// Copyright (C) 2019 Storj Labs, Inc.
// See LICENSE for copying information.

package audit

import (
	"context"
	"math/rand"
	"time"

	"go.uber.org/zap"

	"storj.io/common/storj"
	"storj.io/common/sync2"
	"storj.io/storj/satellite/metainfo"
)

// Chore populates reservoirs and the audit queue.
//
// architecture: Chore
type Chore struct {
	log   *zap.Logger
	rand  *rand.Rand
	queue *Queue
	Loop  *sync2.Cycle

	metainfoLoop *metainfo.Loop
	config       Config
}

// NewChore instantiates Chore.
func NewChore(log *zap.Logger, queue *Queue, metaLoop *metainfo.Loop, config Config) *Chore {
	return &Chore{
		log:   log,
		rand:  rand.New(rand.NewSource(time.Now().Unix())),
		queue: queue,
		Loop:  sync2.NewCycle(config.ChoreInterval),

		metainfoLoop: metaLoop,
		config:       config,
	}
}

// Run starts the chore.
func (chore *Chore) Run(ctx context.Context) (err error) {
	defer mon.Task()(&ctx)(&err)
	return chore.Loop.Run(ctx, func(ctx context.Context) (err error) {
		defer mon.Task()(&ctx)(&err)

		pathCollector := NewPathCollector(chore.config.Slots, chore.rand)
		err = chore.metainfoLoop.Join(ctx, pathCollector)
		if err != nil {
			chore.log.Error("error joining metainfoloop", zap.Error(err))
			return nil
		}

		var newQueue []storj.Path
		queuePaths := make(map[storj.Path]struct{})

		// Add reservoir paths to queue in pseudorandom order.
		for i := 0; i < chore.config.Slots; i++ {
			for _, res := range pathCollector.Reservoirs {
				// Skip reservoir if no path at this index.
				if len(res.Paths) <= i {
					continue
				}
				path := res.Paths[i]
				if path == "" {
					continue
				}
				if _, ok := queuePaths[path]; !ok {
					newQueue = append(newQueue, path)
					queuePaths[path] = struct{}{}
				}
			}
		}

		// Wait for active queue to be completed, then swap with the new one.
		err = chore.queue.WaitForSwap(ctx, newQueue)
		if err != nil {
			return err
		}

		return nil
	})
}

// Close closes chore.
func (chore *Chore) Close() error {
	chore.Loop.Close()
	return nil
}