feature(db): add get and query

Author: robwormald

spec/db_spec.ts

@@ -96,13 +96,55 @@ describe('database functionality', () => {
     idb.changes.subscribe(notif => {
       notificationCount++;
     });
-    idb.insert('todos',[{name: 'todo3'}, {name: 'todo4'}])
+    idb.insert('todos',[{name: 'todo5'}, {name: 'todo6'}])
       .toArray()
       .subscribe(() => {}, (err) => {}, () => {
         expect(notificationCount).toBe(2);
         done();
       });
   });
 
+  it('should get a record by key', (done) => {
+    let found;
+    idb.get('todos', 3)
+      .subscribe(record => {
+        found = record;
+      }, err => {
+        console.error(err);
+        done(err);
+      }, () => {
+        expect(found).toEqual({name: 'todo3'});
+        done()
+      });
+  });
+  
+  it('should iterate records', (done) => {
+    let found;
+    idb.query('todos').toArray()
+      .subscribe(records => {
+        found = records;
+      }, err => {
+        console.error(err);
+        done(err);
+      }, () => {
+        expect(found.length).toEqual(6);
+        done()
+      });
+  });
+  
+  it('should iterate records with a predicate fn', (done) => {
+    let found;
+    idb.query('todos', (rec) => rec.name === 'todo5').toArray()
+      .subscribe(records => {
+        found = records;
+      }, err => {
+        console.error(err);
+        done(err);
+      }, () => {
+        expect(found.length).toEqual(1);
+        done()
+      });
+  });
+  
 });
 

src/database.ts

@@ -9,7 +9,7 @@ const IDB_COMPLETE = 'complete';
 const IDB_ERROR = 'error';
 const IDB_UPGRADE_NEEDED = 'upgradeneeded';
 
-const IDB_TXN_READ = 'read';
+const IDB_TXN_READ = 'readonly';
 const IDB_TXN_READWRITE = 'readwrite';
 
 export const DB_INSERT = 'DB_INSERT';
@@ -120,6 +120,80 @@ export class Database {
       .do(payload => notify ? this.changes.next({type: DB_INSERT, payload }) : ({}));
   }
 
+  get(storeName:string, key:any){
+    return this.open(this._schema.name)
+      .mergeMap(db => {
+        return new Observable(txnObserver => {
+         const txn = db.transaction([storeName], IDB_TXN_READ);
+         const objectStore = txn.objectStore(storeName);
+         
+         const getRequest = objectStore.get(key);
+         
+         const onTxnError = (err) => txnObserver.error(err);
+         const onTxnComplete = () => txnObserver.complete();
+         const onRecordFound = (ev) => txnObserver.next(getRequest.result);
+          
+         txn.addEventListener(IDB_COMPLETE, onTxnComplete);
+         txn.addEventListener(IDB_ERROR, onTxnError);
+         
+         getRequest.addEventListener(IDB_SUCCESS, onRecordFound);
+         getRequest.addEventListener(IDB_ERROR, onTxnError);
+         
+         return () => {
+           getRequest.removeEventListener(IDB_SUCCESS, onRecordFound);
+           getRequest.removeEventListener(IDB_ERROR, onTxnError);
+           txn.removeEventListener(IDB_COMPLETE, onTxnComplete);
+           txn.removeEventListener(IDB_ERROR, onTxnError);
+         }
+         
+        });
+      });
+  }
+  
+  query(storeName:string, predicate?:(rec:any) => boolean){
+    return this.open(this._schema.name)
+      .mergeMap(db => {
+        return new Observable(txnObserver => {
+         const txn = db.transaction([storeName], IDB_TXN_READ);
+         const objectStore = txn.objectStore(storeName);
+         
+         const getRequest = objectStore.openCursor();
+         
+         const onTxnError = (err) => txnObserver.error(err);
+         const onRecordFound = (ev) => {
+           let cursor = ev.target.result;
+           if(cursor){
+             if(predicate){
+               const match = predicate(cursor.value);
+               if(match){
+                 txnObserver.next(cursor.value);
+               }
+             }
+             else{
+               txnObserver.next(cursor.value);
+             }
+             cursor.continue();
+           }
+           else {
+             txnObserver.complete();
+           }
+         }
+          
+         txn.addEventListener(IDB_ERROR, onTxnError);
+         
+         getRequest.addEventListener(IDB_SUCCESS, onRecordFound);
+         getRequest.addEventListener(IDB_ERROR, onTxnError);
+         
+         return () => {
+           getRequest.removeEventListener(IDB_SUCCESS, onRecordFound);
+           getRequest.removeEventListener(IDB_ERROR, onTxnError);
+           txn.removeEventListener(IDB_ERROR, onTxnError);
+         }
+         
+        });
+      });
+  }
+  
   executeWrite(storeName:string, actionType:string, records:any[]){
     const changes = this.changes;
     return this.open(this._schema.name)