package tui

import (
	"context"
	"sync"

	tea "charm.land/bubbletea/v2"
)

type tuiObservations struct {
	mu      sync.Mutex
	ctx     context.Context
	cancel  context.CancelFunc
	workers sync.WaitGroup
	closed  bool
}

// Register before returning the command, so exit also owns a refresh that the
// command loop has not yet scheduled. Results are buffered independently of it.
func (m *Model) observationCmd(fn func(context.Context) tea.Msg) tea.Cmd {
	if m.observations == nil {
		m.observations = &tuiObservations{}
	}
	m.observations.mu.Lock()
	if m.observations.closed {
		m.observations.mu.Unlock()
		return nil
	}
	if m.observations.ctx == nil {
		m.observations.ctx, m.observations.cancel = context.WithCancel(context.Background())
	}
	ctx := m.observations.ctx
	m.observations.workers.Add(1)
	m.observations.mu.Unlock()
	result := make(chan tea.Msg, 1)
	go func() {
		defer m.observations.workers.Done()
		result <- fn(ctx)
	}()
	return func() tea.Msg { return <-result }
}

func (m *Model) cancelObservations() {
	if m.observations == nil {
		m.observations = &tuiObservations{}
	}
	m.observations.mu.Lock()
	m.observations.closed = true
	if m.observations.cancel != nil {
		m.observations.cancel()
	}
	m.observations.mu.Unlock()
}

func (m *Model) stopObservations() {
	m.cancelObservations()
	m.observations.workers.Wait()
}