svelte/src/utils/CodeBuilder.js

const LINE = {};
const BLOCK = {};

export default class CodeBuilder {
	constructor ( str = '' ) {
		this.result = str;

		const initial = str ? ( /\n/.test( str ) ? BLOCK : LINE ) : null;
		this.first = initial;
		this.last = initial;

		this.lastCondition = null;
	}

	addConditionalLine ( condition, line ) {
		if ( condition === this.lastCondition ) {
			this.result += `\n\t${line}`;
		} else {
			if ( this.lastCondition ) {
				this.result += `\n}\n\n`;
			}

			this.result += `if ( ${condition} ) {\n\t${line}`;
			this.lastCondition = condition;
		}

		this.last = BLOCK;
	}

	addLine ( line ) {
		if ( this.lastCondition ) {
			this.result += `\n}`;
			this.lastCondition = null;
		}

		if ( this.last === BLOCK ) {
			this.result += `\n\n${line}`;
		} else if ( this.last === LINE ) {
			this.result += `\n${line}`;
		} else {
			this.result += line;
		}

		this.last = LINE;
		if ( !this.first ) this.first = LINE;
	}

	addLineAtStart ( line ) {
		if ( this.first === BLOCK ) {
			this.result = `${line}\n\n${this.result}`;
		} else if ( this.first === LINE ) {
			this.result = `${line}\n${this.result}`;
		} else {
			this.result += line;
		}

		this.first = LINE;
		if ( !this.last ) this.last = LINE;
	}

	addBlock ( block ) {
		if ( this.lastCondition ) {
			this.result += `\n}`;
			this.lastCondition = null;
		}

		if ( this.result ) {
			this.result += `\n\n${block}`;
		} else {
			this.result += block;
		}

		this.last = BLOCK;
		if ( !this.first ) this.first = BLOCK;
	}

	addBlockAtStart ( block ) {
		if ( this.result ) {
			this.result = `${block}\n\n${this.result}`;
		} else {
			this.result += block;
		}

		this.first = BLOCK;
		if ( !this.last ) this.last = BLOCK;
	}

	isEmpty () {
		return this.result === '';
	}

	toString () {
		return this.result.trim() + ( this.lastCondition ? `\n}` : `` );
	}
}