package auth

import (
	"strings"

	"github.com/mileusna/useragent"
)

const (
	unknownDeviceSystem  = "unknown"
	unknownDeviceBrowser = "unknown"
)

func deviceSessionFromMetadata(metadata RequestMetadata) DeviceSession {
	parsed := useragent.Parse(strings.TrimSpace(metadata.UserAgent))
	deviceType := "desktop"
	client := "PC-WEB"
	if clientHintMobile(metadata.Mobile) || parsed.Mobile || parsed.Tablet {
		deviceType = "mobile"
		client = "MOBILE-WEB"
	}

	system := cleanDeviceLabel(parsed.OS, unknownDeviceSystem)
	if platform := cleanClientHint(metadata.Platform); platform != "" {
		system = platform
	}
	browser := cleanDeviceLabel(parsed.Name, unknownDeviceBrowser)
	if parsed.Version != "" && browser != unknownDeviceBrowser {
		browser += " " + majorVersion(parsed.Version)
	}

	return DeviceSession{
		DeviceType: deviceType,
		System:     system,
		Browser:    browser,
		Client:     client,
		UserAgent:  limitMetadata(strings.TrimSpace(metadata.UserAgent), 1024),
	}
}

func clientHintMobile(value string) bool {
	value = strings.Trim(strings.TrimSpace(value), `"`)
	return value == "1" || strings.EqualFold(value, "true") || strings.EqualFold(value, "?1")
}

func cleanClientHint(value string) string {
	value = strings.Trim(strings.TrimSpace(value), `"`)
	if value == "" || strings.EqualFold(value, "unknown") {
		return ""
	}
	return limitMetadata(value, 80)
}

func cleanDeviceLabel(value string, fallback string) string {
	value = strings.TrimSpace(value)
	if value == "" || strings.EqualFold(value, "unknown") {
		return fallback
	}
	return limitMetadata(value, 80)
}

func majorVersion(version string) string {
	version = strings.TrimSpace(version)
	if index := strings.IndexByte(version, '.'); index >= 0 {
		version = version[:index]
	}
	return limitMetadata(version, 16)
}

func limitMetadata(value string, maxRunes int) string {
	if maxRunes <= 0 {
		return ""
	}
	runes := []rune(value)
	if len(runes) <= maxRunes {
		return value
	}
	return string(runes[:maxRunes])
}