146 lines
4.0 KiB
Go
146 lines
4.0 KiB
Go
package wasm
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import "syscall/js"
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// Promise is an instance of a JS promise.
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// The zero value of this struct is not a valid Promise.
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type Promise struct {
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Object
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}
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// FromJSValue turns a JS value to a Promise.
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func (p *Promise) FromJSValue(value js.Value) error {
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var err error
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p.Object, err = NewObject(value)
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return err
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}
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// NewPromise returns a promise that is fulfilled or rejected when the provided handler returns.
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// The handler is spawned in its own goroutine.
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func NewPromise(handler func() (interface{}, error)) Promise {
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resultChan := make(chan interface{})
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errChan := make(chan error)
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// Invoke the handler in a new goroutine.
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go func() {
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result, err := handler()
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if err != nil {
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errChan <- err
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return
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}
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resultChan <- result
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}()
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// Create a JS promise handler.
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var jsHandler js.Func
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jsHandler = js.FuncOf(func(this js.Value, args []js.Value) interface{} {
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if len(args) < 2 {
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panic("not enough arguments are passed to the Promise constructor handler")
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}
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resolve := args[0]
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reject := args[1]
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if resolve.Type() != js.TypeFunction || reject.Type() != js.TypeFunction {
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panic("invalid type passed to Promise constructor handler")
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}
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go func() {
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select {
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case r := <-resultChan:
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resolve.Invoke(ToJSValue(r))
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case err := <-errChan:
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reject.Invoke(NewError(err))
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}
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// Free up resources now that we are done.
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jsHandler.Release()
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}()
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return nil
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})
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promise, err := Global().Expect(js.TypeFunction, "Promise")
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if err != nil {
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panic("Promise constructor not found")
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}
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return mustJSValueToPromise(promise.New(jsHandler))
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}
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// PromiseAll creates a promise that is fulfilled when all the provided promises have been fulfilled.
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// The promise is rejected when any of the promises provided rejects.
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// It is implemented by calling Promise.all on JS.
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func PromiseAll(promise ...Promise) Promise {
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promiseAll, err := Global().Expect(js.TypeFunction, "Promise", "all")
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if err != nil {
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panic("Promise.all not found")
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}
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pInterface := make([]interface{}, 0, len(promise))
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for _, v := range promise {
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pInterface = append(pInterface, v)
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}
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return mustJSValueToPromise(promiseAll.Invoke(pInterface))
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}
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// PromiseAllSettled creates a promise that is fulfilled when all the provided promises have been fulfilled or rejected.
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// It is implemented by calling Promise.allSettled on JS.
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func PromiseAllSettled(promise ...Promise) Promise {
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promiseAllSettled, err := Global().Expect(js.TypeFunction, "Promise", "allSettled")
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if err != nil {
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panic("Promise.allSettled not found")
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}
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pInterface := make([]interface{}, 0, len(promise))
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for _, v := range promise {
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pInterface = append(pInterface, v)
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}
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return mustJSValueToPromise(promiseAllSettled.Invoke(pInterface))
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}
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// PromiseAny creates a promise that is fulfilled when any of the provided promises have been fulfilled.
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// The promise is rejected when all of the provided promises gets rejected.
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// It is implemented by calling Promise.any on JS.
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func PromiseAny(promise ...Promise) Promise {
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promiseAny, err := Global().Expect(js.TypeFunction, "Promise", "any")
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if err != nil {
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panic("Promise.any not found")
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}
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pInterface := make([]interface{}, 0, len(promise))
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for _, v := range promise {
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pInterface = append(pInterface, v)
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}
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return mustJSValueToPromise(promiseAny.Invoke(pInterface))
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}
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// PromiseRace creates a promise that is fulfilled or rejected when one of the provided promises fulfill or reject.
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// It is implemented by calling Promise.race on JS.
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func PromiseRace(promise ...Promise) Promise {
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promiseRace, err := Global().Expect(js.TypeFunction, "Promise", "race")
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if err != nil {
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panic("Promise.race not found")
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}
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pInterface := make([]interface{}, 0, len(promise))
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for _, v := range promise {
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pInterface = append(pInterface, v)
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}
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return mustJSValueToPromise(promiseRace.Invoke(pInterface))
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}
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func mustJSValueToPromise(v js.Value) Promise {
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var p Promise
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err := p.FromJSValue(v)
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if err != nil {
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panic("Expected a Promise from JS standard library")
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}
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return p
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}
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