//                           _       _
// __      _____  __ ___   ___  __ _| |_ ___
// \ \ /\ / / _ \/ _` \ \ / / |/ _` | __/ _ \
//  \ V  V /  __/ (_| |\ V /| | (_| | ||  __/
//   \_/\_/ \___|\__,_| \_/ |_|\__,_|\__\___|
//
//  Copyright © 2016 - 2024 Weaviate B.V. All rights reserved.
//
//  CONTACT: hello@weaviate.io
//

package classification

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

	"github.com/pkg/errors"
	"github.com/weaviate/weaviate/entities/errorcompounder"
	"github.com/weaviate/weaviate/entities/models"
	"github.com/weaviate/weaviate/entities/search"
)

type runWorker struct {
	jobs         []search.Result
	successCount *int64
	errorCount   *int64
	ec           *errorcompounder.SafeErrorCompounder
	classify     ClassifyItemFn
	batchWriter  Writer
	params       models.Classification
	filters      Filters
	id           int
	workerCount  int
}

func (w *runWorker) addJob(job search.Result) {
	w.jobs = append(w.jobs, job)
}

func (w *runWorker) work(ctx context.Context, wg *sync.WaitGroup) {
	defer wg.Done()

	for i, item := range w.jobs {
		// check if the whole classification operation has been cancelled
		// if yes, then abort the classifier worker
		if err := ctx.Err(); err != nil {
			w.ec.Add(err)
			atomic.AddInt64(w.errorCount, 1)
			break
		}
		originalIndex := (i * w.workerCount) + w.id
		err := w.classify(item, originalIndex, w.params, w.filters, w.batchWriter)
		if err != nil {
			w.ec.Add(err)
			atomic.AddInt64(w.errorCount, 1)
		} else {
			atomic.AddInt64(w.successCount, 1)
		}
	}
}

func newRunWorker(id int, workerCount int, rw *runWorkers) *runWorker {
	return &runWorker{
		successCount: rw.successCount,
		errorCount:   rw.errorCount,
		ec:           rw.ec,
		params:       rw.params,
		filters:      rw.filters,
		classify:     rw.classify,
		batchWriter:  rw.batchWriter,
		id:           id,
		workerCount:  workerCount,
	}
}

type runWorkers struct {
	workers      []*runWorker
	successCount *int64
	errorCount   *int64
	ec           *errorcompounder.SafeErrorCompounder
	classify     ClassifyItemFn
	params       models.Classification
	filters      Filters
	batchWriter  Writer
}

func newRunWorkers(amount int, classifyFn ClassifyItemFn,
	params models.Classification, filters Filters, vectorRepo vectorRepo,
) *runWorkers {
	var successCount int64
	var errorCount int64

	rw := &runWorkers{
		workers:      make([]*runWorker, amount),
		successCount: &successCount,
		errorCount:   &errorCount,
		ec:           &errorcompounder.SafeErrorCompounder{},
		classify:     classifyFn,
		params:       params,
		filters:      filters,
		batchWriter:  newBatchWriter(vectorRepo),
	}

	for i := 0; i < amount; i++ {
		rw.workers[i] = newRunWorker(i, amount, rw)
	}

	return rw
}

func (ws *runWorkers) addJobs(jobs []search.Result) {
	for i, job := range jobs {
		ws.workers[i%len(ws.workers)].addJob(job)
	}
}

func (ws *runWorkers) work(ctx context.Context) runWorkerResults {
	ws.batchWriter.Start()

	wg := &sync.WaitGroup{}
	for _, worker := range ws.workers {
		wg.Add(1)
		go worker.work(ctx, wg)
	}

	wg.Wait()

	res := ws.batchWriter.Stop()

	if res.SuccessCount() != *ws.successCount || res.ErrorCount() != *ws.errorCount {
		ws.ec.Add(errors.New("data save error"))
	}

	if res.Err() != nil {
		ws.ec.Add(res.Err())
	}

	return runWorkerResults{
		successCount: *ws.successCount,
		errorCount:   *ws.errorCount,
		err:          ws.ec.ToError(),
	}
}

type runWorkerResults struct {
	successCount int64
	errorCount   int64
	err          error
}