Tabs can be added and removed.

client/src/components/MainWindow.tsx

@@ -1,8 +1,8 @@
-import React, { useReducer } from 'react';
+import React, { useReducer, useState, Reducer } from 'react';
 import { ThemeProvider, CssBaseline, createMuiTheme } from '@material-ui/core';
 import { grey } from '@material-ui/core/colors';
 import AppBar from './appbar/AppBar';
-import QueryWindow, { QueryWindowReducer } from './windows/QueryWindow';
+import QueryWindow, { QueryWindowReducer, QueryWindowState } from './windows/QueryWindow';
 var _ = require('lodash');
 
 const darkTheme = createMuiTheme({
@@ -14,19 +14,101 @@ const darkTheme = createMuiTheme({
     },
 });
 
+export interface MainWindowState {
+    tabLabels: string[],
+    tabStates: any[],
+    tabReducers: Reducer<any, any>[],
+    activeTab: number,
+}
+
+export enum MainWindowStateActions {
+    SetActiveTab = "setActiveTab",
+    DispatchToTab = "dispatchToTab",
+    CloseTab = "closeTab",
+    AddTab = "addTab",
+}
+
+export function MainWindowReducer(state: MainWindowState, action: any) {
+    switch (action.type) {
+        case MainWindowStateActions.SetActiveTab:
+            return { ...state, activeTab: action.value }
+        case MainWindowStateActions.CloseTab:
+            const newSize = state.tabStates.length - 1;
+            return {
+                ...state,
+                tabStates: state.tabStates.filter((i: any, idx: number) => idx != action.idx),
+                tabLabels: state.tabLabels.filter((i: any, idx: number) => idx != action.idx),
+                tabReducers: state.tabReducers.filter((i: any, idx: number) => idx != action.idx),
+                activeTab: state.activeTab >= (newSize-1) ? (newSize-1) : state.activeTab,
+            }
+        case MainWindowStateActions.AddTab:
+            return {
+                ...state,
+                tabStates: [...state.tabStates, action.tabState],
+                tabLabels: [...state.tabLabels, action.tabLabel],
+                tabReducers: [...state.tabReducers, action.tabReducer],
+            }
+        case MainWindowStateActions.DispatchToTab:
+            return {
+                ...state,
+                tabStates: state.tabStates.map((item: any, i: number) => {
+                    return i === action.idx ?
+                        state.tabReducers[i](item, action.tabAction) :
+                        item;
+                })
+            }
+        default:
+            throw new Error("Unimplemented QueryWindow state update.")
+    }
+}
+
 export default function MainWindow(props: any) {
-    const [state, dispatch] = useReducer(QueryWindowReducer, {
-        query: null,
-        resultsForQuery: null,
-        editingQuery: false,
+    const [state, dispatch] = useReducer(MainWindowReducer, {
+        tabLabels: ["Query"],
+        tabStates: [
+            {
+                editingQuery: false,
+                query: null,
+                resultsForQuery: null,
+            },
+        ],
+        tabReducers: [QueryWindowReducer, QueryWindowReducer],
+        activeTab: 0
+    })
+
+    const queryWindows = state.tabStates.map((state: QueryWindowState, i: number) => {
+        return <QueryWindow
+            state={state}
+            dispatch={(action: any) => {
+                dispatch({
+                    type: MainWindowStateActions.DispatchToTab,
+                    tabAction: action,
+                    idx: i
+                });
+            }}
+        />
     });
 
     return <ThemeProvider theme={darkTheme}>
         <CssBaseline />
-        <AppBar />
-        <QueryWindow
-            state={state}
-            dispatch={dispatch}
+        <AppBar
+            tabLabels={state.tabLabels}
+            selectedTab={state.activeTab}
+            setSelectedTab={(t: number) => dispatch({ type: MainWindowStateActions.SetActiveTab, value: t })}
+            onCloseTab={(t: number) => dispatch({ type: MainWindowStateActions.CloseTab, idx: t })}
+            onAddTab={() => {
+                dispatch({
+                    type: MainWindowStateActions.AddTab,
+                    tabState: {
+                        editingQuery: false,
+                        query: null,
+                        resultsForQuery: null,
+                    },
+                    tabLabel: "Query",
+                    tabReducer: QueryWindowReducer,
+                })
+            }}
         />
+        {queryWindows[state.activeTab]}
     </ThemeProvider>
 }

client/src/components/appbar/AppBar.tsx

@@ -1,14 +1,63 @@
-import React from 'react';
-import { AppBar as MuiAppBar, Box } from '@material-ui/core';
+import React, { useState } from 'react';
+import { AppBar as MuiAppBar, Box, Tab as MuiTab, Tabs, IconButton } from '@material-ui/core';
+import CloseIcon from '@material-ui/icons/Close';
+import AddIcon from '@material-ui/icons/Add';
 
 export interface IProps {
+    tabLabels: string[],
+    selectedTab: number,
+    setSelectedTab: (n: number) => void,
+    onCloseTab: (idx: number) => void,
+    onAddTab: () => void,
+}
+
+export interface TabProps {
+    onClose: () => void,
+}
+
+export function Tab(props: any) {
+    const { onClose, label, ...restProps } = props;
+    const [hover, setHover] = useState<boolean>(false);
+
+    const labelElem = <Box
+        display="flex"
+        alignItems="center"
+        justifyContent="center"
+    >
+        {label}
+        {hover && <Box ml={1}>
+            <IconButton
+                size="small"
+                color="inherit"
+                onClick={onClose}
+            >
+                <CloseIcon />
+            </IconButton>
+        </Box>}
+    </Box>;
 
+    return <MuiTab
+        onMouseEnter={() => setHover(true)}
+        onMouseLeave={() => setHover(false)}
+        label={labelElem}
+        {...restProps}
+    />
 }
 
 export default function AppBar(props: IProps) {
     return <MuiAppBar position="static" style={{ background: 'grey' }}>
-        <Box m={0.5} display="flex" alignItems="center">
-            <img height="30px" src={process.env.PUBLIC_URL + "/logo.svg"} alt="error"></img>
+        <Box display="flex" alignItems="center">
+            <Box m={0.5} display="flex" alignItems="center">
+                <img height="30px" src={process.env.PUBLIC_URL + "/logo.svg"} alt="error"></img>
+            </Box>
+            <Tabs value={props.selectedTab} onChange={(e: any, v: number) => props.setSelectedTab(v)}>
+                {props.tabLabels.map((l: string, idx: number) => <Tab
+                    label={l}
+                    value={idx}
+                    onClose={() => props.onCloseTab(idx)}
+                />)}
+            </Tabs>
+            <IconButton color="inherit" onClick={props.onAddTab}><AddIcon/></IconButton>
         </Box>
     </MuiAppBar>
 }