import deindent from '../../../utils/deindent';
import getGlobals from './getGlobals';
import { CompileOptions, ModuleFormat, Node } from '../../../interfaces';

export default function getIntro(
	format: ModuleFormat,
	options: CompileOptions,
	imports: Node[]
) {
	if (format === 'es') return '';
	if (format === 'amd') return getAmdIntro(options, imports);
	if (format === 'cjs') return getCjsIntro(options, imports);
	if (format === 'iife') return getIifeIntro(options, imports);
	if (format === 'umd') return getUmdIntro(options, imports);
	if (format === 'eval') return getEvalIntro(options, imports);

	throw new Error(`Not implemented: ${format}`);
}

function getAmdIntro(options: CompileOptions, imports: Node[]) {
	const sourceString = imports.length
		? `[${imports
				.map(declaration => `'${removeExtension(declaration.source.value)}'`)
				.join(', ')}], `
		: '';

	const id = options.amd && options.amd.id;

	return `define(${id
		? `"${id}", `
		: ''}${sourceString}function(${paramString(imports)}) { 'use strict';\n\n`;
}

function getCjsIntro(options: CompileOptions, imports: Node[]) {
	const requireBlock = imports
		.map(
			declaration =>
				`var ${declaration.name} = require('${declaration.source.value}');`
		)
		.join('\n\n');

	if (requireBlock) {
		return `'use strict';\n\n${requireBlock}\n\n`;
	}

	return `'use strict';\n\n`;
}

function getIifeIntro(options: CompileOptions, imports: Node[]) {
	if (!options.name) {
		throw new Error(`Missing required 'name' option for IIFE export`);
	}

	return `var ${options.name} = (function(${paramString(imports)}) { 'use strict';\n\n`;
}

function getUmdIntro(options: CompileOptions, imports: Node[]) {
	if (!options.name) {
		throw new Error(`Missing required 'name' option for UMD export`);
	}

	const amdId = options.amd && options.amd.id ? `'${options.amd.id}', ` : '';

	const amdDeps = imports.length
		? `[${imports
				.map(declaration => `'${removeExtension(declaration.source.value)}'`)
				.join(', ')}], `
		: '';
	const cjsDeps = imports
		.map(declaration => `require('${declaration.source.value}')`)
		.join(', ');
	const globalDeps = getGlobals(imports, options);

	return (
		deindent`
		(function(global, factory) {
			typeof exports === 'object' && typeof module !== 'undefined' ? module.exports = factory(${cjsDeps}) :
			typeof define === 'function' && define.amd ? define(${amdId}${amdDeps}factory) :
			(global.${options.name} = factory(${globalDeps}));
		}(this, (function (${paramString(imports)}) { 'use strict';` + '\n\n'
	);
}

function getEvalIntro(options: CompileOptions, imports: Node[]) {
	return `(function (${paramString(imports)}) { 'use strict';\n\n`;
}

function paramString(imports: Node[]) {
	return imports.map(dep => dep.name).join(', ');
}

function removeExtension(file: string) {
	const index = file.lastIndexOf('.');
	return ~index ? file.slice(0, index) : file;
}