package agent

import (

"context"

"runtime"

"sync"

"cdr.dev/slog"

)

// checkpoint allows a goroutine to communicate when it is OK to proceed beyond some async condition

// to other dependent goroutines.

type checkpoint struct {

logger slog.Logger

mu sync.Mutex

called bool

done chan struct{}

err error

}

// complete the checkpoint. Pass nil to indicate the checkpoint was ok. It is an error to call this

// more than once.

func (c *checkpoint) complete(err error) {

c.mu.Lock()

defer c.mu.Unlock()

if c.called {

b := make([]byte, 2048)

n := runtime.Stack(b, false)

c.logger.Critical(context.Background(), "checkpoint complete called more than once", slog.F("stacktrace", b[:n]))

return

}

c.called = true

c.err = err

close(c.done)

}

func (c *checkpoint) wait(ctx context.Context) error {

select {

case <-ctx.Done():

return ctx.Err()

case <-c.done:

return c.err

}

}

func newCheckpoint(logger slog.Logger) *checkpoint {

return &checkpoint{

logger: logger,

done: make(chan struct{}),

}

}