package http

import (
	"bytes"
	"encoding/json"
	"io"
	"mime"
	"net/http"
	"time"
)

const maxUpdateResultBody = 8 << 20

type resultHTTPClient interface {
	Do(*http.Request) (*http.Response, error)
}

type updateResultForwarder struct {
	targetURL string
	client    resultHTTPClient
}

// NewUpdateResultForwarder relays the original JSON body to CPONE without
// forwarding the caller's Authorization header or cookies.
func NewUpdateResultForwarder(targetURL string, client resultHTTPClient) http.Handler {
	if client == nil {
		client = &http.Client{Timeout: 30 * time.Second}
	}
	return updateResultForwarder{
		targetURL: targetURL,
		client:    client,
	}
}

func (h updateResultForwarder) ServeHTTP(w http.ResponseWriter, r *http.Request) {
	mediaType, _, err := mime.ParseMediaType(r.Header.Get("Content-Type"))
	if err != nil || mediaType != "application/json" {
		WriteJSON(w, http.StatusUnsupportedMediaType, Response{Success: false, Message: "Content-Type harus application/json"})
		return
	}
	body, err := io.ReadAll(io.LimitReader(r.Body, maxUpdateResultBody+1))
	if err != nil {
		WriteJSON(w, http.StatusBadRequest, Response{Success: false, Message: "Gagal membaca payload hasil pemeriksaan"})
		return
	}
	if len(body) > maxUpdateResultBody {
		WriteJSON(w, http.StatusRequestEntityTooLarge, Response{Success: false, Message: "Payload hasil pemeriksaan terlalu besar"})
		return
	}
	var payload map[string]json.RawMessage
	if err := json.Unmarshal(body, &payload); err != nil || payload == nil {
		WriteJSON(w, http.StatusBadRequest, Response{Success: false, Message: "Payload harus berupa object JSON"})
		return
	}
	upstreamRequest, err := http.NewRequestWithContext(r.Context(), http.MethodPost, h.targetURL, bytes.NewReader(body))
	if err != nil {
		WriteJSON(w, http.StatusBadGateway, Response{Success: false, Message: "URL tujuan CPONE tidak valid"})
		return
	}
	upstreamRequest.Header.Set("Content-Type", "application/json")
	upstreamRequest.Header.Set("Accept", "application/json")
	upstreamResponse, err := h.client.Do(upstreamRequest)
	if err != nil {
		WriteJSON(w, http.StatusBadGateway, Response{Success: false, Message: "Gagal menghubungi API hasil pemeriksaan CPONE"})
		return
	}
	defer upstreamResponse.Body.Close()
	if contentType := upstreamResponse.Header.Get("Content-Type"); contentType != "" {
		w.Header().Set("Content-Type", contentType)
	}
	w.WriteHeader(upstreamResponse.StatusCode)
	_, _ = io.Copy(w, upstreamResponse.Body)
}