package websvc

import (
	"encoding/json"
	"fmt"
	"net/http"
	"net/netip"
	"time"

	"github.com/AdguardTeam/AdGuardHome/internal/next/dnssvc"
)

// DNS Settings Handlers

// ReqPatchSettingsDNS describes the request to the PATCH /api/v1/settings/dns
// HTTP API.
type ReqPatchSettingsDNS struct {
	// TODO(a.garipov): Add more as we go.

	Addresses           []netip.AddrPort `json:"addresses"`
	BootstrapServers    []string         `json:"bootstrap_servers"`
	UpstreamServers     []string         `json:"upstream_servers"`
	DNS64Prefixes       []netip.Prefix   `json:"dns64_prefixes"`
	UpstreamTimeout     JSONDuration     `json:"upstream_timeout"`
	BootstrapPreferIPv6 bool             `json:"bootstrap_prefer_ipv6"`
	UseDNS64            bool             `json:"use_dns64"`
}

// HTTPAPIDNSSettings are the DNS settings as used by the HTTP API.  See the
// DnsSettings object in the OpenAPI specification.
type HTTPAPIDNSSettings struct {
	// TODO(a.garipov): Add more as we go.

	Addresses           []netip.AddrPort `json:"addresses"`
	BootstrapServers    []string         `json:"bootstrap_servers"`
	UpstreamServers     []string         `json:"upstream_servers"`
	DNS64Prefixes       []netip.Prefix   `json:"dns64_prefixes"`
	UpstreamTimeout     JSONDuration     `json:"upstream_timeout"`
	BootstrapPreferIPv6 bool             `json:"bootstrap_prefer_ipv6"`
	UseDNS64            bool             `json:"use_dns64"`
}

// handlePatchSettingsDNS is the handler for the PATCH /api/v1/settings/dns HTTP
// API.
func (svc *Service) handlePatchSettingsDNS(w http.ResponseWriter, r *http.Request) {
	req := &ReqPatchSettingsDNS{
		Addresses:        []netip.AddrPort{},
		BootstrapServers: []string{},
		UpstreamServers:  []string{},
	}

	// TODO(a.garipov): Validate nulls and proper JSON patch.

	err := json.NewDecoder(r.Body).Decode(&req)
	if err != nil {
		writeJSONErrorResponse(w, r, fmt.Errorf("decoding: %w", err))

		return
	}

	newConf := &dnssvc.Config{
		Addresses:           req.Addresses,
		BootstrapServers:    req.BootstrapServers,
		UpstreamServers:     req.UpstreamServers,
		DNS64Prefixes:       req.DNS64Prefixes,
		UpstreamTimeout:     time.Duration(req.UpstreamTimeout),
		BootstrapPreferIPv6: req.BootstrapPreferIPv6,
		UseDNS64:            req.UseDNS64,
	}

	ctx := r.Context()
	err = svc.confMgr.UpdateDNS(ctx, newConf)
	if err != nil {
		writeJSONErrorResponse(w, r, fmt.Errorf("updating: %w", err))

		return
	}

	newSvc := svc.confMgr.DNS()
	err = newSvc.Start()
	if err != nil {
		writeJSONErrorResponse(w, r, fmt.Errorf("starting new service: %w", err))

		return
	}

	writeJSONOKResponse(w, r, &HTTPAPIDNSSettings{
		Addresses:           newConf.Addresses,
		BootstrapServers:    newConf.BootstrapServers,
		UpstreamServers:     newConf.UpstreamServers,
		DNS64Prefixes:       newConf.DNS64Prefixes,
		UpstreamTimeout:     JSONDuration(newConf.UpstreamTimeout),
		BootstrapPreferIPv6: newConf.BootstrapPreferIPv6,
		UseDNS64:            newConf.UseDNS64,
	})
}