Push the rest

backend/analytics/internal/export/xlsx.go

@@ -0,0 +1,106 @@
+package export
+
+import (
+	"context"
+	"fmt"
+	"sort"
+
+	"github.com/xuri/excelize/v2"
+	"go.opentelemetry.io/otel"
+	"go.opentelemetry.io/otel/attribute"
+	"go.opentelemetry.io/otel/metric"
+	"go.opentelemetry.io/otel/trace"
+)
+
+var (
+	exportTracer = otel.Tracer("otel-bi.export")
+	exportMeter  = otel.Meter("otel-bi.export")
+
+	exportRowsTotal, _ = exportMeter.Int64Counter(
+		"export.rows_total",
+		metric.WithDescription("Total rows exported to XLSX"),
+	)
+	exportSizeBytes, _ = exportMeter.Int64Histogram(
+		"export.file_size_bytes",
+		metric.WithDescription("XLSX file size in bytes"),
+		metric.WithUnit("By"),
+	)
+)
+
+type Column struct {
+	Key   string
+	Label string
+}
+
+// ToXLSXBytes writes rows to a single-sheet Excel workbook using the given
+// column spec (controls header labels and order) and returns the raw bytes.
+func ToXLSXBytes(ctx context.Context, sheetName string, cols []Column, rows []map[string]any) ([]byte, error) {
+	ctx, span := exportTracer.Start(ctx, "export.xlsx",
+		trace.WithAttributes(attribute.String("sheet_name", sheetName)),
+	)
+	defer span.End()
+
+	f := excelize.NewFile()
+	defer f.Close()
+
+	sheet := f.GetSheetName(0)
+	if err := f.SetSheetName(sheet, sheetName); err != nil {
+		return nil, err
+	}
+
+	// Header row
+	for col, c := range cols {
+		cell, _ := excelize.CoordinatesToCellName(col+1, 1)
+		if err := f.SetCellValue(sheetName, cell, c.Label); err != nil {
+			return nil, err
+		}
+	}
+
+	// Data rows
+	for rowIdx, row := range rows {
+		for colIdx, c := range cols {
+			cell, _ := excelize.CoordinatesToCellName(colIdx+1, rowIdx+2)
+			_ = f.SetCellValue(sheetName, cell, fmtCell(row[c.Key]))
+		}
+	}
+
+	buf, err := f.WriteToBuffer()
+	if err != nil {
+		return nil, err
+	}
+	b := buf.Bytes()
+
+	span.SetAttributes(
+		attribute.Int("row_count", len(rows)),
+		attribute.Int("file_size_bytes", len(b)),
+	)
+	exportRowsTotal.Add(ctx, int64(len(rows)), metric.WithAttributes(attribute.String("sheet", sheetName)))
+	exportSizeBytes.Record(ctx, int64(len(b)), metric.WithAttributes(attribute.String("sheet", sheetName)))
+
+	return b, nil
+}
+
+// GenericXLSX converts a slice of maps to XLSX with alphabetically-sorted headers.
+// Use ToXLSXBytes when column order matters.
+func GenericXLSX(ctx context.Context, sheetName string, rows []map[string]any) ([]byte, error) {
+	if len(rows) == 0 {
+		return ToXLSXBytes(ctx, sheetName, nil, nil)
+	}
+	keys := make([]string, 0, len(rows[0]))
+	for k := range rows[0] {
+		keys = append(keys, k)
+	}
+	sort.Strings(keys)
+	cols := make([]Column, len(keys))
+	for i, k := range keys {
+		cols[i] = Column{Key: k, Label: k}
+	}
+	return ToXLSXBytes(ctx, sheetName, cols, rows)
+}
+
+func fmtCell(v any) string {
+	if v == nil {
+		return ""
+	}
+	return fmt.Sprintf("%v", v)
+}