export interface SelectedGameFile { path: string; file: File }
export interface SelectedGameFolder { name: string; files: SelectedGameFile[]; size: number }

/** Directory inputs include the selected folder in every relative path. Remove
 * that one component and retain the complete game directory below it. */
export function selectGameFolder(selection: Iterable<File>): SelectedGameFolder {
    const files: SelectedGameFile[] = [];
    const paths = new Set<string>();
    let name = '';
    let size = 0;
    for (const file of selection) {
        const [root, ...parts] = file.webkitRelativePath.split('/');
        if (!root || root === '.' || root === '..' || !parts.length || name && root !== name) throw new Error('Choose one game folder with the folder picker.');
        name = root;
        const path = parts.join('/');
        if (path.length > 1024 || /[\\\x00-\x1f\x7f:]/.test(path) || parts.some(part => !part || part === '.' || part === '..' || /[. ]$/.test(part))) {
            throw new Error(`This file has an unsupported game path: ${file.webkitRelativePath}`);
        }
        const key = path.toLowerCase();
        if (paths.has(key)) throw new Error(`This folder has duplicate game paths: ${path}`);
        paths.add(key);
        size += file.size;
        if (!Number.isSafeInteger(size)) throw new Error('This folder exceeds the supported upload size.');
        files.push({ path, file });
        if (files.length > 200_000) throw new Error('Choose a folder with no more than 200,000 files.');
    }
    if (!files.length) throw new Error('The selected folder contains no files.');
    for (const { path } of files) {
        const parents = path.toLowerCase().split('/');
        parents.pop();
        while (parents.length) {
            if (paths.has(parents.join('/'))) throw new Error(`This folder uses the same game path for a file and a directory: ${path}`);
            parents.pop();
        }
    }
    files.sort((a, b) => a.path < b.path ? -1 : a.path > b.path ? 1 : 0);
    return { name, files, size };
}