package lwb

import (
	"fmt"
	"runtime"
)

// getSystemInfo returns a string describing the OS and architecture
// in a style similar to what many browsers use in their UA string.
func getSystemInfo() string {
	os := runtime.GOOS
	arch := runtime.GOARCH

	switch os {
	case "windows":
		// We assume Windows NT 10.0 for simplicity.
		if arch == "amd64" {
			return "Windows NT 10.0; Win64; x64"
		} else if arch == "386" {
			return "Windows NT 10.0"
		} else {
			return "Windows NT 10.0; " + arch
		}
	case "linux":
		// Many Linux browsers use "X11" in the UA string.
		if arch == "amd64" {
			return "X11; Linux x86_64"
		} else if arch == "386" {
			return "X11; Linux i686"
		} else {
			return "X11; Linux " + arch
		}
	case "darwin":
		// For macOS we have to invent a version number since Go doesn't provide one.
		// Here we assume a recent macOS version.
		if arch == "amd64" {
			return "Macintosh; Intel Mac OS X 10_15_7"
		} else if arch == "arm64" {
			return "Macintosh; ARM Mac OS X 11_0"
		} else {
			return "Macintosh; Mac OS X"
		}
	default:
		// For other operating systems, just output the raw GOOS and GOARCH.
		return fmt.Sprintf("%s; %s", os, arch)
	}
}

// BuildFirefoxUserAgent builds a Firefox UA string using the given version.
// Example output on Windows:
// "Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:135.0) Gecko/20100101 Firefox/135.0"
func BuildFirefoxUserAgent(firefoxVersion string) string {
	systemInfo := getSystemInfo()
	return fmt.Sprintf(
		"Mozilla/5.0 (%s; rv:%s) Gecko/20100101 Firefox/%s",
		systemInfo,
		firefoxVersion,
		firefoxVersion,
	)
}

// BuildChromeUserAgent builds a Chrome UA string using the given version.
// Example output on Windows:
// "Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/133.0.6943.53 Safari/537.36"
func BuildChromeUserAgent(chromeVersion string) string {
	systemInfo := getSystemInfo()
	return fmt.Sprintf(
		"Mozilla/5.0 (%s) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/%s Safari/537.36",
		systemInfo,
		chromeVersion,
	)
}