// Copyright The OpenTelemetry Authors
// SPDX-License-Identifier: Apache-2.0

package queue // import "go.opentelemetry.io/collector/exporter/internal/queue"

import (
	"context"
	"sync/atomic"
	"time"

	"go.opentelemetry.io/collector/exporter/exporterbatcher"
	"go.opentelemetry.io/collector/exporter/internal"
)

type fakeRequestSink struct {
	requestsCount *atomic.Int64
	itemsCount    *atomic.Int64
}

func newFakeRequestSink() *fakeRequestSink {
	return &fakeRequestSink{
		requestsCount: new(atomic.Int64),
		itemsCount:    new(atomic.Int64),
	}
}

type fakeRequest struct {
	items     int
	exportErr error

	mergeErr error
	delay    time.Duration
	sink     *fakeRequestSink
}

func (r *fakeRequest) Export(ctx context.Context) error {
	select {
	case <-ctx.Done():
		return ctx.Err()
	case <-time.After(r.delay):
	}
	if r.exportErr != nil {
		return r.exportErr
	}
	if r.sink != nil {
		r.sink.requestsCount.Add(1)
		r.sink.itemsCount.Add(int64(r.items))
	}
	return nil
}

func (r *fakeRequest) ItemsCount() int {
	return r.items
}

func (r *fakeRequest) Merge(_ context.Context,
	r2 internal.Request,
) (internal.Request, error) {
	fr2 := r2.(*fakeRequest)
	if fr2.mergeErr != nil {
		return nil, fr2.mergeErr
	}
	return &fakeRequest{
		items:     r.items + fr2.items,
		sink:      r.sink,
		exportErr: fr2.exportErr,
		delay:     r.delay + fr2.delay,
	}, nil
}

func (r *fakeRequest) MergeSplit(ctx context.Context, cfg exporterbatcher.MaxSizeConfig,
	r2 internal.Request,
) ([]internal.Request, error) {
	if r.mergeErr != nil {
		return nil, r.mergeErr
	}

	maxItems := cfg.MaxSizeItems
	if maxItems == 0 {
		r, err := r.Merge(ctx, r2)
		return []internal.Request{r}, err
	}

	var fr2 *fakeRequest
	if r2 == nil {
		fr2 = &fakeRequest{sink: r.sink, exportErr: r.exportErr, delay: r.delay}
	} else {
		if r2.(*fakeRequest).mergeErr != nil {
			return nil, r2.(*fakeRequest).mergeErr
		}
		fr2 = r2.(*fakeRequest)
		fr2 = &fakeRequest{items: fr2.items, sink: fr2.sink, exportErr: fr2.exportErr, delay: fr2.delay}
	}
	var res []internal.Request
	r = &fakeRequest{items: r.items, sink: fr2.sink, exportErr: fr2.exportErr, delay: fr2.delay}
	if fr2.items <= maxItems-r.items {
		r.items += fr2.items
		if fr2.exportErr != nil {
			r.exportErr = fr2.exportErr
		}
		return []internal.Request{r}, nil
	}
	// if split is needed, we don't propagate exportErr from fr2 to fr1 to test more cases
	fr2.items -= maxItems - r.items
	r.items = maxItems
	res = append(res, r)

	// split fr2 to maxItems
	for {
		if fr2.items <= maxItems {
			res = append(res, &fakeRequest{items: fr2.items, sink: fr2.sink, exportErr: fr2.exportErr, delay: fr2.delay})
			break
		}
		res = append(res, &fakeRequest{items: maxItems, sink: fr2.sink, exportErr: fr2.exportErr, delay: fr2.delay})
		fr2.items -= maxItems
	}

	return res, nil
}
