From 58d6726380722cb120c0428aa9b1f081b291a8db Mon Sep 17 00:00:00 2001
From: Asim Aslam <asim@aslam.me>
Date: Thu, 9 Jul 2020 12:11:32 +0100
Subject: [PATCH] The start of mud - the micro data model (#1811)

* The start of mud - the micro data model

* add comments
---
 model/model.go      |   2 +
 model/mud/entity.go |  52 ++++++++++++++++++++++
 model/mud/mud.go    | 104 ++++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 158 insertions(+)
 create mode 100644 model/mud/entity.go
 create mode 100644 model/mud/mud.go

diff --git a/model/model.go b/model/model.go
index 05c3de02..ea5d7f28 100644
--- a/model/model.go
+++ b/model/model.go
@@ -39,6 +39,8 @@ type Entity interface {
 }
 
 type Options struct {
+	// Database to write to
+	Database string
 	// for serialising
 	Codec codec.Marshaler
 	// for locking
diff --git a/model/mud/entity.go b/model/mud/entity.go
new file mode 100644
index 00000000..03936598
--- /dev/null
+++ b/model/mud/entity.go
@@ -0,0 +1,52 @@
+package mud
+
+import (
+	"github.com/google/uuid"
+	"github.com/micro/go-micro/v2/codec"
+	"github.com/micro/go-micro/v2/model"
+)
+
+type mudEntity struct {
+	id         string
+	name       string
+	value      interface{}
+	codec      codec.Marshaler
+	attributes map[string]interface{}
+}
+
+func (m *mudEntity) Attributes() map[string]interface{} {
+	return m.attributes
+}
+
+func (m *mudEntity) Id() string {
+	return m.id
+}
+
+func (m *mudEntity) Name() string {
+	return m.name
+}
+
+func (m *mudEntity) Value() interface{} {
+	return m.value
+}
+
+func (m *mudEntity) Read(v interface{}) error {
+	switch m.value.(type) {
+	case []byte:
+		b := m.value.([]byte)
+		return m.codec.Unmarshal(b, v)
+	default:
+		v = m.value
+	}
+	return nil
+}
+
+func newEntity(name string, value interface{}, codec codec.Marshaler) model.Entity {
+	return &mudEntity{
+		id:         uuid.New().String(),
+		name:       name,
+		value:      value,
+		codec:      codec,
+		attributes: make(map[string]interface{}),
+	}
+}
diff --git a/model/mud/mud.go b/model/mud/mud.go
new file mode 100644
index 00000000..a01bc882
--- /dev/null
+++ b/model/mud/mud.go
@@ -0,0 +1,104 @@
+// Package mud is the micro data model implementation
+package mud
+
+import (
+	"github.com/micro/go-micro/v2/codec/json"
+	"github.com/micro/go-micro/v2/model"
+	"github.com/micro/go-micro/v2/store"
+	"github.com/micro/go-micro/v2/store/memory"
+	memsync "github.com/micro/go-micro/v2/sync/memory"
+)
+
+type mudModel struct {
+	options model.Options
+}
+
+func (m *mudModel) Init(opts ...model.Option) error {
+	for _, o := range opts {
+		o(&m.options)
+	}
+	return nil
+}
+
+func (m *mudModel) NewEntity(name string, value interface{}) model.Entity {
+	// TODO: potentially pluralise name for tables
+	return newEntity(name, value, m.options.Codec)
+}
+
+func (m *mudModel) Create(e model.Entity) error {
+	// lock on the name of entity
+	if err := m.options.Sync.Lock(e.Name()); err != nil {
+		return err
+	}
+	// TODO: deal with the error
+	defer m.options.Sync.Unlock(e.Name())
+
+	// TODO: potentially add encode to entity?
+	v, err := m.options.Codec.Marshal(e.Value())
+	if err != nil {
+		return err
+	}
+
+	// TODO: include metadata and set database
+	return m.options.Store.Write(&store.Record{
+		Key:   e.Id(),
+		Value: v,
+	}, store.WriteTo(m.options.Database, e.Name()))
+}
+
+func (m *mudModel) Read(opts ...model.ReadOption) ([]model.Entity, error) {
+	var options model.ReadOptions
+	for _, o := range opts {
+		o(&options)
+	}
+	// TODO: implement the options that allow querying
+	return nil, nil
+}
+
+func (m *mudModel) Update(e model.Entity) error {
+	// TODO: read out the record first, update the fields and store
+
+	// lock on the name of entity
+	if err := m.options.Sync.Lock(e.Name()); err != nil {
+		return err
+	}
+	// TODO: deal with the error
+	defer m.options.Sync.Unlock(e.Name())
+
+	// TODO: potentially add encode to entity?
+	v, err := m.options.Codec.Marshal(e.Value())
+	if err != nil {
+		return err
+	}
+
+	// TODO: include metadata and set database
+	return m.options.Store.Write(&store.Record{
+		Key:   e.Id(),
+		Value: v,
+	}, store.WriteTo(m.options.Database, e.Name()))
+}
+
+func (m *mudModel) Delete(opts ...model.DeleteOption) error {
+	var options model.DeleteOptions
+	for _, o := range opts {
+		o(&options)
+	}
+	// TODO: implement the options that allow deleting
+	return nil
+}
+
+func (m *mudModel) String() string {
+	return "mud"
+}
+
+func NewModel(opts ...model.Option) model.Model {
+	options := model.Options{
+		Codec: new(json.Marshaler),
+		Sync:  memsync.NewSync(),
+		Store: memory.NewStore(),
+	}
+
+	return &mudModel{
+		options: options,
+	}
+}