// backend/server_folders_proxy.go

package main

import (
	"bytes"
	"context"
	"fmt"
	"io"
	"net/http"
	"net/url"
	"strings"
	"time"
)

type serverFoldersAgentConfig struct {
	MilestoneHost string
	Scheme        string
	Port          string
	Token         string
}

func (s *Server) handleProxyListServerFolders(w http.ResponseWriter, r *http.Request) {
	s.proxyServerFoldersRequest(w, r, http.MethodGet)
}

func (s *Server) handleProxyCreateServerFolder(w http.ResponseWriter, r *http.Request) {
	s.proxyServerFoldersRequest(w, r, http.MethodPost)
}

func (s *Server) proxyServerFoldersRequest(w http.ResponseWriter, r *http.Request, method string) {
	config, err := s.getServerFoldersAgentConfig(r.Context())
	if err != nil {
		writeError(w, http.StatusBadGateway, "Server-Folders-Agent-Konfiguration konnte nicht geladen werden")
		return
	}

	targetURL, err := serverFoldersAgentURL(config, forwardedServerFoldersQuery(r.URL.Query()))
	if err != nil {
		writeError(w, http.StatusBadGateway, err.Error())
		return
	}

	var body []byte
	if method == http.MethodPost {
		body, err = io.ReadAll(io.LimitReader(r.Body, 1<<20))
		if err != nil {
			writeError(w, http.StatusBadRequest, "Request konnte nicht gelesen werden")
			return
		}
	}

	request, err := http.NewRequestWithContext(
		r.Context(),
		method,
		targetURL,
		bytes.NewReader(body),
	)
	if err != nil {
		writeError(w, http.StatusBadGateway, "Proxy-Request konnte nicht erstellt werden")
		return
	}

	request.Header.Set("Accept", "application/json")

	if method == http.MethodPost {
		request.Header.Set("Content-Type", "application/json")
	}

	if config.Token != "" {
		request.Header.Set("X-Server-Folders-Token", config.Token)
	}

	client := &http.Client{
		Timeout: 20 * time.Second,
	}

	response, err := client.Do(request)
	if err != nil {
		writeError(w, http.StatusBadGateway, "Server-Folders-Agent ist nicht erreichbar")
		return
	}
	defer response.Body.Close()

	responseBody, err := io.ReadAll(io.LimitReader(response.Body, 4<<20))
	if err != nil {
		writeError(w, http.StatusBadGateway, "Antwort vom Server-Folders-Agent konnte nicht gelesen werden")
		return
	}

	contentType := response.Header.Get("Content-Type")
	if strings.TrimSpace(contentType) == "" {
		contentType = "application/json"
	}

	w.Header().Set("Content-Type", contentType)
	w.WriteHeader(response.StatusCode)
	_, _ = w.Write(responseBody)
}

func (s *Server) getServerFoldersAgentConfig(ctx context.Context) (serverFoldersAgentConfig, error) {
	var config serverFoldersAgentConfig

	err := s.db.QueryRow(
		ctx,
		`
		SELECT
			host,
			COALESCE(server_folders_agent_scheme, 'http'),
			COALESCE(server_folders_agent_port, '8099'),
			COALESCE(pgp_sym_decrypt(server_folders_agent_token_encrypted, $1), '')
		FROM milestone_settings
		WHERE id = 1
		LIMIT 1
		`,
		s.milestoneEncryptionKey(),
	).Scan(
		&config.MilestoneHost,
		&config.Scheme,
		&config.Port,
		&config.Token,
	)
	if err != nil {
		return config, err
	}

	config.Scheme = normalizeServerFoldersAgentScheme(config.Scheme)
	if config.Scheme == "" {
		config.Scheme = "http"
	}

	config.Port = normalizeServerFoldersAgentPort(config.Port)
	if config.Port == "" {
		config.Port = "8099"
	}

	config.MilestoneHost = strings.TrimSpace(config.MilestoneHost)
	config.Token = strings.TrimSpace(config.Token)

	return config, nil
}

func serverFoldersAgentURL(config serverFoldersAgentConfig, rawQuery string) (string, error) {
	if strings.TrimSpace(config.MilestoneHost) == "" {
		return "", fmt.Errorf("Milestone Host fehlt")
	}

	normalizedMilestoneHost := strings.TrimSpace(config.MilestoneHost)
	if !strings.Contains(normalizedMilestoneHost, "://") {
		normalizedMilestoneHost = "http://" + normalizedMilestoneHost
	}

	parsedMilestoneURL, err := url.Parse(normalizedMilestoneHost)
	if err != nil || parsedMilestoneURL.Hostname() == "" {
		return "", fmt.Errorf("Milestone Host ist ungültig")
	}

	agentURL := url.URL{
		Scheme:   config.Scheme,
		Host:     parsedMilestoneURL.Hostname() + ":" + config.Port,
		Path:     "/server-folders",
		RawQuery: rawQuery,
	}

	return agentURL.String(), nil
}

func forwardedServerFoldersQuery(values url.Values) string {
	// rootType=storage/archive wird bewusst weitergeleitet.
	// Nur Verbindungs-/Auth-Parameter werden entfernt.
	nextValues := url.Values{}

	for key, value := range values {
		switch strings.ToLower(strings.TrimSpace(key)) {
		case "schema", "scheme", "agentschema", "agentscheme", "port", "agentport", "token", "agenttoken":
			continue
		default:
			for _, item := range value {
				nextValues.Add(key, item)
			}
		}
	}

	return nextValues.Encode()
}

func normalizeServerFoldersAgentScheme(value string) string {
	value = strings.TrimSpace(strings.ToLower(value))

	switch value {
	case "", "http", "https":
		return value
	default:
		return ""
	}
}

func normalizeServerFoldersAgentPort(value string) string {
	value = strings.TrimSpace(value)
	value = strings.TrimPrefix(value, ":")

	if value == "" {
		return ""
	}

	for _, char := range value {
		if char < '0' || char > '9' {
			return ""
		}
	}

	return value
}