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core.go
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core.go
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package submodule
import (
"fmt"
"reflect"
)
var inType = reflect.TypeOf(In{})
var selfType = reflect.TypeOf(Self{})
type submodule[T any] struct {
input any
provideType reflect.Type
dependencies []Retrievable
}
// Non generic representation of a submodule
type Retrievable interface {
retrieve(Scope) (any, error)
canResolve(reflect.Type) bool
}
// Submodule is a container holding a factory and its meta information
// Submodule will not hold the result on its own, but rather resolving it against a scope
type Submodule[T any] interface {
Retrievable
// Substitute the implementation with another submodule. Very useful for testing as well as changing reusable graph
// Be warned that this may cause a circular dependency
Substitute(Submodule[T])
// SafeResolve will resolve the submodule against the global scope and giving out errors of the factory and all of its dependencies
SafeResolve() (T, error)
// Resolve will resolve the submodule against the global scope. If the factory function or any of its dependencies return an error, panic will be called
Resolve() T
// Force the submodule to resolve to specific value to the global scope
ResolveTo(T)
// Same as resolve, but with a scope
ResolveWith(Scope) T
// Same as SafeResolve, but with a scope
SafeResolveWith(Scope) (T, error)
// Same as ResolveTo, but with a scope
ResolveToWith(Scope, T)
}
func (s *submodule[T]) Substitute(other Submodule[T]) {
o, ok := other.(*submodule[T])
if !ok {
panic(fmt.Sprintf("only submodule can be substituted, received: %v", reflect.TypeOf(other)))
}
s.input = o.input
s.provideType = o.provideType
s.dependencies = o.dependencies
}
func (s *submodule[T]) SafeResolve() (t T, e error) {
return s.SafeResolveWith(nil)
}
func (s *submodule[T]) ResolveWith(as Scope) T {
t, e := s.SafeResolveWith(as)
if e != nil {
panic(e)
}
return t
}
func (s *submodule[T]) SafeResolveWith(as Scope) (t T, e error) {
logger().Debug("resolving",
"targetType", s.provideType,
"dependencies", s.dependencies,
)
scope := globalScope
if as != nil {
scope = as
}
var v *value
if scope.has(s) {
v = scope.get(s)
logger().Debug("cache hit", "targetType", s.provideType)
} else {
inputType := reflect.TypeOf(s.input)
argsTypes := make([]reflect.Type, inputType.NumIn())
args := make([]reflect.Value, inputType.NumIn())
for i := 0; i < inputType.NumIn(); i++ {
argsTypes[i] = inputType.In(i)
if isSelf(argsTypes[i]) {
args[i] = reflect.ValueOf(Self{
Scope: scope,
Dependencies: s.dependencies,
})
continue
}
v, err := resolveType(scope, argsTypes[i], s.dependencies)
if err != nil {
return t, err
}
args[i] = v
}
result := reflect.ValueOf(s.input).Call(args)
if len(result) == 1 {
v = scope.initValue(s, result[0])
} else {
v = scope.initValue(s, result[0])
if !result[1].IsNil() {
v.e = result[1]
}
}
}
if v.e.IsValid() {
return t, v.e.Interface().(error)
}
if v.value.IsZero() {
return t, e
}
return v.value.Interface().(T), nil
}
func (s *submodule[T]) Resolve() T {
r, e := s.SafeResolve()
if e != nil {
panic(e)
}
return r
}
func (s *submodule[T]) ResolveTo(t T) {
s.ResolveToWith(globalScope, t)
}
func (s *submodule[T]) ResolveToWith(as Scope, t T) {
as.InitValue(s, t)
}
func (s *submodule[T]) retrieve(scope Scope) (any, error) {
return s.SafeResolveWith(scope)
}
func (s *submodule[T]) canResolve(key reflect.Type) bool {
return s.provideType.AssignableTo(key)
}
func validateInput(input any, isProvider bool) error {
inputType := reflect.TypeOf(input)
if inputType.Kind() != reflect.Func {
return fmt.Errorf("only func(...any) is accepted, received: %v", inputType.String())
}
if isProvider {
if inputType.NumOut() == 0 {
return fmt.Errorf("provider must return something %v", inputType.String())
}
if inputType.NumOut() > 2 {
return fmt.Errorf("provider must return only one or two values %v", inputType.String())
}
if inputType.NumOut() == 2 && !inputType.Out(1).AssignableTo(reflect.TypeOf((*error)(nil)).Elem()) {
return fmt.Errorf("provider returning a tuple, the 2nd type must be error %v", inputType.String())
}
} else {
if inputType.NumOut() > 1 {
return fmt.Errorf("run fn can only return none or error %v", inputType.String())
}
if inputType.NumOut() == 1 && !inputType.Out(0).AssignableTo(reflect.TypeOf((*error)(nil)).Elem()) {
return fmt.Errorf("run fn can only return none or error %v", inputType.String())
}
}
return nil
}
func construct[T any](
input any,
dependencies ...Retrievable,
) Submodule[T] {
inputType := reflect.TypeOf(input)
if err := validateInput(input, true); err != nil {
panic(err)
}
provideType := inputType.Out(0)
if provideType.Kind() == reflect.Interface {
gt := reflect.TypeOf((*T)(nil)).Elem()
if !gt.AssignableTo(provideType) {
panic(
fmt.Sprintf(
"generic type output mismatch. \n Expect: %s \n Providing: %s",
gt.String(),
provideType.String(),
),
)
}
} else {
ot := reflect.New(provideType).Elem().Interface()
_, ok := ot.(T)
if !ok {
panic(
fmt.Sprintf(
"generic type output mismatch. \n Expect: %s \n Providing: %s",
ot,
provideType.String(),
),
)
}
}
// check feasibility
for i := 0; i < inputType.NumIn(); i++ {
canResolve := false
pt := inputType.In(i)
if isSelf(pt) {
continue
}
if isInEmbedded(pt) {
for fi := 0; fi < pt.NumField(); fi++ {
f := pt.Field(fi)
if f.Type == inType {
continue
}
for _, d := range dependencies {
if d.canResolve(f.Type) {
canResolve = true
break
}
}
if !canResolve {
panic(
fmt.Sprintf(
"unable to resolve dependency for type: %s. \n Unable to resolve: %s of %s",
inputType.String(),
f.Type.String(),
pt.String(),
),
)
}
}
continue
}
for _, d := range dependencies {
if d.canResolve(pt) {
canResolve = true
break
}
}
if !canResolve {
panic(
fmt.Sprintf(
"unable to resolve dependency for type: %s. \n Unable to resolve: %s",
inputType.String(),
pt.String(),
),
)
}
}
return &submodule[T]{
input: input,
provideType: provideType,
dependencies: dependencies,
}
}