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package tasks
import (
"bufio"
"fmt"
"io"
"os/exec"
"strings"
"sync"
"time"
"github.com/jesseduffield/lazygit/pkg/commands/oscommands"
"github.com/jesseduffield/lazygit/pkg/utils"
"github.com/sirupsen/logrus"
)
const THROTTLE_TIME = time.Millisecond * 30
// we use this to check if the system is under stress right now. Hopefully this makes sense on other machines
const COMMAND_START_THRESHOLD = time.Millisecond * 10
type ViewBufferManager struct {
// this blocks until the task has been properly stopped
stopCurrentTask func()
// this is what we write the output of the task to. It's typically a view
writer io.Writer
// this is for when we wait to get
waitingMutex sync.Mutex
taskIDMutex sync.Mutex
Log *logrus.Entry
newTaskId int
readLines chan int
taskKey string
onNewKey func()
// beforeStart is the function that is called before starting a new task
beforeStart func()
refreshView func()
onEndOfInput func()
// if the user flicks through a heap of items, with each one
// spawning a process to render something to the main view,
// it can slow things down quite a bit. In these situations we
// want to throttle the spawning of processes.
throttle bool
}
func (m *ViewBufferManager) GetTaskKey() string {
return m.taskKey
}
func NewViewBufferManager(
log *logrus.Entry,
writer io.Writer,
beforeStart func(),
refreshView func(),
onEndOfInput func(),
onNewKey func(),
) *ViewBufferManager {
return &ViewBufferManager{
Log: log,
writer: writer,
beforeStart: beforeStart,
refreshView: refreshView,
onEndOfInput: onEndOfInput,
readLines: make(chan int, 1024),
onNewKey: onNewKey,
}
}
func (m *ViewBufferManager) ReadLines(n int) {
go utils.Safe(func() {
m.readLines <- n
})
}
// note: onDone may be called twice
func (m *ViewBufferManager) NewCmdTask(start func() (*exec.Cmd, io.Reader), prefix string, linesToRead int, onDone func()) func(chan struct{}) error {
return func(stop chan struct{}) error {
var once sync.Once
var onDoneWrapper func()
if onDone != nil {
onDoneWrapper = func() { once.Do(onDone) }
}
if m.throttle {
m.Log.Info("throttling task")
time.Sleep(THROTTLE_TIME)
}
select {
case <-stop:
return nil
default:
}
startTime := time.Now()
cmd, r := start()
timeToStart := time.Since(startTime)
go utils.Safe(func() {
<-stop
// we use the time it took to start the program as a way of checking if things
// are running slow at the moment. This is admittedly a crude estimate, but
// the point is that we only want to throttle when things are running slow
// and the user is flicking through a bunch of items.
m.throttle = time.Since(startTime) < THROTTLE_TIME && timeToStart > COMMAND_START_THRESHOLD
if err := oscommands.Kill(cmd); err != nil {
if !strings.Contains(err.Error(), "process already finished") {
m.Log.Errorf("error when running cmd task: %v", err)
}
}
// for pty's we need to call onDone here so that cmd.Wait() doesn't block forever
if onDoneWrapper != nil {
onDoneWrapper()
}
})
loadingMutex := sync.Mutex{}
// not sure if it's the right move to redefine this or not
m.readLines = make(chan int, 1024)
done := make(chan struct{})
scanner := bufio.NewScanner(r)
scanner.Split(bufio.ScanLines)
loaded := false
go utils.Safe(func() {
ticker := time.NewTicker(time.Millisecond * 200)
defer ticker.Stop()
select {
case <-stop:
return
case <-ticker.C:
loadingMutex.Lock()
if !loaded {
m.beforeStart()
_, _ = m.writer.Write([]byte("loading..."))
m.refreshView()
}
loadingMutex.Unlock()
}
})
go utils.Safe(func() {
outer:
for {
select {
case <-stop:
break outer
case linesToRead := <-m.readLines:
for i := 0; i < linesToRead; i++ {
select {
case <-stop:
break outer
default:
}
ok := scanner.Scan()
loadingMutex.Lock()
if !loaded {
m.beforeStart()
if prefix != "" {
_, _ = m.writer.Write([]byte(prefix))
}
loaded = true
}
loadingMutex.Unlock()
if !ok {
// if we're here then there's nothing left to scan from the source
// so we're at the EOF and can flush the stale content
m.onEndOfInput()
break outer
}
_, _ = m.writer.Write(append(scanner.Bytes(), '\n'))
}
m.refreshView()
}
}
m.refreshView()
if err := cmd.Wait(); err != nil {
// it's fine if we've killed this program ourselves
if !strings.Contains(err.Error(), "signal: killed") {
m.Log.Error(err)
}
}
// calling onDoneWrapper here again in case the program ended on its own accord
if onDoneWrapper != nil {
onDoneWrapper()
}
close(done)
})
m.readLines <- linesToRead
<-done
return nil
}
}
// Close closes the task manager, killing whatever task may currently be running
func (t *ViewBufferManager) Close() {
if t.stopCurrentTask == nil {
return
}
c := make(chan struct{})
go utils.Safe(func() {
t.stopCurrentTask()
c <- struct{}{}
})
select {
case <-c:
return
case <-time.After(3 * time.Second):
fmt.Println("cannot kill child process")
}
}
// different kinds of tasks:
// 1) command based, where the manager can be asked to read more lines, but the command can be killed
// 2) string based, where the manager can also be asked to read more lines
func (m *ViewBufferManager) NewTask(f func(stop chan struct{}) error, key string) error {
go utils.Safe(func() {
m.taskIDMutex.Lock()
m.newTaskId++
taskID := m.newTaskId
if m.GetTaskKey() != key && m.onNewKey != nil {
m.onNewKey()
}
m.taskKey = key
m.taskIDMutex.Unlock()
m.waitingMutex.Lock()
defer m.waitingMutex.Unlock()
if taskID < m.newTaskId {
return
}
if m.stopCurrentTask != nil {
m.stopCurrentTask()
}
stop := make(chan struct{})
notifyStopped := make(chan struct{})
var once sync.Once
onStop := func() {
close(stop)
<-notifyStopped
}
m.stopCurrentTask = func() { once.Do(onStop) }
go utils.Safe(func() {
if err := f(stop); err != nil {
m.Log.Error(err) // might need an onError callback
}
close(notifyStopped)
})
})
return nil
}
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