feat: implement output formatting and display (HAN-383)

Add text and JSON formatters with real-time progress via traverser hooks,
summary statistics, and CLI integration for --show-* and --json flags.

Co-authored-by: multica-agent <github@multica.ai>

internal/output/json.go

@@ -0,0 +1,191 @@
+package output
+
+import (
+	"encoding/json"
+	"io"
+
+	"github.com/hits/ExploreDNS/internal/dns"
+	"github.com/hits/ExploreDNS/internal/traverse"
+)
+
+type jsonFormatter struct {
+	cfg     *Config
+	w       io.Writer
+	payload jsonDocument
+}
+
+type jsonDocument struct {
+	Domain    string              `json:"domain"`
+	QueryType string              `json:"query_type"`
+	Progress  []jsonProgressEvent `json:"progress,omitempty"`
+	Resolves  []jsonProgressEvent `json:"resolves,omitempty"`
+	Results   []jsonResult        `json:"results,omitempty"`
+	Servers   []jsonServer        `json:"servers,omitempty"`
+	Summary   jsonSummary         `json:"summary,omitempty"`
+}
+
+type jsonProgressEvent struct {
+	Stage     string `json:"stage"`
+	Depth     int    `json:"depth"`
+	Name      string `json:"name"`
+	QType     string `json:"qtype"`
+	Server    string `json:"server,omitempty"`
+	Bailiwick string `json:"bailiwick,omitempty"`
+	Resolving bool   `json:"resolving,omitempty"`
+}
+
+type jsonResult struct {
+	Depth        int      `json:"depth"`
+	Probability  float64  `json:"probability"`
+	ResponseType string   `json:"response_type"`
+	Server       string   `json:"server,omitempty"`
+	Answers      []string `json:"answers,omitempty"`
+	CNAMEChain   []string `json:"cname_chain,omitempty"`
+}
+
+type jsonServer struct {
+	Name string   `json:"name"`
+	IPs  []string `json:"ips"`
+}
+
+type jsonSummary struct {
+	ByType  map[string]float64 `json:"by_type,omitempty"`
+	Answers []jsonAnswerStat   `json:"answers,omitempty"`
+}
+
+type jsonAnswerStat struct {
+	RData       string  `json:"rdata"`
+	Probability float64 `json:"probability"`
+	Records     []string `json:"records,omitempty"`
+}
+
+func newJSONFormatter(cfg *Config, w io.Writer) *jsonFormatter {
+	return &jsonFormatter{
+		cfg: cfg,
+		w:   w,
+		payload: jsonDocument{
+			Domain:    cfg.Domain,
+			QueryType: cfg.QueryType,
+		},
+	}
+}
+
+func (f *jsonFormatter) WriteProgress(event traverse.TraversalEvent) error {
+	if !f.cfg.ShowProgress {
+		return nil
+	}
+	f.payload.Progress = append(f.payload.Progress, f.eventToJSON(event))
+	return nil
+}
+
+func (f *jsonFormatter) WriteResolve(event traverse.TraversalEvent) error {
+	if !f.cfg.ShowResolves {
+		return nil
+	}
+	f.payload.Resolves = append(f.payload.Resolves, f.eventToJSON(event))
+	return nil
+}
+
+func (f *jsonFormatter) WriteResult(result traverse.TraversalResult) error {
+	if !f.cfg.ShowAllStats {
+		return nil
+	}
+	f.payload.Results = append(f.payload.Results, f.resultToJSON(result))
+	return nil
+}
+
+func (f *jsonFormatter) WriteSummary(results []traverse.TraversalResult) error {
+	if f.cfg.ShowResults {
+		for _, result := range terminalResults(results) {
+			f.payload.Results = append(f.payload.Results, f.resultToJSON(result))
+		}
+	}
+
+	if f.cfg.ShowServers {
+		servers := collectServers(results)
+		for name, ips := range servers {
+			f.payload.Servers = append(f.payload.Servers, jsonServer{
+				Name: name,
+				IPs:  ips,
+			})
+		}
+	}
+
+	if f.cfg.ShowSummaryResults {
+		stats := ComputeSummary(results)
+		if stats != nil {
+			f.payload.Summary = jsonSummary{
+				ByType: stats.ByType,
+			}
+			for _, answer := range stats.Answers {
+				f.payload.Summary.Answers = append(f.payload.Summary.Answers, jsonAnswerStat{
+					RData:       answer.RData,
+					Probability: answer.Prob,
+					Records:     answer.RRs,
+				})
+			}
+		}
+	}
+
+	return nil
+}
+
+func (f *jsonFormatter) Flush() error {
+	enc := json.NewEncoder(f.w)
+	enc.SetIndent("", "  ")
+	return enc.Encode(f.payload)
+}
+
+func (f *jsonFormatter) eventToJSON(event traverse.TraversalEvent) jsonProgressEvent {
+	ref := event.Result.Referral
+	if ref == nil {
+		return jsonProgressEvent{}
+	}
+
+	item := jsonProgressEvent{
+		Stage:     stageName(event.Stage),
+		Depth:     ref.Depth,
+		Name:      trimDomain(ref.Name),
+		QType:     dns.QNameType(ref.Qtype),
+		Bailiwick: trimDomain(ref.Bailiwick),
+		Resolving: !ref.HasAddresses(),
+	}
+	if event.Result.Response != nil && event.Result.Response.Server != nil {
+		item.Server = event.Result.Response.Server.String()
+	} else {
+		item.Server = referralServerLabel(ref, event.Result.Response)
+	}
+	return item
+}
+
+func (f *jsonFormatter) resultToJSON(result traverse.TraversalResult) jsonResult {
+	item := jsonResult{}
+	if result.Referral != nil {
+		item.Depth = result.Referral.Depth
+		item.Probability = result.Referral.Prob
+	}
+	if result.Response != nil {
+		item.ResponseType = result.Response.Type.String()
+		if result.Response.Server != nil {
+			item.Server = result.Response.Server.String()
+		}
+		if result.Response.Decoded != nil {
+			for _, rr := range result.Response.Decoded.Answers {
+				item.Answers = append(item.Answers, dns.FormatRecord(rr))
+			}
+			item.CNAMEChain = append(item.CNAMEChain, result.Response.Decoded.CNAMEChain...)
+		}
+	}
+	return item
+}
+
+func stageName(stage traverse.EventStage) string {
+	switch stage {
+	case traverse.EventStart:
+		return "start"
+	case traverse.EventComplete:
+		return "complete"
+	default:
+		return "unknown"
+	}
+}