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app.go
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app.go
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package app
import (
"fmt"
"reflect"
)
var (
sp = fmt.Sprintf
)
type defineInfo struct {
ptr interface{}
provides bool
}
type Application struct {
provides map[string]interface{}
requires map[string][]interface{}
defs map[string]defineInfo
impls map[string][]interface{}
}
func New() *Application {
app := &Application{
provides: make(map[string]interface{}),
requires: make(map[string][]interface{}),
defs: make(map[string]defineInfo),
impls: make(map[string][]interface{}),
}
return app
}
type Loader struct {
Provide func(name string, fn interface{})
Require func(name string, fn interface{})
Define func(name string, fnPtr interface{})
Implement func(name string, fn interface{})
DefineProvide func(name string, fnPtr interface{})
}
func (a *Application) Load(module interface{}) {
modType := reflect.TypeOf(module)
loader := Loader{
Provide: func(name string, fn interface{}) {
if _, in := a.provides[name]; in {
panic(sp("module %v: multiple provides of %s", modType, name))
}
a.provides[name] = fn
},
Require: func(name string, fn interface{}) {
t := reflect.TypeOf(fn)
if t.Kind() != reflect.Ptr {
panic(sp("module %v: required %s is not a pointer", modType, name))
}
a.requires[name] = append(a.requires[name], fn)
},
Define: func(name string, fnPtr interface{}) {
t := reflect.TypeOf(fnPtr)
if t.Kind() != reflect.Ptr || t.Elem().Kind() != reflect.Func {
panic(sp("module %v: argument is not a pointer to function", modType))
}
if _, in := a.defs[name]; in {
panic(sp("module %v: multiple definition of %s", modType, name))
}
a.defs[name] = defineInfo{fnPtr, false}
},
Implement: func(name string, fn interface{}) {
t := reflect.TypeOf(fn)
if t.Kind() != reflect.Func {
panic(sp("module %v: implementation of %s is not a function", modType, name))
}
a.impls[name] = append(a.impls[name], fn)
},
DefineProvide: func(name string, fnPtr interface{}) {
t := reflect.TypeOf(fnPtr)
if t.Kind() != reflect.Ptr || t.Elem().Kind() != reflect.Func {
panic(sp("module %v: argument is not a pointer to function", modType))
}
if _, in := a.defs[name]; in {
panic(sp("module %v: multiple definition of %s", modType, name))
}
a.defs[name] = defineInfo{fnPtr, true}
},
}
if mod, ok := module.(interface {
Load(Loader)
}); ok {
mod.Load(loader)
}
if mod, ok := module.(func(Loader)); ok {
mod(loader)
}
}
var fnHandlers = make(map[reflect.Type]func(interface{}, []interface{}))
func AddFuncType(fnNilPtr interface{}, handler func(impls []interface{}) interface{}) {
fnHandlers[reflect.TypeOf(fnNilPtr).Elem()] = func(fnPtr interface{}, impls []interface{}) {
fn := handler(impls)
reflect.ValueOf(fnPtr).Elem().Set(reflect.ValueOf(fn))
}
}
func (a *Application) FinishLoad() {
// handle defs / impls
for name, info := range a.defs {
fnPtr := info.ptr
impls := a.impls[name]
if len(impls) == 0 {
panic(sp("no implementation for %s", name))
}
fnType := reflect.TypeOf(fnPtr).Elem()
for _, impl := range impls {
if t := reflect.TypeOf(impl); t != fnType {
panic(sp("defined %v, implemented %v", fnType, t))
}
}
handler, ok := fnHandlers[fnType]
if ok {
handler(fnPtr, impls)
} else {
implValues := make([]reflect.Value, 0, len(impls))
for _, impl := range impls {
implValues = append(implValues, reflect.ValueOf(impl))
}
reflect.ValueOf(fnPtr).Elem().Set(reflect.MakeFunc(fnType,
func(args []reflect.Value) (ret []reflect.Value) {
for _, impl := range implValues {
impl.Call(args)
}
return
}))
}
if info.provides {
a.provides[name] = reflect.ValueOf(fnPtr).Elem().Interface()
}
}
// match provides and requires
for name, provide := range a.provides {
requires := a.requires[name]
provideValue := reflect.ValueOf(provide)
for _, require := range requires {
requireValue := reflect.ValueOf(require).Elem()
if provideValue.Type() != requireValue.Type() {
panic(sp("%s not match, %v provided, %v required", name, provideValue.Type(), requireValue.Type()))
}
requireValue.Set(provideValue)
}
delete(a.requires, name)
}
for name, _ := range a.requires {
panic(sp("%s not provided", name))
}
}