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/* This Source Code Form is subject to the terms of the Mozilla Public
* License, v. 2.0. If a copy of the MPL was not distributed with this
// Command-line argument parser, modeled after but not identical to Python's
// argparse.
var ArgParser = class {
constructor(desc) {
this._params = [];
this._doc = desc;
this.add_argument("--help", {
help: "display this help message",
});
}
// name is '--foo', '-f', or an array of aliases.
//
// spec is an options object with keys:
// dest: key name to store the result in (optional for long options)
// default: value to use if not passed on command line (optional)
// help: description of the option to show in --help
// options: array of valid choices
//
// Prefixes of long option names are allowed. If a prefix is ambiguous, it
// will match the first parameter added to the ArgParser.
add_argument(name, spec) {
const names = Array.isArray(name) ? name : [name];
spec = Object.assign({}, spec);
spec.aliases = names;
for (const name of names) {
if (!name.startsWith("-")) {
throw new Error(`unhandled argument syntax '${name}'`);
}
if (name.startsWith("--")) {
spec.dest = spec.dest || name.substr(2);
}
this._params.push({ name, spec });
}
}
parse_args(args) {
const opts = {};
const rest = [];
for (const { spec } of this._params) {
if (spec.default !== undefined) {
opts[spec.dest] = spec.default;
}
}
const seen = new Set();
for (let i = 0; i < args.length; i++) {
const arg = args[i];
if (!arg.startsWith("-")) {
rest.push(arg);
continue;
} else if (arg === "--") {
rest.push(args.slice(i+1));
break;
}
if (arg == "--help" || arg == "-h") {
this.help();
}
let parameter;
let [passed, value] = arg.split("=");
for (const { name, spec } of this._params) {
if (passed.startsWith("--")) {
if (name.startsWith(passed)) {
parameter = spec;
}
} else if (passed.startsWith("-") && passed === name) {
parameter = spec;
}
if (parameter) {
if (value === undefined) {
value = args[++i];
}
opts[parameter.dest] = value;
break;
}
}
if (parameter) {
if (seen.has(parameter)) {
throw new Error(`${parameter.aliases[0]} given multiple times`);
}
seen.add(parameter);
} else {
throw new Error(`invalid command-line argument '${arg}'`);
}
}
for (const { name, spec } of this._params) {
if (spec.options && !spec.options.includes(opts[spec.dest])) {
throw new Error(`invalid ${name} value '${opts[spec.dest]}'`);
opts[spec.dest] = spec.default;
}
}
return { opts, rest };
}
help() {
print(`Usage: ${this._doc}`);
const specs = new Set(this._params.map(p => p.spec));
const optstrs = [...specs].map(p => p.aliases.join(", "));
let maxlen = Math.max(...optstrs.map(s => s.length));
for (const spec of specs) {
const name = spec.aliases[0];
let helptext = spec.help ?? "undocumented";
if ("options" in spec) {
helptext += ` (one of ${spec.options.map(x => `'${x}'`).join(", ")})`;
}
if ("default" in spec) {
helptext += ` (default '${spec.default}')`;
}
const optstr = spec.aliases.join(", ");
print(` ${optstr.padEnd(maxlen)} ${helptext}`);
}
quit(0);
}
};