/**
 * Copyright 2019 Google LLC
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 *
 * Modified from: https://github.com/GoogleChromeLabs/text-editor/blob/main/src/inline-scripts/fs-helpers.js
 */

/**
 * Open a handle to an existing file on the local file system.
 *
 * @return {!Promise<FileSystemFileHandle>} Handle to the existing file.
 *
 * @category File System
 */
export async function getFileHandle(): Promise<FileSystemFileHandle> {
    // For Chrome 86 and later...
    if ('showOpenFilePicker' in window) {
        return window.showOpenFilePicker().then((handles) => handles[0]);
    }
    // For Chrome 85 and earlier...
    return (window as any).chooseFileSystemEntries();
}

/**
 * Create a handle to a new (text) file on the local file system.
 *
 * @return {!Promise<FileSystemFileHandle>} Handle to the new file.
 *
 * @category File System
 */
export function getNewFileHandle(): Promise<FileSystemFileHandle> {
    // For Chrome 86 and later...
    if ('showSaveFilePicker' in window) {
        const opts = {
            types: [{
                description: 'Text file',
                accept: {'text/plain': ['.txt']},
            }],
        };
        return window.showSaveFilePicker(opts);
    }
    // For Chrome 85 and earlier...
    const opts = {
        type: 'save-file',
        accepts: [{
            description: 'Text file',
            extensions: ['txt'],
            mimeTypes: ['text/plain'],
        }],
    };
    return (window as any).chooseFileSystemEntries(opts);
}

/**
 * Reads the raw text from a file.
 *
 * @param {File} file
 * @return {!Promise<string>} A promise that resolves to the parsed string.
 *
 * @category File System
 */
export function readFile(file: File): Promise<string> {
    // If the new .text() reader is available, use it.
    if (file.text) {
        return file.text();
    }
    // Otherwise use the traditional file reading technique.
    return _readFileLegacy(file);
}

/**
 * Reads the raw text from a file.
 *
 * @private
 * @param {File} file
 * @return {Promise<string>} A promise that resolves to the parsed string.
 *
 * @category File System
 */
function _readFileLegacy(file: File): Promise<string> {
    return new Promise((resolve) => {
        const reader = new FileReader();
        reader.addEventListener('loadend', (e) => {
            const text = (e.srcElement as any || e.target).result;
            resolve(text);
        });
        reader.readAsText(file);
    });
}

/**
 * Writes the contents to disk.
 *
 * @param {FileSystemFileHandle} fileHandle File handle to write to.
 * @param {string} contents Contents to write.
 *
 * @category File System
 */
export async function writeFile(fileHandle: FileSystemFileHandle, contents: FileSystemWriteChunkType) {
    // Support for Chrome 82 and earlier.
    if ((fileHandle as any).createWriter) {
        // Create a writer (request permission if necessary).
        const writer = await (fileHandle as any).createWriter()
        // Write the full length of the contents
        await writer.write(0, contents)
        // Close the file and write the contents to disk
        await writer.close()
        return
    }
    // For Chrome 83 and later.
    // Create a FileSystemWritableFileStream to write to.
    const writable = await fileHandle.createWritable()
    // Write the contents of the file to the stream.
    await writable.write(contents as any)
    // Close the file and write the contents to disk.
    await writable.close()
}

/**
 * Verify the user has granted permission to read or write to the file, if
 * permission hasn't been granted, request permission.
 *
 * @param fileHandle File handle to check.
 * @param withWrite True if write permission should be checked.
 * @return True if the user has granted read/write permission.
 *
 * @category File System
 */
export async function verifyPermission(fileHandle: FileSystemFileHandle, withWrite: boolean) {
    const opts: any = {}
    if (withWrite) {
        opts.writable = true
        // For Chrome 86 and later...
        opts.mode = 'readwrite'
    }
    // Check if we already have permission, if so, return true.
    if (await fileHandle.queryPermission(opts) === 'granted') {
        return true
    }
    // Request permission to the file, if the user grants permission, return true.
    if (await fileHandle.requestPermission(opts) === 'granted') {
        return true
    }
    // The user did nt grant permission, return false.
    return false
}