package app

import (
	"fmt"
	"strings"
)

func transportMigrateSingBoxDNSConfigMap(root map[string]any) (bool, []string) {
	if root == nil {
		return false, nil
	}
	rawDNS, ok := root["dns"].(map[string]any)
	if !ok || rawDNS == nil {
		return false, nil
	}
	rawServers, ok := rawDNS["servers"].([]any)
	if !ok || len(rawServers) == 0 {
		return false, nil
	}

	changed := false
	warnings := make([]string, 0)
	migratedFakeIP := false
	fakeIPCfg, _ := rawDNS["fakeip"].(map[string]any)

	for i, raw := range rawServers {
		srv, ok := raw.(map[string]any)
		if !ok || srv == nil {
			continue
		}
		if strings.EqualFold(strings.TrimSpace(asString(srv["detour"])), "direct") {
			delete(srv, "detour")
			rawServers[i] = srv
			changed = true
		}

		if strings.TrimSpace(asString(srv["type"])) != "" {
			continue
		}
		addr := strings.TrimSpace(asString(srv["address"]))
		if addr == "" {
			continue
		}
		converted, warn, ok := convertLegacyDNSServer(addr)
		if !ok {
			warnings = append(warnings, fmt.Sprintf("dns.servers[%d]: %s", i, warn))
			continue
		}

		legacyAddrResolver := strings.TrimSpace(asString(srv["address_resolver"]))
		legacyAddrStrategy := strings.TrimSpace(asString(srv["address_strategy"]))
		legacyStrategy := strings.TrimSpace(asString(srv["strategy"]))
		legacySubnet := strings.TrimSpace(asString(srv["client_subnet"]))
		tag := strings.TrimSpace(asString(srv["tag"]))

		// Required new fields for typed DNS server.
		for k, v := range converted {
			srv[k] = v
		}
		delete(srv, "address")

		if legacyAddrResolver != "" && strings.TrimSpace(asString(srv["domain_resolver"])) == "" {
			srv["domain_resolver"] = legacyAddrResolver
		}
		delete(srv, "address_resolver")
		if legacyAddrStrategy != "" && strings.TrimSpace(asString(srv["domain_strategy"])) == "" {
			srv["domain_strategy"] = legacyAddrStrategy
		}
		delete(srv, "address_strategy")

		if legacyStrategy != "" {
			if strings.TrimSpace(asString(rawDNS["strategy"])) == "" {
				rawDNS["strategy"] = legacyStrategy
			} else if tag != "" {
				transportAppendDNSRule(rawDNS, map[string]any{
					"server":   tag,
					"strategy": legacyStrategy,
				})
			} else {
				warnings = append(warnings, fmt.Sprintf("dns.servers[%d]: strategy moved partially (missing tag)", i))
			}
			delete(srv, "strategy")
		}

		if legacySubnet != "" {
			if tag != "" {
				transportAppendDNSRule(rawDNS, map[string]any{
					"server":        tag,
					"client_subnet": legacySubnet,
				})
			} else if strings.TrimSpace(asString(rawDNS["client_subnet"])) == "" {
				rawDNS["client_subnet"] = legacySubnet
			} else {
				warnings = append(warnings, fmt.Sprintf("dns.servers[%d]: client_subnet moved partially (missing tag)", i))
			}
			delete(srv, "client_subnet")
		}

		if strings.EqualFold(asString(srv["type"]), "fakeip") && fakeIPCfg != nil {
			if _, ok := srv["inet4_range"]; !ok {
				if v, ok := fakeIPCfg["inet4_range"]; ok {
					srv["inet4_range"] = v
				}
			}
			if _, ok := srv["inet6_range"]; !ok {
				if v, ok := fakeIPCfg["inet6_range"]; ok {
					srv["inet6_range"] = v
				}
			}
			migratedFakeIP = true
		}

		rawServers[i] = srv
		changed = true
	}

	if changed {
		rawDNS["servers"] = rawServers
		if migratedFakeIP {
			delete(rawDNS, "fakeip")
		}
		root["dns"] = rawDNS
	}
	return changed, dedupeStrings(warnings)
}