// Package memory is a in-memory store store
package memory

import (
	"path/filepath"
	"sort"
	"strings"
	"time"

	"github.com/micro/go-micro/v3/store"
	"github.com/patrickmn/go-cache"
	"github.com/pkg/errors"
)

// NewStore returns a memory store
func NewStore(opts ...store.Option) store.Store {
	s := &memoryStore{
		options: store.Options{
			Database: "micro",
			Table:    "micro",
		},
		store: cache.New(cache.NoExpiration, 5*time.Minute),
	}
	for _, o := range opts {
		o(&s.options)
	}
	return s
}

type memoryStore struct {
	options store.Options

	store *cache.Cache
}

type storeRecord struct {
	key       string
	value     []byte
	metadata  map[string]interface{}
	expiresAt time.Time
}

func (m *memoryStore) key(prefix, key string) string {
	return filepath.Join(prefix, key)
}

func (m *memoryStore) prefix(database, table string) string {
	if len(database) == 0 {
		database = m.options.Database
	}
	if len(table) == 0 {
		table = m.options.Table
	}
	return filepath.Join(database, table)
}

func (m *memoryStore) get(prefix, key string) (*store.Record, error) {
	key = m.key(prefix, key)

	var storedRecord *storeRecord
	r, found := m.store.Get(key)
	if !found {
		return nil, store.ErrNotFound
	}

	storedRecord, ok := r.(*storeRecord)
	if !ok {
		return nil, errors.New("Retrieved a non *storeRecord from the cache")
	}

	// Copy the record on the way out
	newRecord := &store.Record{}
	newRecord.Key = strings.TrimPrefix(storedRecord.key, prefix+"/")
	newRecord.Value = make([]byte, len(storedRecord.value))
	newRecord.Metadata = make(map[string]interface{})

	// copy the value into the new record
	copy(newRecord.Value, storedRecord.value)

	// check if we need to set the expiry
	if !storedRecord.expiresAt.IsZero() {
		newRecord.Expiry = time.Until(storedRecord.expiresAt)
	}

	// copy in the metadata
	for k, v := range storedRecord.metadata {
		newRecord.Metadata[k] = v
	}

	return newRecord, nil
}

func (m *memoryStore) set(prefix string, r *store.Record) {
	key := m.key(prefix, r.Key)

	// copy the incoming record and then
	// convert the expiry in to a hard timestamp
	i := &storeRecord{}
	i.key = r.Key
	i.value = make([]byte, len(r.Value))
	i.metadata = make(map[string]interface{})

	// copy the the value
	copy(i.value, r.Value)

	// set the expiry
	if r.Expiry != 0 {
		i.expiresAt = time.Now().Add(r.Expiry)
	}

	// set the metadata
	for k, v := range r.Metadata {
		i.metadata[k] = v
	}

	m.store.Set(key, i, r.Expiry)
}

func (m *memoryStore) delete(prefix, key string) {
	key = m.key(prefix, key)
	m.store.Delete(key)
}

func (m *memoryStore) list(prefix string, limit, offset uint) []string {
	allItems := m.store.Items()
	keys := make([]string, len(allItems))
	i := 0

	for k := range allItems {
		if !strings.HasPrefix(k, prefix+"/") {
			continue
		}
		keys[i] = strings.TrimPrefix(k, prefix+"/")
		i++
	}

	sort.Slice(keys, func(i, j int) bool { return keys[i] < keys[j] })
	return applyLimitAndOffset(keys, limit, offset)
}

func (m *memoryStore) Close() error {
	m.store.Flush()
	return nil
}

func (m *memoryStore) Init(opts ...store.Option) error {
	for _, o := range opts {
		o(&m.options)
	}
	return nil
}

func (m *memoryStore) String() string {
	return "memory"
}

func (m *memoryStore) Read(key string, opts ...store.ReadOption) ([]*store.Record, error) {
	readOpts := store.ReadOptions{}
	for _, o := range opts {
		o(&readOpts)
	}

	prefix := m.prefix(readOpts.Database, readOpts.Table)

	var keys []string
	// Handle Prefix / suffix
	if readOpts.Prefix || readOpts.Suffix {
		// apply limit / offset once filtering is complete
		for _, kk := range m.list(prefix, 0, 0) {
			if readOpts.Prefix && !strings.HasPrefix(kk, key) {
				continue
			}

			if readOpts.Suffix && !strings.HasSuffix(kk, key) {
				continue
			}

			keys = append(keys, kk)
		}

		keys = applyLimitAndOffset(keys, readOpts.Limit, readOpts.Offset)
	} else {
		keys = []string{key}
	}

	var results []*store.Record

	for _, k := range keys {
		r, err := m.get(prefix, k)
		if err != nil {
			return results, err
		}
		results = append(results, r)
	}

	return results, nil
}

func (m *memoryStore) Write(r *store.Record, opts ...store.WriteOption) error {
	writeOpts := store.WriteOptions{}
	for _, o := range opts {
		o(&writeOpts)
	}

	prefix := m.prefix(writeOpts.Database, writeOpts.Table)

	if len(opts) > 0 {
		// Copy the record before applying options, or the incoming record will be mutated
		newRecord := store.Record{}
		newRecord.Key = r.Key
		newRecord.Value = make([]byte, len(r.Value))
		newRecord.Metadata = make(map[string]interface{})
		copy(newRecord.Value, r.Value)
		newRecord.Expiry = r.Expiry

		if !writeOpts.Expiry.IsZero() {
			newRecord.Expiry = time.Until(writeOpts.Expiry)
		}
		if writeOpts.TTL != 0 {
			newRecord.Expiry = writeOpts.TTL
		}

		for k, v := range r.Metadata {
			newRecord.Metadata[k] = v
		}

		m.set(prefix, &newRecord)
		return nil
	}

	// set
	m.set(prefix, r)

	return nil
}

func (m *memoryStore) Delete(key string, opts ...store.DeleteOption) error {
	deleteOptions := store.DeleteOptions{}
	for _, o := range opts {
		o(&deleteOptions)
	}

	prefix := m.prefix(deleteOptions.Database, deleteOptions.Table)
	m.delete(prefix, key)
	return nil
}

func (m *memoryStore) Options() store.Options {
	return m.options
}

func (m *memoryStore) List(opts ...store.ListOption) ([]string, error) {
	listOptions := store.ListOptions{}

	for _, o := range opts {
		o(&listOptions)
	}

	prefix := m.prefix(listOptions.Database, listOptions.Table)
	keys := m.list(prefix, listOptions.Limit, listOptions.Offset)

	if len(listOptions.Prefix) > 0 {
		var prefixKeys []string
		for _, k := range keys {
			if strings.HasPrefix(k, listOptions.Prefix) {
				prefixKeys = append(prefixKeys, k)
			}
		}
		keys = prefixKeys
	}

	if len(listOptions.Suffix) > 0 {
		var suffixKeys []string
		for _, k := range keys {
			if strings.HasSuffix(k, listOptions.Suffix) {
				suffixKeys = append(suffixKeys, k)
			}
		}
		keys = suffixKeys
	}

	return keys, nil
}

func applyLimitAndOffset(keys []string, limit, offset uint) []string {
	if limit == 0 && offset == 0 {
		return keys
	}

	end := len(keys)
	if limit > 0 {
		calcLimit := int(offset + limit)
		if calcLimit < end {
			end = calcLimit
		}
	}

	if int(offset) >= end {
		return nil
	}

	return keys[offset:end]
}