package useCases

import (
	"RenewCMS/internal/domain/image"
	"errors"
	"sync"
)

var errFlightAbandoned = errors.New("shared call ended without a result")

type flightCall struct {
	done  chan struct{}
	value image.VariantFile
	err   error
}

type flightGroup struct {
	mu    sync.Mutex
	calls map[string]*flightCall
}

func (g *flightGroup) do(key string, work func() (image.VariantFile, error)) (image.VariantFile, error) {
	g.mu.Lock()
	if existing, running := g.calls[key]; running {
		g.mu.Unlock()
		<-existing.done
		return existing.value, existing.err
	}
	if g.calls == nil {
		g.calls = map[string]*flightCall{}
	}
	call := &flightCall{done: make(chan struct{}), err: errFlightAbandoned}
	g.calls[key] = call
	g.mu.Unlock()

	defer func() {
		g.mu.Lock()
		delete(g.calls, key)
		g.mu.Unlock()
		close(call.done)
	}()

	call.value, call.err = work()
	return call.value, call.err
}