package wasmhttp

import (
	"fmt"
	"net/http"
	"os"
	"strings"
	"syscall/js"

	"github.com/nlepage/go-wasm-http-server/internal/whutil"
)

// Serve serves HTTP requests using handler or http.DefaultServeMux if handler is nil.
func Serve(handler http.Handler) func() {
	h := handler
	if h == nil {
		h = http.DefaultServeMux
	}

	path := os.Getenv("WASMHTTP_PATH")
	if !strings.HasSuffix(path, "/") {
		path = path + "/"
	}

	if path != "" { // FIXME always true since / suffix is added to path
		prefix := os.Getenv("WASMHTTP_PATH")
		for strings.HasSuffix(prefix, "/") {
			prefix = strings.TrimSuffix(prefix, "/")
		}

		mux := http.NewServeMux()
		mux.Handle(path, http.StripPrefix(prefix, h))
		h = mux
	}

	cb := js.FuncOf(func(_ js.Value, args []js.Value) interface{} {
		jsReq := whutil.Request{args[0]}

		var resPromise = whutil.NewPromise(func(resolve whutil.PromiseResolve, reject whutil.PromiseReject) {
			go func() {
				defer func() {
					r := recover()
					if r != nil {
						if err, ok := r.(error); ok {
							reject(fmt.Sprintf("wasmhttp: panic: %+v\n", err))
						} else {
							reject(fmt.Sprintf("wasmhttp: panic: %v\n", r))
						}
					}
				}()

				req, err := jsReq.HTTPRequest()
				if err != nil {
					panic(err)
				}

				res := whutil.NewResponseWriter()

				h.ServeHTTP(res, req)

				resolve(res)
			}()
		})

		return resPromise
	})

	js.Global().Get("wasmhttp").Call("registerHandler", os.Getenv("WASMHTTP_HANDLER_ID"), cb)

	return cb.Release
}