package mgr

import (
	olog "ollie/log"
	"context"
	"fmt"
	"ollie/paths"
	"ollie/session"
	"ollie/skills"
	"ollie/tools"
	"olliesrv/fs"
	"os"
	"strconv"
	"strings"
	"sync"
	"sync/atomic"
)

var sessionFileOrder = []string{"new", "idx", "ls", "kill", "sh", "b", "bfg", "bbg", "cleanup"}

// FileMode returns the mode for a fixed session file,
// or 0 and false if the name is not a fixed file.
func FileMode(name string) (os.FileMode, bool) {
	m, ok := fs.Perms[fs.PathSessions].Files[name]
	return m, ok
}

// ManagerConfig holds the dependencies for a Manager.
type ManagerConfig struct {
	AgentsDir   string
	SessionsDir string

	Log      *olog.Logger
	Sink     *olog.Sink
	ReadFile func(string) ([]byte, error)
	MkdirAll func(string, os.FileMode) error
	// NewCore, if non-nil, replaces the default backend.New + agent.New
	// path. It receives the session ID, agent name, and cwd, and returns a Session.
	NewCore func(sessionID, agentName, cwd string) (*session.Session, error)
	// Strict rejects inline code steps; only tool steps are allowed.
	Strict bool
	// Yolo skips the landrun sandbox.
	Yolo bool
	// NoMount disables the per-session FUSE mount (e.g. when listening on TCP).
	NoMount bool
	// Enable9P indicates the 9P listener is active (for operational model injection).
	Enable9P bool
	// EnableDBus indicates the D-Bus adapter is active (for operational model injection).
	EnableDBus bool
	// InvalidateModels clears the model cache, forcing a refresh.
	InvalidateModels func()
	// ResetElevation resets the per-turn elevation rate limiter for a session.
	ResetElevation func(sessionID string)
	// ToolRegistry is the shared tool registry for lazy tool promotion.
	ToolRegistry *tools.Registry
	// SkillsRegistry is the shared skills registry for skill loading.
	SkillsRegistry *skills.Registry
	// OnSessionCreated is called after a new session is added to the manager.
	// Receives the session ID and the Session pointer.
	OnSessionCreated func(id string, sess *Session)
	// OnSessionKilled is called after a session is removed from the manager.
	OnSessionKilled func(id string)
	// OnSessionRenamed is called after a session is renamed.
	OnSessionRenamed func(oldID, newID string)
}

// Manager manages session lifecycle and exposes sessions as a Tree.
type Manager struct {
	tree     *fs.Tree
	cfg      ManagerConfig
	mu       sync.RWMutex
	sessions map[string]*Session
	nextUID  atomic.Uint32 // incrementing principal counter
}

// Tree returns the Tree view of the session namespace.
func (s *Manager) Tree() *fs.Tree { return s.tree }

// nextUname generates the next uname atomically.
func (s *Manager) nextUname() string {
	return fmt.Sprintf("%d", s.nextUID.Add(1))
}

func NewManager(cfg ManagerConfig) *Manager {
	if cfg.ReadFile == nil {
		cfg.ReadFile = os.ReadFile
	}
	if cfg.MkdirAll == nil {
		cfg.MkdirAll = os.MkdirAll
	}
	ss := &Manager{
		cfg:      cfg,
		sessions: make(map[string]*Session),
	}
	ss.nextUID.Store(9999)
	ss.restoreAllSessions()
	ss.tree = fs.NewTree(nil, 0,
		fs.WithStat(func(_ []string, name string) (os.FileInfo, error) { return ss.stat(name) }),
		fs.WithOpener(func(_ []string, name string) (fs.File, error) { return ss.openEntry(name) }),
		fs.WithLister(func(_ []string) ([]os.DirEntry, error) { return ss.list() }),
		fs.WithReaddir(func(_ []string, name string) ([]os.DirEntry, error) { return ss.Readdir(name) }),
		fs.WithDeleter(func(_ []string, name string) error { return ss.del(name) }),
		fs.WithCreator(func(_ []string, name string, _ os.FileMode) error { return ss.create(name) }),
		fs.WithRenamer(func(_ []string, old, new string) error { return ss.renameSession(old, new) }),
	)
	return ss
}

// AddSession inserts a pre-built session into the fs.
func (s *Manager) AddSession(sess *Session) {
	s.mu.Lock()
	s.sessions[sess.RunnableID()] = sess
	s.mu.Unlock()
}

// List returns all root-level entries (fixed files + session directories).
func (s *Manager) List() ([]os.DirEntry, error) {
	return s.list()
}

func (s *Manager) list() ([]os.DirEntry, error) {
	entries := make([]os.DirEntry, 0, len(sessionFileOrder))
	for _, name := range sessionFileOrder {
		entries = append(entries, fs.FileEntry(name, fs.Perms[fs.PathSessions].Files[name]))
	}
	s.mu.RLock()
	for id := range s.sessions {
		entries = append(entries, fs.DirEntry(id, fs.Perms[fs.PathSessionDir].DirMode))
	}
	s.mu.RUnlock()
	return entries, nil
}

// Readdir lists entries in a subdirectory.
func (s *Manager) Readdir(name string) ([]os.DirEntry, error) {
	parts := strings.SplitN(name, "/", 4)
	sessID := parts[0]
	sess := s.Session(sessID)
	if sess == nil {
		return nil, fmt.Errorf("session not found: %s", sessID)
	}
	// {id} — list session-level files + agent/
	if len(parts) == 1 {
		entries := []os.DirEntry{
			fs.FileEntry("plan", 0666),
			fs.FileEntry("env", 0444),
			fs.DirEntry("agent", 0755),
		}
		return entries, nil
	}
	// {id}/agent — list agent IDs
	if parts[1] == "agent" {
		if len(parts) == 2 {
			// Currently single-agent: use the agent's ID
			aid := sess.Core.Agent().ID()
			if aid == "" {
				aid = "0" // fallback for sessions without explicit agent ID
			}
			entries := []os.DirEntry{fs.DirEntry(aid, 0755)}
			return entries, nil
		}
		// {id}/agent/{aid} — list agent files + proc/
		if len(parts) == 3 {
			afs, err := s.openAgentTree(sess)
			if err != nil {
				return nil, err
			}
			entries, err := afs.List()
			if err != nil {
				return nil, err
			}
			entries = append(entries, fs.DirEntry("proc", 0755))
			return entries, nil
		}
		// {id}/agent/{aid}/proc — list detached process PIDs
		if len(parts) == 4 && parts[3] == "proc" {
			procs := sess.Core.ListDetached()
			entries := make([]os.DirEntry, len(procs))
			for i, p := range procs {
				entries[i] = fs.FileEntry(fmt.Sprintf("%d", p.PID), 0666)
			}
			return entries, nil
		}
	}
	// {id}/peer — list peer session IDs
	if len(parts) == 2 && parts[1] == "peer" {
		peers, _ := s.PeerList(sessID)
		entries := make([]os.DirEntry, len(peers))
		for i, p := range peers {
			entries[i] = fs.FileEntry(p, 0666)
		}
		return entries, nil
	}
	return nil, fmt.Errorf("%s: not a directory", name)
}

// --- Peer Management ---

// PeerAdd creates a bidirectional peer link between two sessions.
func (s *Manager) PeerAdd(sessID, peerID string) error {
	s.mu.RLock()
	sess, ok := s.sessions[sessID]
	peer, peerOk := s.sessions[peerID]
	s.mu.RUnlock()
	if !ok {
		return fmt.Errorf("session not found: %s", sessID)
	}
	if !peerOk {
		return fmt.Errorf("peer session not found: %s", peerID)
	}
	if sessID == peerID {
		return fmt.Errorf("cannot peer a session with itself")
	}

	sess.mu.Lock()
	if sess.peers == nil {
		sess.peers = make(map[string]bool)
	}
	sess.peers[peerID] = true
	sess.mu.Unlock()

	peer.mu.Lock()
	if peer.peers == nil {
		peer.peers = make(map[string]bool)
	}
	peer.peers[sessID] = true
	peer.mu.Unlock()
	return nil
}

// PeerRemove removes a bidirectional peer link between two sessions.
func (s *Manager) PeerRemove(sessID, peerID string) error {
	s.mu.RLock()
	sess, ok := s.sessions[sessID]
	peer, peerOk := s.sessions[peerID]
	s.mu.RUnlock()
	if !ok {
		return fmt.Errorf("session not found: %s", sessID)
	}

	sess.mu.Lock()
	delete(sess.peers, peerID)
	sess.mu.Unlock()

	if peerOk {
		peer.mu.Lock()
		delete(peer.peers, sessID)
		peer.mu.Unlock()
	}
	return nil
}

// PeerList returns the peer session IDs for a session.
func (s *Manager) PeerList(sessID string) ([]string, error) {
	s.mu.RLock()
	sess, ok := s.sessions[sessID]
	s.mu.RUnlock()
	if !ok {
		return nil, fmt.Errorf("session not found: %s", sessID)
	}
	sess.mu.RLock()
	result := make([]string, 0, len(sess.peers))
	for id := range sess.peers {
		result = append(result, id)
	}
	sess.mu.RUnlock()
	return result, nil
}

// PeerSubmit sends a prompt to a peer session.
func (s *Manager) PeerSubmit(sessID, peerID, prompt string) error {
	s.mu.RLock()
	sess, ok := s.sessions[sessID]
	peer, peerOk := s.sessions[peerID]
	s.mu.RUnlock()
	if !ok {
		return fmt.Errorf("session not found: %s", sessID)
	}
	if !peerOk {
		return fmt.Errorf("peer session not found: %s", peerID)
	}
	sess.mu.RLock()
	isPeer := sess.peers[peerID]
	sess.mu.RUnlock()
	if !isPeer {
		return fmt.Errorf("%s is not a peer of %s", peerID, sessID)
	}
	go peer.Core.Submit(peer.Ctx, prompt)
	return nil
}

func (s *Manager) stat(name string) (os.FileInfo, error) {
	// Top-level fixed files (new, idx, sh, etc.)
	if mode, ok := fs.Perms[fs.PathSessions].Files[name]; ok {
		return &fs.SyntheticFileInfo{Name_: name, Mode_: mode}, nil
	}
	parts := strings.SplitN(name, "/", 4)
	sessID := parts[0]
	s.mu.RLock()
	sess, ok := s.sessions[sessID]
	s.mu.RUnlock()
	if !ok {
		return nil, fmt.Errorf("%s: not found", name)
	}
	// Session directory: {id}
	if len(parts) == 1 {
		return &fs.SyntheticFileInfo{Name_: sessID, Mode_: fs.Perms[fs.PathSessionDir].DirMode, IsDir_: true}, nil
	}
	// Agent directory: {id}/agent
	if parts[1] == "agent" {
		if len(parts) == 2 {
			return &fs.SyntheticFileInfo{Name_: "agent", Mode_: 0755, IsDir_: true}, nil
		}
		// Agent instance: {id}/agent/{aid}
		if len(parts) == 3 {
			return &fs.SyntheticFileInfo{Name_: parts[2], Mode_: 0755, IsDir_: true}, nil
		}
		// Agent file: {id}/agent/{aid}/{file}
		if parts[3] == "proc" {
			return &fs.SyntheticFileInfo{Name_: "proc", Mode_: 0755, IsDir_: true}, nil
		}
		afs, err := s.openAgentTree(sess)
		if err != nil {
			return nil, err
		}
		return afs.Stat(parts[3])
	}
	// Peer directory: {id}/peer
	if parts[1] == "peer" {
		if len(parts) == 2 {
			return &fs.SyntheticFileInfo{Name_: "peer", Mode_: 0755, IsDir_: true}, nil
		}
		// Peer file: {id}/peer/{peer-id}
		peerID := parts[2]
		sess.mu.RLock()
		isPeer := sess.peers[peerID]
		sess.mu.RUnlock()
		if !isPeer {
			return nil, fmt.Errorf("%s: not found", name)
		}
		return &fs.SyntheticFileInfo{Name_: peerID, Mode_: 0666}, nil
	}
	// Session file: {id}/{file} (plan, env)
	sfs, err := s.openSessionTree(sess)
	if err != nil {
		return nil, err
	}
	return sfs.Stat(parts[1])
}

func (s *Manager) openEntry(name string) (fs.File, error) {
	notBlocking := func(context.Context, string) ([]byte, string, error) {
		return nil, "", fmt.Errorf("blocking read not supported")
	}

	// Peer file: {id}/peer/{peer-id} — write submits prompt to peer
	parts := strings.SplitN(name, "/", 3)

	// Proc file: {id}/proc/{pid} — read returns ring buffer output
	if len(parts) == 3 && parts[1] == "proc" {
		sessID := parts[0]
		sess := s.Session(sessID)
		if sess == nil {
			return nil, fmt.Errorf("%s: not found", name)
		}
		pidStr := parts[2]
		pid, err := strconv.Atoi(pidStr)
		if err != nil {
			return nil, fmt.Errorf("invalid pid: %s", pidStr)
		}
		return &fs.FileConfig{
			StatFn: func() (os.FileInfo, error) {
				return &fs.SyntheticFileInfo{Name_: pidStr, Mode_: 0444}, nil
			},
			ReadFn: func() ([]byte, error) {
				output, err := sess.Core.GetDetachedOutput(pid)
				if err != nil {
					return nil, err
				}
				return []byte(output), nil
			},
			WriteFn:        func([]byte) error { return fmt.Errorf("read-only") },
			BlockingReadFn: notBlocking,
		}, nil
	}

	if len(parts) == 3 && parts[1] == "peer" {
		sessID := parts[0]
		peerID := parts[2]
		return &fs.FileConfig{
			StatFn: func() (os.FileInfo, error) {
				return &fs.SyntheticFileInfo{Name_: peerID, Mode_: 0666}, nil
			},
			ReadFn: func() ([]byte, error) {
				return nil, nil // empty read
			},
			WriteFn: func(data []byte) error {
				prompt := strings.TrimSpace(string(data))
				if prompt == "" {
					return nil
				}
				return s.PeerSubmit(sessID, peerID, prompt)
			},
			BlockingReadFn: notBlocking,
		}, nil
	}

	// Top-level fixed files.
	switch name {
	case "new":
		return &fs.FileConfig{
			StatFn: func() (os.FileInfo, error) {
				return &fs.SyntheticFileInfo{Name_: "new", Mode_: fs.Perms[fs.PathSessions].Files["new"]}, nil
			},
			ReadFn: func() ([]byte, error) {
				return []byte("name=\ncwd=\nremote=\nbackend=\nmodel=\nagent=\nmaxTokens=\nmaxCompletionTokens=\ntemperature=\ntopP=\ntopK=\nminP=\ntopA=\nfrequencyPenalty=\npresencePenalty=\nrepetitionPenalty=\nreasoning=\nreasoningEffort=\nincludeReasoning=\nresponseFormat=\nstop=\nverbosity=\n"), nil
			},
			WriteFn: func(data []byte) error {
				_, err := s.CreateSession(strings.Fields(strings.TrimSpace(string(data))))
				return err
			},
			BlockingReadFn: notBlocking,
		}, nil
	case "idx":
		return &fs.FileConfig{
			StatFn: func() (os.FileInfo, error) {
				return &fs.SyntheticFileInfo{Name_: "idx", Mode_: fs.Perms[fs.PathSessions].Files["idx"]}, nil
			},
			ReadFn:         func() ([]byte, error) { return s.index(), nil },
			WriteFn:        func([]byte) error { return fmt.Errorf("idx: read-only") },
			BlockingReadFn: notBlocking,
		}, nil
	}
	if _, ok := fs.Perms[fs.PathSessions].Files[name]; ok {
		return &fs.FileConfig{
			StatFn: func() (os.FileInfo, error) {
				return &fs.SyntheticFileInfo{Name_: name, Mode_: fs.Perms[fs.PathSessions].Files[name]}, nil
			},
			ReadFn: func() ([]byte, error) {
				return s.cfg.ReadFile(paths.CfgDir() + "/scripts/session/" + name)
			},
			WriteFn:        func([]byte) error { return fmt.Errorf("%s: not writable", name) },
			BlockingReadFn: notBlocking,
		}, nil
	}

	// Hierarchical paths: {id}/{file} or {id}/agent/{aid}/{file}
	parts = strings.SplitN(name, "/", 4)
	sessID := parts[0]
	sess := s.Session(sessID)
	if sess == nil {
		return nil, fmt.Errorf("%s: not found", name)
	}
	if len(parts) == 1 {
		return nil, fmt.Errorf("%s: is a directory", name)
	}

	// Agent file: {id}/agent/{aid}/{file}
	if parts[1] == "agent" {
		if len(parts) < 4 {
			return nil, fmt.Errorf("%s: is a directory", name)
		}
		// parts[2] = aid, parts[3] = file
		afs, err := s.openAgentTree(sess)
		if err != nil {
			return nil, err
		}
		return afs.Open(parts[3])
	}

	// Session file: {id}/{file}
	sfs, err := s.openSessionTree(sess)
	if err != nil {
		return nil, err
	}
	return sfs.Open(parts[1])
}

func (s *Manager) create(name string) error {
	// Peer creation: {id}/peer/{peer-id}
	parts := strings.SplitN(name, "/", 3)
	if len(parts) == 3 && parts[1] == "peer" {
		return s.PeerAdd(parts[0], parts[2])
	}
	return fmt.Errorf("create not supported: %s", name)
}

func (s *Manager) del(name string) error {
	parts := strings.SplitN(name, "/", 3)
	sessID := parts[0]
	// Delete session directory itself.
	if len(parts) == 1 {
		s.mu.RLock()
		_, ok := s.sessions[sessID]
		s.mu.RUnlock()
		if ok {
			s.KillSession(sessID)
			return nil
		}
		return fmt.Errorf("session not found: %s", sessID)
	}
	// Peer removal: {id}/peer/{peer-id}
	if len(parts) == 3 && parts[1] == "peer" {
		return s.PeerRemove(sessID, parts[2])
	}
	// Proc dismiss: {id}/proc/{pid}
	if len(parts) == 3 && parts[1] == "proc" {
		sess := s.Session(sessID)
		if sess == nil {
			return fmt.Errorf("session not found: %s", sessID)
		}
		pid, err := strconv.Atoi(parts[2])
		if err != nil {
			return fmt.Errorf("invalid pid: %s", parts[2])
		}
		if !sess.Core.DismissDetached(pid) {
			return fmt.Errorf("process %d not found or still running", pid)
		}
		return nil
	}
	// Session files are synthetic; allow rm -r to continue.
	return nil
}

// Session returns the session for the given ID, or nil.
func (s *Manager) Session(id string) *Session {
	s.mu.RLock()
	defer s.mu.RUnlock()
	return s.sessions[id]
}

// SessionByUname returns the session with the given uname (principal), or nil.
func (s *Manager) SessionByUname(uname string) *Session {
	s.mu.RLock()
	defer s.mu.RUnlock()
	for _, sess := range s.sessions {
		if sess.uname == uname {
			return sess
		}
	}
	return nil
}

// OpenSessionTree returns a Tree for the given session ID.
func (s *Manager) OpenSessionTree(id string) (*fs.Tree, error) {
	if sess := s.Session(id); sess != nil {
		return s.openSessionTree(sess)
	}
	return nil, fmt.Errorf("session not found: %s", id)
}

func (s *Manager) openSessionTree(sess *Session) (*fs.Tree, error) {
	var resetElev func()
	if s.cfg.ResetElevation != nil {
		id := sess.id
		resetElev = func() { s.cfg.ResetElevation(id) }
	}
	return NewSessionTree(
		sess,
		s.cfg.Log,
		func() { s.KillSession(sess.id) },
		func(newID string) error { return s.renameSession(sess.id, newID) },
		nil, // no transcript saving
		s.cfg.InvalidateModels,
		resetElev,
		s.cfg.ToolRegistry,
	), nil
}

func (s *Manager) openAgentTree(sess *Session) (*fs.Tree, error) {
	var resetElev func()
	if s.cfg.ResetElevation != nil {
		id := sess.id
		resetElev = func() { s.cfg.ResetElevation(id) }
	}
	return NewAgentTree(
		sess,
		s.cfg.Log,
		nil, // no transcript saving
		s.cfg.InvalidateModels,
		resetElev,
		s.cfg.ToolRegistry,
	), nil
}

// InterruptAll interrupts every active session.
func (s *Manager) InterruptAll() {
	s.mu.RLock()
	defer s.mu.RUnlock()
	for _, sess := range s.sessions {
		sess.Core.Interrupt(session.ErrInterrupted)
	}
}

// Shutdown kills all active sessions.