package app

import (
	"os"
	"strings"
)

func smartDNSRuntimeEnabledFromConfig() (bool, error) {
	data, err := os.ReadFile(smartdnsMainConfig)
	if err != nil {
		return false, err
	}
	for _, raw := range strings.Split(string(data), "\n") {
		trimmed := strings.TrimSpace(raw)
		if trimmed == "" || strings.HasPrefix(trimmed, "#") {
			continue
		}
		if strings.Contains(trimmed, "nftset") &&
			strings.Contains(trimmed, "domain-set:agvpn_wild") &&
			strings.Contains(trimmed, "agvpn_dyn4") {
			return true, nil
		}
	}
	return false, nil
}

func normalizeSmartDNSMainConfig(content string, enabled bool) string {
	normalized := strings.ReplaceAll(content, "\r\n", "\n")
	lines := strings.Split(normalized, "\n")
	out := make([]string, 0, len(lines)+4)

	seenDomain := false
	seenNftset := false

	isDomainLine := func(raw string) bool {
		t := strings.TrimSpace(raw)
		if strings.HasPrefix(t, "#") {
			t = strings.TrimSpace(strings.TrimPrefix(t, "#"))
		}
		return strings.HasPrefix(t, "domain-set ") &&
			strings.Contains(t, "-name agvpn_wild") &&
			strings.Contains(t, "/etc/selective-vpn/smartdns.conf")
	}
	isNftsetLine := func(raw string) bool {
		t := strings.TrimSpace(raw)
		if strings.HasPrefix(t, "#") {
			t = strings.TrimSpace(strings.TrimPrefix(t, "#"))
		}
		return strings.HasPrefix(t, "nftset ") &&
			strings.Contains(t, "domain-set:agvpn_wild") &&
			strings.Contains(t, "agvpn_dyn4")
	}

	for _, raw := range lines {
		switch {
		case isDomainLine(raw):
			if !seenDomain {
				if enabled {
					out = append(out, smartdnsRuntimeDomainSetLine)
				} else {
					out = append(out, "# "+smartdnsRuntimeDomainSetLine)
				}
				seenDomain = true
			}
		case isNftsetLine(raw):
			if !seenNftset {
				if enabled {
					out = append(out, smartdnsRuntimeNftsetLine)
				} else {
					out = append(out, "# "+smartdnsRuntimeNftsetLine)
				}
				seenNftset = true
			}
		default:
			out = append(out, raw)
		}
	}

	if enabled && (!seenDomain || !seenNftset) {
		if len(out) > 0 && strings.TrimSpace(out[len(out)-1]) != "" {
			out = append(out, "")
		}
		if !seenDomain {
			out = append(out, smartdnsRuntimeDomainSetLine)
		}
		if !seenNftset {
			out = append(out, smartdnsRuntimeNftsetLine)
		}
	}

	rendered := strings.Join(out, "\n")
	if !strings.HasSuffix(rendered, "\n") {
		rendered += "\n"
	}
	return rendered
}

func applySmartDNSRuntimeConfig(enabled bool) (bool, error) {
	data, err := os.ReadFile(smartdnsMainConfig)
	if err != nil {
		return false, err
	}
	current := strings.ReplaceAll(string(data), "\r\n", "\n")
	next := normalizeSmartDNSMainConfig(current, enabled)
	if next == current {
		return false, nil
	}
	tmp := smartdnsMainConfig + ".tmp"
	if err := os.WriteFile(tmp, []byte(next), 0o644); err != nil {
		return false, err
	}
	if err := os.Rename(tmp, smartdnsMainConfig); err != nil {
		return false, err
	}
	return true, nil
}