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// Package apiutil contains utilities which are useful for implementing api
// endpoints.
package apiutil
import (
"context"
"crypto/rand"
"encoding/hex"
"encoding/json"
"errors"
"fmt"
"net/http"
"strconv"
"strings"
"github.com/mediocregopher/mediocre-go-lib/v2/mlog"
)
type loggerCtxKey int
// SetRequestLogger sets the given Logger onto the given Request's Context,
// returning a copy.
func SetRequestLogger(r *http.Request, logger *mlog.Logger) *http.Request {
ctx := r.Context()
ctx = context.WithValue(ctx, loggerCtxKey(0), logger)
return r.WithContext(ctx)
}
// GetRequestLogger returns the Logger which was set by SetRequestLogger onto
// this Request, or nil.
func GetRequestLogger(r *http.Request) *mlog.Logger {
ctx := r.Context()
logger, _ := ctx.Value(loggerCtxKey(0)).(*mlog.Logger)
if logger == nil {
logger = mlog.Null
}
return logger
}
// JSONResult writes the JSON encoding of the given value as the response body.
func JSONResult(rw http.ResponseWriter, r *http.Request, v interface{}) {
b, err := json.Marshal(v)
if err != nil {
InternalServerError(rw, r, err)
return
}
b = append(b, '\n')
rw.Header().Set("Content-Type", "application/json")
rw.Write(b)
}
// BadRequest writes a 400 status and a JSON encoded error struct containing the
// given error as the response body.
func BadRequest(rw http.ResponseWriter, r *http.Request, err error) {
GetRequestLogger(r).Warn(r.Context(), "bad request", err)
rw.WriteHeader(400)
JSONResult(rw, r, struct {
Error string `json:"error"`
}{
Error: err.Error(),
})
}
// InternalServerError writes a 500 status and a JSON encoded error struct
// containing a generic error as the response body (though it will log the given
// one).
func InternalServerError(rw http.ResponseWriter, r *http.Request, err error) {
GetRequestLogger(r).Error(r.Context(), "internal server error", err)
rw.WriteHeader(500)
JSONResult(rw, r, struct {
Error string `json:"error"`
}{
Error: "internal server error",
})
}
// StrToInt parses the given string as an integer, or returns the given default
// integer if the string is empty.
func StrToInt(str string, defaultVal int) (int, error) {
if str == "" {
return defaultVal, nil
}
return strconv.Atoi(str)
}
// GetCookie returns the namd cookie's value, or the given default value if the
// cookie is not set.
//
// This will only return an error if there was an unexpected error parsing the
// Request's cookies.
func GetCookie(r *http.Request, cookieName, defaultVal string) (string, error) {
c, err := r.Cookie(cookieName)
if errors.Is(err, http.ErrNoCookie) {
return defaultVal, nil
} else if err != nil {
return "", fmt.Errorf("reading cookie %q: %w", cookieName, err)
}
return c.Value, nil
}
// RandStr returns a human-readable random string with the given number of bytes
// of randomness.
func RandStr(numBytes int) string {
b := make([]byte, numBytes)
if _, err := rand.Read(b); err != nil {
panic(err)
}
return hex.EncodeToString(b)
}
// MethodMux will take the request method (GET, POST, etc...) and handle the
// request using the corresponding Handler in the given map.
//
// If no Handler is defined for a method then a 405 Method Not Allowed error is
// returned.
//
// If the method "*" is defined then all methods not defined will be directed to
// that handler, and 405 Method Not Allowed is never returned.
//
// If the GET argument 'method' is present then the ToUpper of that is taken to
// be the name of the method.
func MethodMux(handlers map[string]http.Handler) http.Handler {
return http.HandlerFunc(func(rw http.ResponseWriter, r *http.Request) {
method := strings.ToUpper(r.Method)
formMethod := strings.ToUpper(r.FormValue("method"))
if formMethod != "" {
method = formMethod
}
if handler, ok := handlers[method]; ok {
handler.ServeHTTP(rw, r)
return
}
if handler, ok := handlers["*"]; ok {
handler.ServeHTTP(rw, r)
return
}
http.Error(rw, "Method not allowed", http.StatusMethodNotAllowed)
})
}
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