ModelRelation: add post-query filters

src/db/ModelRelation.ts

@@ -6,6 +6,7 @@ export default abstract class ModelRelation<S extends Model, O extends Model, R
     protected readonly model: S;
     protected readonly foreignFactory: ModelFactory<O>;
     protected readonly query: ModelQuery<O>;
+    protected readonly filters: ModelFilter<O>[] = [];
     protected cachedModels?: R;
 
     protected constructor(model: S, foreignFactory: ModelFactory<O>) {
@@ -21,6 +22,11 @@ export default abstract class ModelRelation<S extends Model, O extends Model, R
         return this;
     }
 
+    public filter(modelFilter: ModelFilter<O>): this {
+        this.filters.push(modelFilter);
+        return this;
+    }
+
     public abstract getModelID(): any;
 
     protected abstract async compute(query: ModelQuery<O>): Promise<R>;
@@ -63,6 +69,18 @@ export class OneModelRelation<S extends Model, O extends Model> extends ModelRel
         return await query.first();
     }
 
+    public async get(): Promise<O | null> {
+        const model = await super.get();
+        if (model) {
+            for (const filter of this.filters) {
+                if (!(await filter(model))) {
+                    return null;
+                }
+            }
+        }
+        return model;
+    }
+
     public async eagerLoad(relations: ModelRelation<S, O, O | null>[]): Promise<ModelQueryResult<O>> {
         this.query.where(
             this.dbProperties.foreignKey,
@@ -103,6 +121,20 @@ export class ManyModelRelation<S extends Model, O extends Model> extends ModelRe
         return await query.get();
     }
 
+    public async get(): Promise<O[]> {
+        let models = await super.get();
+        for (const filter of this.filters) {
+            const newModels = [];
+            for (const model of models) {
+                if (await filter(model)) {
+                    newModels.push(model);
+                }
+            }
+            models = newModels;
+        }
+        return models;
+    }
+
     public async eagerLoad(relations: ModelRelation<S, O, O[]>[]): Promise<ModelQueryResult<O>> {
         this.query.where(
             this.dbProperties.foreignKey,
@@ -142,6 +174,20 @@ export class ManyThroughModelRelation<S extends Model, O extends Model> extends
         return await query.get();
     }
 
+    public async get(): Promise<O[]> {
+        let models = await super.get();
+        for (const filter of this.filters) {
+            const newModels = [];
+            for (const model of models) {
+                if (await filter(model)) {
+                    newModels.push(model);
+                }
+            }
+            models = newModels;
+        }
+        return models;
+    }
+
     public async eagerLoad(relations: ModelRelation<S, O, O[]>[]): Promise<ModelQueryResult<O>> {
         this.query.where(
             `pivot.${this.dbProperties.localPivotKey}`,
@@ -163,6 +209,8 @@ export class ManyThroughModelRelation<S extends Model, O extends Model> extends
 
 export type QueryModifier<M extends Model> = (query: ModelQuery<M>) => ModelQuery<M>;
 
+export type ModelFilter<O extends Model> = (model: O) => boolean | Promise<boolean>;
+
 export type RelationDatabaseProperties = {
     localKey: string;
     foreignKey: string;