package main

import (
	"crypto/sha256"
	"encoding/hex"
	"fmt"
	"log"
	"strings"
	"sync"
	"time"
)

const sessPrefix = "helm-"

// SessionState is what clients see for one managed tmux session.
type SessionState struct {
	Name     string    `json:"name"`     // API name (without tmux prefix)
	Tmux     string    `json:"tmux"`     // tmux session name
	Cmd      string    `json:"cmd"`      // command line launched in the pane
	Alive    bool      `json:"alive"`    // pane process still running
	Seq      uint64    `json:"seq"`      // bumped on every screen change
	Question *Question `json:"question"` // pending question, if any
	Changed  time.Time `json:"changed"`  // last screen change
	Created  time.Time `json:"created"`
}

type Event struct {
	Type    string      `json:"type"` // screen | question | session | share
	Session string      `json:"session,omitempty"`
	Data    interface{} `json:"data,omitempty"`
}

type Manager struct {
	cfg  *Config
	ntfy *Ntfy

	mu       sync.Mutex
	sessions map[string]*SessionState
	notified map[string]string // session -> last question hash sent to ntfy

	subMu sync.Mutex
	subs  map[chan Event]struct{}
}

func NewManager(cfg *Config, ntfy *Ntfy) *Manager {
	m := &Manager{
		cfg:      cfg,
		ntfy:     ntfy,
		sessions: map[string]*SessionState{},
		notified: map[string]string{},
		subs:     map[chan Event]struct{}{},
	}
	m.adoptExisting()
	go m.pollLoop()
	return m
}

// adoptExisting re-registers helm-* tmux sessions after a helmd restart:
// tmux is the source of truth, helmd only mirrors it.
func (m *Manager) adoptExisting() {
	for _, t := range tmuxListSessions() {
		if strings.HasPrefix(t, sessPrefix) {
			name := strings.TrimPrefix(t, sessPrefix)
			m.sessions[name] = &SessionState{
				Name: name, Tmux: t, Cmd: "(adopterad)",
				Created: time.Now(), Changed: time.Now(),
			}
			log.Printf("adopterade befintlig tmux-session %s", t)
		}
	}
}

func (m *Manager) Subscribe() chan Event {
	ch := make(chan Event, 32)
	m.subMu.Lock()
	m.subs[ch] = struct{}{}
	m.subMu.Unlock()
	return ch
}

func (m *Manager) Unsubscribe(ch chan Event) {
	m.subMu.Lock()
	delete(m.subs, ch)
	m.subMu.Unlock()
}

func (m *Manager) emit(ev Event) {
	m.subMu.Lock()
	for ch := range m.subs {
		select {
		case ch <- ev:
		default: // slow client: drop rather than block the poller
		}
	}
	m.subMu.Unlock()
}

func (m *Manager) List() []*SessionState {
	m.mu.Lock()
	defer m.mu.Unlock()
	out := make([]*SessionState, 0, len(m.sessions))
	for _, s := range m.sessions {
		out = append(out, s)
	}
	return out
}

func (m *Manager) Get(name string) (*SessionState, bool) {
	m.mu.Lock()
	defer m.mu.Unlock()
	s, ok := m.sessions[name]
	return s, ok
}

// Create starts a new tmux session running the agent (or a custom
// command). An empty cmd uses the configured agent + args.
func (m *Manager) Create(name, cmdline, cwd string) (*SessionState, error) {
	if name == "" || strings.ContainsAny(name, " \t/.:") {
		return nil, fmt.Errorf("ogiltigt sessionsnamn %q", name)
	}
	m.mu.Lock()
	defer m.mu.Unlock()
	if _, exists := m.sessions[name]; exists {
		return nil, fmt.Errorf("sessionen %s finns redan", name)
	}
	tmuxName := sessPrefix + name
	if tmuxHasSession(tmuxName) {
		return nil, fmt.Errorf("tmux-sessionen %s finns redan (adoptera med POST {\"adopt\":true})", tmuxName)
	}
	if cmdline == "" {
		cmdline = m.cfg.AgentCmd
		if len(m.cfg.AgentArgs) > 0 {
			cmdline += " " + strings.Join(m.cfg.AgentArgs, " ")
		}
	}
	if cwd == "" {
		cwd = m.cfg.Workdir
	}
	if err := tmuxNewSession(tmuxName, cwd, m.cfg.Cols, m.cfg.Rows, cmdline); err != nil {
		return nil, err
	}
	s := &SessionState{
		Name: name, Tmux: tmuxName, Cmd: cmdline, Alive: true,
		Created: time.Now(), Changed: time.Now(),
	}
	m.sessions[name] = s
	m.emit(Event{Type: "session", Session: name, Data: "created"})
	return s, nil
}

// Adopt registers an already-running tmux session under helmd control.
func (m *Manager) Adopt(name, tmuxName string) (*SessionState, error) {
	if tmuxName == "" {
		tmuxName = sessPrefix + name
	}
	if !tmuxHasSession(tmuxName) {
		return nil, fmt.Errorf("ingen tmux-session %q", tmuxName)
	}
	m.mu.Lock()
	defer m.mu.Unlock()
	if _, exists := m.sessions[name]; exists {
		return nil, fmt.Errorf("sessionen %s finns redan", name)
	}
	s := &SessionState{
		Name: name, Tmux: tmuxName, Cmd: "(adopterad)", Alive: true,
		Created: time.Now(), Changed: time.Now(),
	}
	m.sessions[name] = s
	m.emit(Event{Type: "session", Session: name, Data: "adopted"})
	return s, nil
}

// Kill terminates the tmux session and forgets it.
func (m *Manager) Kill(name string) error {
	m.mu.Lock()
	s, ok := m.sessions[name]
	if ok {
		delete(m.sessions, name)
		delete(m.notified, name)
	}
	m.mu.Unlock()
	if !ok {
		return fmt.Errorf("ingen session %q", name)
	}
	m.emit(Event{Type: "session", Session: name, Data: "killed"})
	if tmuxHasSession(s.Tmux) {
		return tmuxKillSession(s.Tmux)
	}
	return nil
}

// Prompt pastes text into the session and (by default) submits it.
func (m *Manager) Prompt(name, text string, submit bool) error {
	s, ok := m.Get(name)
	if !ok {
		return fmt.Errorf("ingen session %q", name)
	}
	if err := tmuxPasteText(s.Tmux, text); err != nil {
		return err
	}
	if submit {
		time.Sleep(150 * time.Millisecond) // let the TUI ingest the paste
		return tmuxSendKeys(s.Tmux, "Enter")
	}
	return nil
}

// Answer picks an option in the pending question. Numbered lists get
// the digit key; unnumbered lists are navigated relative to the
// current selection.
func (m *Manager) Answer(name string, option int) error {
	s, ok := m.Get(name)
	if !ok {
		return fmt.Errorf("ingen session %q", name)
	}
	q := s.Question
	if q == nil {
		return fmt.Errorf("ingen väntande fråga i %s", name)
	}
	if option < 1 || option > len(q.Options) {
		return fmt.Errorf("option %d utanför 1..%d", option, len(q.Options))
	}
	idx := option - 1
	if q.Numbered {
		num := q.Options[idx].Num
		if err := tmuxSendKeys(s.Tmux, fmt.Sprint(num)); err != nil {
			return err
		}
		time.Sleep(200 * time.Millisecond)
		// Digit selection auto-confirms in agy; if the prompt is still
		// up (pure highlight moved), Enter confirms. Extra Enter on an
		// already-gone prompt lands in the input box and is harmless
		// only if empty — so only confirm when the question persists.
		if cur, err := tmuxCapture(s.Tmux, false, 0); err == nil {
			if nq := DetectQuestion(cur); nq != nil && nq.Hash == q.Hash {
				return tmuxSendKeys(s.Tmux, "Enter")
			}
		}
		return nil
	}
	if q.Selected < 0 {
		return fmt.Errorf("okänd markering — svara med raw keys i stället")
	}
	diff := idx - q.Selected
	key, n := "Down", diff
	if diff < 0 {
		key, n = "Up", -diff
	}
	for i := 0; i < n; i++ {
		if err := tmuxSendKeys(s.Tmux, key); err != nil {
			return err
		}
		time.Sleep(60 * time.Millisecond)
	}
	return tmuxSendKeys(s.Tmux, "Enter")
}

// Keys sends raw tmux key names (Escape, BTab, C-c, y, ...).
func (m *Manager) Keys(name string, keys []string) error {
	s, ok := m.Get(name)
	if !ok {
		return fmt.Errorf("ingen session %q", name)
	}
	return tmuxSendKeys(s.Tmux, keys...)
}

func (m *Manager) Screen(name string, ansi bool, history int) (string, error) {
	s, ok := m.Get(name)
	if !ok {
		return "", fmt.Errorf("ingen session %q", name)
	}
	return tmuxCapture(s.Tmux, ansi, history)
}

// pollLoop watches every session for screen changes and questions.
func (m *Manager) pollLoop() {
	interval := time.Duration(m.cfg.PollMs) * time.Millisecond
	if interval <= 0 {
		interval = 500 * time.Millisecond
	}
	hashes := map[string]string{}
	for {
		time.Sleep(interval)
		for _, s := range m.List() {
			alive := tmuxHasSession(s.Tmux) && tmuxSessionAlive(s.Tmux)
			if !alive {
				if s.Alive {
					s.Alive = false
					m.emit(Event{Type: "session", Session: s.Name, Data: "exited"})
					m.ntfy.Publish("", "helm: "+s.Name+" avslutades", "Agentprocessen i "+s.Tmux+" kör inte längre.", "default")
				}
				continue
			}
			s.Alive = true
			screen, err := tmuxCapture(s.Tmux, false, 0)
			if err != nil {
				continue
			}
			sum := sha256.Sum256([]byte(screen))
			h := hex.EncodeToString(sum[:8])
			if h == hashes[s.Name] {
				continue
			}
			hashes[s.Name] = h
			s.Seq++
			s.Changed = time.Now()
			s.Question = DetectQuestion(screen)
			m.emit(Event{Type: "screen", Session: s.Name, Data: s.Seq})
			if s.Question != nil {
				m.emit(Event{Type: "question", Session: s.Name, Data: s.Question})
				m.mu.Lock()
				already := m.notified[s.Name] == s.Question.Hash
				if !already {
					m.notified[s.Name] = s.Question.Hash
				}
				m.mu.Unlock()
				if !already {
					m.ntfy.Question(s.Name, s.Question)
				}
			}
		}
	}
}