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document_meta.go
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document_meta.go
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package rel
import (
"reflect"
"strings"
"sync"
"time"
"github.com/jinzhu/inflection"
"github.com/serenize/snaker"
)
var (
primariesCache sync.Map
documentMetaCache sync.Map
rtTime = reflect.TypeOf(time.Time{})
rtBool = reflect.TypeOf(false)
rtInt = reflect.TypeOf(int(0))
rtTable = reflect.TypeOf((*table)(nil)).Elem()
rtPrimary = reflect.TypeOf((*primary)(nil)).Elem()
)
// DocumentFlag stores information about document as a flag.
type DocumentFlag int8
// Is returns true if it's defined.
func (df DocumentFlag) Is(flag DocumentFlag) bool {
return (df & flag) == flag
}
const (
// Invalid flag.
Invalid DocumentFlag = 1 << iota
// HasCreatedAt flag.
HasCreatedAt
// HasUpdatedAt flag.
HasUpdatedAt
// HasDeletedAt flag.
HasDeletedAt
// HasDeleted flag.
HasDeleted
// Versioning
HasVersioning
)
type table interface {
Table() string
}
type primary interface {
PrimaryFields() []string
PrimaryValues() []any
}
type primaryData struct {
field []string
index [][]int
}
type cachedDocumentMeta struct {
table string
index map[string][]int
fields []string
belongsTo []string
hasOne []string
hasMany []string
primaryField []string
primaryIndex [][]int
preload []string
flag DocumentFlag
}
// Adds a prefix to field names
func appendWithPrefix(target, fieldNames []string, prefix string) []string {
if prefix == "" {
return append(target, fieldNames...)
}
for _, name := range fieldNames {
target = append(target, prefix+name)
}
return target
}
// Adds a field index and checks for conflicts
func (cdm *cachedDocumentMeta) addFieldIndex(name string, index []int) {
if _, ok := cdm.index[name]; ok {
panic("rel: conflicting field (" + name + ") in struct")
}
cdm.index[name] = index
}
// Transfer values from other document data
func (cdm *cachedDocumentMeta) mergeEmbedded(other cachedDocumentMeta, indexPrefix int, namePrefix string) {
for name, path := range other.index {
cdm.addFieldIndex(namePrefix+name, append([]int{indexPrefix}, path...))
}
cdm.fields = appendWithPrefix(cdm.fields, other.fields, namePrefix)
cdm.belongsTo = appendWithPrefix(cdm.belongsTo, other.belongsTo, namePrefix)
cdm.hasOne = appendWithPrefix(cdm.hasOne, other.hasOne, namePrefix)
cdm.hasMany = appendWithPrefix(cdm.hasMany, other.hasMany, namePrefix)
cdm.primaryField = appendWithPrefix(cdm.primaryField, other.primaryField, namePrefix)
for _, index := range other.primaryIndex {
cdm.primaryIndex = append(cdm.primaryIndex, append([]int{indexPrefix}, index...))
}
cdm.preload = appendWithPrefix(cdm.preload, other.preload, namePrefix)
cdm.flag |= other.flag
}
type DocumentMeta struct {
rt reflect.Type
cachedDocumentMeta
}
// Table returns name of the table.
func (dm DocumentMeta) Table() string {
return dm.table
}
// PrimaryFields column name of this document.
func (dm DocumentMeta) PrimaryFields() []string {
if len(dm.primaryField) == 0 {
panic("rel: failed to infer primary key for type " + dm.rt.String())
}
return dm.primaryField
}
// PrimaryField column name of this document.
// panic if document uses composite key.
func (dm DocumentMeta) PrimaryField() string {
if fields := dm.PrimaryFields(); len(fields) == 1 {
return fields[0]
}
panic("rel: composite primary key is not supported")
}
// Index returns map of column name and it's struct index.
func (dm DocumentMeta) Index() map[string][]int {
return dm.index
}
// Fields returns list of fields available on this document.
func (dm DocumentMeta) Fields() []string {
return dm.fields
}
// Type returns reflect.Type of given field. if field does not exist, second returns value will be false.
func (dm DocumentMeta) Type(field string) (reflect.Type, bool) {
if i, ok := dm.index[field]; ok {
var (
ft = dm.rt.FieldByIndex(i).Type
)
if ft.Kind() == reflect.Ptr {
ft = ft.Elem()
} else if ft.Kind() == reflect.Slice && ft.Elem().Kind() == reflect.Ptr {
ft = reflect.SliceOf(ft.Elem().Elem())
}
return ft, true
}
return nil, false
}
// BelongsTo fields of this document.
func (dm DocumentMeta) BelongsTo() []string {
return dm.belongsTo
}
// HasOne fields of this document.
func (dm DocumentMeta) HasOne() []string {
return dm.hasOne
}
// HasMany fields of this document.
func (dm DocumentMeta) HasMany() []string {
return dm.hasMany
}
// Preload fields of this document.
func (dm DocumentMeta) Preload() []string {
return dm.preload
}
// Association of this document with given name.
func (dm DocumentMeta) Association(name string) AssociationMeta {
if assoc, ok := dm.association(name); ok {
return assoc
}
panic("rel: no field named (" + name + ") in type " + dm.rt.String() + " found ")
}
func (dm DocumentMeta) association(name string) (AssociationMeta, bool) {
index, ok := dm.index[name]
if !ok {
return AssociationMeta{}, false
}
return getAssociationMeta(dm.rt, index), true
}
// Flag returns true if struct contains specified flag.
func (dm DocumentMeta) Flag(flag DocumentFlag) bool {
return dm.flag.Is(flag)
}
func getDocumentMeta(rt reflect.Type, skipAssoc bool) DocumentMeta {
if meta, cached := documentMetaCache.Load(rt); cached {
return DocumentMeta{
cachedDocumentMeta: meta.(cachedDocumentMeta),
rt: rt,
}
}
var (
meta = cachedDocumentMeta{
table: tableName(rt),
index: make(map[string][]int, rt.NumField()),
}
)
// TODO probably better to use slice index instead.
for i := 0; i < rt.NumField(); i++ {
var (
sf = rt.Field(i)
typ = sf.Type
name, tagged = fieldName(sf)
)
if c := sf.Name[0]; c < 'A' || c > 'Z' || name == "" {
continue
}
for typ.Kind() == reflect.Ptr || typ.Kind() == reflect.Interface || typ.Kind() == reflect.Slice {
typ = typ.Elem()
}
if typ.Kind() == reflect.Struct && isEmbedded(sf) {
embedded := getDocumentMeta(typ, skipAssoc)
embeddedName := ""
if tagged {
embeddedName = name
}
meta.mergeEmbedded(embedded.cachedDocumentMeta, i, embeddedName)
continue
}
meta.addFieldIndex(name, sf.Index)
if flag := extractFlag(typ, name); flag != Invalid {
meta.fields = append(meta.fields, name)
meta.flag |= flag
continue
}
if typ.Kind() != reflect.Struct {
meta.fields = append(meta.fields, name)
continue
}
// struct without primary key is a field
// TODO: test by scanner/valuer instead?
if pk, _ := searchPrimary(typ); len(pk) == 0 {
meta.fields = append(meta.fields, name)
continue
}
if !skipAssoc {
var (
assocMeta = getAssociationMeta(rt, sf.Index)
)
switch assocMeta.typ {
case BelongsTo:
meta.belongsTo = append(meta.belongsTo, name)
case HasOne:
meta.hasOne = append(meta.hasOne, name)
case HasMany:
meta.hasMany = append(meta.hasMany, name)
}
if assocMeta.autoload {
meta.preload = append(meta.preload, name)
}
}
}
primaryField, primaryIndex := searchPrimary(rt)
meta.primaryField = append(meta.primaryField, primaryField...)
meta.primaryIndex = append(meta.primaryIndex, primaryIndex...)
if !skipAssoc {
documentMetaCache.Store(rt, meta)
}
return DocumentMeta{
rt: rt,
cachedDocumentMeta: meta,
}
}
func extractTimeFlag(name string) DocumentFlag {
switch name {
case "created_at", "inserted_at":
return HasCreatedAt
case "updated_at":
return HasUpdatedAt
case "deleted_at":
return HasDeletedAt
}
return Invalid
}
func extractBoolFlag(name string) DocumentFlag {
if name == "deleted" {
return HasDeleted
}
return Invalid
}
func extractIntFlag(name string) DocumentFlag {
if name == "lock_version" {
return HasVersioning
}
return Invalid
}
func extractFlag(rt reflect.Type, name string) DocumentFlag {
if rt == rtTime {
return extractTimeFlag(name)
}
if rt == rtBool {
return extractBoolFlag(name)
}
if rt == rtInt {
return extractIntFlag(name)
}
return Invalid
}
func fieldName(sf reflect.StructField) (string, bool) {
if tag := sf.Tag.Get("db"); tag != "" {
name := strings.Split(tag, ",")[0]
if name == "-" {
return "", true
}
if name != "" {
return name, true
}
}
return snaker.CamelToSnake(sf.Name), false
}
func isEmbedded(sf reflect.StructField) bool {
// anonymous structs are always embedded
if sf.Anonymous {
return true
}
if tag := sf.Tag.Get("db"); strings.HasSuffix(tag, ",embedded") {
return true
}
return false
}
func searchPrimary(rt reflect.Type) ([]string, [][]int) {
if result, cached := primariesCache.Load(rt); cached {
p := result.(primaryData)
return p.field, p.index
}
var (
field []string
index [][]int
fallbackIndex = -1
)
if rt.Implements(rtPrimary) {
var (
v = reflect.Zero(rt).Interface().(primary)
)
field = v.PrimaryFields()
// index kept nil to mark interface usage
} else {
for i := 0; i < rt.NumField(); i++ {
sf := rt.Field(i)
if tag := sf.Tag.Get("db"); strings.HasSuffix(tag, ",primary") {
index = append(index, sf.Index)
name, _ := fieldName(sf)
field = append(field, name)
continue
}
// check fallback for id field
if strings.EqualFold("id", sf.Name) {
fallbackIndex = i
}
}
}
if len(field) == 0 && fallbackIndex >= 0 {
field = []string{"id"}
index = [][]int{{fallbackIndex}}
}
primariesCache.Store(rt, primaryData{
field: field,
index: index,
})
return field, index
}
func tableName(rt reflect.Type) string {
var name string
if rt.Implements(rtTable) {
name = reflect.Zero(rt).Interface().(table).Table()
} else {
name = inflection.Plural(rt.Name())
name = snaker.CamelToSnake(name)
}
return name
}