map chooser dialog (#19)

tank-frontend/src/App.tsx

@@ -8,26 +8,27 @@ import Scoreboard from './Scoreboard.tsx';
 import Button from './components/Button.tsx';
 import MapChooser from './MapChooser.tsx';
 import './App.css';
-import {getRandomTheme, useStoredTheme} from "./theme.ts";
+import {ThemeContext, getRandomTheme, useStoredTheme} from './theme.ts';
 import {useState} from 'react';
 
 export default function App() {
     const [theme, setTheme] = useStoredTheme();
     const [name, setName] = useState<string | null>(null);
 
-    return <Column className="flex-grow">
+    return <ThemeContext.Provider value={theme}>
+        <Column className="flex-grow">
 
-        <ClientScreen theme={theme} player={name}/>
+            <ClientScreen player={name}/>
 
             <Row>
                 <h1 className="flex-grow">CCCB-Tanks!</h1>
                 <MapChooser />
-            <Button text="change colors" onClick={() => setTheme(_ => getRandomTheme())}/>
+                <Button text="☼ change colors" onClick={() => setTheme(_ => getRandomTheme())}/>
                 <Button
                     onClick={() => window.open('https://github.com/kaesaecracker/cccb-tanks-cs', '_blank')?.focus()}
-                text="GitHub"/>
+                    text="⌂ source"/>
                 {name !== '' &&
-                <Button onClick={() => setName(_ => '')} text="logout"/>}
+                    <Button onClick={() => setName(_ => '')} text="∩ logout"/>}
             </Row>
 
             {name || <JoinForm onDone={name => setName(_ => name)}/>}
@@ -38,5 +39,6 @@ export default function App() {
                 <Scoreboard/>
             </Row>
 
-    </Column>;
+        </Column>
+    </ThemeContext.Provider>;
 }

tank-frontend/src/ClientScreen.tsx

@@ -1,107 +1,12 @@
-import {useEffect, useRef, useState} from 'react';
-import './ClientScreen.css';
-import {hslToString, Theme} from './theme.ts';
+import {useEffect, useState} from 'react';
 import {makeApiUrl, useMyWebSocket} from './serverCalls.tsx';
 import {ReadyState} from 'react-use-websocket';
+import PixelGridCanvas from './components/PixelGridCanvas.tsx';
 
-const pixelsPerRow = 352;
-const pixelsPerCol = 160;
-const observerMessageSize = pixelsPerCol * pixelsPerRow / 8;
 
-enum GamePixelEntityType {
-    Wall = 0x0,
-    Tank = 0x1,
-    Bullet = 0x2
-}
-
-function getPixelDataIndexes(bitIndex: number) {
-    return {
-        byteIndex: Math.floor(bitIndex / 8),
-        bitInByteIndex: 7 - bitIndex % 8
-    };
-}
-
-function normalizeColor(context: CanvasRenderingContext2D, color: string) {
-    context.fillStyle = color;
-    context.fillRect(0, 0, 1, 1);
-    return context.getImageData(0, 0, 1, 1).data;
-}
-
-function parseAdditionalDataNibble(nibble: number) {
-    const isPlayerMask = 1;
-    const entityTypeMask = 12;
-
-    return {
-        isCurrentPlayer: (nibble & isPlayerMask) != 0,
-        entityType: ((nibble & entityTypeMask) >> 2) as GamePixelEntityType,
-    };
-}
-
-function drawPixelsToCanvas(
-    {
-        context, width, height, pixels, additional, foreground, background, playerColor, otherTanksColor
-    }: {
-        context: CanvasRenderingContext2D,
-        width: number,
-        height: number,
-        pixels: Uint8ClampedArray,
-        additional: Uint8ClampedArray | null,
-        background: Uint8ClampedArray,
-        foreground: Uint8ClampedArray,
-        playerColor: Uint8ClampedArray,
-        otherTanksColor: Uint8ClampedArray
-    }
-) {
-    let additionalDataIndex = 0;
-    let additionalDataByte: number | null = null;
-    const nextPixelColor = (isOn: boolean) => {
-        if (!isOn)
-            return background;
-        if (!additional)
-            return foreground;
-
-        let info;
-        if (additionalDataByte === null) {
-            additionalDataByte = additional[additionalDataIndex];
-            additionalDataIndex++;
-            info = parseAdditionalDataNibble(additionalDataByte);
-        } else {
-            info = parseAdditionalDataNibble(additionalDataByte >> 4);
-            additionalDataByte = null;
-        }
-
-        if (info.isCurrentPlayer)
-            return playerColor;
-
-        if (info.entityType == GamePixelEntityType.Tank)
-            return otherTanksColor;
-
-        return foreground;
-    };
-
-    const imageData = context.getImageData(0, 0, width, height, {colorSpace: 'srgb'});
-    const data = imageData.data;
-
-    for (let y = 0; y < height; y++) {
-        for (let x = 0; x < width; x++) {
-            const pixelIndex = y * pixelsPerRow + x;
-            const {byteIndex, bitInByteIndex} = getPixelDataIndexes(pixelIndex);
-            const isOn = (pixels[byteIndex] & (1 << bitInByteIndex)) !== 0;
-            const color = nextPixelColor(isOn);
-
-            for (let colorChannel of [0, 1, 2, 3])
-                data[pixelIndex * 4 + colorChannel] = color[colorChannel];
-        }
-    }
-
-    context.putImageData(imageData, 0, 0);
-}
-
-export default function ClientScreen({theme, player}: {
-    theme: Theme,
+export default function ClientScreen({player}: {
     player: string | null
 }) {
-    const canvasRef = useRef<HTMLCanvasElement>(null);
     const [shouldSendMessage, setShouldSendMessage] = useState(false);
 
     const url = makeApiUrl('/screen', 'ws');
@@ -114,7 +19,8 @@ export default function ClientScreen({theme, player}: {
         getWebSocket,
         readyState
     } = useMyWebSocket(url.toString(), {
-        onOpen: _ => setShouldSendMessage(true)
+        onOpen: _ => setShouldSendMessage(true),
+        onMessage: _ => setShouldSendMessage(true)
     });
 
     const socket = getWebSocket();
@@ -128,54 +34,9 @@ export default function ClientScreen({theme, player}: {
         sendMessage('');
     }, [readyState, shouldSendMessage]);
 
+    if (!lastMessage)
+        return <></>;
 
-    useEffect(() => {
-        if (lastMessage === null)
-            return;
-
-        let ignore = false;
-        const start = async () => {
-            const canvas = canvasRef.current;
-            if (canvas === null)
-                throw new Error('canvas null');
-
-            const drawContext = canvas.getContext('2d');
-            if (!drawContext)
-                throw new Error('could not get draw context');
-
-            let pixels = new Uint8ClampedArray(lastMessage.data);
-            let additionalData: Uint8ClampedArray | null = null;
-            if (pixels.length > observerMessageSize) {
-                additionalData = pixels.slice(observerMessageSize);
-                pixels = pixels.slice(0, observerMessageSize);
-            }
-
-            if (ignore)
-                return;
-
-            drawPixelsToCanvas({
-                context: drawContext,
-                width: canvas.width,
-                height: canvas.height,
-                pixels,
-                additional: additionalData,
-                background: normalizeColor(drawContext, hslToString(theme.background)),
-                foreground: normalizeColor(drawContext, hslToString(theme.primary)),
-                playerColor: normalizeColor(drawContext, hslToString(theme.secondary)),
-                otherTanksColor: normalizeColor(drawContext, hslToString(theme.tertiary))
-            });
-
-            if (ignore)
-                return;
-
-            setShouldSendMessage(true);
-        };
-
-        start();
-        return () => {
-            ignore = true;
-        };
-    }, [lastMessage, canvasRef.current, theme]);
-
-    return <canvas ref={canvasRef} id="screen" width={pixelsPerRow} height={pixelsPerCol}/>;
+    const pixels = new Uint8ClampedArray(lastMessage.data);
+    return <PixelGridCanvas pixels={pixels}/>;
 }

tank-frontend/src/JoinForm.css

@@ -9,18 +9,6 @@
 }
 
 .JoinForm {
-    border: solid var(--border-size-thick) var(--color-secondary);
-
-    position: absolute;
-    top: 50%;
-    left: 50%;
-    transform: translate(-50%, -50%);
-
-    background: var(--color-background);
-
-    gap: 16px;
-    padding: 16px;
-
     animation-duration: 1s;
     animation-name: BlinkJoinFormBorder;
     animation-iteration-count: infinite;

tank-frontend/src/JoinForm.tsx

@@ -1,10 +1,11 @@
 import {useState} from 'react';
-import './JoinForm.css';
+import {useMutation} from '@tanstack/react-query';
+
 import {makeApiUrl} from './serverCalls';
-import Column from './components/Column.tsx';
 import Button from './components/Button.tsx';
 import TextInput from './components/TextInput.tsx';
-import {useMutation} from '@tanstack/react-query';
+import Dialog from './components/Dialog.tsx';
+import './JoinForm.css';
 
 export default function JoinForm({onDone}: {
     onDone: (name: string) => void;
@@ -29,7 +30,7 @@ export default function JoinForm({onDone}: {
 
     const confirm = () => postPlayer.mutate({name});
 
-    return <Column className="JoinForm">
+    return <Dialog className="JoinForm">
         <h3> Enter your name to play </h3>
         <TextInput
             value={name}
@@ -40,7 +41,7 @@ export default function JoinForm({onDone}: {
         <Button
             onClick={confirm}
             disabled={disableButtons}
-            text="INSERT COIN"/>
+            text="¢ INSERT COIN"/>
         {postPlayer.isError && <p>{postPlayer.error.message}</p>}
-    </Column>;
+    </Dialog>;
 }

tank-frontend/src/MapChooser.css

@@ -7,3 +7,17 @@
     border-color: var(--color-primary);
     color: var(--color-primary);
 }
+
+.MapChooser-Row {
+    flex-wrap: wrap;
+}
+
+.MapChooser-Preview {
+    flex-grow: 1;
+    padding: var(--padding-normal);
+    border: solid var(--border-size-thin) var(--color-primary);
+}
+
+.MapChooser-Preview-Highlight {
+    border-color: var(--color-secondary);
+}

tank-frontend/src/MapChooser.tsx

@@ -1,9 +1,81 @@
-import {ChangeEvent} from 'react';
-import {makeApiUrl} from './serverCalls';
-import './MapChooser.css';
+import {useState} from 'react';
 import {useMutation, useQuery} from '@tanstack/react-query';
+import {makeApiUrl, MapInfo} from './serverCalls';
+import Dialog from './components/Dialog.tsx';
+import PixelGridCanvas from './components/PixelGridCanvas.tsx';
+import Column from './components/Column.tsx';
+import Button from './components/Button.tsx';
+import Row from './components/Row.tsx';
+import './MapChooser.css';
 
-export default function MapChooser() {
+function base64ToArrayBuffer(base64: string) {
+    const binaryString = atob(base64);
+    const bytes = new Uint8ClampedArray(binaryString.length);
+    for (let i = 0; i < binaryString.length; i++) {
+        bytes[i] = binaryString.charCodeAt(i);
+    }
+    return bytes;
+}
+
+function MapPreview({mapName, highlight, onClick}: {
+    readonly mapName: string,
+    readonly highlight: boolean,
+    readonly onClick: () => void
+}) {
+    const query = useQuery({
+        queryKey: ['get-map', mapName],
+        queryFn: async () => {
+            const url = makeApiUrl(`/map/${mapName}`);
+            const response = await fetch(url, {method: 'GET'});
+            if (!response.ok)
+                throw new Error(`response failed with code ${response.status} (${response.status})${await response.text()}`);
+            return await response.json() as MapInfo;
+        }
+    });
+
+    if (query.isError)
+        return <p>{query.error.message}</p>;
+    else if (query.isPending)
+        return <p>loading...</p>;
+
+    const {name, preview} = query.data;
+
+    return <Column
+        key={mapName}
+        className={'MapChooser-Preview' + (highlight ? ' MapChooser-Preview-Highlight' : '')}
+        onClick={onClick}
+    >
+        <PixelGridCanvas pixels={base64ToArrayBuffer(preview)}/>
+        <p>{name}</p>
+    </Column>;
+}
+
+
+function MapChooserDialog({mapNames, onClose, onConfirm}: {
+    readonly mapNames: string[];
+    readonly onConfirm: (mapName: string) => void;
+    readonly onClose: () => void;
+}) {
+    const [chosenMap, setChosenMap] = useState<string>();
+    return <Dialog>
+        <h3>Choose a map</h3>
+        <Row className="MapChooser-Row overflow-scroll">
+            {mapNames.map(name => <MapPreview
+                key={name}
+                mapName={name}
+                highlight={chosenMap == name}
+                onClick={() => setChosenMap(name)}
+            />)}
+        </Row>
+        <Row>
+            <div className="flex-grow"/>
+            <Button text="« cancel" onClick={onClose}/>
+            <Button text="√ confirm" disabled={!chosenMap} onClick={() => chosenMap && onConfirm(chosenMap)}/>
+        </Row>
+    </Dialog>;
+}
+
+export default function MapChooser({}: {}) {
     const query = useQuery({
         queryKey: ['get-maps'],
         queryFn: async () => {
@@ -27,22 +99,21 @@ export default function MapChooser() {
         }
     });
 
-    const onChange = (event: ChangeEvent<HTMLSelectElement>) => {
-        if (event.target.selectedIndex < 1)
-            return;
-        event.preventDefault();
+    const [open, setOpen] = useState(false);
 
-        const chosenMap = event.target.options[event.target.selectedIndex].value;
-        postMap.mutate(chosenMap);
-    };
-
-    if (query.isError)
-        return <></>;
-
-    const disabled = !query.isSuccess || postMap.isPending;
-
-    return <select className="MapChooser-DropDown" onChange={onChange} disabled={disabled}>
-        <option value="" defaultValue={''}>Choose map</option>
-        {query.isSuccess && query.data.map(m => <option key={m} value={m}>{m}</option>)}
-    </select>;
+    return <>
+        <Button text="▓ Change map"
+                disabled={!query.isSuccess || postMap.isPending}
+                onClick={() => setOpen(true)}/>
+        {query.isSuccess && open &&
+            <MapChooserDialog
+                mapNames={query.data!}
+                onClose={() => setOpen(false)}
+                onConfirm={name => {
+                    setOpen(false);
+                    postMap.mutate(name);
+                }}
+            />
+        }
+    </>;
 }

tank-frontend/src/PlayerInfo.tsx

@@ -1,4 +1,4 @@
-import {makeApiUrl, Scores, useMyWebSocket} from './serverCalls';
+import {makeApiUrl, PlayerInfoMessage, useMyWebSocket} from './serverCalls';
 import Column from './components/Column.tsx';
 import {ReadyState} from 'react-use-websocket';
 import {useEffect, useState} from 'react';
@@ -21,21 +21,6 @@ function ScoreRow({name, value}: {
     </tr>;
 }
 
-type TankInfo = {
-    readonly magazine: string;
-    readonly position: { x: number; y: number };
-    readonly orientation: number;
-    readonly moving: boolean;
-}
-
-type PlayerInfoMessage = {
-    readonly name: string;
-    readonly scores: Scores;
-    readonly controls: string;
-    readonly tank?: TankInfo;
-    readonly openConnections: number;
-}
-
 export default function PlayerInfo({player}: { player: string }) {
     const [shouldSendMessage, setShouldSendMessage] = useState(false);
 

tank-frontend/src/components/Column.tsx

@@ -1,12 +1,13 @@
-import {ReactNode} from "react";
+import {MouseEventHandler, ReactNode} from 'react';
 
 import './Column.css'
 
-export default function Column({children, className}: {
-    children: ReactNode,
-    className?: string
+export default function Column({children, className, onClick}: {
+    children: ReactNode;
+    className?: string;
+    onClick?: MouseEventHandler<HTMLDivElement>;
 }) {
-    return <div className={'Column flex-column ' + (className ?? '')}>
+    return <div className={'Column flex-column ' + (className ?? '')} onClick={onClick}>
         {children}
     </div>
 }

tank-frontend/src/components/Dialog.css

@@ -0,0 +1,16 @@
+
+.Dialog {
+    border: solid var(--border-size-thick) var(--color-secondary);
+    position: absolute;
+    top: 50%;
+    left: 50%;
+    transform: translate(-50%, -50%);
+
+    background: var(--color-background);
+
+    gap: 16px;
+    padding: 16px;
+
+    max-height: 75vh;
+    max-width: 75vw;
+}

tank-frontend/src/components/Dialog.tsx

@@ -0,0 +1,12 @@
+import {ReactNode} from 'react';
+import Column from './Column.tsx';
+import './Dialog.css';
+
+export default function Dialog({children, className}: {
+    children: ReactNode;
+    className?: string;
+}) {
+    return <Column className={'Dialog overflow-scroll ' + (className ?? '')}>
+        {children}
+    </Column>
+}

tank-frontend/src/components/PixelGridCanvas.css

@@ -1,5 +1,5 @@
 
-#screen {
+.PixelGridCanvas {
     aspect-ratio: calc(352 / 160);
     flex-grow: 1;
     object-fit: contain;

tank-frontend/src/components/PixelGridCanvas.tsx

@@ -0,0 +1,162 @@
+import {hslToString, ThemeContext} from '../theme.ts';
+import {useContext, useEffect, useRef} from 'react';
+import './PixelGridCanvas.css';
+
+const pixelsPerRow = 352;
+const pixelsPerCol = 160;
+const observerMessageSize = pixelsPerCol * pixelsPerRow / 8;
+
+enum GamePixelEntityType {
+    Wall = 0x0,
+    Tank = 0x1,
+    Bullet = 0x2,
+    PowerUp = 0x3
+}
+
+function getPixelDataIndexes(bitIndex: number) {
+    return {
+        byteIndex: Math.floor(bitIndex / 8),
+        bitInByteIndex: 7 - bitIndex % 8
+    };
+}
+
+function normalizeColor(context: CanvasRenderingContext2D, color: string) {
+    context.fillStyle = color;
+    context.fillRect(0, 0, 1, 1);
+    return context.getImageData(0, 0, 1, 1).data;
+}
+
+function parseAdditionalDataNibble(nibble: number) {
+    const isPlayerMask = 1;
+    const entityTypeMask = 12;
+
+    return {
+        isCurrentPlayer: (nibble & isPlayerMask) != 0,
+        entityType: ((nibble & entityTypeMask) >> 2) as GamePixelEntityType,
+    };
+}
+
+function drawPixelsToCanvas(
+    {
+        context, width, height, pixels, additional, colors
+    }: {
+        context: CanvasRenderingContext2D,
+        width: number,
+        height: number,
+        pixels: Uint8ClampedArray,
+        additional: Uint8ClampedArray | null,
+        colors: {
+            background: Uint8ClampedArray,
+            foreground: Uint8ClampedArray,
+            player: Uint8ClampedArray,
+            tanks: Uint8ClampedArray,
+            powerUps: Uint8ClampedArray,
+            bullets: Uint8ClampedArray
+        }
+    }
+) {
+    let additionalDataIndex = 0;
+    let additionalDataByte: number | null = null;
+    const nextPixelColor = (isOn: boolean) => {
+        if (!isOn)
+            return colors.background;
+        if (!additional)
+            return colors.foreground;
+
+        let info;
+        if (additionalDataByte === null) {
+            additionalDataByte = additional[additionalDataIndex];
+            additionalDataIndex++;
+            info = parseAdditionalDataNibble(additionalDataByte);
+        } else {
+            info = parseAdditionalDataNibble(additionalDataByte >> 4);
+            additionalDataByte = null;
+        }
+
+        if (info.isCurrentPlayer)
+            return colors.player;
+
+        if (info.entityType === GamePixelEntityType.Tank)
+            return colors.tanks;
+        if (info.entityType === GamePixelEntityType.PowerUp)
+            return colors.powerUps;
+        if (info.entityType === GamePixelEntityType.Bullet)
+            return colors.bullets;
+
+        return colors.foreground;
+    };
+
+    const imageData = context.getImageData(0, 0, width, height, {colorSpace: 'srgb'});
+    const data = imageData.data;
+
+    for (let y = 0; y < height; y++) {
+        for (let x = 0; x < width; x++) {
+            const pixelIndex = y * pixelsPerRow + x;
+            const {byteIndex, bitInByteIndex} = getPixelDataIndexes(pixelIndex);
+            const isOn = (pixels[byteIndex] & (1 << bitInByteIndex)) !== 0;
+            const color = nextPixelColor(isOn);
+
+            for (let colorChannel of [0, 1, 2, 3])
+                data[pixelIndex * 4 + colorChannel] = color[colorChannel];
+        }
+    }
+
+    context.putImageData(imageData, 0, 0);
+}
+
+export default function PixelGridCanvas({pixels}: {
+    readonly pixels: Uint8ClampedArray;
+}) {
+    const theme = useContext(ThemeContext);
+    const canvasRef = useRef<HTMLCanvasElement>(null);
+
+    useEffect(() => {
+        let ignore = false;
+        const start = async () => {
+            const canvas = canvasRef.current;
+            if (canvas === null)
+                throw new Error('canvas null');
+
+            const drawContext = canvas.getContext('2d');
+            if (!drawContext)
+                throw new Error('could not get draw context');
+
+            let additionalData: Uint8ClampedArray | null = null;
+            if (pixels.length > observerMessageSize) {
+                additionalData = pixels.slice(observerMessageSize);
+                pixels = pixels.slice(0, observerMessageSize);
+            }
+
+            if (ignore)
+                return;
+
+            drawPixelsToCanvas({
+                context: drawContext,
+                width: canvas.width,
+                height: canvas.height,
+                pixels,
+                additional: additionalData,
+                colors: {
+                    background: normalizeColor(drawContext, hslToString(theme.background)),
+                    foreground: normalizeColor(drawContext, hslToString(theme.primary)),
+                    player: normalizeColor(drawContext, hslToString(theme.secondary)),
+                    tanks: normalizeColor(drawContext, hslToString(theme.tertiary)),
+                    powerUps: normalizeColor(drawContext, hslToString(theme.tertiary)),
+                    bullets: normalizeColor(drawContext, hslToString(theme.tertiary))
+                }
+            });
+        };
+
+        start();
+        return () => {
+            ignore = true;
+        };
+    }, [pixels, canvasRef.current, theme]);
+
+    return <canvas
+        ref={canvasRef}
+        className="PixelGridCanvas"
+        width={pixelsPerRow}
+        height={pixelsPerCol}
+    />;
+}

tank-frontend/src/index.css

@@ -60,3 +60,7 @@ html, body {
     display: flex;
     flex-direction: row;
 }
+
+.overflow-scroll {
+    overflow: scroll;
+}

tank-frontend/src/serverCalls.tsx

@@ -19,6 +19,27 @@ export type Player = {
     readonly scores: Scores;
 };
 
+type TankInfo = {
+    readonly magazine: string;
+    readonly position: { x: number; y: number };
+    readonly orientation: number;
+    readonly moving: boolean;
+}
+
+export type PlayerInfoMessage = {
+    readonly name: string;
+    readonly scores: Scores;
+    readonly controls: string;
+    readonly tank?: TankInfo;
+    readonly openConnections: number;
+}
+
+export type MapInfo = {
+    readonly name: string;
+    readonly typeName: string;
+    readonly preview: string;
+}
+
 export function useMyWebSocket<T = unknown>(url: string, options: Options = {}) {
     return useWebSocket<T>(url, {
         shouldReconnect: () => true,

tank-frontend/src/theme.ts

@@ -1,4 +1,5 @@
-import {useStoredObjectState} from "./useStoredState.ts";
+import {useStoredObjectState} from './useStoredState.ts';
+import {createContext} from 'react';
 
 export type Theme = {
     primary: HSL;
@@ -88,3 +89,5 @@ export function useStoredTheme() {
         save: applyTheme
     });
 }
+
+export const ThemeContext = createContext<Theme>(getRandomTheme());

tanks-backend/TanksServer/Endpoints.cs

@@ -24,14 +24,18 @@ internal sealed class Endpoints(
         app.Map("/controls", ConnectControlsAsync);
         app.MapGet("/map", () => mapService.MapNames);
         app.MapPost("/map", PostMap);
+        app.MapGet("/map/{name}", GetMapByName);
     }
 
     private Results<BadRequest<string>, NotFound<string>, Ok> PostMap([FromQuery] string name)
     {
         if (string.IsNullOrWhiteSpace(name))
             return TypedResults.BadRequest("invalid map name");
-        if (!mapService.TryGetMapByName(name, out var map))
+
+        name = name.Trim().ToUpperInvariant();
+        if (!mapService.TryGetPrototype(name, out var map))
             return TypedResults.NotFound("map with name not found");
+
         changeToRequestedMap.Request(map);
         return TypedResults.Ok();
     }
@@ -88,4 +92,19 @@ internal sealed class Endpoints(
         var player = playerService.GetOrAdd(name);
         return TypedResults.Ok(player.Name);
     }
+
+    private Results<Ok<MapInfo>, NotFound, BadRequest<string>> GetMapByName(string name)
+    {
+        name = name.Trim().ToUpperInvariant();
+        if (string.IsNullOrEmpty(name))
+            return TypedResults.BadRequest("map name cannot be empty");
+
+        if (!mapService.TryGetPrototype(name, out var prototype))
+            return TypedResults.NotFound();
+        if (!mapService.TryGetPreview(name, out var preview))
+            return TypedResults.NotFound();
+
+        var mapInfo = new MapInfo(prototype.Name, prototype.GetType().Name, preview.Data);
+        return TypedResults.Ok(mapInfo);
+    }
 }

tanks-backend/TanksServer/GameLogic/MapPrototype.cs

@@ -0,0 +1,8 @@
+namespace TanksServer.GameLogic;
+
+internal abstract class MapPrototype
+{
+    public abstract string Name { get; }
+
+    public abstract Map CreateInstance();
+}

tanks-backend/TanksServer/GameLogic/MapService.cs

@@ -1,14 +1,10 @@
 using System.Diagnostics.CodeAnalysis;
 using System.IO;
+using DisplayCommands;
 using TanksServer.Graphics;
 
 namespace TanksServer.GameLogic;
 
-internal abstract class MapPrototype
-{
-    public abstract Map CreateInstance();
-}
-
 internal sealed class MapService
 {
     public const ushort TilesPerRow = 44;
@@ -17,9 +13,10 @@ internal sealed class MapService
     public const ushort PixelsPerRow = TilesPerRow * TileSize;
     public const ushort PixelsPerColumn = TilesPerColumn * TileSize;
 
-    private readonly Dictionary<string, MapPrototype> _maps = new();
+    private readonly Dictionary<string, MapPrototype> _mapPrototypes = new();
+    private readonly Dictionary<string, PixelGrid> _mapPreviews = new();
 
-    public IEnumerable<string> MapNames => _maps.Keys;
+    public IEnumerable<string> MapNames => _mapPrototypes.Keys;
 
     public Map Current { get; private set; }
 
@@ -29,29 +26,49 @@ internal sealed class MapService
             LoadMapString(file);
         foreach (var file in Directory.EnumerateFiles("./assets/maps/", "*.png"))
             LoadMapPng(file);
-
-        var chosenMapIndex = Random.Shared.Next(_maps.Count);
-        var chosenMapName = _maps.Keys.Skip(chosenMapIndex).First();
-        Current = _maps[chosenMapName].CreateInstance();
+        Current = GetRandomMap();
     }
 
-    public bool TryGetMapByName(string name, [MaybeNullWhen(false)] out MapPrototype map)
-        => _maps.TryGetValue(name, out map);
+    public bool TryGetPrototype(string name, [MaybeNullWhen(false)] out MapPrototype map)
+        => _mapPrototypes.TryGetValue(name, out map);
 
     public void SwitchTo(MapPrototype prototype) => Current = prototype.CreateInstance();
 
+    public bool TryGetPreview(string name, [MaybeNullWhen(false)] out PixelGrid pixelGrid)
+    {
+        if (_mapPreviews.TryGetValue(name, out pixelGrid))
+            return true; // already generated
+        if (!_mapPrototypes.TryGetValue(name, out var prototype))
+            return false; // name not found
+
+        pixelGrid = new PixelGrid(PixelsPerRow, PixelsPerColumn);
+        DrawMapStep.Draw(pixelGrid, prototype.CreateInstance());
+
+        _mapPreviews.TryAdd(name, pixelGrid); // another thread may have added the map already
+        return true; // new preview
+    }
+
     private void LoadMapPng(string file)
     {
-        var name = Path.GetFileName(file);
+        var name = MapNameFromFilePath(file);
         var prototype = new SpriteMapPrototype(name, Sprite.FromImageFile(file));
-        _maps.Add(Path.GetFileName(file), prototype);
+        _mapPrototypes.Add(name, prototype);
     }
 
     private void LoadMapString(string file)
     {
+        var name = MapNameFromFilePath(file);
         var map = File.ReadAllText(file).ReplaceLineEndings(string.Empty).Trim();
-        var name = Path.GetFileName(file);
         var prototype = new TextMapPrototype(name, map);
-        _maps.Add(name, prototype);
+        _mapPrototypes.Add(name, prototype);
+    }
+
+    private static string MapNameFromFilePath(string filePath) => Path.GetFileName(filePath).ToUpperInvariant();
+
+    private Map GetRandomMap()
+    {
+        var chosenMapIndex = Random.Shared.Next(_mapPrototypes.Count);
+        var chosenMapName = _mapPrototypes.Keys.Skip(chosenMapIndex).First();
+        return _mapPrototypes[chosenMapName].CreateInstance();
     }
 }

tanks-backend/TanksServer/GameLogic/SpriteMapPrototype.cs

@@ -5,17 +5,18 @@ namespace TanksServer.GameLogic;
 
 internal sealed class SpriteMapPrototype : MapPrototype
 {
-    private readonly string _name;
-    private readonly Sprite _sprite;
+    public override string Name { get; }
+
+    public Sprite Sprite { get; }
 
     public SpriteMapPrototype(string name, Sprite sprite)
     {
         if (sprite.Width != MapService.PixelsPerRow || sprite.Height != MapService.PixelsPerColumn)
-            throw new FileLoadException($"invalid image size in file {_name}");
+            throw new FileLoadException($"invalid image size in file {Name}");
 
-        _name = name;
-        _sprite = sprite;
+        Name = name;
+        Sprite = sprite;
     }
 
-    public override Map CreateInstance() => new(_name, _sprite.ToBoolArray());
+    public override Map CreateInstance() => new(Name, Sprite.ToBoolArray());
 }

tanks-backend/TanksServer/GameLogic/TextMapPrototype.cs

@@ -2,17 +2,19 @@ namespace TanksServer.GameLogic;
 
 internal sealed class TextMapPrototype : MapPrototype
 {
-    private readonly string _name;
-    private readonly string _text;
+    public override string Name { get; }
+
+    public string Text { get; }
 
     public TextMapPrototype(string name, string text)
     {
         if (text.Length != MapService.TilesPerColumn * MapService.TilesPerRow)
             throw new ArgumentException($"cannot load map {name}: invalid length");
-        _name = name;
-        _text = text;
+        Name = name;
+        Text = text;
     }
 
+
     public override Map CreateInstance()
     {
         var walls = new bool[MapService.PixelsPerRow, MapService.PixelsPerColumn];
@@ -21,7 +23,7 @@ internal sealed class TextMapPrototype : MapPrototype
         for (ushort tileY = 0; tileY < MapService.TilesPerColumn; tileY++)
         {
             var tile = new TilePosition(tileX, tileY);
-            if (_text[tileX + tileY * MapService.TilesPerRow] != '#')
+            if (Text[tileX + tileY * MapService.TilesPerRow] != '#')
                 continue;
 
             for (byte pixelInTileX = 0; pixelInTileX < MapService.TileSize; pixelInTileX++)
@@ -32,6 +34,6 @@ internal sealed class TextMapPrototype : MapPrototype
             }
         }
 
-        return new Map(_name, walls);
+        return new Map(Name, walls);
     }
 }

tanks-backend/TanksServer/Graphics/DrawMapStep.cs

@@ -1,18 +1,32 @@
+using DisplayCommands;
 using TanksServer.GameLogic;
 
 namespace TanksServer.Graphics;
 
 internal sealed class DrawMapStep(MapService map) : IDrawStep
 {
-    public void Draw(GamePixelGrid pixels)
+    public void Draw(GamePixelGrid pixels) => Draw(pixels, map.Current);
+
+    private static void Draw(GamePixelGrid pixels, Map map)
     {
         for (ushort y = 0; y < MapService.PixelsPerColumn; y++)
         for (ushort x = 0; x < MapService.PixelsPerRow; x++)
         {
-            if (!map.Current.IsWall(x, y))
+            if (!map.IsWall(x, y))
                 continue;
 
             pixels[x, y].EntityType = GamePixelEntityType.Wall;
         }
     }
+
+    public static void Draw(PixelGrid pixels, Map map)
+    {
+        for (ushort y = 0; y < MapService.PixelsPerColumn; y++)
+        for (ushort x = 0; x < MapService.PixelsPerRow; x++)
+        {
+            if (!map.IsWall(x, y))
+                continue;
+            pixels[x, y] = true;
+        }
+    }
 }

tanks-backend/TanksServer/Interactivity/AppSerializerContext.cs

@@ -7,5 +7,6 @@ namespace TanksServer.Interactivity;
 [JsonSerializable(typeof(IEnumerable<Player>))]
 [JsonSerializable(typeof(IEnumerable<string>))]
 [JsonSerializable(typeof(PlayerInfo))]
+[JsonSerializable(typeof(MapInfo))]
 [JsonSourceGenerationOptions(JsonSerializerDefaults.Web)]
 internal sealed partial class AppSerializerContext : JsonSerializerContext;

tanks-backend/TanksServer/Models/MapInfo.cs

@@ -0,0 +1,3 @@
+namespace TanksServer.Models;
+
+public record MapInfo(string Name, string TypeName, Memory<byte> Preview);