planning

node_modules/@mapbox/mapbox-gl-style-spec/expression/definitions/at.js

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+// @flow
+
+import {array, ValueType, NumberType} from '../types.js';
+
+import RuntimeError from '../runtime_error.js';
+
+import type {Expression, SerializedExpression} from '../expression.js';
+import type ParsingContext from '../parsing_context.js';
+import type EvaluationContext from '../evaluation_context.js';
+import type {Type, ArrayType} from '../types.js';
+import type {Value} from '../values.js';
+
+class At implements Expression {
+    type: Type;
+    index: Expression;
+    input: Expression;
+
+    constructor(type: Type, index: Expression, input: Expression) {
+        this.type = type;
+        this.index = index;
+        this.input = input;
+    }
+
+    static parse(args: $ReadOnlyArray<mixed>, context: ParsingContext): ?At {
+        if (args.length !== 3)
+            return context.error(`Expected 2 arguments, but found ${args.length - 1} instead.`);
+
+        const index = context.parse(args[1], 1, NumberType);
+        const input = context.parse(args[2], 2, array(context.expectedType || ValueType));
+
+        if (!index || !input) return null;
+
+        const t: ArrayType = (input.type: any);
+        return new At(t.itemType, index, input);
+    }
+
+    evaluate(ctx: EvaluationContext): Value {
+        const index = ((this.index.evaluate(ctx): any): number);
+        const array = ((this.input.evaluate(ctx): any): Array<Value>);
+
+        if (index < 0) {
+            throw new RuntimeError(`Array index out of bounds: ${index} < 0.`);
+        }
+
+        if (index >= array.length) {
+            throw new RuntimeError(`Array index out of bounds: ${index} > ${array.length - 1}.`);
+        }
+
+        if (index !== Math.floor(index)) {
+            throw new RuntimeError(`Array index must be an integer, but found ${index} instead.`);
+        }
+
+        return array[index];
+    }
+
+    eachChild(fn: (_: Expression) => void) {
+        fn(this.index);
+        fn(this.input);
+    }
+
+    outputDefined(): boolean {
+        return false;
+    }
+
+    serialize(): SerializedExpression {
+        return ["at", this.index.serialize(), this.input.serialize()];
+    }
+}
+
+export default At;