57 lines
1.3 KiB
Go
57 lines
1.3 KiB
Go
package types
|
|
|
|
// A Decorator executes before/during/after a handler to enhance functionality.
|
|
type Decorator func(ctx Context, tx Tx, next Handler) Result
|
|
|
|
// Return a decorated handler
|
|
func Decorate(dec Decorator, next Handler) Handler {
|
|
return func(ctx Context, tx Tx) Result {
|
|
return dec(ctx, tx, next)
|
|
}
|
|
}
|
|
|
|
//----------------------------------------
|
|
|
|
/*
|
|
Helper to construct a decorated Handler from a stack of Decorators
|
|
(first-decorator-first-call as in Python @decorators) , w/ Handler provided
|
|
last for syntactic sugar of ChainDecorators().WithHandler()
|
|
|
|
Usage:
|
|
|
|
handler := sdk.ChainDecorators(
|
|
decorator1,
|
|
decorator2,
|
|
...,
|
|
).WithHandler(myHandler)
|
|
|
|
*/
|
|
func ChainDecorators(decorators ...Decorator) stack {
|
|
return stack{
|
|
decs: decorators,
|
|
}
|
|
}
|
|
|
|
// No need to expose this.
|
|
type stack struct {
|
|
decs []Decorator
|
|
}
|
|
|
|
// WithHandler sets the final handler for the stack and
|
|
// returns the decoratored Handler.
|
|
func (s stack) WithHandler(handler Handler) Handler {
|
|
if handler == nil {
|
|
panic("WithHandler() requires a non-nil Handler")
|
|
}
|
|
return build(s.decs, handler)
|
|
}
|
|
|
|
// build wraps each decorator around the next, so that
|
|
// the last in the list is closest to the handler
|
|
func build(stack []Decorator, end Handler) Handler {
|
|
if len(stack) == 0 {
|
|
return end
|
|
}
|
|
return Decorate(stack[0], build(stack[1:], end))
|
|
}
|