fix(optimiser): account for non-overlapping same-timeslot courses (#4101)

* feat(optimiser): enhance module slot structure with weeks support

* Added Weeks field to ModuleSlot for better week management.
* Introduced WeeksSet and WeeksString for efficient week handling in module timetable processing.
* Updated merge and filter logic to incorporate weeks in combination keys and conflict checks.

* refactor(optimiser): update Weeks field type and handling in module slots

* Changed Weeks field in ModuleSlot from []int to any for flexible week representation.
* Updated parsing logic to handle weeks as any type, ensuring compatibility with existing functionality.
* Enhanced conflict checking to skip week validation for non-[]int types.

* removed debug prints

---------

Co-authored-by: Leslie Yip <[email protected]>
Co-authored-by: Ravern Koh <[email protected]>

Author: 3 people

website/api/optimiser/_models/models.go

@@ -34,12 +34,15 @@ type ModuleSlot struct {
 	StartTime   string      `json:"startTime"`
 	Venue       string      `json:"venue"`
 	Coordinates Coordinates `json:"coordinates"`
+	Weeks       any       `json:"weeks"`
 
 	// Parsed fields
-	StartMin  int    // Minutes from 00:00 (e.g., 540 for 09:00)
-	EndMin    int    // Minutes from 00:00
-	DayIndex  int    // 0=Monday, 1=Tuesday, 2=Wednesday, 3=Thursday, 4=Friday, 5=Saturday
-	LessonKey string // "MODULE|LessonType"
+	StartMin    int    // Minutes from 00:00 (e.g., 540 for 09:00)
+	EndMin      int    // Minutes from 00:00
+	DayIndex    int    // 0=Monday, 1=Tuesday, 2=Wednesday, 3=Thursday, 4=Friday, 5=Saturday
+	LessonKey   string // "MODULE|LessonType"
+	WeeksSet    map[int]bool
+	WeeksString string
 }
 
 // ParseModuleSlotFields parses and populates the parsed fields in ModuleSlot for faster computation

website/api/optimiser/_modules/modules.go

@@ -2,11 +2,12 @@ package modules
 
 import (
 	"encoding/json"
+	"strconv"
 	"strings"
 
-	"github.com/nusmodifications/nusmods/website/api/optimiser/_client"
-	"github.com/nusmodifications/nusmods/website/api/optimiser/_constants"
-	"github.com/nusmodifications/nusmods/website/api/optimiser/_models"
+	client "github.com/nusmodifications/nusmods/website/api/optimiser/_client"
+	constants "github.com/nusmodifications/nusmods/website/api/optimiser/_constants"
+	models "github.com/nusmodifications/nusmods/website/api/optimiser/_models"
 )
 
 /*
@@ -47,6 +48,27 @@ func GetAllModuleSlots(optimiserRequest models.OptimiserRequest) (map[string]map
 			}
 		}
 
+		// Parse the weeks
+		for i := range moduleTimetable {
+
+			// Note: if weeks is not a []int, then skip parsing
+			// Currently we are not handling week conflict for non-[]int weeks
+			if _, ok := moduleTimetable[i].Weeks.([]any); !ok {
+				continue
+			}
+
+			moduleTimetable[i].WeeksSet = make(map[int]bool)
+			weeks := moduleTimetable[i].Weeks.([]any)
+			weeksStrings := make([]string, len(weeks))
+
+			for j, week := range weeks {
+				weekInt := int(week.(float64))
+				moduleTimetable[i].WeeksSet[weekInt] = true
+				weeksStrings[j] = strconv.Itoa(weekInt)
+			}
+			moduleTimetable[i].WeeksString = strings.Join(weeksStrings, ",")
+		}
+
 		// Store the module slots for the module
 		moduleSlots[module] = mergeAndFilterModuleSlots(moduleTimetable, venues, optimiserRequest, module)
 
@@ -77,7 +99,8 @@ func mergeAndFilterModuleSlots(timetable []models.ModuleSlot, venues map[string]
 	*/
 
 	classGroups := make(map[string][]models.ModuleSlot)
-	for _, slot := range timetable {
+	for i := range timetable {
+		slot := &timetable[i]
 		// Skip venues without location data, except E-Venues (virtual venue)
 		if !constants.E_Venues[slot.Venue] {
 			venueLocation := venues[slot.Venue].Location
@@ -90,7 +113,7 @@ func mergeAndFilterModuleSlots(timetable []models.ModuleSlot, venues map[string]
 		slot.Coordinates = venues[slot.Venue].Location
 
 		groupKey := slot.LessonType + "|" + slot.ClassNo
-		classGroups[groupKey] = append(classGroups[groupKey], slot)
+		classGroups[groupKey] = append(classGroups[groupKey], *slot)
 	}
 
 	/*
@@ -107,14 +130,15 @@ func mergeAndFilterModuleSlots(timetable []models.ModuleSlot, venues map[string]
 
 		// Only apply filters to physical lessons
 		if !isRecorded {
-			for _, slot := range slots {
+			for i := range slots {
+				slot := &slots[i]
 				// Check free days
 				if freeDaysMap[slot.Day] {
 					allValid = false
 					break
 				}
 
-				if isSlotOutsideTimeRange(slot, earliestMin, latestMin) {
+				if isSlotOutsideTimeRange(*slot, earliestMin, latestMin) {
 					allValid = false
 					break
 				}
@@ -128,7 +152,7 @@ func mergeAndFilterModuleSlots(timetable []models.ModuleSlot, venues map[string]
 	}
 
 	/*
-		Now merge all slots of the same lessonType, slot, startTime and building
+		Now merge all slots of the same lessonType, slot, startTime, weeks and building
 		We are doing this to avoid unnecessary calculations & reduce search space
 	*/
 
@@ -137,12 +161,11 @@ func mergeAndFilterModuleSlots(timetable []models.ModuleSlot, venues map[string]
 
 	for _, slots := range validClassGroups {
 		for _, slot := range slots {
-			lessonKey := module + " " + slot.LessonType
-			isRecorded := recordingsMap[lessonKey]
 
-			if !isRecorded && !constants.E_Venues[slot.Venue] {
+			if !constants.E_Venues[slot.Venue] {
 				buildingName := extractBuildingName(slot.Venue)
-				combinationKey := slot.LessonType + "|" + slot.Day + "|" + slot.StartTime + "|" + buildingName
+
+				combinationKey := slot.LessonType + "|" + slot.Day + "|" + slot.StartTime + "|" + buildingName + "|" + slot.WeeksString
 
 				if seenCombinations[combinationKey] {
 					continue

website/api/optimiser/_solver/solver.go

@@ -6,9 +6,9 @@ import (
 	"sort"
 	"strings"
 
-	"github.com/nusmodifications/nusmods/website/api/optimiser/_constants"
-	"github.com/nusmodifications/nusmods/website/api/optimiser/_models"
-	"github.com/nusmodifications/nusmods/website/api/optimiser/_modules"
+	constants "github.com/nusmodifications/nusmods/website/api/optimiser/_constants"
+	models "github.com/nusmodifications/nusmods/website/api/optimiser/_models"
+	modules "github.com/nusmodifications/nusmods/website/api/optimiser/_modules"
 	"github.com/umahmood/haversine"
 )
 
@@ -48,14 +48,20 @@ func BeamSearch(
 		slotGroups := lessonToSlots[lessonKey]
 		limit := min(len(slotGroups), branchingFactor)
 
+		// iterate over all partial timetables in the beam
 		for _, state := range beam {
+
+			// iterate over all slot groups for the current lesson
 			for i := 0; i < limit; i++ {
 				group := slotGroups[i]
-
+				
+				// Filters out invalid slots by checking if
+				// DayIndex is not -1 which marks invalid slots when parsing in ParseModuleSlotFields func
 				validGroup := make([]models.ModuleSlot, 0, len(group))
-				for _, slot := range group {
+				for i := range group {
+					slot := &group[i]
 					if slot.DayIndex >= 0 && slot.DayIndex < 6 {
-						validGroup = append(validGroup, slot)
+						validGroup = append(validGroup, *slot)
 					}
 				}
 
@@ -81,8 +87,10 @@ func BeamSearch(
 			}
 		}
 
+		// if no valid partial timetables found then skip to next lesson 
+		// by keeping the beam to create partial timetables
 		if len(nextBeam) == 0 {
-			return models.TimetableState{}
+			continue
 		}
 
 		sort.Slice(nextBeam, func(i, j int) bool {
@@ -164,7 +172,22 @@ func hasConflict(state models.TimetableState, newSlots []models.ModuleSlot) bool
 		for _, oldSlot := range state.DaySlots[newSlot.DayIndex] {
 			// Check if slots overlap in time
 			if newSlot.StartMin < oldSlot.EndMin && oldSlot.StartMin < newSlot.EndMin {
-				return true
+
+				// if weeks is not a []int, then skip checking for week conflict
+				if _, ok := newSlot.Weeks.([]any); !ok {
+					return true
+				}
+				if _, ok := oldSlot.Weeks.([]any); !ok {
+					return true
+				}
+
+				// check if the weeks overlap
+				for _, week := range newSlot.Weeks.([]any) {
+					weekInt := int(week.(float64))
+					if oldSlot.WeeksSet[weekInt] {
+						return true
+					}
+				}
 			}
 		}
 	}
@@ -204,9 +227,10 @@ func getPhysicalSlots(daySlots []models.ModuleSlot, recordings map[string]bool)
 	}
 
 	physicalSlots := make([]models.ModuleSlot, 0, len(daySlots))
-	for _, slot := range daySlots {
+	for i := range daySlots {
+		slot := &daySlots[i]
 		if !isLessonRecorded(slot.LessonKey, recordings) {
-			physicalSlots = append(physicalSlots, slot)
+			physicalSlots = append(physicalSlots, *slot)
 		}
 	}