orm/model.go

package orm

import (
	"context"
	"encoding/json"
	"fmt"
	"reflect"
	"strings"
	"sync"
	"time"
)

// Model is a generic mixin embedded in every ORM entity.
// It replaces mixin.Model from commerce with type-safe generics.
//
// Usage:
//
//	type PaymentIntent struct {
//	    orm.Model[PaymentIntent]
//	    Amount   int64  `json:"amount"`
//	    Currency string `json:"currency" orm:"default:usd"`
//	}
//
//	func init() { orm.Register[PaymentIntent]("payment-intent") }
type Model[T any] struct {
	db        DB     `json:"-"`
	parent    Key    `json:"-"`
	key       Key    `json:"-"`
	namespace string `json:"-"`
	snapshot  []byte `json:"-"` // JSON snapshot from last DB load, for old-entity hooks
	mock      bool

	// Persisted fields
	Id_       string    `json:"id,omitempty"`
	CreatedAt time.Time `json:"createdAt,omitempty"`
	UpdatedAt time.Time `json:"updatedAt,omitempty"`
	Deleted   bool      `json:"deleted,omitempty"`
}

// Init wires the model to a database. Called by New[T] and by the compat layer.
func (m *Model[T]) Init(db DB) {
	m.db = db
}

// DB returns the database this model is wired to.
func (m *Model[T]) DB() DB {
	return m.db
}

// SetDB replaces the database reference (used during transaction rebinding).
func (m *Model[T]) SetDB(db DB) {
	m.db = db
}

// Namespace returns the entity's namespace for multi-tenant isolation.
func (m *Model[T]) Namespace() string {
	return m.namespace
}

// SetNamespace sets the entity's namespace for multi-tenant isolation.
func (m *Model[T]) SetNamespace(ns string) {
	m.namespace = ns
}

// Kind returns the registered kind string for T.
func (m Model[T]) Kind() string {
	var zero T
	typ := reflect.TypeOf(zero)
	if typ.Kind() == reflect.Pointer {
		typ = typ.Elem()
	}
	meta, ok := LookupType(typ)
	if !ok {
		panic(fmt.Sprintf("orm: type %v not registered", typ))
	}
	return meta.Kind
}

// Id returns the entity's string ID, allocating a new key if needed.
func (m *Model[T]) Id() string {
	if m.Id_ == "" {
		m.Key()
	}
	return m.Id_
}

// SetId sets the entity's ID directly and invalidates the cached key.
func (m *Model[T]) SetId(id string) {
	m.Id_ = id
	m.key = nil // force Key() to regenerate from new Id_
}

// Key returns the entity's datastore key, allocating one if necessary.
func (m *Model[T]) Key() Key {
	if m.key != nil {
		return m.key
	}

	// Regenerate from Id_ if available
	if m.Id_ != "" {
		kind := m.Kind()
		m.key = m.db.NewKey(kind, m.Id_, 0, m.parent)
		return m.key
	}

	// Allocate new key
	kind := m.Kind()
	meta := MustLookup(kind)

	if meta.ParentFn != nil && m.parent == nil {
		m.parent = meta.ParentFn(m.db)
	}

	if meta.StringKey {
		m.key = m.db.NewIncompleteKey(kind, m.parent)
	} else {
		ids, err := m.db.AllocateIDs(kind, m.parent, 1)
		if err != nil {
			// Fallback to incomplete key
			m.key = m.db.NewIncompleteKey(kind, m.parent)
		} else {
			m.key = ids[0]
		}
	}

	// Update Id_ from key
	m.updateIdFromKey()
	return m.key
}

// SetKey sets the entity's key.
func (m *Model[T]) SetKey(key Key) {
	m.key = key
	if key != nil {
		p := key.Parent()
		if p != nil {
			m.parent = p
		}
		m.updateIdFromKey()
	}
}

// Parent returns the parent key.
func (m *Model[T]) Parent() Key {
	return m.parent
}

// SetParent sets the parent key.
func (m *Model[T]) SetParent(parent Key) {
	m.parent = parent
}

// SetMock enables mock mode (no actual DB operations).
func (m *Model[T]) SetMock(mock bool) {
	m.mock = mock
}

// IsMock returns whether the model is in mock mode.
func (m *Model[T]) IsMock() bool {
	return m.mock
}

// Created returns true if the entity has been persisted at least once.
func (m *Model[T]) Created() bool {
	return !m.CreatedAt.IsZero()
}

// self returns a pointer to the outermost struct that embeds this Model.
// This relies on the fact that Model[T] is always embedded as the first field.
func (m *Model[T]) self() *T {
	// We use unsafe pointer arithmetic equivalent via reflect.
	// The Model[T] is embedded in T, so we can recover *T from *Model[T].
	return (*T)(reflect.NewAt(
		reflect.TypeFor[T](),
		reflect.ValueOf(m).UnsafePointer(),
	).UnsafePointer())
}

// captureSnapshot saves a JSON snapshot of the current state for old-entity hooks.
func (m *Model[T]) captureSnapshot() {
	m.snapshot, _ = json.Marshal(m.self())
}

// oldFromSnapshot reconstructs the old entity from the last-loaded snapshot.
// If no snapshot exists (entity was never loaded from DB), returns a clone of current state.
func (m *Model[T]) oldFromSnapshot() *T {
	if len(m.snapshot) == 0 {
		return m.Clone()
	}
	old := new(T)
	json.Unmarshal(m.snapshot, old)
	return old
}

// PutCtx persists the entity with context, setting timestamps.
func (m *Model[T]) PutCtx(ctx context.Context) error {
	now := time.Now()
	if !m.Created() {
		m.CreatedAt = now
	}
	m.UpdatedAt = now

	if m.mock {
		return m.mockPut()
	}

	entity := m.self()

	// Auto-serialize underscore fields before save
	if err := SerializeFields(entity); err != nil {
		return fmt.Errorf("orm: serialize: %w", err)
	}

	key, err := m.db.Put(ctx, m.Key(), entity)
	if err != nil {
		return err
	}

	if key != nil && m.key == nil {
		m.SetKey(key)
	}

	// Update snapshot after successful write
	m.captureSnapshot()

	return nil
}

// Put persists the entity, setting timestamps.
func (m *Model[T]) Put() error {
	return m.PutCtx(context.Background())
}

// CreateCtx persists a new entity with context, executing Before/AfterCreate hooks.
func (m *Model[T]) CreateCtx(ctx context.Context) error {
	entity := m.self()

	if hook, ok := any(entity).(BeforeCreator); ok {
		if err := hook.BeforeCreate(); err != nil {
			return err
		}
	}

	if err := m.PutCtx(ctx); err != nil {
		return err
	}

	if hook, ok := any(entity).(AfterCreator); ok {
		if err := hook.AfterCreate(); err != nil {
			return err
		}
	}

	return nil
}

// Create persists a new entity, executing Before/AfterCreate hooks.
func (m *Model[T]) Create() error {
	return m.CreateCtx(context.Background())
}

// MustCreate persists a new entity or panics.
func (m *Model[T]) MustCreate() {
	if err := m.Create(); err != nil {
		panic(fmt.Sprintf("orm: MustCreate: %v", err))
	}
}

// UpdateCtx persists changes with context, executing Before/AfterUpdate hooks.
// The hooks receive the old entity state (from last DB load) for diffing.
func (m *Model[T]) UpdateCtx(ctx context.Context) error {
	entity := m.self()
	old := m.oldFromSnapshot()

	if hook, ok := any(entity).(BeforeUpdater[T]); ok {
		if err := hook.BeforeUpdate(old); err != nil {
			return err
		}
	}

	if err := m.PutCtx(ctx); err != nil {
		return err
	}

	if hook, ok := any(entity).(AfterUpdater[T]); ok {
		if err := hook.AfterUpdate(old); err != nil {
			return err
		}
	}

	return nil
}

// Update persists changes, executing Before/AfterUpdate hooks.
func (m *Model[T]) Update() error {
	return m.UpdateCtx(context.Background())
}

// MustUpdate persists changes or panics.
func (m *Model[T]) MustUpdate() {
	if err := m.Update(); err != nil {
		panic(fmt.Sprintf("orm: MustUpdate: %v", err))
	}
}

// DeleteCtx removes the entity with context, executing Before/AfterDelete hooks.
func (m *Model[T]) DeleteCtx(ctx context.Context) error {
	if m.mock {
		return nil
	}

	entity := m.self()

	if hook, ok := any(entity).(BeforeDeleter); ok {
		if err := hook.BeforeDelete(); err != nil {
			return err
		}
	}

	if err := m.db.Delete(ctx, m.key); err != nil {
		return err
	}

	if hook, ok := any(entity).(AfterDeleter); ok {
		if err := hook.AfterDelete(); err != nil {
			return err
		}
	}

	return nil
}

// Delete removes the entity, executing Before/AfterDelete hooks.
func (m *Model[T]) Delete() error {
	return m.DeleteCtx(context.Background())
}

// MustDelete removes the entity or panics.
func (m *Model[T]) MustDelete() {
	if err := m.Delete(); err != nil {
		panic(fmt.Sprintf("orm: MustDelete: %v", err))
	}
}

// Get loads the entity by its current key.
func (m *Model[T]) Get(key Key) error {
	if key != nil {
		m.SetKey(key)
	}

	entity := m.self()
	if err := m.db.Get(nil, m.key, entity); err != nil {
		return err
	}

	// Capture snapshot for old-entity hooks in Update()
	m.captureSnapshot()

	// Auto-deserialize underscore fields after load
	return DeserializeFields(entity)
}

// GetById loads the entity by its string ID.
func (m *Model[T]) GetById(id string) error {
	entity := m.self()
	kind := m.Kind()

	q := m.db.Query(kind)
	key, ok, err := q.ById(id, entity)
	if err != nil {
		return err
	}
	if !ok {
		return ErrNotFound
	}

	m.SetKey(key)

	// Capture snapshot for old-entity hooks
	m.captureSnapshot()

	// Auto-deserialize
	return DeserializeFields(entity)
}

// GetByIdForUpdate is GetById + row-level exclusive lock. Only valid inside
// an enclosing RunInTransactionWith block. The lock is held for the lifetime
// of the transaction; concurrent GetByIdForUpdate callers block until commit.
func (m *Model[T]) GetByIdForUpdate(id string) error {
	entity := m.self()
	kind := m.Kind()
	key := m.db.NewKey(kind, id, 0, nil)
	if err := m.db.GetForUpdate(context.Background(), key, entity); err != nil {
		return err
	}
	m.SetKey(key)
	m.captureSnapshot()
	return DeserializeFields(entity)
}

// Exists checks if the entity exists in the database.
func (m *Model[T]) Exists() (bool, error) {
	kind := m.Kind()
	q := m.db.Query(kind)
	return q.KeyExists(m.Key())
}

// Clone creates a deep copy of the entity via JSON round-trip.
func (m *Model[T]) Clone() *T {
	entity := m.self()
	data, err := json.Marshal(entity)
	if err != nil {
		return new(T)
	}
	clone := new(T)
	json.Unmarshal(data, clone)
	return clone
}

// JSON serializes the entity to JSON bytes.
func (m *Model[T]) JSON() []byte {
	data, _ := json.Marshal(m.self())
	return data
}

// JSONString serializes the entity to a JSON string.
func (m *Model[T]) JSONString() string {
	return string(m.JSON())
}

// Query returns a typed model query for this entity.
func (m *Model[T]) Query() *ModelQuery[T] {
	return &ModelQuery[T]{
		model: m,
		query: m.db.Query(m.Kind()),
	}
}

// updateIdFromKey updates Id_ from the current key.
func (m *Model[T]) updateIdFromKey() {
	if m.key == nil {
		return
	}
	if sid := m.key.StringID(); sid != "" {
		m.Id_ = sid
	} else if m.key.Encode() != "" {
		m.Id_ = m.key.Encode()
	}
}

func (m *Model[T]) mockPut() error {
	if m.key == nil {
		kind := m.Kind()
		m.key = m.db.NewKey(kind, fmt.Sprintf("mock-%d", time.Now().UnixNano()), 0, m.parent)
		m.updateIdFromKey()
	}
	return nil
}

// models holds metadata for every registered model type.
var models = &registry{
	byKind: make(map[string]*Meta),
	byType: make(map[reflect.Type]*Meta),
}

type registry struct {
	mu     sync.RWMutex
	byKind map[string]*Meta
	byType map[reflect.Type]*Meta
}

// Meta holds parsed metadata for a registered model type.
type Meta struct {
	Kind        string
	Type        reflect.Type // the concrete struct type T (not *T)
	StringKey   bool
	ParentFn    func(DB) Key      // optional parent key factory
	InitFn      func(DB, any)     // optional custom init
	DefaultsFn  func(any)         // optional custom defaults
	Defaults    map[string]string // field name → default value from tags
	Serialized  map[string]string // JSON field name → underscore field name
	CacheConfig *CacheConfig      // per-model cache settings (nil = use global)
}

// CacheConfig controls per-model caching behavior.
type CacheConfig struct {
	Enabled   bool
	EntityTTL int // seconds, 0 = use global default
	QueryTTL  int // seconds, 0 = use global default
}

// serializedField records a pair of fields for auto-serialization.
type serializedField struct {
	JSONField       string // the exported field name (e.g. "Variants")
	StorageField    string // the underscore field name (e.g. "Variants_")
	JSONFieldIndex  int
	StorageFieldIdx int
}

// Register records type T under the given kind string.
// Must be called from init() or before any ORM operations.
func Register[T any](kind string, opts ...Option[T]) {
	var zero T
	typ := reflect.TypeOf(zero)
	if typ.Kind() == reflect.Pointer {
		typ = typ.Elem()
	}

	meta := &Meta{
		Kind:       kind,
		Type:       typ,
		Defaults:   make(map[string]string),
		Serialized: make(map[string]string),
	}

	// Parse struct tags for defaults and serialization hints
	parseStructTags(typ, meta)

	// Apply options
	for _, opt := range opts {
		opt.apply(meta)
	}

	models.mu.Lock()
	defer models.mu.Unlock()

	if existing, ok := models.byKind[kind]; ok {
		panic(fmt.Sprintf("orm: kind %q already registered by type %v", kind, existing.Type))
	}

	models.byKind[kind] = meta
	models.byType[typ] = meta
}

// MustLookup returns the metadata for kind or panics.
func MustLookup(kind string) *Meta {
	models.mu.RLock()
	defer models.mu.RUnlock()
	meta, ok := models.byKind[kind]
	if !ok {
		panic(fmt.Sprintf("orm: kind %q not registered", kind))
	}
	return meta
}

// Lookup returns the metadata for kind.
func Lookup(kind string) (*Meta, bool) {
	models.mu.RLock()
	defer models.mu.RUnlock()
	meta, ok := models.byKind[kind]
	return meta, ok
}

// LookupType returns the metadata for the given type.
func LookupType(typ reflect.Type) (*Meta, bool) {
	if typ.Kind() == reflect.Pointer {
		typ = typ.Elem()
	}
	models.mu.RLock()
	defer models.mu.RUnlock()
	meta, ok := models.byType[typ]
	return meta, ok
}

// Kinds returns all registered kind strings.
func Kinds() []string {
	models.mu.RLock()
	defer models.mu.RUnlock()
	kinds := make([]string, 0, len(models.byKind))
	for k := range models.byKind {
		kinds = append(kinds, k)
	}
	return kinds
}

// parseStructTags scans T for orm:"..." tags.
//
// Supported tags:
//   - orm:"default:value"     — sets default value on New()
//   - orm:"serialize"         — marks field for auto Load/Save with its _ sibling
//
// Legacy detection: if a field has `datastore:"-"` and a sibling Foo_ exists,
// it is treated as serialized automatically.
func parseStructTags(typ reflect.Type, meta *Meta) {
	if typ.Kind() == reflect.Pointer {
		typ = typ.Elem()
	}

	// Build a set of field names for sibling detection
	fieldNames := make(map[string]bool, typ.NumField())
	for field := range typ.Fields() {
		fieldNames[field.Name] = true
	}

	for f := range typ.Fields() {

		// Skip unexported
		if !f.IsExported() {
			continue
		}

		// Parse orm tag
		ormTag := f.Tag.Get("orm")
		if ormTag != "" {
			for part := range strings.SplitSeq(ormTag, ",") {
				part = strings.TrimSpace(part)

				if after, ok := strings.CutPrefix(part, "default:"); ok {
					meta.Defaults[f.Name] = after
				}

				if part == "serialize" {
					underscoreName := f.Name + "_"
					if fieldNames[underscoreName] {
						meta.Serialized[f.Name] = underscoreName
					}
				}
			}
		}

		// Legacy detection: datastore:"-" + Foo_ sibling
		dsTag := f.Tag.Get("datastore")
		if dsTag == "-" && !strings.HasSuffix(f.Name, "_") {
			underscoreName := f.Name + "_"
			if fieldNames[underscoreName] {
				// Don't overwrite explicit orm:"serialize"
				if _, exists := meta.Serialized[f.Name]; !exists {
					meta.Serialized[f.Name] = underscoreName
				}
			}
		}
	}
}

// resetRegistry clears the registry (for testing).
func resetRegistry() {
	models.mu.Lock()
	defer models.mu.Unlock()
	models.byKind = make(map[string]*Meta)
	models.byType = make(map[reflect.Type]*Meta)
}