function sampleBase64PNGImageData() {
    // A 60 by 60 solid red square.
    return "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";
}

function imageBlob(base64String = sampleBase64PNGImageData()) {
    return textBlob(atob(base64String), "image/png");
}

function textBlob(data, type = "text/plain") {
    const array = [...data].map(char => char.charCodeAt(0));
    return new Blob([new Uint8Array(array)], { "type" : type });
}

function loadText(blob) {
    return new Promise((resolve, reject) => {
        const reader = new FileReader;
        reader.addEventListener("load", () => resolve(reader.result), { once: true });
        reader.addEventListener("error", reject, { once: true });
        reader.readAsText(blob);
    });
}

function loadImage(blob) {
    return new Promise((resolve, reject) => {
        const image = new Image;
        image.addEventListener("load", () => resolve(image), { once: true });
        image.addEventListener("error", reject, { once: true });
        image.src = URL.createObjectURL(blob);
    });
}

function loadDocument(blob) {
    return new Promise(async resolve => {
        resolve(new DOMParser().parseFromString(await loadText(blob), "text/html"));
    });
}

function writeToClipboardUsingDataTransfer(data) {
    const input = document.createElement("input");
    document.body.appendChild(input);
    input.value = "a";
    input.setSelectionRange(0, 1);
    input.addEventListener("copy", event => {
        for (const type of Object.keys(data))
            event.clipboardData.setData(type, data[type]);
        event.preventDefault();
    }, { once: true });
    document.execCommand("copy");
    input.remove();
}


async function triggerProgrammaticPaste(locationOrElement, options = []) {
    let x, y;
    if (locationOrElement instanceof Element)
        [x, y] = [locationOrElement.offsetLeft + locationOrElement.offsetWidth / 2, locationOrElement.offsetTop + locationOrElement.offsetHeight / 2];
    else
        [x, y] = [locationOrElement.x, locationOrElement.y];

    return new Promise(resolve => {
        testRunner.runUIScript(`
            (() => {
                doneCount = 0;
                function checkDone() {
                    if (++doneCount === 3)
                        uiController.uiScriptComplete();
                }

                uiController.didHideMenuCallback = checkDone;

                function resolveDOMPasteRequest() {
                    if (${options.includes("ChangePasteboardWhenGrantingAccess")})
                        uiController.copyText("*** this text should never appear in a passing layout test ***");
                    uiController.chooseMenuAction("Paste", checkDone);
                }

                if (uiController.isShowingMenu)
                    resolveDOMPasteRequest();
                else
                    uiController.didShowMenuCallback = resolveDOMPasteRequest;

                uiController.activateAtPoint(${x}, ${y}, checkDone);
            })()`, resolve);
    });
}

async function checkClipboardItemString(item, type, expectedString)
{
    const observedString = await loadText(await item.getType(type));
    if (observedString === expectedString)
        testPassed(`getType("${type}") resolved to "${expectedString}"`);
    else
        testFailed(`getType("${type}") resolved to "${observedString}; expected "${expectedString}"`);
}