package writecachebitcask

import (
	"time"

	"git.frostfs.info/TrueCloudLab/frostfs-node/pkg/local_object_storage/writecache"
	"git.frostfs.info/TrueCloudLab/frostfs-node/pkg/util/logger"
	"go.uber.org/zap"
)

// Option represents write-cache configuration option.
type Option func(*options)

type options struct {
	path     string
	log      *logger.Logger
	blobstor writecache.MainStorage
	metabase writecache.Metabase
	metrics  writecache.Metrics

	// reportError is the function called when encountering disk errors in background workers.
	reportError func(string, error)

	maxObjectSize          uint64
	bucketCount            int
	regionCount            int
	maxLogSize             uint64
	maxBatchDelay          time.Duration
	maxPendingLogFileFlush int
}

// WithPath sets path to writecache data.
func WithPath(path string) Option {
	return func(o *options) {
		o.path = path
	}
}

// WithLogger sets logger.
func WithLogger(log *logger.Logger) Option {
	return func(o *options) {
		o.log = &logger.Logger{Logger: log.With(zap.String("component", "WriteCache"))}
	}
}

// WithBlobstor sets main object storage.
func WithBlobstor(bs writecache.MainStorage) Option {
	return func(o *options) {
		o.blobstor = bs
	}
}

// WithMetabase sets metabase.
func WithMetabase(db writecache.Metabase) Option {
	return func(o *options) {
		o.metabase = db
	}
}

// WithMetrics sets metrics implementation.
func WithMetrics(metrics writecache.Metrics) Option {
	return func(o *options) {
		o.metrics = metrics
	}
}

// WithReportErrorFunc sets error reporting function.
func WithReportErrorFunc(f func(string, error)) Option {
	return func(o *options) {
		o.reportError = f
	}
}

// WithMaxObjectSize sets maximum object size to be stored in write-cache.
func WithMaxObjectSize(sz uint64) Option {
	return func(o *options) {
		if sz > 0 {
			o.maxObjectSize = sz
		}
	}
}

// WithBucketCount sets the number of buckets to use.
//
// This value determines the total number of buckets to use by the internal hash table.
// More buckets means fewer collisions but also increased memory usage.
//
// Default value is 2^16.
func WithBucketCount(bucketCount int) Option {
	return func(o *options) {
		o.bucketCount = bucketCount
	}
}

// WithRegionCount sets the number of regions to use.
//
// This is the number of independent partitions of the key space. Each region contains its
// own lock, key directory, membuffer, log files and flushing process.
//
// Default value is 4.
func WithRegionCount(regionCount int) Option {
	return func(o *options) {
		o.regionCount = regionCount
	}
}

// WithLogFileSize sets the maximum size of a log file.
//
// After a log file grows to this size, it will be closed and passed to the flushing process.
//
// Default value is 64 MiB.
func WithLogFileSize(logSize uint64) Option {
	return func(o *options) {
		o.maxLogSize = logSize
	}
}

// WithMaxBatchDelay sets for how long to keep current write batch.
//
// Any pending write batch will be flushed to the current log file after at most this duration.
// This helps minimize the number of sync IO operations under heavy load.
//
// Default value is 1ms.
func WithMaxBatchDelay(d time.Duration) Option {
	return func(o *options) {
		o.maxBatchDelay = d
	}
}

// WithMaxPendingLogFileFlush sets the maximum number of pending log files to be flushed per region.
//
// This is the maximum size of the queue of log files for the flushing process. After this many
// files are enqueued for flushing, requests will block until the flushing process can keep up.
//
// Default value is 4.
func WithMaxPendingLogFileFlush(n int) Option {
	return func(o *options) {
		o.maxPendingLogFileFlush = n
	}
}