package httpapi

import (
	"encoding/json"
	"net/http"
	"strings"
	"time"
)

const (
	reasonMalformedRequest = "MALFORMED_REQUEST"
	reasonMethodNotAllowed = "METHOD_NOT_ALLOWED"
	reasonForbidden        = "FORBIDDEN"
	reasonInternal         = "INTERNAL"
)

type apiError struct {
	Code       int            `json:"code"`
	Reason     string         `json:"reason"`
	Message    string         `json:"message"`
	Details    map[string]any `json:"details,omitempty"`
	RequestID  string         `json:"request_id,omitempty"`
	ServerTime string         `json:"server_time"`
}

func writeSuccess(w http.ResponseWriter, r *http.Request, data any) {
	writeJSON(w, r, http.StatusOK, map[string]any{
		"code": 0, "data": data, "request_id": requestID(r),
		"server_time": time.Now().UTC().Format(time.RFC3339Nano),
	})
}

func writeError(w http.ResponseWriter, r *http.Request, status, code int, reason, message string, details map[string]any) {
	writeJSON(w, r, status, apiError{Code: code, Reason: reason, Message: message, Details: details,
		RequestID: requestID(r), ServerTime: time.Now().UTC().Format(time.RFC3339Nano)})
}

func writeJSON(w http.ResponseWriter, r *http.Request, status int, value any) {
	w.Header().Set("Content-Type", "application/json; charset=utf-8")
	if requestID := requestID(r); requestID != "" {
		w.Header().Set("X-Request-ID", requestID)
	}
	w.WriteHeader(status)
	_ = json.NewEncoder(w).Encode(value)
}

func requestID(r *http.Request) string {
	return r.Header.Get("X-Request-ID")
}

func decodeBody(w http.ResponseWriter, r *http.Request, dst any) bool {
	defer r.Body.Close()
	decoder := json.NewDecoder(r.Body)
	decoder.DisallowUnknownFields()
	if err := decoder.Decode(dst); err != nil {
		writeError(w, r, http.StatusBadRequest, 30000, reasonMalformedRequest, "malformed request", nil)
		return false
	}
	return true
}

func methodNotAllowed(w http.ResponseWriter, r *http.Request, allowed ...string) {
	if len(allowed) == 0 {
		allowed = []string{http.MethodPost}
	}
	w.Header().Set("Allow", strings.Join(allowed, ", "))
	writeError(w, r, http.StatusMethodNotAllowed, 30005, reasonMethodNotAllowed, "method not allowed", nil)
}