Initial commit

server/internal/userdata/diffset.go

@@ -0,0 +1,132 @@
+package userdata
+
+import (
+	"encoding/json"
+	"fmt"
+	"strings"
+
+	pb "lunar-tear/server/gen/proto"
+	"lunar-tear/server/internal/store"
+)
+
+type DiffSet struct {
+	updates map[string]string
+	deletes map[string]string
+}
+
+func NewDiffSet(tables map[string]string) *DiffSet {
+	return &DiffSet{
+		updates: tables,
+		deletes: make(map[string]string),
+	}
+}
+
+func (ds *DiffSet) WithDeletes(table, deleteKeysJSON string) *DiffSet {
+	if deleteKeysJSON != "" && deleteKeysJSON != "[]" {
+		ds.deletes[table] = deleteKeysJSON
+	}
+	return ds
+}
+
+func (ds *DiffSet) Build() map[string]*pb.DiffData {
+	diff := make(map[string]*pb.DiffData, len(ds.updates))
+	for table, payload := range ds.updates {
+		diff[table] = ds.entry(table, payload)
+	}
+	return diff
+}
+
+func (ds *DiffSet) BuildOrdered(order []string) map[string]*pb.DiffData {
+	diff := make(map[string]*pb.DiffData, len(order))
+	for _, table := range order {
+		payload := ds.updates[table]
+		diff[table] = ds.entry(table, payload)
+	}
+	return diff
+}
+
+func (ds *DiffSet) entry(table, payload string) *pb.DiffData {
+	if payload == "" {
+		payload = "[]"
+	}
+	deleteKeys := "[]"
+	if dk, ok := ds.deletes[table]; ok {
+		deleteKeys = dk
+	}
+	return &pb.DiffData{
+		UpdateRecordsJson: payload,
+		DeleteKeysJson:    deleteKeys,
+	}
+}
+
+type trackedTable struct {
+	tableName  string
+	keyFields  []string
+	oldRecords []map[string]any
+	recordsFn  func(store.UserState) []map[string]any
+}
+
+type DeleteTracker struct {
+	entries []trackedTable
+}
+
+func NewDeleteTracker() *DeleteTracker {
+	return &DeleteTracker{}
+}
+
+func (dt *DeleteTracker) Track(tableName string, old store.UserState, recordsFn func(store.UserState) []map[string]any, keyFields []string) *DeleteTracker {
+	dt.entries = append(dt.entries, trackedTable{
+		tableName:  tableName,
+		keyFields:  keyFields,
+		oldRecords: recordsFn(old),
+		recordsFn:  recordsFn,
+	})
+	return dt
+}
+
+func (dt *DeleteTracker) Apply(newState store.UserState, tables map[string]string) map[string]*pb.DiffData {
+	ds := NewDiffSet(tables)
+	for _, e := range dt.entries {
+		newRecords := e.recordsFn(newState)
+		ds.WithDeletes(e.tableName, ComputeDeleteKeys(e.oldRecords, newRecords, e.keyFields))
+	}
+	return ds.Build()
+}
+
+func ComputeDeleteKeys(oldRecords, newRecords []map[string]any, keyFields []string) string {
+	if len(oldRecords) == 0 {
+		return "[]"
+	}
+
+	newSet := make(map[string]struct{}, len(newRecords))
+	for _, r := range newRecords {
+		newSet[compositeKey(r, keyFields)] = struct{}{}
+	}
+
+	var deleted []map[string]any
+	for _, r := range oldRecords {
+		if _, exists := newSet[compositeKey(r, keyFields)]; !exists {
+			deleted = append(deleted, r)
+		}
+	}
+
+	if len(deleted) == 0 {
+		return "[]"
+	}
+	b, err := json.Marshal(deleted)
+	if err != nil {
+		return "[]"
+	}
+	return string(b)
+}
+
+func compositeKey(record map[string]any, fields []string) string {
+	var sb strings.Builder
+	for i, f := range fields {
+		if i > 0 {
+			sb.WriteByte('|')
+		}
+		sb.WriteString(fmt.Sprint(record[f]))
+	}
+	return sb.String()
+}