"use strict"

var fs = require("fs")
var path = require("path")
var proc = require("child_process")

function read(filepath) {
	try {return fs.readFileSync(filepath, "utf8")} catch (e) {throw new Error("File does not exist: " + filepath)}
}
function isFile(filepath) {
	try {return fs.statSync(filepath).isFile()} catch (e) {return false}
}
function parse(file) {
	var json = read(file)
	try {return JSON.parse(json)} catch (e) {throw new Error("invalid JSON: " + json)}
}

var error
function run(input, output) {
	try {
		var modules = {}
		var bindings = {}
		var declaration = /^\s*(?:var|let|const|function)[\t ]+([\w_$]+)/gm
		var include = /(?:((?:var|let|const|,|)[\t ]*)([\w_$\.\[\]"'`]+)(\s*=\s*))?require\(([^\)]+)\)(\s*[`\.\(\[])?/gm
		var uuid = 0
		var process = function(filepath, data) {
			data.replace(declaration, function(match, binding) {bindings[binding] = 0})
			
			return data.replace(include, function(match, def, variable, eq, dep, rest) {
				var filename = new Function("return " + dep).call(), pre = ""
				
				def = def || "", variable = variable || "", eq = eq || "", rest = rest || ""
				if (def[0] === ",") def = "\nvar ", pre = "\n"
				var dependency = resolve(filepath, filename)
				var localUUID = uuid // global uuid can update from nested `process` call, ensure same id is used on declaration and consumption
				var code = process(dependency, pre + (modules[dependency] == null ? exportCode(filename, dependency, def, variable, eq, rest, localUUID) : def + variable + eq + modules[dependency]))
				modules[dependency] = rest ? "_" + localUUID : variable
				uuid++
				return code + rest
			})
		}
		
		var resolve = function(filepath, filename) {
			if (filename[0] !== ".") {
				// resolve as npm dependency
				var packagePath = "./node_modules/" + filename + "/package.json"
				var meta = isFile(packagePath) ? parse(packagePath) : {}
				var main = "./node_modules/" + filename + "/" + (meta.main || filename + ".js")
				return path.resolve(isFile(main) ? main : "./node_modules/" + filename + "/index.js")
			}
			else {
				// resolve as local dependency
				return path.resolve(path.dirname(filepath), filename + ".js")
			}
		}
		
		var exportCode = function(filename, filepath, def, variable, eq, rest, uuid) {
			var code = read(filepath)
			// if there's a syntax error, report w/ proper stack trace
			try {new Function(code)} catch (e) {
				proc.exec("node " + filepath, function(e) {
					if (e !== null && e.message !== error) {
						error = e.message
						console.log("\x1b[31m" + e.message + "\x1b[0m")
					}
				})
			}
			
			// disambiguate collisions
			var ignored = {}
			code.replace(include, function(match, def, variable, eq, dep) {
				var filename = new Function("return " + dep).call()
				var binding = modules[resolve(filepath, filename)]
				if (binding != null) ignored[binding] = true
			})
			if (code.match(new RegExp("module\\.exports\\s*=\\s*" + variable + "\s*$", "m"))) ignored[variable] = true
			for (var binding in bindings) {
				if (!ignored[binding]) {
					var before = code
					code = code.replace(new RegExp("(\\b)" + binding + "\\b", "g"), binding + bindings[binding])
					if (before !== code) bindings[binding]++
				}
			}
			
			// fix strings that got mangled by collision disambiguation
			var string = /(["'])((?:\\\1|.)*?)(\1)/g
			var candidates = Object.keys(bindings).map(function(binding) {return binding + (bindings[binding] - 1)}).join("|")
			code = code.replace(string, function(match, open, data, close) {
				var variables = new RegExp(Object.keys(bindings).map(function(binding) {return binding + (bindings[binding] - 1)}).join("|"), "g")
				var fixed = data.replace(variables, function(match) {
					return match.replace(/\d+$/, "")
				})
				return open + fixed + close
			})
			
			//fix props
			var props = new RegExp("(\\.\\s*)(" + candidates + ")|([\\{,]\\s*)(" + candidates + ")(\\s*:)", "gm")
			code = code.replace(props, function(match, dot, a, pre, b, post) {
				if (dot) return dot + a.replace(/\d+$/, "")
				else return pre + b.replace(/\d+$/, "") + post
			})
			
			return code
				.replace(/("|')use strict\1;?/gm, "") // remove extraneous "use strict"
				.replace(/module\.exports\s*=\s*/gm, rest ? "var _" + uuid + eq : def + (rest ? "_" : "") + variable + eq) // export
				+ (rest ? "\n" + def + variable + eq + "_" + uuid : "") // if `rest` is truthy, it means the expression is fluent or higher-order (e.g. require(path).foo or require(path)(foo)
		}
		
		var versionTag = "bleeding-edge"
		var packageFile = __dirname + "/../package.json"
		var code = process(path.resolve(input), read(input))
			.replace(/^\s*((?:var|let|const|)[\t ]*)([\w_$\.]+)(\s*=\s*)(\2)(?=[\s]+(\w)|;|$)/gm, "") // remove assignments to self
			.replace(/;+(\r|\n|$)/g, ";$1") // remove redundant semicolons
			.replace(/(\r|\n)+/g, "\n").replace(/(\r|\n)$/, "") // remove multiline breaks
			.replace(versionTag, isFile(packageFile) ? parse(packageFile).version : versionTag) // set version
		
		code = "new function() {\n" + code + "\n}"
		
		if (!isFile(output) || code !== read(output)) {
			//try {new Function(code); console.log("build completed at " + new Date())} catch (e) {}
			error = null
			fs.writeFileSync(output, code, "utf8")
		}
	}
	catch (e) {
		console.error(e.message)
	}
}

module.exports = function(input, output, options) {
	run(input, output)
	if (options && options.watch) {
		fs.watch(process.cwd(), {recursive: true}, function(file) {
			if (typeof file === "string" && path.resolve(output) !== path.resolve(file)) run(input, output)
		})
	}
}