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parse.js
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parse.js
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// (C) 2020 Robert Grimm
import { strict as assert } from 'assert';
import expat from 'node-expat';
const { create } = Object;
const identity = v => v;
const print = console.log;
const { stringify } = JSON;
let indent = '';
const doDebug = (opcode, ...data) => {
switch (opcode) {
case 'open':
print(`${indent}<${data[0]}>`);
indent += ' ';
break;
case 'elide':
print(`${indent}...`);
break;
case 'ignore':
print(`${indent}[${stringify(data[0]).slice(1, -1)}]`);
break;
case 'content':
print(`${indent}${stringify(data[0])}`);
break;
case 'close':
indent = indent.slice(2);
print(`${indent}</${data[0]}>`);
break;
default:
throw new Error(`Invalid opcode "${opcode}"`);
}
};
const debug = false ? doDebug : () => { };
// -----------------------------------------------------------------------------
const coercion = {
integer: (s) => Number(s),
real: (s) => Number(s),
string: (s) => String(s),
data: (s) => Buffer.from(s, 'base64'),
date: (s) => new Date(s),
true: () => true,
false: () => false,
};
const open = (state, tag) => {
if (state.ignoring > 0) {
state.ignoring++;
return;
}
debug('open', tag);
const { keys, pending, withPlaylists } = state;
if (!withPlaylists && keys.length === 1 && keys[0] === 'Playlists') {
debug('elide');
state.ignoring++;
}
let value = '';
if (tag === 'array') {
value = [];
} else if (tag === 'dict') {
value = create(null);
}
pending.push({ tag, value });
};
const content = (state, text) => {
if (state.ignoring > 0) return;
const { pending } = state;
const top = pending[pending.length - 1];
const { tag } = top;
if (tag === 'array' || tag === 'dict' || tag === 'plist') {
debug('ignore', text);
} else {
debug('content', text);
top.value += text;
}
};
const close = (state, tag) => {
if (state.ignoring > 0) {
state.ignoring--;
if (state.ignoring > 0) return;
}
debug('close', tag);
const { keys, pending } = state;
let { tag: tag2, value } = pending.pop();
assert(tag === tag2);
if (tag === 'plist') {
assert(pending.length === 0);
assert(keys.length === 0);
state.result = value;
return;
} else if (tag === 'key') {
keys.push(value);
return;
}
value = (coercion[tag] ?? identity)(value);
const top = pending[pending.length - 1];
const target = top.tag;
if (target === 'plist') {
top.value = value;
} else if (target === 'array') {
top.value.push(value);
} else if (target === 'dict') {
assert(keys.length > 0);
top.value[keys.pop()] = value;
} else {
throw new Error(`Not a container "${target}"`);
}
};
const parse = (data, { withPlaylists = false } = {}) => {
const state = { keys: [], pending: [], ignoring: 0, withPlaylists };
const engine = new expat.Parser('UTF-8')
.on('startElement', tag => open(state, tag))
.on('text', text => content(state, text))
.on('endElement', tag => close(state, tag));
if (!engine.parse(data, true)) {
throw engine.getError();
}
return state.result;
};
export default parse;