package session

import (
	"context"
	"encoding/json"
	"fmt"
	"log"
	"os"
	"path/filepath"
	"strings"
	"sync"
	"time"

	"github.com/fmartingr/ccrm/daemon/internal/claude"
	"github.com/fmartingr/ccrm/daemon/internal/tmux"
)

// OnMessageFunc is called by the manager when a subprocess emits a message.
// The session name is provided so the caller can route the message.
type OnMessageFunc func(sessionName string, msg *claude.CLIMessage)

// OnProcessExitFunc is called when a subprocess exits. The manager handles
// respawning internally; this callback is for logging/relay purposes only.
type OnProcessExitFunc func(sessionName string, willRespawn bool)

// Manager manages the lifecycle of Claude Code sessions.
type Manager struct {
	mu            sync.RWMutex
	sessions      map[string]*Session // keyed by session name
	prefix        string
	claudeBin     string
	dataDir       string
	onMessage     OnMessageFunc
	onProcessExit OnProcessExitFunc
}

// NewManager creates a new session manager.
func NewManager(prefix, claudeBin, dataDir string, onMessage OnMessageFunc, onProcessExit OnProcessExitFunc) *Manager {
	return &Manager{
		sessions:      make(map[string]*Session),
		prefix:        prefix,
		claudeBin:     claudeBin,
		dataDir:       dataDir,
		onMessage:     onMessage,
		onProcessExit: onProcessExit,
	}
}

// Start creates a new session by creating a tmux session and spawning a Claude subprocess.
func (m *Manager) Start(name, projectPath string, claudeArgs []string) (*Session, error) {
	m.mu.Lock()
	defer m.mu.Unlock()

	if _, exists := m.sessions[name]; exists {
		return nil, fmt.Errorf("session %q already exists", name)
	}

	tmuxName := m.prefix + name

	// Create tmux session
	if err := tmux.CreateSession(tmuxName, projectPath); err != nil {
		return nil, fmt.Errorf("creating tmux session: %w", err)
	}

	now := time.Now().UTC()

	// Create log file directory
	sessionsDir := filepath.Join(m.dataDir, "sessions")
	if err := os.MkdirAll(sessionsDir, 0755); err != nil {
		_ = tmux.KillSession(tmuxName)
		return nil, fmt.Errorf("creating sessions directory: %w", err)
	}
	logPath := filepath.Join(sessionsDir, name+".jsonl")

	// Create log file so tail -f works immediately
	if f, err := os.OpenFile(logPath, os.O_CREATE|os.O_WRONLY|os.O_APPEND, 0644); err == nil {
		f.Close()
	}

	s := &Session{
		Name:        name,
		TmuxSession: tmuxName,
		ProjectPath: projectPath,
		LogPath:     logPath,
		ClaudeArgs:  claudeArgs,
		Status:      StatusStarting,
		Mode:        ModeSubprocess,
		CreatedAt:   now,
		LastEventAt: now,
	}

	// Set tmux metadata options
	m.setTmuxMetadata(s)

	// Start monitoring in tmux pane
	m.restartMonitoring(s)

	// Spawn subprocess
	if err := m.spawnSubprocess(s); err != nil {
		_ = tmux.KillSession(tmuxName)
		return nil, fmt.Errorf("starting claude subprocess: %w", err)
	}

	m.sessions[name] = s

	return s, nil
}

// Stop gracefully stops a session. Marks it as explicitly stopped so it
// won't be respawned.
func (m *Manager) Stop(name string) error {
	m.mu.Lock()
	defer m.mu.Unlock()

	s, exists := m.sessions[name]
	if !exists {
		return fmt.Errorf("session %q not found", name)
	}

	s.ExplicitStop = true

	switch s.Mode {
	case ModeSubprocess:
		if s.Process != nil && s.Process.Alive() {
			_ = s.Process.Kill()
			<-s.Process.Done()
		}
	case ModeInteractive:
		_ = tmux.SendKeys(s.TmuxSession, "/exit")
		_ = tmux.SendEnter(s.TmuxSession)
		time.Sleep(500 * time.Millisecond)
	}

	s.Status = StatusStopped
	s.Process = nil
	m.syncToTmux(s)

	// Kill the tmux session
	_ = tmux.KillSession(s.TmuxSession)

	return nil
}

// Kill force-kills a session.
func (m *Manager) Kill(name string) error {
	m.mu.Lock()
	defer m.mu.Unlock()

	s, exists := m.sessions[name]
	if !exists {
		return fmt.Errorf("session %q not found", name)
	}

	s.ExplicitStop = true

	if s.Process != nil {
		_ = s.Process.Kill()
	}

	s.Status = StatusStopped
	s.Process = nil
	m.syncToTmux(s)

	// Kill the tmux session
	_ = tmux.KillSession(s.TmuxSession)

	return nil
}

// Get returns a session by name.
func (m *Manager) Get(name string) (*Session, bool) {
	m.mu.RLock()
	defer m.mu.RUnlock()
	s, ok := m.sessions[name]
	return s, ok
}

// List returns all tracked sessions.
func (m *Manager) List() []*Session {
	m.mu.RLock()
	defer m.mu.RUnlock()
	result := make([]*Session, 0, len(m.sessions))
	for _, s := range m.sessions {
		result = append(result, s)
	}
	return result
}

// UpdateStatus changes the status of a session.
func (m *Manager) UpdateStatus(name string, status Status) {
	m.mu.Lock()
	defer m.mu.Unlock()
	if s, ok := m.sessions[name]; ok {
		s.Status = status
		s.LastEventAt = time.Now().UTC()
		m.syncToTmux(s)
	}
}

// UpdateClaudeSession updates the Claude session ID and transcript path.
func (m *Manager) UpdateClaudeSession(name, claudeSessionID, transcriptPath string) {
	m.mu.Lock()
	defer m.mu.Unlock()
	if s, ok := m.sessions[name]; ok {
		if claudeSessionID != "" {
			s.ClaudeSessionID = claudeSessionID
		}
		if transcriptPath != "" {
			s.TranscriptPath = transcriptPath
		}
		m.syncToTmux(s)
	}
}

// SendPrompt sends a prompt to a session. If the subprocess has exited
// (normal for --print mode), it respawns with --resume before sending.
func (m *Manager) SendPrompt(name, prompt string) error {
	m.mu.Lock()
	defer m.mu.Unlock()

	s, exists := m.sessions[name]
	if !exists {
		return fmt.Errorf("session %q not found", name)
	}

	if s.Mode == ModeInteractive {
		return fmt.Errorf("session is in interactive mode, use the terminal")
	}

	if s.ExplicitStop {
		return fmt.Errorf("session is stopped")
	}

	switch s.Status {
	case StatusActive:
		s.PendingPrompts = append(s.PendingPrompts, prompt)
		return nil
	case StatusWaitingPermission:
		return fmt.Errorf("session is waiting for permission, cannot send prompt")
	}

	// Respawn subprocess if needed (--print exits after each turn)
	if s.Process == nil || !s.Process.Alive() {
		if err := m.spawnSubprocess(s); err != nil {
			return fmt.Errorf("respawning subprocess: %w", err)
		}
	}

	if err := s.Process.WriteMessage(&claude.UserMessage{
		Type:    "user_message",
		Content: prompt,
	}); err != nil {
		return fmt.Errorf("writing prompt to subprocess: %w", err)
	}

	s.Status = StatusActive
	s.LastEventAt = time.Now().UTC()
	m.syncToTmux(s)
	return nil
}

// DrainPendingPrompts sends the next queued prompt to a session.
func (m *Manager) DrainPendingPrompts(name string) {
	m.mu.Lock()
	defer m.mu.Unlock()

	s, exists := m.sessions[name]
	if !exists || len(s.PendingPrompts) == 0 || s.ExplicitStop {
		return
	}

	// Respawn subprocess if needed (--print exits after each turn)
	if s.Process == nil || !s.Process.Alive() {
		if err := m.spawnSubprocess(s); err != nil {
			log.Printf("failed to respawn subprocess for pending prompt %s: %v", name, err)
			return
		}
	}

	prompt := s.PendingPrompts[0]
	s.PendingPrompts = s.PendingPrompts[1:]

	if err := s.Process.WriteMessage(&claude.UserMessage{
		Type:    "user_message",
		Content: prompt,
	}); err != nil {
		log.Printf("failed to drain pending prompt for %s: %v", name, err)
		return
	}

	s.Status = StatusActive
	s.LastEventAt = time.Now().UTC()
	m.syncToTmux(s)
}

// RespondToPermission responds to a tool permission request.
func (m *Manager) RespondToPermission(name, requestID string, allow bool, reason string) error {
	m.mu.Lock()
	defer m.mu.Unlock()

	s, exists := m.sessions[name]
	if !exists {
		return fmt.Errorf("session %q not found", name)
	}

	if s.Mode != ModeSubprocess || s.Process == nil || !s.Process.Alive() {
		return fmt.Errorf("session is not in subprocess mode or process is not running")
	}

	return s.Process.WriteMessage(&claude.ControlResponse{
		Type:      "tool_use_permission_response",
		RequestID: requestID,
		Allow:     allow,
		Reason:    reason,
	})
}

// Attach switches a session from subprocess mode to interactive mode.
// Returns the tmux session name for the CLI to attach to.
func (m *Manager) Attach(name string) (string, error) {
	m.mu.Lock()
	defer m.mu.Unlock()

	s, exists := m.sessions[name]
	if !exists {
		return "", fmt.Errorf("session %q not found", name)
	}

	if s.Mode == ModeInteractive {
		// Already in interactive mode, return existing tmux session
		return s.TmuxSession, nil
	}

	if s.ClaudeSessionID == "" {
		return "", fmt.Errorf("session %q has no Claude session ID yet (send a prompt first)", name)
	}

	// Kill subprocess if alive
	if s.Process != nil && s.Process.Alive() {
		_ = s.Process.Kill()
		<-s.Process.Done()
	}
	s.Process = nil

	// Interrupt the monitoring command in the tmux pane
	_ = tmux.SendCtrlC(s.TmuxSession)
	time.Sleep(100 * time.Millisecond)

	// Send claude --resume into the existing tmux pane
	cmd := fmt.Sprintf("%s --resume %s", m.claudeBin, s.ClaudeSessionID)
	if err := tmux.SendKeys(s.TmuxSession, cmd); err != nil {
		// Recover: restart monitoring and respawn subprocess
		m.restartMonitoring(s)
		_ = m.spawnSubprocess(s)
		return "", fmt.Errorf("sending resume command: %w", err)
	}
	if err := tmux.SendEnter(s.TmuxSession); err != nil {
		m.restartMonitoring(s)
		_ = m.spawnSubprocess(s)
		return "", fmt.Errorf("sending enter: %w", err)
	}

	s.Mode = ModeInteractive
	s.Status = StatusActive
	s.LastEventAt = time.Now().UTC()
	m.syncToTmux(s)

	// Monitor the interactive session in the background
	go m.watchInteractiveSession(name)

	return s.TmuxSession, nil
}

// Detach switches a session from interactive mode back to subprocess mode.
func (m *Manager) Detach(name string) error {
	m.mu.Lock()
	defer m.mu.Unlock()

	s, exists := m.sessions[name]
	if !exists {
		return fmt.Errorf("session %q not found", name)
	}

	if s.Mode != ModeInteractive {
		return nil // already in subprocess mode
	}

	// Send /exit to claude in the tmux pane
	_ = tmux.SendKeys(s.TmuxSession, "/exit")
	_ = tmux.SendEnter(s.TmuxSession)
	time.Sleep(500 * time.Millisecond)

	// Ensure clean state
	_ = tmux.SendCtrlC(s.TmuxSession)
	time.Sleep(100 * time.Millisecond)

	// Restart monitoring in the tmux pane
	m.restartMonitoring(s)

	// Switch back to subprocess mode. Don't spawn yet — it will be
	// spawned on demand when the next prompt arrives.
	s.Process = nil
	s.Mode = ModeSubprocess
	s.Status = StatusIdle
	s.LastEventAt = time.Now().UTC()
	m.syncToTmux(s)

	return nil
}

// Remove removes a session from the registry.
func (m *Manager) Remove(name string) {
	m.mu.Lock()
	defer m.mu.Unlock()
	delete(m.sessions, name)
}

// FindByClaudeSessionID finds a session by its Claude session ID.
func (m *Manager) FindByClaudeSessionID(claudeSessionID string) (*Session, bool) {
	m.mu.RLock()
	defer m.mu.RUnlock()
	for _, s := range m.sessions {
		if s.ClaudeSessionID == claudeSessionID {
			return s, true
		}
	}
	return nil, false
}

// RecoverSessions scans tmux for existing ccrm sessions and recovers them
// into the in-memory session map. Called on daemon startup.
func (m *Manager) RecoverSessions() error {
	m.mu.Lock()
	defer m.mu.Unlock()

	tmuxSessions, err := tmux.ListSessionsWithPrefix(m.prefix)
	if err != nil {
		return fmt.Errorf("listing tmux sessions: %w", err)
	}

	for _, tmuxName := range tmuxSessions {
		name := strings.TrimPrefix(tmuxName, m.prefix)

		// Skip if already tracked
		if _, exists := m.sessions[name]; exists {
			continue
		}

		// Read metadata from tmux options
		status, _ := tmux.GetOption(tmuxName, "@ccrm_status")
		if status == string(StatusStopped) {
			// Clean up stopped sessions
			_ = tmux.KillSession(tmuxName)
			continue
		}

		mode, _ := tmux.GetOption(tmuxName, "@ccrm_mode")
		projectPath, _ := tmux.GetOption(tmuxName, "@ccrm_project_path")
		claudeSessionID, _ := tmux.GetOption(tmuxName, "@ccrm_claude_session_id")
		createdAtStr, _ := tmux.GetOption(tmuxName, "@ccrm_created_at")
		claudeArgsJSON, _ := tmux.GetOption(tmuxName, "@ccrm_claude_args")

		createdAt, _ := time.Parse(time.RFC3339, createdAtStr)
		if createdAt.IsZero() {
			createdAt = time.Now().UTC()
		}

		var claudeArgs []string
		if claudeArgsJSON != "" {
			_ = json.Unmarshal([]byte(claudeArgsJSON), &claudeArgs)
		}

		sessionsDir := filepath.Join(m.dataDir, "sessions")
		logPath := filepath.Join(sessionsDir, name+".jsonl")

		s := &Session{
			Name:            name,
			TmuxSession:     tmuxName,
			ProjectPath:     projectPath,
			ClaudeSessionID: claudeSessionID,
			LogPath:         logPath,
			ClaudeArgs:      claudeArgs,
			Mode:            Mode(mode),
			CreatedAt:       createdAt,
			LastEventAt:     time.Now().UTC(),
		}

		if s.Mode == ModeInteractive {
			s.Status = StatusActive
			m.sessions[name] = s
			go m.watchInteractiveSession(name)
			log.Printf("Recovered interactive session %q from tmux", name)
		} else {
			s.Mode = ModeSubprocess
			s.Status = StatusIdle
			// Restart monitoring in case it was interrupted
			m.restartMonitoring(s)
			m.sessions[name] = s
			log.Printf("Recovered subprocess session %q from tmux (idle, will spawn on next prompt)", name)
		}
	}

	return nil
}

// spawnSubprocess spawns a new Claude subprocess for the session.
// Uses --resume if a ClaudeSessionID is available.
// Must be called with m.mu held.
func (m *Manager) spawnSubprocess(s *Session) error {
	cfg := claude.ProcessConfig{
		ClaudeBin: m.claudeBin,
		WorkDir:   s.ProjectPath,
		ExtraArgs: s.ClaudeArgs,
	}
	if s.ClaudeSessionID != "" {
		cfg.ResumeSessionID = s.ClaudeSessionID
	}

	proc := claude.NewProcess(cfg)

	name := s.Name
	if err := proc.Start(context.Background(), func(msg *claude.CLIMessage) {
		// Append raw JSON line to session log
		m.appendToLog(s.LogPath, msg.Raw)

		if m.onMessage != nil {
			m.onMessage(name, msg)
		}
	}); err != nil {
		return err
	}

	s.Process = proc
	s.Mode = ModeSubprocess
	s.LastEventAt = time.Now().UTC()

	go m.watchProcessExit(name)

	return nil
}

// appendToLog appends a raw JSON line to the session log file.
func (m *Manager) appendToLog(logPath string, raw json.RawMessage) {
	if logPath == "" || len(raw) == 0 {
		return
	}

	f, err := os.OpenFile(logPath, os.O_APPEND|os.O_CREATE|os.O_WRONLY, 0644)
	if err != nil {
		log.Printf("Failed to open log file %s: %v", logPath, err)
		return
	}
	defer f.Close()

	line := append(raw, '\n')
	if _, err := f.Write(line); err != nil {
		log.Printf("Failed to write to log file %s: %v", logPath, err)
	}
}

// syncToTmux writes session state to tmux options.
// Must be called with m.mu held.
func (m *Manager) syncToTmux(s *Session) {
	if s.TmuxSession == "" || !tmux.HasSession(s.TmuxSession) {
		return
	}
	_ = tmux.SetOption(s.TmuxSession, "@ccrm_status", string(s.Status))
	_ = tmux.SetOption(s.TmuxSession, "@ccrm_mode", string(s.Mode))
	if s.ClaudeSessionID != "" {
		_ = tmux.SetOption(s.TmuxSession, "@ccrm_claude_session_id", s.ClaudeSessionID)
	}
}

// setTmuxMetadata writes all initial metadata to tmux options.
// Must be called with m.mu held.
func (m *Manager) setTmuxMetadata(s *Session) {
	if s.TmuxSession == "" {
		return
	}
	_ = tmux.SetOption(s.TmuxSession, "@ccrm_name", s.Name)
	_ = tmux.SetOption(s.TmuxSession, "@ccrm_project_path", s.ProjectPath)
	_ = tmux.SetOption(s.TmuxSession, "@ccrm_created_at", s.CreatedAt.Format(time.RFC3339))
	_ = tmux.SetOption(s.TmuxSession, "@ccrm_status", string(s.Status))
	_ = tmux.SetOption(s.TmuxSession, "@ccrm_mode", string(s.Mode))
	if len(s.ClaudeArgs) > 0 {
		argsJSON, _ := json.Marshal(s.ClaudeArgs)
		_ = tmux.SetOption(s.TmuxSession, "@ccrm_claude_args", string(argsJSON))
	}
}

// restartMonitoring restarts the tail -f command in the tmux pane.
// Must be called with m.mu held.
func (m *Manager) restartMonitoring(s *Session) {
	if s.TmuxSession == "" || s.LogPath == "" {
		return
	}
	_ = tmux.RespawnPane(s.TmuxSession, fmt.Sprintf("tail -f %s", s.LogPath))
}

// watchProcessExit waits for the subprocess to exit and handles the lifecycle.
// With --print mode, the process exits after each turn. This is normal —
// the session stays alive and a new process is spawned on the next prompt.
func (m *Manager) watchProcessExit(name string) {
	m.mu.RLock()
	s, exists := m.sessions[name]
	if !exists || s.Process == nil {
		m.mu.RUnlock()
		return
	}
	proc := s.Process
	m.mu.RUnlock()

	<-proc.Done()

	m.mu.RLock()
	s, exists = m.sessions[name]
	if !exists {
		m.mu.RUnlock()
		return
	}
	// Only act if this is still the same process (not replaced by respawn/attach)
	if s.Process != proc {
		m.mu.RUnlock()
		return
	}
	explicitStop := s.ExplicitStop
	mode := s.Mode
	m.mu.RUnlock()

	if explicitStop || mode == ModeInteractive {
		// User explicitly stopped or session switched to interactive mode.
		// Don't respawn.
		return
	}

	// Normal --print exit: set idle, notify, and let next SendPrompt respawn.
	log.Printf("Session %s: subprocess exited (normal turn completion)", name)

	m.mu.Lock()
	if s, ok := m.sessions[name]; ok && s.Process == proc {
		s.Process = nil
		if s.Status != StatusIdle {
			s.Status = StatusIdle
		}
		m.syncToTmux(s)
	}
	m.mu.Unlock()

	if m.onProcessExit != nil {
		m.onProcessExit(name, true)
	}

	// Drain pending prompts if any (will respawn subprocess)
	m.DrainPendingPrompts(name)
}

// watchInteractiveSession periodically checks if the interactive tmux session
// still has attached clients. When the user detaches or the session ends,
// it switches back to subprocess mode.
func (m *Manager) watchInteractiveSession(name string) {
	ticker := time.NewTicker(2 * time.Second)
	defer ticker.Stop()

	for range ticker.C {
		m.mu.RLock()
		s, exists := m.sessions[name]
		if !exists || s.Mode != ModeInteractive {
			m.mu.RUnlock()
			return
		}
		tmuxName := s.TmuxSession
		m.mu.RUnlock()

		if tmuxName == "" {
			return
		}

		// Check if tmux session still exists
		if !tmux.HasSession(tmuxName) {
			log.Printf("Interactive session %s ended, switching back to subprocess mode", name)
			_ = m.Detach(name)
			return
		}

		// Check if any clients are attached
		numClients, err := tmux.SessionAttachedClients(tmuxName)
		if err != nil {
			continue
		}
		if numClients == 0 {
			log.Printf("User detached from interactive session %s, switching back to subprocess mode", name)
			_ = m.Detach(name)
			return
		}
	}
}