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term.go
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term.go
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// Copyright 2022 Namespace Labs Inc; All rights reserved.
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
package keyboard
import (
"context"
"fmt"
"io"
"os"
"strings"
"sync"
tea "github.com/charmbracelet/bubbletea"
"github.com/morikuni/aec"
"namespacelabs.dev/foundation/internal/console"
"namespacelabs.dev/foundation/internal/console/termios"
"namespacelabs.dev/foundation/internal/executor"
"namespacelabs.dev/foundation/internal/observers"
"namespacelabs.dev/foundation/internal/protos"
)
type Handler interface {
// Key MUST be a pure function. E.g. "l"
Key() string
// Must only leave when chan Event is closed. OpSet events must be Acknowledged by writing to Control.
Handle(context.Context, chan Event, chan<- Control)
// The first state is the initial state as well.
States() []HandlerState
}
type HandlerState struct {
State string
Label string
}
type EventOp string
type ControlOp string
const (
OpStackUpdate EventOp = "op.stackupdate"
OpSet EventOp = "op.set"
)
type Event struct {
EventID string
Operation EventOp
StackUpdate *observers.StackUpdateEvent
CurrentState string
}
type Control struct {
HandlerID int
AckEvent struct {
EventID string
}
SetEnabled *bool
}
type HandleOpts struct {
Provider observers.SessionProvider
Keybindings []Handler
Handler func(context.Context) error
}
// Handle processes user keystroke events and dev workflow updates. Here we also
// take care on calling `onDone` callback on user exiting.
func Handle(ctx context.Context, opts HandleOpts) error {
if !termios.IsTerm(os.Stdin.Fd()) {
return opts.Handler(ctx)
}
obs, err := opts.Provider.NewStackClient()
if err != nil {
return err
}
defer obs.Close()
keych := make(chan tea.KeyMsg)
ctx, cancelContext := context.WithCancel(ctx)
defer cancelContext()
go handleEvents(ctx, obs, opts.Keybindings, keych)
eg := executor.New(ctx, "keyboard-handler")
eg.Go(opts.Handler)
eg.Go(func(ctx context.Context) error {
defer close(keych)
p := tea.NewProgram(&program{ch: keych, w: console.Stderr(ctx)}, tea.WithoutRenderer(), tea.WithContext(ctx))
m, err := p.Run()
if err == tea.ErrProgramKilled {
return context.Canceled
} else if err != nil {
return err
} else if m.(*program).quit {
return context.Canceled
}
return nil
})
return eg.Wait()
}
type program struct {
ch chan tea.KeyMsg
quit bool
w io.Writer
}
func (m *program) Init() tea.Cmd { return nil }
func (m *program) View() string { return "" }
func (m *program) Update(msg tea.Msg) (tea.Model, tea.Cmd) {
switch msg := msg.(type) {
case tea.KeyMsg:
switch msg.Type {
case tea.KeyCtrlC:
m.quit = true
return m, tea.Quit
default:
if msg.String() == "q" {
m.quit = true
return m, tea.Quit
}
m.ch <- msg
}
case tea.WindowSizeMsg:
}
return m, nil
}
type internalState struct {
Handler Handler
HandlerID int
Ch chan Event
Enabled bool
HandlingEvent string
States []HandlerState
Current int
}
func handleEvents(ctx context.Context, obs observers.StackSession, handlers []Handler, keych chan tea.KeyMsg) {
control := make(chan Control, 100) // TODO NSL-383 this is a mitigation to avoid deadlocks. handleEvents needs a redesign to eliminate them altogether.
state := make([]*internalState, len(handlers))
var goroutines sync.WaitGroup
for k, handler := range handlers {
k := k // Close k.
st := &internalState{
Handler: handler,
HandlerID: k,
Ch: make(chan Event, 1),
States: handler.States(),
Current: 0,
Enabled: false,
}
state[k] = st
goroutines.Add(1)
go func() {
handlerControl := make(chan Control, 1)
go func() {
for op := range handlerControl {
op.HandlerID = k
control <- op
}
goroutines.Done()
}()
st.Handler.Handle(ctx, st.Ch, handlerControl)
}()
}
defer func() {
for _, state := range state {
close(state.Ch)
}
// Wait until the go routine exits.
goroutines.Wait()
// Only close control after all goroutines have exited.
close(control)
}()
eventID := uint64(0)
for {
var labels []string
for _, state := range state {
if !state.Enabled || state.HandlingEvent != "" {
labels = append(labels, aec.LightBlackF.Apply(fmt.Sprintf(" (%s): %s", state.Handler.Key(), state.States[state.Current].Label)))
} else {
labels = append(labels, fmt.Sprintf(" (%s): %s", aec.Bold.Apply(state.Handler.Key()), state.States[state.Current].Label))
}
}
keybindings := fmt.Sprintf(" %s%s (%s): quit", aec.LightBlackF.Apply("Key bindings"), strings.Join(labels, ""), aec.Bold.Apply("q"))
console.SetStickyContent(ctx, "commands", keybindings)
eventID++
select {
case update, ok := <-obs.StackEvents():
if !ok {
return
}
if len(state) > 0 {
for _, handler := range state {
handler.Ch <- Event{
EventID: fmt.Sprintf("%d", eventID),
Operation: OpStackUpdate,
// Decouple changes made by devsession. Handlers should be able
// to assume that the received event data is immutable.
StackUpdate: protos.Clone(update),
}
}
}
case key, ok := <-keych:
if !ok {
return
}
for _, state := range state {
if state.Handler.Key() != key.String() {
continue
}
// Don't allow multiple state changes until the handler acknowledges the command.
if state.HandlingEvent == "" && state.Enabled {
state.HandlingEvent = fmt.Sprintf("%d", eventID)
state.Current++
if state.Current >= len(state.States) {
state.Current = 0
}
state.Ch <- Event{
EventID: state.HandlingEvent,
Operation: OpSet,
CurrentState: state.States[state.Current].State,
}
}
break
}
case c := <-control:
if c.HandlerID < 0 || c.HandlerID >= len(state) {
panic("handler id is invalid")
}
state := state[c.HandlerID]
if state.HandlingEvent == c.AckEvent.EventID {
state.HandlingEvent = ""
}
if c.SetEnabled != nil {
state.Enabled = *c.SetEnabled
}
case <-ctx.Done():
return
}
}
}