
			if c != nil {
				m.primary = a
				break
			}
		}
	}

	return fmt.Sprintf("Disconnected '%s'", alias), nil
}

// resolveTarget returns the target alias.
func (m *Manager) resolveTarget(target string) (string, error) {
	if target != "" && target != "primary" {
		m.mu.RLock()
		_, ok := m.connections[target]
		m.mu.RUnlock()
		if !ok {
			return "", fmt.Errorf("no connection with alias '%s'", target)
		}
		return target, nil
	}

	m.mu.RLock()
	primary := m.primary
	m.mu.RUnlock()

	if primary == "" {
		return "", errors.New("no active connection")
	}
	return primary, nil
}

// Run executes a command on the target connection.
func (m *Manager) Run(ctx context.Context, cmd, target string) (*RunResult, error) {
	alias, err := m.resolveTarget(target)
	if err != nil {
		return nil, err
	}

	lock := m.getAliasLock(alias)
	lock.Lock()
	defer lock.Unlock()

	m.mu.RLock()
	client := m.connections[alias]
	m.mu.RUnlock()

	if client == nil {
		return nil, fmt.Errorf("connection '%s' not found", alias)
	}

	result, err := client.Run(ctx, cmd)
	if err != nil {
		if isConnectionError(err) {
			// Check reconnect backoff
			m.mu.RLock()
			lastFail := m.reconnectFails[alias]
			m.mu.RUnlock()
			if time.Since(lastFail) < 5*time.Second {
				return nil, fmt.Errorf("connection lost (reconnect backoff): %w", err)
			}

			log.Printf("ssh: connection lost for %s, reconnecting", alias)
			if reconnErr := client.Reconnect(ctx, m.getJumpClient(client.creds.Via)); reconnErr != nil {
				m.mu.Lock()
				m.reconnectFails[alias] = time.Now()
				m.mu.Unlock()
				return nil, fmt.Errorf("reconnect failed: %w", reconnErr)
			}
			// Clear backoff on success
			m.mu.Lock()
			delete(m.reconnectFails, alias)
			m.mu.Unlock()
			return client.Run(ctx, cmd)
		}
		return nil, err
	}

	return result, nil
}

// getJumpClient returns the jump client.
func (m *Manager) getJumpClient(via string) *Client {
	if via == "" {
		return nil
	}
	m.mu.RLock()
	defer m.mu.RUnlock()
	return m.connections[via]
}

// isConnectionError checks if error indicates lost connection.
func isConnectionError(err error) bool {
	if err == nil {
		return false
	}

	// Type-safe checks first
	if errors.Is(err, io.EOF) {
		return true
	}
	var netErr *net.OpError
	if errors.As(err, &netErr) {
		return true
	}

	// String matching for SSH-specific errors
	errStr := err.Error()
	return strings.Contains(errStr, "connection reset") ||
		strings.Contains(errStr, "broken pipe") ||
		strings.Contains(errStr, "connection refused") ||
		strings.Contains(errStr, "use of closed network connection")
}

// Execute runs a command and returns formatted output.
func (m *Manager) Execute(ctx context.Context, cmd, target string) (string, error) {
	result, err := m.Run(ctx, cmd, target)
	if err != nil {
		return "", err
	}

	var output strings.Builder
	if result.Stdout != "" {
		output.WriteString(result.Stdout)
	}
	if result.Stderr != "" {
		if output.Len() > 0 {
			output.WriteString("\n")
		}
		output.WriteString(result.Stderr)
	}

	if output.Len() == 0 {
		return "(No output)", nil
	}

	if result.ExitCode != 0 {
		fmt.Fprintf(&output, "\n[Exit Code: %d]", result.ExitCode)
	}

	// Truncate if too long
	const maxBytes = 51200
	outputStr := output.String()
	if len(outputStr) > maxBytes {
		outputStr = outputStr[:maxBytes] + "\n... [Output truncated]"
	}

	return outputStr, nil
}

// resolvePath resolves a path to an absolute path using the connection's CWD.
// No path restrictions — the connected user's OS permissions are the only boundary.
func (m *Manager) resolvePath(path, alias string) string {
	m.mu.RLock()
	client := m.connections[alias]
	m.mu.RUnlock()

	cwd := "/"
	if client != nil {
		cwd = client.CWD()
	}

	if !filepath.IsAbs(path) {
		path = filepath.Join(cwd, path)
	}

	return filepath.Clean(path)
}

// ReadFile reads a file.
func (m *Manager) ReadFile(ctx context.Context, path, target string) (string, error) {
	alias, err := m.resolveTarget(target)
	if err != nil {
		return "", err
	}

	resolved := m.resolvePath(path, alias)

	lock := m.getAliasLock(alias)
	lock.Lock()
	defer lock.Unlock()

	m.mu.RLock()
	client := m.connections[alias]
	m.mu.RUnlock()

	if client == nil {
		return "", fmt.Errorf("connection '%s' is no longer active", alias)
	}

	sftpClient, err := client.SFTP()
	if err != nil {
		return "", err
	}

	file, err := sftpClient.Open(resolved)
	if err != nil {
		return "", fmt.Errorf("failed to open file: %w", err)
	}
	defer file.Close()

	// Check file size before reading to prevent OOM
	const maxReadSize = 10 * 1024 * 1024 // 10 MB
	stat, err := file.Stat()
	if err != nil {
		return "", fmt.Errorf("failed to stat file: %w", err)
	}
	if stat.Size() > maxReadSize {
		return "", fmt.Errorf("file too large (%d bytes, max %d bytes); use 'run' with head/tail to read portions", stat.Size(), maxReadSize)
	}

	content, err := io.ReadAll(file)
	if err != nil {
		return "", fmt.Errorf("failed to read file: %w", err)
	}

	return string(content), nil
}

// WriteFile writes content to a file.
func (m *Manager) WriteFile(ctx context.Context, path, content, target string) error {
	alias, err := m.resolveTarget(target)
	if err != nil {
		return err
	}

	resolved := m.resolvePath(path, alias)

	lock := m.getAliasLock(alias)
	lock.Lock()
	defer lock.Unlock()

	m.mu.RLock()
	client := m.connections[alias]
	m.mu.RUnlock()

	if client == nil {
		return fmt.Errorf("connection '%s' is no longer active", alias)
	}

	sftpClient, err := client.SFTP()
	if err != nil {
		return err
	}

	file, err := sftpClient.Create(resolved)
	if err != nil {
		return fmt.Errorf("failed to create file: %w", err)
	}
	defer file.Close()

	_, err = file.Write([]byte(content))
	if err != nil {
		return fmt.Errorf("failed to write file: %w", err)
	}

	return nil
}

// ListDir lists directory contents.
func (m *Manager) ListDir(ctx context.Context, path, target string) ([]FileInfo, error) {
	alias, err := m.resolveTarget(target)
	if err != nil {
		return nil, err
	}

	resolved := m.resolvePath(path, alias)

	lock := m.getAliasLock(alias)
	lock.Lock()
	defer lock.Unlock()

	m.mu.RLock()
	client := m.connections[alias]
	m.mu.RUnlock()

	if client == nil {
		return nil, fmt.Errorf("connection '%s' is no longer active", alias)
	}

	sftpClient, err := client.SFTP()
	if err != nil {
		return nil, err
	}

	entries, err := sftpClient.ReadDir(resolved)
	if err != nil {
		return nil, fmt.Errorf("failed to list directory: %w", err)
	}

	var files []FileInfo
	for _, entry := range entries {
		ftype := "file"
		if entry.IsDir() {
			ftype = "dir"
		}
		files = append(files, FileInfo{
			Name:        entry.Name(),
			Type:        ftype,
			Size:        entry.Size(),
			Permissions: entry.Mode().String(),
		})
	}

	return files, nil
}

// FileInfo represents file metadata.
type FileInfo struct {
	Name        string `json:"name"`
	Type        string `json:"type"`
	Size        int64  `json:"size"`
	Permissions string `json:"permissions"`
}

// GetPublicKey returns the system's public SSH key.
func (m *Manager) GetPublicKey() (string, error) {
	return m.keyManager.GetPublicKey()
}

// IsDockerAvailable checks if Docker is available on the target, with per-alias caching.
func (m *Manager) IsDockerAvailable(ctx context.Context, target string) (bool, error) {
	alias, err := m.resolveTarget(target)
	if err != nil {
		return false, err
	}

	m.mu.RLock()
	cached := m.dockerCache[alias]
	m.mu.RUnlock()

	if cached != nil {
		return *cached, nil
	}

	output, err := m.Execute(ctx, "command -v docker >/dev/null 2>&1 && echo 'ok' || echo 'missing'", target)
	if err != nil {
		return false, err
	}

	available := strings.Contains(output, "ok")
	m.mu.Lock()
	m.dockerCache[alias] = &available
	m.mu.Unlock()

	return available, nil
}

// Close closes all connections.
func (m *Manager) Close() {
	m.mu.Lock()
	defer m.mu.Unlock()

	for _, client := range m.connections {
		if client != nil {
			client.Close()
		}
	}
	m.connections = make(map[string]*Client)
	m.aliasLocks = make(map[string]*sync.Mutex)
	m.reconnectFails = make(map[string]time.Time)
	m.dockerCache = make(map[string]*bool)
	m.primary = ""
}