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collection.go
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collection.go
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package inventory
import (
"fmt"
"slices"
)
// NewCollection creates a Collection of T with the provided opts; PrimaryKey
// and Extractor are mandatory
func NewCollection[T any](db DB, kind string, opts ...CollectionOpt[T]) (c *Collection[T]) {
c = &Collection[T]{
db: db,
kind: kind,
}
return c.With(opts...)
}
// Collection is like a typed access layer to the db defined by a schema but
// because the purpose of this repository is IoC of the data, it also defines
// how the data is loaded from the cold source.
type Collection[T any] struct {
db DB
kind string
pk index[T]
keys []index[T]
extract extractFn[T]
inferences []inferFn[T]
}
// With instruments the collection with the provided opts
func (c *Collection[T]) With(opts ...CollectionOpt[T]) *Collection[T] {
for _, opt := range opts {
opt(c)
}
return c
}
// Infer creates a "chained" collection in a way that for every loaded item on
// the base collection, the provided mapFn is called to load the inferred item
func Infer[Base, Inferred any](baseCol *Collection[Base], mapBy string, mapFn mapFn[Base, Inferred]) *InferredCollection[Inferred] {
inferredCol := NewCollection[Inferred](baseCol.db, mapBy)
baseCol.inferences = append(baseCol.inferences, func(writer DBWriter, base Base) {
mapFn(base, func(kv string, items ...Inferred) {
inferredCol.indexer(items, func(key string, item Inferred) {
inferredCol.loadItem(writer, key, item)
baseCol.pk.ref(base, func(v string) {
tag := mkKey(baseCol.kind, mapBy, kv)
writer.Tag(key, tag)
})
})
})
})
q := func(val string, filters ...func(Inferred) bool) (res []Inferred, err error) {
inferredCol.db.Iter(mkKey(baseCol.kind, mapBy, val), func(key string, getVal func() (any, bool)) (proceed bool) {
item, ok := getVal()
if !ok {
err = fmt.Errorf("failed to retrieve value of %q", key)
return false
}
t, ok := item.(Inferred)
if !ok {
err = fmt.Errorf("expected type %T for %q. got %T", t, key, item)
return false
}
for _, f := range filters {
if !f(t) {
return true
}
}
res = append(res, t)
return true
})
return
}
return &InferredCollection[Inferred]{inferredCol, q}
}
type InferredCollection[T any] struct {
*Collection[T]
q Query[T]
}
// With is just a proxy of the underlying Collection's method
func (i *InferredCollection[T]) With(opts ...CollectionOpt[T]) *InferredCollection[T] {
i.Collection.With(opts...)
return i
}
// Query is the Query that created by the inferencee. the key is necessarily the
// primary key of the base collection.
func (i *InferredCollection[T]) Query(key string, filters ...func(T) bool) ([]T, error) {
return i.q(key, filters...)
}
// Derive creates a Derivative item fetcher that is stored under the
// provided subKey in relation to the provided item
func Derive[In, Out any](collection *Collection[In], name string, fn func(in In) (out Out, err error)) Derivative[In, Out] {
return func(in In) (out Out, err error) {
if collection.pk.ref == nil {
err = fmt.Errorf("collection %q has no primary key", collection.kind)
return
}
var key string
collection.pk.ref(in, func(v string) {
key = mkKey(fmt.Sprintf("%s/%s", collection.kind, name), collection.pk.key, v)
})
val, err := collection.db.GetOrFill(key, func() (res any, err error) {
res, err = fn(in)
if err != nil {
return
}
return
}, collection.kind)
if err != nil {
return
}
out, ok := val.(Out)
if !ok {
err = fmt.Errorf("type assertion error. expected: %T; actual: %T", out, val)
}
return
}
}
// Extractor sets the extractFn of the collection. extractFn is a function
// that extracts the data from the origin source
func Extractor[T any](x extractFn[T]) CollectionOpt[T] {
return func(c *Collection[T]) {
c.extract = x
}
}
// PrimaryKey sets the primary index of the collection
func PrimaryKey[T any](name string, value indexFn[T]) CollectionOpt[T] {
return func(c *Collection[T]) {
c.addIndex(c.kind, name, true, value)
}
}
// AdditionalKey adds a secondary index of the collection
func AdditionalKey[T any](name string, value indexFn[T]) CollectionOpt[T] {
return func(c *Collection[T]) {
c.addIndex(c.kind, name, false, value)
}
}
func (c *Collection[T]) addIndex(kind, key string, primary bool, value indexFn[T]) bool {
if slices.ContainsFunc(c.keys, func(i index[T]) bool { return i.key == key }) {
return false
}
idx := index[T]{primary, kind, key, value}
if primary {
c.pk = idx
} else {
c.keys = append(c.keys, idx)
}
return true
}
func (c *Collection[T]) index(key string, primary bool, value indexFn[T]) Getter[T] {
c.addIndex(c.kind, key, primary, value)
return c.getter(key, primary)
}
func (c *Collection[T]) getter(key string, primary bool) Getter[T] {
return func(val string) (t T, ok bool) {
var i any
if !primary {
c.db.Iter(mkKey(c.kind, key, val), func(key string, getVal func() (any, bool)) (proceed bool) {
i, ok = getVal()
return false
})
} else {
i, ok = c.db.Get(mkKey(c.kind, key, val))
}
if !ok {
return
}
t, ok = i.(T)
return
}
}
// PrimaryKey creates a primary index on the collection using an indexFn
//
// for example;
// c.PrimaryKey("id", func(f Foo, val func(string)) { val(f.id) })
func (c *Collection[T]) PrimaryKey(key string, value indexFn[T]) Getter[T] {
return c.index(key, true, value)
}
// AdditionalKey creates an additional index on the collection using an indexFn
//
// for example;
// c.AdditionalKey("name", func(f Foo, val func(string)) { val(f.name) })
func (c *Collection[T]) AdditionalKey(key string, value indexFn[T]) Getter[T] {
return c.index(key, false, value)
}
// GetBy creates a getter from existing index
func (c *Collection[T]) GetBy(key string) Getter[T] {
return c.getter(key, key == c.pk.key)
}
// Scalar creates a "static" Getter that will require no key
func (c *Collection[T]) Scalar(key, value string) Scalar[T] {
k := mkKey(c.kind, key, value)
return func() (t T, ok bool) {
i, ok := c.db.Get(k)
if !ok {
return
}
t, ok = i.(T)
return
}
}
// MapBy creates a Query from the provided key mapped by the provided indexFn,
// to be used for querying the collection by a non-unique attribute
func (c *Collection[T]) MapBy(key string, ref indexFn[T]) Query[T] {
c.addIndex(c.kind, key, false, ref)
return func(val string, filters ...func(T) bool) (res []T, err error) {
c.db.Iter(mkKey(c.kind, key, val), func(key string, getVal func() (any, bool)) (proceed bool) {
item, ok := getVal()
if !ok {
err = fmt.Errorf("failed to retrieve value of %q", key)
return false
}
t, ok := item.(T)
if !ok {
err = fmt.Errorf("expected type %T for %q. got %T", t, key, item)
return false
}
for _, f := range filters {
if !f(t) {
return true
}
}
res = append(res, t)
return true
})
return
}
}
// Scan iterates over all items in the collection, not sorted
func (c *Collection[T]) Scan(consume func(T) bool, filters ...func(T) bool) {
var (
key string
ok bool
item any
t T
)
c.db.Iter(c.kind, func(itemKey string, getVal func() (any, bool)) (proceed bool) {
_, key, _, ok = parseKey(itemKey)
if !ok || key != c.pk.key {
return true
}
item, ok = getVal()
if !ok {
return true
}
t, ok = item.(T)
if !ok {
return true
}
for _, f := range filters {
if !f(t) {
return true
}
}
return consume(t)
})
}
// Invalidate reloads all data from the origin source, defined by the Extractor
func (c *Collection[T]) Invalidate() {
_ = c.db.Update(func(writer DBWriter) error {
writer.Invalidate(c.kind)
c.Load(writer)
return nil
})
}
// Load loads all data from the origin source, defined by the Extractor
func (c *Collection[T]) Load(writer DBWriter) {
c.extract(func(items ...T) {
c.indexer(items, func(key string, item T) {
c.loadItem(writer, key, item)
})
})
}
func (c *Collection[T]) loadItem(writer DBWriter, key string, item T) {
writer.Put(key, item)
writer.Tag(key, c.kind)
c.tagItemWithIndexes(writer, key, item)
for _, infer := range c.inferences {
infer(writer, item)
}
return
}
func (c *Collection[T]) tagItemWithIndexes(writer DBWriter, key string, item T) {
for _, idx := range c.keys {
idx.ref(item, func(v string) {
tag := mkKey(c.kind, idx.key, v)
writer.Tag(key, tag)
})
}
}
func (c *Collection[T]) indexer(items []T, fn func(key string, item T)) {
if c.pk.ref == nil {
return
}
for _, item := range items {
c.pk.ref(item, func(v string) {
fn(mkKey(c.kind, c.pk.key, v), item)
})
}
}
type index[T any] struct {
pk bool
kind string
key string
ref indexFn[T]
}
type CollectionOpt[T any] func(*Collection[T])
type indexFn[T any] func(item T, keyVal func(string))
type mapFn[From, To any] func(From, func(kv string, items ...To))
type inferFn[T any] func(DBWriter, T)
type extractFn[T any] func(load func(in ...T))