package dnscfg

import "strings"

type Upstreams struct {
	Default1 string
	Default2 string
	Meta1    string
	Meta2    string
}

type UpstreamPoolItem struct {
	Addr    string
	Enabled bool
}

func NormalizeUpstreamPoolItems(items []UpstreamPoolItem, normalizeUpstream func(raw string, defaultPort string) string) []UpstreamPoolItem {
	if len(items) == 0 {
		return nil
	}
	seen := map[string]struct{}{}
	out := make([]UpstreamPoolItem, 0, len(items))
	for _, item := range items {
		addr := strings.TrimSpace(item.Addr)
		if normalizeUpstream != nil {
			addr = normalizeUpstream(addr, "53")
		}
		if addr == "" {
			continue
		}
		if _, ok := seen[addr]; ok {
			continue
		}
		seen[addr] = struct{}{}
		out = append(out, UpstreamPoolItem{
			Addr:    addr,
			Enabled: item.Enabled,
		})
	}
	return out
}

func UpstreamPoolFromLegacy(cfg Upstreams, normalizeUpstream func(raw string, defaultPort string) string) []UpstreamPoolItem {
	out := []UpstreamPoolItem{
		{Addr: cfg.Default1, Enabled: true},
		{Addr: cfg.Default2, Enabled: true},
		{Addr: cfg.Meta1, Enabled: true},
		{Addr: cfg.Meta2, Enabled: true},
	}
	return NormalizeUpstreamPoolItems(out, normalizeUpstream)
}

func UpstreamPoolToLegacy(items []UpstreamPoolItem, defaults Upstreams, normalizeUpstream func(raw string, defaultPort string) string) Upstreams {
	items = NormalizeUpstreamPoolItems(items, normalizeUpstream)
	out := defaults
	enabled := make([]string, 0, len(items))
	for _, item := range items {
		if !item.Enabled {
			continue
		}
		addr := strings.TrimSpace(item.Addr)
		if normalizeUpstream != nil {
			addr = normalizeUpstream(addr, "53")
		}
		if addr != "" {
			enabled = append(enabled, addr)
		}
	}
	if len(enabled) > 0 {
		out.Default1 = enabled[0]
	}
	if len(enabled) > 1 {
		out.Default2 = enabled[1]
	}
	if len(enabled) > 2 {
		out.Meta1 = enabled[2]
	}
	if len(enabled) > 3 {
		out.Meta2 = enabled[3]
	}
	return out
}

func EnabledPool(items []UpstreamPoolItem, normalizeUpstream func(raw string, defaultPort string) string) []string {
	items = NormalizeUpstreamPoolItems(items, normalizeUpstream)
	out := make([]string, 0, len(items))
	for _, item := range items {
		if !item.Enabled {
			continue
		}
		addr := strings.TrimSpace(item.Addr)
		if normalizeUpstream != nil {
			addr = normalizeUpstream(addr, "53")
		}
		if addr != "" {
			out = append(out, addr)
		}
	}
	return out
}