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nanodi.go
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nanodi.go
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package nanodi
import "strings"
type Provider interface {
GetService(name string) interface{}
GetServices(name string) []interface{}
}
type Assembly interface {
GetService(name string) interface{}
}
type Builder interface {
CommandName() string
Options() BuilderOptions
Build(provider Provider) (interface{}, error)
}
type BuilderOptions struct {
IsShared bool
}
type BuilderFn func(provider Provider) (interface{}, error)
func NewBuilder(name string, fn BuilderFn) Builder {
defaultOptions := BuilderOptions{
IsShared: true,
}
return &builder{name: name, fn: fn, options: defaultOptions}
}
func NewBuilderWithOptions(name string, fn BuilderFn, options BuilderOptions) Builder {
return &builder{name: name, fn: fn, options: options}
}
func Assemble(builders []Builder) Assembly {
return newBuildContext(builders)
}
func CombineBuilders(builders ...[]Builder) []Builder {
count := 0
for _, outer := range builders {
count += len(outer)
}
combined := make([]Builder, count)
index := 0
for _, outer := range builders {
for _, inner := range outer {
combined[index] = inner
index++
}
}
return combined
}
type builder struct {
name string
fn BuilderFn
options BuilderOptions
}
type buildContext struct {
builders map[string][]Builder
built map[string]interface{}
// Lists the current dependency stack to detect dependency cycles.
buildStack []string
}
func (b *builder) CommandName() string {
return b.name
}
func (b *builder) Options() BuilderOptions {
return b.options
}
func (b *builder) Build(provider Provider) (interface{}, error) {
return b.fn(provider)
}
func newBuildContext(builders []Builder) *buildContext {
builderMap := make(map[string][]Builder)
for _, builder := range builders {
name := builder.CommandName()
builderMap[name] = append(builderMap[name], builder)
}
built := make(map[string]interface{})
return &buildContext{
builders: builderMap,
built: built,
}
}
func (c *buildContext) GetService(name string) interface{} {
if c.isInBuildStack(name) {
c.panicCircular(name)
}
c.buildStack = append(c.buildStack, name)
defer func() {
c.buildStack = c.buildStack[:len(c.buildStack)-1]
}()
built, ok := c.built[name]
if ok {
return built
}
builders, ok := c.builders[name]
if !ok {
panic("builder does not exist for the type")
}
if len(builders) > 1 {
panic("ambiguous: several builders for the type")
}
builder := builders[0]
built, err := builder.Build(c)
if err != nil {
panic("failed to build service")
}
if builder.Options().IsShared {
c.built[name] = built
}
return built
}
func (c *buildContext) GetServices(name string) []interface{} {
if c.isInBuildStack(name) {
c.panicCircular(name)
}
c.buildStack = append(c.buildStack, name)
defer func() {
c.buildStack = c.buildStack[:len(c.buildStack)-1]
}()
built, ok := c.built[name]
if ok {
return built.([]interface{})
}
builders, ok := c.builders[name]
if !ok {
return nil
}
result := make([]interface{}, len(builders))
for i, builder := range builders {
built, err := builder.Build(c)
if err != nil {
panic("failed to build service")
}
result[i] = built
}
c.built[name] = result
return result
}
func (c *buildContext) isInBuildStack(name string) bool {
for _, dep := range c.buildStack {
if dep == name {
return true
}
}
return false
}
func (c *buildContext) panicCircular(offendingDep string) {
strBuilder := strings.Builder{}
for _, dep := range c.buildStack {
strBuilder.WriteString(dep)
strBuilder.WriteString(" > ")
}
strBuilder.WriteString(offendingDep)
panic("circular dependency detected: " + strBuilder.String())
}