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|
package askcli
import (
"bytes"
"context"
"fmt"
"io"
"time"
)
const (
watchInterval = 2 * time.Second
ansiClearScreen = "\033[2J\033[H"
)
type watchTicker interface {
C() <-chan time.Time
Stop()
}
type realWatchTicker struct {
ticker *time.Ticker
}
func (t realWatchTicker) C() <-chan time.Time {
return t.ticker.C
}
func (t realWatchTicker) Stop() {
t.ticker.Stop()
}
var newWatchTicker = func(interval time.Duration) watchTicker {
return realWatchTicker{ticker: time.NewTicker(interval)}
}
// deferredWriter buffers writes for capture while preserving terminal
// width detection by delegating Fd to the underlying writer.
type deferredWriter struct {
w io.Writer
buf bytes.Buffer
}
func (dw *deferredWriter) Write(p []byte) (int, error) {
return dw.buf.Write(p)
}
func (dw *deferredWriter) Fd() uintptr {
type fder interface{ Fd() uintptr }
if f, ok := dw.w.(fder); ok {
return f.Fd()
}
return 0
}
func (d *Dispatcher) handleWatch(ctx context.Context, args []string, stdout, stderr io.Writer) (int, error) {
watchArgs := args[1:]
if len(watchArgs) == 0 {
watchArgs = []string{"list"}
}
if !watchCommandAllowed(watchArgs) {
_, _ = io.WriteString(stderr, "error: ask watch supports read-only subcommands: list, all, ready, completed, info, dep list, urgency, help\n")
return 1, nil
}
ticker := newWatchTicker(watchInterval)
defer ticker.Stop()
var lastOutput []byte
for {
output, code, err := d.watchOutput(ctx, watchArgs, stdout, stderr)
if err != nil {
return code, err
}
if !bytes.Equal(output, lastOutput) {
_, _ = io.WriteString(stdout, ansiClearScreen)
_, _ = stdout.Write(output)
lastOutput = bytes.Clone(output)
}
if code != 0 {
return code, nil
}
select {
case <-ctx.Done():
return 0, nil
case <-ticker.C():
}
}
}
func watchCommandAllowed(args []string) bool {
entry, ok := commandRegistry.get(args[0])
if !ok {
return false
}
if entry.readOnly {
return true
}
// dep is not read-only as a whole, but dep list is.
if args[0] == "dep" {
return len(args) >= 2 && args[1] == "list"
}
return false
}
func (d *Dispatcher) watchOutput(ctx context.Context, args []string, realStdout, realStderr io.Writer) ([]byte, int, error) {
outW := &deferredWriter{w: realStdout}
errW := &deferredWriter{w: realStderr}
code, err := d.dispatchCommand(ctx, append([]string(nil), args...), nil, outW, errW)
if err != nil {
return nil, code, fmt.Errorf("watch %s: %w", args[0], err)
}
// Combine stdout and stderr so warnings or errors emitted by the
// watched subcommand are visible in the watched display.
out := make([]byte, 0, outW.buf.Len()+errW.buf.Len())
out = append(out, outW.buf.Bytes()...)
out = append(out, errW.buf.Bytes()...)
return out, code, nil
}
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