We have UI! kind of

src/counter.cg

@@ -0,0 +1,16 @@
+init = 0;
+
+update = state event \ state + 1;
+
+view = count \
+    Column {
+        gap = 20,
+        children = [
+            Clickable {
+                event = "increment",
+                child = Rect { w = 100, h = 40, color = "blue" }
+            }
+        ]
+    };
+
+{ init = init, update = update, view = view }

src/main.ts

@@ -1,30 +1,30 @@
-import type { UIValue } from './types';
+import { evaluate } from './interpreter'
-import { render } from './ui';
+import type { Env } from './env'
+import { tokenize } from './lexer'
+import { Parser } from './parser'
+import cgCode from './counter.cg?raw';
+import { runApp } from './runtime';
 
 const canvas = document.createElement('canvas');
 canvas.width = 800;
 canvas.height = 600;
 document.body.appendChild(canvas);
 
-const ui: UIValue = {
+const tokens = tokenize(cgCode);
-    kind: 'column',
+const parser = new Parser(tokens);
-    gap: 10,
+const ast = parser.parse();
-    children: [
+console.log(ast);
-        { kind: 'text', content: "Hello CG World", x: 0, y: 20 },
-        { kind: 'rect', w: 200, h: 50, color: 'blue' },
-        { kind: 'text', content: "YESS", x: 0, y: 20 },
-        { kind: 'row', gap: 13, children:
-            [
-                { kind: 'text', content: "In a row", x: 0, y: 10 },
-                { kind: 'clickable', event: "test", child: {
-                    kind: 'padding', amount: 10, child: {
-                        kind: 'rect', w: 80, h: 30, color: '#4a90e2'
-                        }
-                    }
-                }
-            ]
-        }
-    ]
-};
 
-render(ui, canvas);
+const env: Env = new Map();
+const appRecord = evaluate(ast, env);
+
+console.log(appRecord);
+
+if (appRecord.kind !== 'record')
+    throw new Error('Expected record');
+
+const init = appRecord.fields.init;
+const update = appRecord.fields.update;
+const view = appRecord.fields.view;
+
+runApp({ init, update, view }, canvas);

src/parser.ts

@@ -281,25 +281,31 @@ export class Parser {
                 const field = (fieldToken as { value: string }).value;
                 expr = { kind: 'record-access', record: expr, field };
             } else if (this.current().kind === 'open-brace') {
-                // Record update
+                if (expr.kind === 'constructor') {
-                this.advance();
+                    // Constructor application
-                const updates: { [key: string]: AST } = {};
+                    const record = this.parsePrimary();
-                let first = true;
+                    expr = { kind: 'apply', func: expr, args: [record] };
-
+                } else {
-                while (this.current().kind !== 'close-brace') {
+                    // Record update
-                    if (!first) {
+                    this.advance();
-                        this.expect('comma');
+                    const updates: { [key: string]: AST } = {};
+                    let first = true;
+
+                    while (this.current().kind !== 'close-brace') {
+                        if (!first) {
+                            this.expect('comma');
+                        }
+                        first = false;
+
+                        const keyToken = this.expect('ident');
+                        const key = (keyToken as { value: string }).value;
+                        this.expect('equals');
+                        updates[key] = this.parseExpression();
                     }
-                    first = false;
 
-                    const keyToken = this.expect('ident');
+                    this.expect('close-brace');
-                    const key = (keyToken as { value: string }).value;
+                    expr = { kind: 'record-update', record: expr, updates }
-                    this.expect('equals');
-                    updates[key] = this.parseExpression();
                 }
-
-                this.expect('close-brace');
-                expr = { kind: 'record-update', record: expr, updates }
             } else {
                 break;
             }

src/runtime.ts

@@ -0,0 +1,56 @@
+import type { Value } from './types';
+import { valueToUI } from './valueToUI';
+import { render, hitTest } from './ui';
+import { evaluate } from './interpreter';
+
+export type App = {
+    init: Value;
+    update: Value; // State / Event / State
+    view: Value; // State / UI
+}
+
+export function runApp(app: App, canvas: HTMLCanvasElement) {
+    let state = app.init;
+
+    function rerender() {
+        if (app.view.kind !== 'closure')
+            throw new Error('view must be a function');
+
+        const callEnv = new Map(app.view.env);
+        callEnv.set(app.view.params[0], state);
+        const uiValue = evaluate(app.view.body, callEnv);
+        const ui = valueToUI(uiValue);
+
+        render(ui, canvas);
+    }
+
+    function handleEvent(eventName: string) {
+        if (app.update.kind !== 'closure')
+            throw new Error('update must be a function');
+
+        if (app.update.params.length !== 2)
+            throw new Error('update must have 2 parameters');
+
+        const event: Value = { kind: 'string', value: eventName };
+        const callEnv = new Map(app.update.env);
+        callEnv.set(app.update.params[0], state);
+        callEnv.set(app.update.params[1], event);
+        const newState = evaluate(app.update.body, callEnv);
+
+        state = newState;
+        rerender();
+    }
+
+    canvas.addEventListener('click', (e) => {
+        const rect = canvas.getBoundingClientRect();
+        const x = e.clientX - rect.left;
+        const y = e.clientY - rect.top;
+
+        const eventName = hitTest(x, y);
+        if (eventName) {
+            handleEvent(eventName);
+        }
+    });
+
+    rerender();
+}

src/types.ts

@@ -47,4 +47,4 @@ export type UIValue =
     | { kind: 'clickable', child: UIValue, event: string }
     | { kind: 'padding', child: UIValue, amount: number }
 
-export type Value = IntValue | FloatValue | StringValue | Closure | ListValue | RecordValue | ConstructorValue | UIValue;
+export type Value = IntValue | FloatValue | StringValue | Closure | ListValue | RecordValue | ConstructorValue;

src/ui.ts

@@ -1,9 +1,20 @@
 import type { UIValue } from './types';
 
+type ClickRegion = {
+    x: number;
+    y: number;
+    width: number;
+    height: number;
+    event: string;
+};
+
+let clickRegions: ClickRegion[] = [];
+
 export function render(ui: UIValue, canvas: HTMLCanvasElement) {
     const ctx = canvas.getContext('2d');
     if (ctx) {
         ctx.clearRect(0, 0, canvas.width, canvas.height);
+        clickRegions = [];
         renderUI(ui, ctx, 0, 0);
     }
 }
@@ -40,6 +51,8 @@ function renderUI(ui: UIValue, ctx: CanvasRenderingContext2D, x: number, y: numb
         }
 
         case 'clickable': {
+            const size = measure(ui.child);
+            clickRegions.push({ x, y, width: size.width, height: size.height, event: ui.event })
             renderUI(ui.child, ctx, x, y);
             break;
         }
@@ -86,5 +99,15 @@ function measure(ui: UIValue): { width: number, height: number } {
         }
     }
 
-    return { width: 0, height: 0 };
+    // return { width: 0, height: 0 };
+}
+
+export function hitTest(x: number, y: number): string | null {
+    for (const region of clickRegions) {
+        if (x >= region.x && x < region.x + region.width &&
+           x >= region.y && y < region.y + region.height) {
+            return region.event;
+        }
+    }
+    return null;
 }

src/valueToUI.ts

@@ -0,0 +1,80 @@
+import type { Value, UIValue } from './types';
+
+export function valueToUI(value: Value): UIValue {
+    console.log("valueToUI", value);
+    if (value.kind !== 'constructor') {
+        throw new Error('UI value must be a constructor');
+    }
+
+    if (value.args.length !== 1 || value.args[0].kind !== 'record')
+        throw new Error('UI constructor must have 1 record argument');
+
+    const fields = value.args[0].fields;
+
+    switch (value.name) {
+        case 'Rect': {
+            const w = fields.w;
+            const h = fields.h;
+            const color = fields.color;
+
+            if (w.kind !== 'int' || h.kind !== 'int' || color.kind !== 'string')
+                throw new Error('Invalid Rect fields');
+
+            return { kind: 'rect', w: w.value, h: h.value, color: color.value };
+        }
+
+        case 'Text': {
+            const x = fields.x;
+            const y = fields.y;
+            const content = fields.content;
+
+            if (content.kind !== 'string' || x.kind !== 'int' || y.kind !== 'int')
+                throw new Error('Invalid Text fields');
+
+            return { kind: 'text', x: x.value, y: y.value, content: content.value };
+        }
+
+        case 'Column': {
+            const children = fields.children;
+            const gap = fields.gap;
+
+            if (children.kind !== 'list' || gap.kind !== 'int')
+                throw new Error('Invalid Column fields');
+
+            return { kind: 'column', gap: gap.value, children: children.elements.map(valueToUI) };
+        }
+
+        case 'Row': {
+            const children = fields.children;
+            const gap = fields.gap;
+
+            if (children.kind !== 'list' || gap.kind !== 'int')
+                throw new Error('Invalid Row fields');
+
+            return { kind: 'row', gap: gap.value, children: children.elements.map(valueToUI) };
+        }
+
+        case 'Clickable': {
+            const child = fields.child;
+            const event = fields.event;
+
+            if (event.kind !== 'string')
+                throw new Error('Invalid Clickable fields');
+
+            return { kind: 'clickable', event: event.value, child: valueToUI(child) };
+        }
+
+        case 'Padding': {
+            const child = fields.child;
+            const amount = fields.amount;
+
+            if (amount.kind !== 'int')
+                throw new Error('Invalid Padding fields');
+
+            return { kind: 'padding', amount: amount.value, child: valueToUI(child) };
+        }
+
+        default:
+            throw new Error(`Unknown UI constructor: ${value.name}`);
+    }
+}