adding revenue

internal/model/periode.go

@@ -0,0 +1,52 @@
+// model/period.go
+package model
+
+import (
+	"fmt"
+	"time"
+)
+
+func QuarterPeriod(year, q int) Period {
+	months := map[int][2]int{
+		1: {1, 3}, 2: {4, 6}, 3: {7, 9}, 4: {10, 12},
+	}
+	m := months[q]
+	return Period{
+		Type:  PeriodQuarter,
+		Year:  year,
+		Index: q,
+		Start: date(year, m[0], 1),
+		End:   date(year, m[1]+1, 0), // last day of end month
+	}
+}
+
+func HalfYearPeriod(year, h int) Period {
+	if h == 1 {
+		return Period{Type: PeriodHalfYear, Year: year, Index: 1,
+			Start: date(year, 1, 1), End: date(year, 7, 0)}
+	}
+	return Period{Type: PeriodHalfYear, Year: year, Index: 2,
+		Start: date(year, 7, 1), End: date(year, 12, 31)}
+}
+
+func FullYearPeriod(year int) Period {
+	return Period{Type: PeriodYear, Year: year, Index: 1,
+		Start: date(year, 1, 1), End: date(year, 12, 31)}
+}
+
+func (p Period) String() string {
+	switch p.Type {
+	case PeriodQuarter:
+		return fmt.Sprintf("Q%d %d", p.Index, p.Year)
+	case PeriodHalfYear:
+		return fmt.Sprintf("H%d %d", p.Index, p.Year)
+	case PeriodYear:
+		return fmt.Sprintf("FY%d", p.Year)
+	}
+	return "unknown"
+}
+
+func date(year, month, day int) time.Time {
+	// day=0 means last day of previous month
+	return time.Date(year, time.Month(month), day, 0, 0, 0, 0, time.UTC)
+}