package main

import (
	"fmt"
	"log"
	"net/http"
	"os"
	"path/filepath"
	"strings"
)

const maxAdminRequestBody = 8 << 20

func writeInternalError(w http.ResponseWriter, operation string, err error) {
	if err != nil {
		log.Printf("%s: %v", operation, err)
	}
	http.Error(w, "internal server error", http.StatusInternalServerError)
}

func writeBadGatewayError(w http.ResponseWriter, operation string, err error) {
	if err != nil {
		log.Printf("%s: %v", operation, err)
	}
	http.Error(w, "managed server request failed", http.StatusBadGateway)
}

// securePanelHandler applies baseline browser protections and a global request
// body ceiling. Endpoint-specific handlers may impose a smaller limit.
func securePanelHandler(next http.Handler) http.Handler {
	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		w.Header().Set("X-Content-Type-Options", "nosniff")
		w.Header().Set("X-Frame-Options", "DENY")
		w.Header().Set("Referrer-Policy", "no-referrer")
		w.Header().Set("Permissions-Policy", "camera=(), microphone=(), geolocation=(), payment=()")
		w.Header().Set("Cross-Origin-Opener-Policy", "same-origin")
		w.Header().Set("Content-Security-Policy", "default-src 'self'; base-uri 'none'; frame-ancestors 'none'; object-src 'none'; form-action 'self'; img-src 'self' data:; connect-src 'self'; style-src 'self' 'unsafe-inline'; script-src 'self' 'unsafe-inline'")
		if strings.HasPrefix(r.URL.Path, "/api/") || r.URL.Path == "/" || r.URL.Path == "/index.html" {
			w.Header().Set("Cache-Control", "no-store")
		}
		if r.Body != nil && r.Method != http.MethodGet && r.Method != http.MethodHead {
			r.Body = http.MaxBytesReader(w, r.Body, maxAdminRequestBody)
		}
		next.ServeHTTP(w, r)
	})
}

// writeFileAtomic replaces a sensitive configuration file without leaving a
// partially written file behind after a crash or interrupted request.
func writeFileAtomic(path string, data []byte, mode os.FileMode) error {
	dir := filepath.Dir(path)
	tmp, err := os.CreateTemp(dir, ".dragoncore-*.tmp")
	if err != nil {
		return err
	}
	tmpName := tmp.Name()
	defer os.Remove(tmpName)
	if err := tmp.Chmod(mode); err != nil {
		tmp.Close()
		return err
	}
	if _, err := tmp.Write(data); err != nil {
		tmp.Close()
		return err
	}
	if err := tmp.Sync(); err != nil {
		tmp.Close()
		return err
	}
	if err := tmp.Close(); err != nil {
		return err
	}
	if err := os.Rename(tmpName, path); err != nil {
		return fmt.Errorf("replace %s: %w", path, err)
	}
	return nil
}