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75 lines
1.8 KiB
75 lines
1.8 KiB
package main
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import (
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"context"
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"encoding/json"
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"log"
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"net/http"
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"github.com/julienschmidt/httprouter"
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)
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// type ContextKeyString is a type that is a string meant for use as the key in an https context value
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type ContextKeyString string
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type args struct {
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A int `json:"a"`
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B int `json:"b"`
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}
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type requestError struct {
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Err string `json:"error"`
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}
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func factorial(a int, ch chan int) {
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r := 1
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for f := 1; f <= a; f++ {
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r *= f
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}
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ch <- r
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}
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func postError(w http.ResponseWriter, r *http.Request, err string) {
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w.Header().Set("Content-Type", "application/json")
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w.WriteHeader(http.StatusBadRequest)
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json.NewEncoder(w).Encode(requestError{Err: err})
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}
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func middleware(f httprouter.Handle) httprouter.Handle {
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return func(w http.ResponseWriter, r *http.Request, p httprouter.Params) {
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var v args
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dec := json.NewDecoder(r.Body)
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dec.DisallowUnknownFields()
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err := dec.Decode(&v)
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if err != nil || v.A < 0 || v.B < 0 {
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postError(w, r, "Incorrect input")
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} else {
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ctx := r.Context()
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// using a new type definition to avoid compiler warnings
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ctx = context.WithValue(ctx, ContextKeyString("a"), v.A)
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ctx = context.WithValue(ctx, ContextKeyString("b"), v.B)
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r = r.WithContext(ctx)
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f(w, r, p)
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}
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}
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}
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func calculate(w http.ResponseWriter, r *http.Request, _ httprouter.Params) {
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var v args
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v.A = r.Context().Value(ContextKeyString("a")).(int)
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v.B = r.Context().Value(ContextKeyString("b")).(int)
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chanA := make(chan int)
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chanB := make(chan int)
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go factorial(v.A, chanA)
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go factorial(v.B, chanB)
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v.B = <-chanB
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v.A = <-chanA
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w.Header().Set("Content-Type", "application/json")
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json.NewEncoder(w).Encode(v)
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}
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func main() {
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router := httprouter.New()
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router.POST("/calculate", middleware(calculate))
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log.Fatal(http.ListenAndServe(":8989", router))
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}
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