package app

import (
	"fmt"
	"strings"
	"time"
)

func readCurrentRoutesTableLines() ([]string, error) {
	out, _, code, err := runCommandTimeout(5*time.Second, "ip", "-4", "route", "show", "table", routesTableName())
	if err != nil && code != 0 {
		return nil, err
	}
	lines := make([]string, 0, 32)
	for _, raw := range strings.Split(out, "\n") {
		ln := strings.TrimSpace(raw)
		if ln == "" {
			continue
		}
		lines = append(lines, ln)
	}
	return lines, nil
}

func detectIfaceFromRoutes(lines []string) string {
	for _, ln := range lines {
		fields := strings.Fields(ln)
		for i := 0; i+1 < len(fields); i++ {
			if fields[i] == "dev" {
				return strings.TrimSpace(fields[i+1])
			}
		}
	}
	return ""
}

func restoreRouteLine(line string) error {
	fields := strings.Fields(strings.TrimSpace(line))
	if len(fields) == 0 {
		return nil
	}
	args := []string{"-4", "route", "replace"}
	args = append(args, fields...)
	hasTable := false
	for i := 0; i+1 < len(fields); i++ {
		if fields[i] == "table" {
			hasTable = true
			break
		}
	}
	if !hasTable {
		args = append(args, "table", routesTableName())
	}
	_, _, code, err := runCommandTimeout(5*time.Second, "ip", args...)
	if err != nil || code != 0 {
		if err == nil {
			err = fmt.Errorf("exit code %d", code)
		}
		return err
	}
	return nil
}

func shouldIgnoreRestoreRouteError(line string, err error) bool {
	ln := strings.ToLower(strings.TrimSpace(line))
	if strings.Contains(ln, " linkdown") {
		return true
	}

	dev := routeLineDevice(ln)
	if dev != "" && !strings.HasPrefix(ln, "default ") && !ifaceExists(dev) {
		return true
	}

	msg := strings.ToLower(strings.TrimSpace(fmt.Sprintf("%v", err)))
	if strings.HasPrefix(ln, "default ") {
		return false
	}
	if strings.Contains(msg, "cannot find device") ||
		strings.Contains(msg, "no such device") ||
		strings.Contains(msg, "network is down") {
		return true
	}
	return false
}

func routeLineDevice(line string) string {
	fields := strings.Fields(strings.TrimSpace(line))
	for i := 0; i+1 < len(fields); i++ {
		if fields[i] == "dev" {
			return strings.TrimSpace(fields[i+1])
		}
	}
	return ""
}