package api

import (
	"encoding/json"
	"fmt"
	"io"
	"log"
	"net/http"

	"github.com/julienschmidt/httprouter"
)

type DispatchFunction func(httprouter.Params, []byte) (interface{}, error)

func apiHandler(f DispatchFunction) func(http.ResponseWriter, *http.Request, httprouter.Params) {
	return func(w http.ResponseWriter, r *http.Request, ps httprouter.Params) {
		if addr := r.Header.Get("X-Forwarded-For"); addr != "" {
			r.RemoteAddr = addr
		}
		log.Printf("%s \"%s %s\" [%s]\n", r.RemoteAddr, r.Method, r.URL.Path, r.UserAgent())

		// Read the body
		if r.ContentLength < 0 || r.ContentLength > 6553600 {
			http.Error(w, fmt.Sprintf("{errmsg:\"Request too large or request size unknown\"}"), http.StatusRequestEntityTooLarge)
			return
		}
		var body []byte
		if r.ContentLength > 0 {
			tmp := make([]byte, 1024)
			for {
				n, err := r.Body.Read(tmp)
				for j := 0; j < n; j++ {
					body = append(body, tmp[j])
				}
				if err != nil || n <= 0 {
					break
				}
			}
		}

		var ret interface{}
		var err error = nil

		ret, err = f(ps, body)

		// Format response
		resStatus := http.StatusOK
		if err != nil {
			ret = map[string]string{"errmsg": err.Error()}
			resStatus = http.StatusBadRequest
			log.Println(r.RemoteAddr, resStatus, err.Error())
		}

		if ret == nil {
			ret = map[string]string{"errmsg": "Page not found"}
			resStatus = http.StatusNotFound
		}

		if str, found := ret.(string); found {
			w.Header().Set("Content-Type", "application/json")
			w.WriteHeader(resStatus)
			io.WriteString(w, str)
		} else if bts, found := ret.([]byte); found {
			w.Header().Set("Content-Type", "application/octet-stream")
			w.Header().Set("Content-Disposition", "attachment")
			w.Header().Set("Content-Transfer-Encoding", "binary")
			w.WriteHeader(resStatus)
			w.Write(bts)
		} else if j, err := json.Marshal(ret); err != nil {
			w.Header().Set("Content-Type", "application/json")
			http.Error(w, fmt.Sprintf("{\"errmsg\":%q}", err), http.StatusInternalServerError)
		} else {
			w.Header().Set("Content-Type", "application/json")
			w.WriteHeader(resStatus)
			w.Write(j)
		}
	}
}

func notFound(ps httprouter.Params, _ []byte) (interface{}, error) {
	return nil, nil
}