import { Transform, ReplaceStep, Step } from "prosemirror-transform";
import { getReplaceStep } from "./getReplaceStep";


// join adjacent ReplaceSteps
export function simplifyTransform(tr: Transform) {
    if (!tr.steps.length) {
        return undefined;
    }

    const newTr = new Transform(tr.docs[0]);
    const oldSteps = tr.steps.slice();

    while (oldSteps.length) {
        let step = oldSteps.shift();
        while (oldSteps.length && step.merge(oldSteps[0])) {
            const addedStep = oldSteps.shift();
            if (step instanceof ReplaceStep && addedStep instanceof ReplaceStep) {
                step = getReplaceStep(newTr.doc, addedStep.apply(step.apply(newTr.doc).doc).doc) as Step<any>;
            } else {
                step = step.merge(addedStep);
            }
        }
        newTr.step(step);
    }
    return newTr;
}