//reserved keywords that can't be used as identifiers
const keywords = require('./keywords.json');
const { eatBlock, checkAlphaNumeric } = require('./utils');
const parseInput = require('./parse-input');

//parse the schema into a type graph
const buildTypeGraph = (schema, options) => {
	//the default graph
	let graph = {
		String: { scalar: true },
		Integer: { scalar: true },
		Float: { scalar: true },
		Boolean: { scalar: true },
	};

	//parse the schema
	const tokens = parseInput(schema, false, options);
	let pos = 0;

	while (tokens[pos++]) {
		//check for keywords
		switch(tokens[pos - 1]) {
			case 'type':
				graph[tokens[pos++]] = parseCompoundType(tokens, pos, options);

				//advance to the end of the compound type
				pos = eatBlock(tokens, pos);

				break;

			case 'scalar':
				if (keywords.includes(graph[tokens[pos - 1]])) {
					throw 'Unexpected keyword ' + graph[tokens[pos - 1]];
				}

				graph[tokens[pos++]] = { scalar: true };
				break;

			default:
				throw 'Unknown token ' + tokens[pos - 1];
		}
	}

	if (options.debug) {
		console.log('Type Graph:\n', graph, '\n');
	}

	return graph;
};

//moved this routine to a separate function for clarity
const parseCompoundType = (tokens, pos, options) => {
	//format check (not strictly necessary, but it looks nice)
	if (tokens[pos] !== '{') {
		throw 'Expected \'{\' in compound type definition';
	}

	//graph component to be returned
	const compound = {};

	//for each line of the compound type
	while (tokens[pos++] && tokens[pos] !== '}') {
		let type = tokens[pos++];
		const name = tokens[pos];

		//no mangled types or names
		checkAlphaNumeric(type);
		checkAlphaNumeric(name);

		//can't use keywords
		if (keywords.includes(type) || keywords.includes(name)) {
			throw 'Unexpected keyword found as type field or type name (' + type + ' ' + name + ')';
		}

		//check for duplicate fields
		if (Object.keys(compound).includes(name)) {
			throw 'Unexpected duplicate field name';
		}

		//finally, push to the compound definition
		compound[name] = {
			typeName: type
		};
	}

	if (options.debug) {
		console.log('Compound Type:\n', compound, '\n');
	}

	return compound;
};

module.exports = buildTypeGraph;