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import {NumberType} from '../types';
import {findStopLessThanOrEqualTo} from '../stops';
import type {Stops} from '../stops';
import type {Expression} from '../expression';
import type ParsingContext from '../parsing_context';
import type EvaluationContext from '../evaluation_context';
import type {Type} from '../types';
class Step implements Expression {
type: Type;
input: Expression;
labels: Array<number>;
outputs: Array<Expression>;
constructor(type: Type, input: Expression, stops: Stops) {
this.type = type;
this.input = input;
this.labels = [];
this.outputs = [];
for (const [label, expression] of stops) {
this.labels.push(label);
this.outputs.push(expression);
}
}
static parse(args: $ReadOnlyArray<mixed>, context: ParsingContext) {
if (args.length - 1 < 4) {
return context.error(`Expected at least 4 arguments, but found only ${args.length - 1}.`);
}
if ((args.length - 1) % 2 !== 0) {
return context.error(`Expected an even number of arguments.`);
}
const input = context.parse(args[1], 1, NumberType);
if (!input) return null;
const stops: Stops = [];
let outputType: Type = (null: any);
if (context.expectedType && context.expectedType.kind !== 'value') {
outputType = context.expectedType;
}
for (let i = 1; i < args.length; i += 2) {
const label = i === 1 ? -Infinity : args[i];
const value = args[i + 1];
const labelKey = i;
const valueKey = i + 1;
if (typeof label !== 'number') {
return context.error('Input/output pairs for "step" expressions must be defined using literal numeric values (not computed expressions) for the input values.', labelKey);
}
if (stops.length && stops[stops.length - 1][0] >= label) {
return context.error('Input/output pairs for "step" expressions must be arranged with input values in strictly ascending order.', labelKey);
}
const parsed = context.parse(value, valueKey, outputType);
if (!parsed) return null;
outputType = outputType || parsed.type;
stops.push([label, parsed]);
}
return new Step(outputType, input, stops);
}
evaluate(ctx: EvaluationContext) {
const labels = this.labels;
const outputs = this.outputs;
if (labels.length === 1) {
return outputs[0].evaluate(ctx);
}
const value = ((this.input.evaluate(ctx): any): number);
if (value <= labels[0]) {
return outputs[0].evaluate(ctx);
}
const stopCount = labels.length;
if (value >= labels[stopCount - 1]) {
return outputs[stopCount - 1].evaluate(ctx);
}
const index = findStopLessThanOrEqualTo(labels, value);
return outputs[index].evaluate(ctx);
}
eachChild(fn: (_: Expression) => void) {
fn(this.input);
for (const expression of this.outputs) {
fn(expression);
}
}
outputDefined(): boolean {
return this.outputs.every(out => out.outputDefined());
}
serialize() {
const serialized = ["step", this.input.serialize()];
for (let i = 0; i < this.labels.length; i++) {
if (i > 0) {
serialized.push(this.labels[i]);
}
serialized.push(this.outputs[i].serialize());
}
return serialized;
}
}
export default Step;
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