// Package memory is a storage backend base on memory
package memory

import (
	"fmt"
	"io"

	"gopkg.in/src-d/go-git.v4/config"
	"gopkg.in/src-d/go-git.v4/core"
)

var ErrUnsupportedObjectType = fmt.Errorf("unsupported object type")

// Storage in memory storage system
type Storage struct {
	c *ConfigStorage
	o *ObjectStorage
	r *ReferenceStorage
}

// NewStorage returns a new Storage
func NewStorage() *Storage {
	return &Storage{}
}

// ConfigStorage return the ConfigStorage, if not exists create a new one
func (s *Storage) ConfigStorage() config.ConfigStorage {
	if s.c != nil {
		return s.c
	}

	s.c = &ConfigStorage{
		RemotesConfig: make(map[string]*config.RemoteConfig),
	}

	return s.c
}

// ObjectStorage returns the ObjectStorage, if not exists creates a new one
func (s *Storage) ObjectStorage() core.ObjectStorage {
	if s.o != nil {
		return s.o
	}

	s.o = &ObjectStorage{
		Objects: make(map[core.Hash]core.Object, 0),
		Commits: make(map[core.Hash]core.Object, 0),
		Trees:   make(map[core.Hash]core.Object, 0),
		Blobs:   make(map[core.Hash]core.Object, 0),
		Tags:    make(map[core.Hash]core.Object, 0),
	}

	return s.o
}

// ReferenceStorage returns the ReferenceStorage if not exists creates a new one
func (s *Storage) ReferenceStorage() core.ReferenceStorage {
	if s.r != nil {
		return s.r
	}

	r := make(ReferenceStorage, 0)
	s.r = &r

	return s.r
}

type ConfigStorage struct {
	RemotesConfig map[string]*config.RemoteConfig
}

func (c *ConfigStorage) Remote(name string) (*config.RemoteConfig, error) {
	r, ok := c.RemotesConfig[name]
	if ok {
		return r, nil
	}

	return nil, config.ErrRemoteConfigNotFound
}

func (c *ConfigStorage) Remotes() ([]*config.RemoteConfig, error) {
	var o []*config.RemoteConfig
	for _, r := range c.RemotesConfig {
		o = append(o, r)
	}

	return o, nil
}
func (c *ConfigStorage) SetRemote(r *config.RemoteConfig) error {
	c.RemotesConfig[r.Name] = r
	return nil
}

func (c *ConfigStorage) DeleteRemote(name string) error {
	delete(c.RemotesConfig, name)
	return nil
}

// ObjectStorage is the implementation of core.ObjectStorage for memory.Object
type ObjectStorage struct {
	Objects map[core.Hash]core.Object
	Commits map[core.Hash]core.Object
	Trees   map[core.Hash]core.Object
	Blobs   map[core.Hash]core.Object
	Tags    map[core.Hash]core.Object
}

// NewObject creates a new MemoryObject
func (o *ObjectStorage) NewObject() core.Object {
	return &core.MemoryObject{}
}

// Writer method not supported on Memory storage
func (o *ObjectStorage) Writer() (io.WriteCloser, error) {
	return nil, core.ErrNotImplemented
}

// Set stores an object, the object should be properly filled before set it.
func (o *ObjectStorage) Set(obj core.Object) (core.Hash, error) {
	h := obj.Hash()
	o.Objects[h] = obj

	switch obj.Type() {
	case core.CommitObject:
		o.Commits[h] = o.Objects[h]
	case core.TreeObject:
		o.Trees[h] = o.Objects[h]
	case core.BlobObject:
		o.Blobs[h] = o.Objects[h]
	case core.TagObject:
		o.Tags[h] = o.Objects[h]
	default:
		fmt.Println(obj.Type())
		return h, ErrUnsupportedObjectType
	}

	return h, nil
}

// Get returns a object with the given hash
func (o *ObjectStorage) Get(t core.ObjectType, h core.Hash) (core.Object, error) {
	obj, ok := o.Objects[h]
	if !ok || (core.AnyObject != t && obj.Type() != t) {
		return nil, core.ErrObjectNotFound
	}

	return obj, nil
}

// Iter returns a core.ObjectIter for the given core.ObjectTybe
func (o *ObjectStorage) Iter(t core.ObjectType) (core.ObjectIter, error) {
	var series []core.Object
	switch t {
	case core.AnyObject:
		series = flattenObjectMap(o.Objects)
	case core.CommitObject:
		series = flattenObjectMap(o.Commits)
	case core.TreeObject:
		series = flattenObjectMap(o.Trees)
	case core.BlobObject:
		series = flattenObjectMap(o.Blobs)
	case core.TagObject:
		series = flattenObjectMap(o.Tags)
	}

	return core.NewObjectSliceIter(series), nil
}

func flattenObjectMap(m map[core.Hash]core.Object) []core.Object {
	objects := make([]core.Object, 0, len(m))
	for _, obj := range m {
		objects = append(objects, obj)
	}
	return objects
}

func (o *ObjectStorage) Begin() core.TxObjectStorage {
	return &TxObjectStorage{
		Storage: o,
		Objects: make(map[core.Hash]core.Object, 0),
	}
}

type TxObjectStorage struct {
	Storage *ObjectStorage
	Objects map[core.Hash]core.Object
}

func (tx *TxObjectStorage) Set(obj core.Object) (core.Hash, error) {
	h := obj.Hash()
	tx.Objects[h] = obj

	return h, nil
}

func (tx *TxObjectStorage) Get(t core.ObjectType, h core.Hash) (core.Object, error) {
	obj, ok := tx.Objects[h]
	if !ok || (core.AnyObject != t && obj.Type() != t) {
		return nil, core.ErrObjectNotFound
	}

	return obj, nil
}

func (tx *TxObjectStorage) Commit() error {
	for h, obj := range tx.Objects {
		delete(tx.Objects, h)
		if _, err := tx.Storage.Set(obj); err != nil {
			return err
		}
	}

	return nil
}

func (tx *TxObjectStorage) Rollback() error {
	tx.Objects = make(map[core.Hash]core.Object, 0)
	return nil
}

type ReferenceStorage map[core.ReferenceName]*core.Reference

// Set stores a reference.
func (r ReferenceStorage) Set(ref *core.Reference) error {
	if ref != nil {
		r[ref.Name()] = ref
	}

	return nil
}

// Get returns a stored reference with the given name
func (r ReferenceStorage) Get(n core.ReferenceName) (*core.Reference, error) {
	ref, ok := r[n]
	if !ok {
		return nil, core.ErrReferenceNotFound
	}

	return ref, nil
}

// Iter returns a core.ReferenceIter
func (r ReferenceStorage) Iter() (core.ReferenceIter, error) {
	var refs []*core.Reference
	for _, ref := range r {
		refs = append(refs, ref)
	}

	return core.NewReferenceSliceIter(refs), nil
}