refactor: move snapshot CSV export out of TUI (task 391)

1 files changed, 103 insertions, 0 deletions

diff --git a/internal/export/snapshot_csv.go b/internal/export/snapshot_csv.go
new file mode 100644
index 0000000..3983b85
--- /dev/null
+++ b/internal/export/snapshot_csv.go
@@ -0,0 +1,103 @@
+package export
+
+import (
+	"encoding/csv"
+	"fmt"
+	"os"
+	"time"
+
+	"ior/internal/statsengine"
+)
+
+// SnapshotCSV writes a dashboard snapshot to a timestamped CSV file.
+func SnapshotCSV(snap *statsengine.Snapshot) (string, error) {
+	filename := fmt.Sprintf("ior-snapshot-%s.csv", time.Now().Format("20060102-150405"))
+	f, err := os.Create(filename)
+	if err != nil {
+		return "", err
+	}
+	defer f.Close()
+
+	w := csv.NewWriter(f)
+
+	rows := [][]string{
+		{"section", "name", "value1", "value2", "value3"},
+		{"summary", "totals", fmt.Sprint(snapValue(snap, func(s *statsengine.Snapshot) uint64 { return s.TotalSyscalls })), fmt.Sprint(snapValue(snap, func(s *statsengine.Snapshot) uint64 { return s.TotalErrors })), fmt.Sprint(snapValue(snap, func(s *statsengine.Snapshot) uint64 { return s.TotalBytes }))},
+		{"summary", "rates_per_sec", fmt.Sprintf("%.2f", snapValueF(snap, func(s *statsengine.Snapshot) float64 { return s.SyscallRatePerSec })), fmt.Sprintf("%.2f", snapValueF(snap, func(s *statsengine.Snapshot) float64 { return s.ReadBytesPerSec })), fmt.Sprintf("%.2f", snapValueF(snap, func(s *statsengine.Snapshot) float64 { return s.WriteBytesPerSec }))},
+		{"summary", "latency_gap_mean_ns", fmt.Sprintf("%.2f", snapValueF(snap, func(s *statsengine.Snapshot) float64 { return s.LatencyMeanNs })), fmt.Sprintf("%.2f", snapValueF(snap, func(s *statsengine.Snapshot) float64 { return s.GapMeanNs })), ""},
+		{"summary", "trend", trendSummary(snap, func(s *statsengine.Snapshot) statsengine.Trend { return s.LatencyTrend }), trendSummary(snap, func(s *statsengine.Snapshot) statsengine.Trend { return s.GapTrend }), trendSummary(snap, func(s *statsengine.Snapshot) statsengine.Trend { return s.ThroughputTrend })},
+	}
+	for _, row := range rows {
+		if err := w.Write(row); err != nil {
+			return "", err
+		}
+	}
+
+	if snap != nil {
+		for _, s := range snap.Syscalls() {
+			if err := w.Write([]string{"syscall", s.Name, fmt.Sprint(s.Count), fmt.Sprintf("%.2f", s.RatePerSec), fmt.Sprint(s.Bytes)}); err != nil {
+				return "", err
+			}
+			if err := w.Write([]string{"syscall_latency_ns", s.Name, fmt.Sprintf("%.2f", s.LatencyMeanNs), fmt.Sprint(s.LatencyMinNs), fmt.Sprint(s.LatencyMaxNs)}); err != nil {
+				return "", err
+			}
+			if err := w.Write([]string{"syscall_percentiles_ns", s.Name, fmt.Sprint(s.LatencyP50Ns), fmt.Sprint(s.LatencyP95Ns), fmt.Sprint(s.LatencyP99Ns)}); err != nil {
+				return "", err
+			}
+		}
+		for _, r := range snap.Files() {
+			if err := w.Write([]string{"file", r.Path, fmt.Sprint(r.Accesses), fmt.Sprint(r.BytesRead), fmt.Sprint(r.BytesWritten)}); err != nil {
+				return "", err
+			}
+			if err := w.Write([]string{"file_latency_ns", r.Path, fmt.Sprintf("%.2f", r.AvgLatencyNs), fmt.Sprint(r.MaxLatencyNs), ""}); err != nil {
+				return "", err
+			}
+		}
+		for _, p := range snap.Processes() {
+			if err := w.Write([]string{"process", fmt.Sprint(p.PID), fmt.Sprint(p.Syscalls), fmt.Sprintf("%.2f", p.RatePerSec), fmt.Sprint(p.Bytes)}); err != nil {
+				return "", err
+			}
+			if err := w.Write([]string{"process_latency_ns", fmt.Sprint(p.PID), fmt.Sprintf("%.2f", p.AvgLatencyNs), "", ""}); err != nil {
+				return "", err
+			}
+		}
+		for _, b := range snap.LatencyHistogram.Buckets() {
+			if err := w.Write([]string{"latency_hist", b.Label, fmt.Sprint(b.Count), fmt.Sprint(b.LowerNs), fmt.Sprint(b.UpperNs)}); err != nil {
+				return "", err
+			}
+		}
+		for _, b := range snap.GapHistogram.Buckets() {
+			if err := w.Write([]string{"gap_hist", b.Label, fmt.Sprint(b.Count), fmt.Sprint(b.LowerNs), fmt.Sprint(b.UpperNs)}); err != nil {
+				return "", err
+			}
+		}
+	}
+
+	w.Flush()
+	if err := w.Error(); err != nil {
+		return "", err
+	}
+	return filename, nil
+}
+
+func snapValue(snap *statsengine.Snapshot, get func(*statsengine.Snapshot) uint64) uint64 {
+	if snap == nil {
+		return 0
+	}
+	return get(snap)
+}
+
+func snapValueF(snap *statsengine.Snapshot, get func(*statsengine.Snapshot) float64) float64 {
+	if snap == nil {
+		return 0
+	}
+	return get(snap)
+}
+
+func trendSummary(snap *statsengine.Snapshot, get func(*statsengine.Snapshot) statsengine.Trend) string {
+	if snap == nil {
+		return "stable:0.00"
+	}
+	trend := get(snap)
+	return fmt.Sprintf("%s:%.2f", trend.Direction, trend.DeltaPercent)
+}