some work on the query/invalidation engine

engine.go

@@ -1,6 +1,7 @@
 package tether
 
 import (
+	"encoding/json"
 	"log/slog"
 	"net/http"
 
@@ -9,11 +10,12 @@ import (
 )
 
 type Engine struct {
-	db        *gorm.DB
-	dbType    string // sqlite or postgres
-	mutations map[string]func(ctx *MutationCtx) error
-	queries   map[string]func(ctx *QueryCtx) error
-	tracker   *reactivity.Tracker
+	db           *gorm.DB
+	dbType       string // sqlite or postgres
+	mutations    map[string]func(ctx *MutationCtx) error
+	queries      map[string]func(ctx *QueryCtx) error
+	dependencies map[string][]string
+	tracker      *reactivity.Tracker
 }
 
 func NewEngine(db *gorm.DB, dbType string) *Engine {
@@ -22,7 +24,14 @@ func NewEngine(db *gorm.DB, dbType string) *Engine {
 	if dbType != "sqlite" && dbType != "postgres" {
 		panic("Invalid database type")
 	}
-	return &Engine{db: db, dbType: dbType, mutations: make(map[string]func(ctx *MutationCtx) error), queries: make(map[string]func(ctx *QueryCtx) error), tracker: tracker}
+	e := &Engine{db: db, dbType: dbType, mutations: make(map[string]func(ctx *MutationCtx) error), queries: make(map[string]func(ctx *QueryCtx) error), dependencies: make(map[string][]string), tracker: tracker}
+	db.Callback().Create().After("gorm:create").Register("tether:after_create", func(tx *gorm.DB) {
+		if dbType == "postgres" {
+			return
+		}
+		e.InvalidateTable(tx.Statement.Table)
+	})
+	return e
 }
 
 func (e *Engine) RegisterMutation(name string, mutation func(ctx *MutationCtx) error) {
@@ -32,6 +41,9 @@ func (e *Engine) RegisterMutation(name string, mutation func(ctx *MutationCtx) e
 
 func (e *Engine) RegisterQuery(name string, query func(ctx *QueryCtx) error, dependencies []string) {
 	e.queries[name] = query // stores the query in the list of valid queries
+	for _, dependency := range dependencies {
+		e.dependencies[dependency] = append(e.dependencies[dependency], name)
+	}
 	slog.Debug("Registered query", "name", name)
 }
 
@@ -56,13 +68,36 @@ func (e *Engine) OnDisconnect(clientID string) error {
 	return nil
 }
 
-func (e *Engine) ExecuteQuery(query string) (interface{}, error) {
+func (e *Engine) GetDependentQueries(tableName string) []string {
+	return e.dependencies[tableName]
+}
+
+func (e *Engine) InvalidateTable(tableName string) {
+	slog.Debug("Invalidating table", "table", tableName)
+	dependentQueries := e.GetDependentQueries(tableName)
+	for _, query := range dependentQueries {
+		slog.Debug("Invalidating query", "query", query)
+		subscriptions := e.tracker.GetQuerySubscriptions(query)
+		for _, subscription := range subscriptions {
+			slog.Debug("Invalidating subscription", "subscription", subscription["clientID"])
+			params := map[string]interface{}{}
+			json.Unmarshal([]byte(subscription["params"]), &params)
+			_, err := e.ExecuteQuery(query, params)
+			if err != nil {
+				slog.Error("Failed to execute query", "error", err)
+				continue
+			}
+		}
+	}
+}
+
+func (e *Engine) ExecuteQuery(query string, params map[string]interface{}) (interface{}, error) {
 	/*
 		TODO: implement the logic to execute the query
 		Steps needed:
-		1. Check which tables updated
-		2. Get the queries that rely on the tables
-		3. Get the subscriptions that need updating
+		1. Check which tables updated ✅
+		2. Get the queries that rely on the tables ✅
+		3. Get the subscriptions that need updating ✅
 		4. Calculate hash for every query
 		5. Send the updated queries if hash changed
 	*/
@@ -78,8 +113,7 @@ func (e *Engine) OnReceiveMessage(clientID string, msg map[string]interface{}) e
 	slog.Debug("Received message", "from", clientID, "message", msg)
 	switch msg["type"] {
 	case "query":
-		query := msg["location"].(string) + "?" + msg["params"].(string)
-		e.tracker.SubscribeToQuery(clientID, query)
+		e.tracker.SubscribeToQuery(clientID, msg["location"].(string), msg["params"].(map[string]string))
 	case "mutation":
 		e.ExecuteMutation(msg["location"].(string), msg["params"].(map[string]interface{}))
 	}

reactivity/tracker.go

@@ -1,6 +1,7 @@
 package reactivity
 
 import (
+	"encoding/json"
 	"log/slog"
 	"sync"
 )
@@ -13,11 +14,11 @@ type Tracker struct {
 	clients map[string]*Client
 
 	// Maps a Query Hash (e.g. "getUser?id=1") to a Set of Client IDs
-	subscriptions map[string]map[string]bool
+	subscriptions map[string][]map[string]string
 }
 
 func NewTracker() *Tracker {
-	return &Tracker{clients: make(map[string]*Client), subscriptions: make(map[string]map[string]bool)}
+	return &Tracker{clients: make(map[string]*Client), subscriptions: make(map[string][]map[string]string)}
 }
 
 func (t *Tracker) Track(c *Client) {
@@ -32,30 +33,37 @@ func (t *Tracker) Untrack(c *Client) {
 	delete(t.clients, c.ID)
 }
 
-func (t *Tracker) SubscribeToQuery(clientID string, query string) {
+func (t *Tracker) SubscribeToQuery(clientID string, query string, params map[string]string) {
 	t.mu.Lock()
 	defer t.mu.Unlock()
 	if t.subscriptions[query] == nil {
-		t.subscriptions[query] = make(map[string]bool)
+		t.subscriptions[query] = make([]map[string]string, 0)
 	}
-	t.subscriptions[query][clientID] = true
+	// set t.subscriptions[query] to a map of client IDs and their params
+	paramsJSON, err := json.Marshal(params)
+	if err != nil {
+		slog.Error("Tracker: Failed to marshal params", "error", err)
+		return
+	}
+	t.subscriptions[query] = append(t.subscriptions[query], map[string]string{"clientID": clientID, "params": string(paramsJSON)})
 }
 
 func (t *Tracker) UnsubscribeFromQuery(clientID string, query string) {
 	t.mu.Lock()
 	defer t.mu.Unlock()
-	delete(t.subscriptions[query], clientID)
+	for i, subscription := range t.subscriptions[query] {
+		if subscription["clientID"] == clientID {
+			t.subscriptions[query] = append(t.subscriptions[query][:i], t.subscriptions[query][i+1:]...)
+			break
+		}
+	}
 }
 
-func (t *Tracker) GetQuerySubscriptions(query string) []string {
+func (t *Tracker) GetQuerySubscriptions(query string) []map[string]string {
 	t.mu.RLock()
 	defer t.mu.RUnlock()
 	subscriptions := t.subscriptions[query]
-	subscriptionIDs := make([]string, 0, len(subscriptions))
-	for clientID := range subscriptions {
-		subscriptionIDs = append(subscriptionIDs, clientID)
-	}
-	return subscriptionIDs
+	return subscriptions
 }
 
 func (t *Tracker) SendMessage(clientID string, message []byte) {