Improve automatic term selection/identification

term.go

@@ -0,0 +1,131 @@
+package main
+
+import (
+	"fmt"
+	"strconv"
+	"time"
+)
+
+// Term selection should yield smart results based on the current time, as well as the input provided.
+// Fall 2024, "spring" => Spring 2025
+// Fall 2024, "fall" => Fall 2025
+// Summer 2024, "fall" => Fall 2024
+
+const (
+	Spring = iota
+	Summer
+	Fall
+)
+
+type Term struct {
+	Year   uint16
+	Season uint8
+}
+
+var (
+	SpringRange, SummerRange, FallRange = GetYearDayRange(uint16(time.Now().Year()))
+	CentralTime                         *time.Location
+)
+
+func init() {
+	var err error
+	CentralTime, err = time.LoadLocation("America/Chicago")
+	if err != nil {
+		panic(err)
+	}
+}
+
+type YearDayRange struct {
+	Start uint16
+	End   uint16
+}
+
+// GetYearDayRange returns the start and end day of each term for the given year.
+// This could technichally introduce race conditions, but it's more likely confusion from UTC will be a greater issue.
+// Spring: January 14th to May
+// Summer: May 25th - August 15th
+// Fall: August 18th - December 10th
+func GetYearDayRange(year uint16) (YearDayRange, YearDayRange, YearDayRange) {
+	springStart := time.Date(int(year), time.January, 14, 0, 0, 0, 0, CentralTime).YearDay()
+	springEnd := time.Date(int(year), time.May, 1, 0, 0, 0, 0, CentralTime).YearDay()
+	summerStart := time.Date(int(year), time.May, 25, 0, 0, 0, 0, CentralTime).YearDay()
+	summerEnd := time.Date(int(year), time.August, 15, 0, 0, 0, 0, CentralTime).YearDay()
+	fallStart := time.Date(int(year), time.August, 18, 0, 0, 0, 0, CentralTime).YearDay()
+	fallEnd := time.Date(int(year), time.December, 10, 0, 0, 0, 0, CentralTime).YearDay()
+
+	return YearDayRange{
+			Start: uint16(springStart),
+			End:   uint16(springEnd),
+		}, YearDayRange{
+			Start: uint16(summerStart),
+			End:   uint16(summerEnd),
+		}, YearDayRange{
+			Start: uint16(fallStart),
+			End:   uint16(fallEnd),
+		}
+}
+
+// GetCurrentTerm returns the current term, and the next term. Only the first term is nillable.
+// YearDay ranges are inclusive of the start, and exclusive of the end.
+func GetCurrentTerm(now time.Time) (*Term, *Term) {
+	year := uint16(now.Year())
+	dayOfYear := uint16(now.YearDay())
+
+	if (dayOfYear < SpringRange.Start) || (dayOfYear >= FallRange.End) {
+		// Fall over, Spring not yet begun
+		return nil, &Term{Year: year + 1, Season: Spring}
+	} else if (dayOfYear >= SpringRange.Start) && (dayOfYear < SpringRange.End) {
+		// Spring
+		return &Term{Year: year, Season: Spring}, &Term{Year: year, Season: Summer}
+	} else if dayOfYear < SummerRange.Start {
+		// Spring over, Summer not yet begun
+		return nil, &Term{Year: year, Season: Summer}
+	} else if (dayOfYear >= SummerRange.Start) && (dayOfYear < SummerRange.End) {
+		// Summer
+		return &Term{Year: year, Season: Summer}, &Term{Year: year, Season: Fall}
+	} else if dayOfYear < FallRange.Start {
+		// Summer over, Fall not yet begun
+		return nil, &Term{Year: year, Season: Fall}
+	} else if (dayOfYear >= FallRange.Start) && (dayOfYear < FallRange.End) {
+		// Fall
+		return &Term{Year: year, Season: Fall}, nil
+	}
+
+	panic(fmt.Sprintf("Impossible Code Reached (dayOfYear: %d)", dayOfYear))
+}
+
+// BannerTermToTerm converts a Banner term code to a Term struct
+func BannerTermToTerm(code string) Term {
+	year, _ := strconv.ParseUint(code[0:4], 10, 16)
+
+	var season uint8
+	termCode := code[4:6]
+	switch termCode {
+	case "10":
+		season = Fall
+	case "20":
+		season = Spring
+	case "30":
+		season = Summer
+	}
+
+	return Term{
+		Year:   uint16(year),
+		Season: season,
+	}
+}
+
+// TermToBannerTerm converts a Term struct to a Banner term code
+func TermToBannerTerm(term Term) string {
+	var season string
+	switch term.Season {
+	case Fall:
+		season = "10"
+	case Spring:
+		season = "20"
+	case Summer:
+		season = "30"
+	}
+
+	return fmt.Sprintf("%d%s", term.Year, season)
+}