feat: move default term acquisition & season range from global into config state, LoadLocation once, remove bare constants

internal/config/terms.go

@@ -0,0 +1,140 @@
+package config
+
+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 (
+	// Fall is the first term of the school year.
+	Fall = iota
+	// Spring is the second term of the school year.
+	Spring
+	// Summer is the third term of the school year.
+	Summer
+)
+
+// Term represents a school term, consisting of a year and a season.
+type Term struct {
+	Year   uint16
+	Season uint8
+}
+
+// SeasonRanges represents the start and end day of each term within a year.
+type SeasonRanges struct {
+	Spring YearDayRange
+	Summer YearDayRange
+	Fall   YearDayRange
+}
+
+// YearDayRange represents the start and end day of a term within a year.
+type YearDayRange struct {
+	Start uint16
+	End   uint16
+}
+
+// GetYearDayRange returns the start and end day of each term for the given year.
+// The ranges are inclusive of the start day and exclusive of the end day.
+func GetYearDayRange(loc *time.Location, year uint16) SeasonRanges {
+	springStart := time.Date(int(year), time.January, 14, 0, 0, 0, 0, loc).YearDay()
+	springEnd := time.Date(int(year), time.May, 1, 0, 0, 0, 0, loc).YearDay()
+	summerStart := time.Date(int(year), time.May, 25, 0, 0, 0, 0, loc).YearDay()
+	summerEnd := time.Date(int(year), time.August, 15, 0, 0, 0, 0, loc).YearDay()
+	fallStart := time.Date(int(year), time.August, 18, 0, 0, 0, 0, loc).YearDay()
+	fallEnd := time.Date(int(year), time.December, 10, 0, 0, 0, 0, loc).YearDay()
+
+	return SeasonRanges{
+		Spring: YearDayRange{
+			Start: uint16(springStart),
+			End:   uint16(springEnd),
+		},
+		Summer: YearDayRange{
+			Start: uint16(summerStart),
+			End:   uint16(summerEnd),
+		},
+		Fall: YearDayRange{
+			Start: uint16(fallStart),
+			End:   uint16(fallEnd),
+		},
+	}
+}
+
+// GetCurrentTerm returns the current and next terms based on the provided time.
+// The current term can be nil if the time falls between terms.
+// The 'year' in the term corresponds to the academic year, which may differ from the calendar year.
+func GetCurrentTerm(ranges SeasonRanges, now time.Time) (*Term, *Term) {
+	literalYear := uint16(now.Year())
+	dayOfYear := uint16(now.YearDay())
+
+	// If we're past the end of the summer term, we're 'in' the next school year.
+	var termYear uint16
+	if dayOfYear > ranges.Summer.End {
+		termYear = literalYear + 1
+	} else {
+		termYear = literalYear
+	}
+
+	if (dayOfYear < ranges.Spring.Start) || (dayOfYear >= ranges.Fall.End) {
+		// Fall over, Spring not yet begun
+		return nil, &Term{Year: termYear, Season: Spring}
+	} else if (dayOfYear >= ranges.Spring.Start) && (dayOfYear < ranges.Spring.End) {
+		// Spring
+		return &Term{Year: termYear, Season: Spring}, &Term{Year: termYear, Season: Summer}
+	} else if dayOfYear < ranges.Summer.Start {
+		// Spring over, Summer not yet begun
+		return nil, &Term{Year: termYear, Season: Summer}
+	} else if (dayOfYear >= ranges.Summer.Start) && (dayOfYear < ranges.Summer.End) {
+		// Summer
+		return &Term{Year: termYear, Season: Summer}, &Term{Year: termYear, Season: Fall}
+	} else if dayOfYear < ranges.Fall.Start {
+		// Summer over, Fall not yet begun
+		return nil, &Term{Year: termYear, Season: Fall}
+	} else if (dayOfYear >= ranges.Fall.Start) && (dayOfYear < ranges.Fall.End) {
+		// Fall
+		return &Term{Year: termYear, Season: Fall}, nil
+	}
+
+	panic(fmt.Sprintf("Impossible Code Reached (dayOfYear: %d)", dayOfYear))
+}
+
+// ParseTerm converts a Banner term code string to a Term struct.
+func ParseTerm(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,
+	}
+}
+
+// ToString converts a Term struct to a Banner term code string.
+func (term Term) ToString() 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)
+}