package main

import (
	"bufio"
	"flag"
	"fmt"
	"io"
	"io/ioutil"
	"net/http"
	"os"
	"path/filepath"
	"strings"

	"github.com/bazelbuild/rules_typescript/devserver/concatjs"
	"github.com/bazelbuild/rules_typescript/devserver/devserver"
)

var (
	port            = flag.Int("port", 5432, "server port to listen on")
	base            = flag.String("base", "", "server base (required, runfiles of the binary)")
	pkgs            = flag.String("packages", "", "root package(s) to serve, comma-separated")
	manifest        = flag.String("manifest", "", "sources manifest (.MF)")
	scriptsManifest = flag.String("scripts_manifest", "", "preScripts manifest (.MF)")
	servingPath     = flag.String("serving_path", "/_/ts_scripts.js", "path to serve the combined sources at")
	entryModule     = flag.String("entry_module", "", "entry module name")
)

func main() {
	flag.Parse()

	if *base == "" || len(*pkgs) == 0 || (*manifest == "") || (*scriptsManifest == "") {
		fmt.Fprintf(os.Stderr, "Required argument not set\n")
		os.Exit(1)
	}

	if _, err := os.Stat(*base); err != nil {
		fmt.Fprintf(os.Stderr, "Cannot read server base %s: %v\n", *base, err)
		os.Exit(1)
	}

	scriptsManifestPath := filepath.Join(*base, *scriptsManifest)
	scriptFiles, err := manifestFiles(scriptsManifestPath)
	if err != nil {
		fmt.Fprintf(os.Stderr, "Failed to read scripts_manifest: %v\n", err)
		os.Exit(1)
	}

	preScripts := make([]string, 0, 100)
	postScripts := make([]string, 0, 1)

	// Include the livereload script if IBAZEL_LIVERELOAD_URL is set.
	livereloadUrl := os.Getenv("IBAZEL_LIVERELOAD_URL")
	if livereloadUrl != "" {
		fmt.Printf("Serving livereload script from %s\n", livereloadUrl)
		livereloadLoaderSnippet := fmt.Sprintf(`(function(){
	const script = document.createElement('script');
	script.src = "%s";
	document.head.appendChild(script);
})();`, livereloadUrl)
		preScripts = append(preScripts, livereloadLoaderSnippet)
	}

	// Include the profiler script if IBAZEL_PROFILER_URL is set.
	profilerScriptURL := os.Getenv("IBAZEL_PROFILER_URL")
	if profilerScriptURL != "" {
		fmt.Printf("Serving profiler script from %s\n", profilerScriptURL)
		profilerLoaderSnippet := fmt.Sprintf(`(function(){
	const script = document.createElement('script');
	script.src = "%s";
	document.head.appendChild(script);
})();`, profilerScriptURL)
		preScripts = append(preScripts, profilerLoaderSnippet)
	}

	// Include all user scripts in preScripts. This should always include
	// the requirejs script which is added to scriptFiles by the devserver
	// skylark rule.
	for _, v := range scriptFiles {
		js, err := loadScript(filepath.Join(*base, v))
		if err != nil {
			fmt.Fprintf(os.Stderr, "Failed to read script %s: %v\n", v, err)
		} else {
			preScripts = append(preScripts, js)
		}
	}

	// If the entryModule is set then add a snippet to load
	// the application to postScripts to be outputted after the sources
	if *entryModule != "" {
		postScripts = append(postScripts, fmt.Sprintf("require([\"%s\"]);", *entryModule))
	}

	http.Handle(*servingPath, concatjs.ServeConcatenatedJS(*manifest, *base, preScripts, postScripts, nil /* realFileSystem */))
	pkgList := strings.Split(*pkgs, ",")
	http.HandleFunc("/", devserver.CreateFileHandler(*servingPath, *manifest, pkgList, *base))

	h, err := os.Hostname()
	if err != nil {
		h = "localhost"
	}

	fmt.Printf("Server listening on http://%s:%d/\n", h, *port)
	fmt.Fprintln(os.Stderr, http.ListenAndServe(fmt.Sprintf(":%d", *port), nil).Error())
	os.Exit(1)
}

func loadScript(path string) (string, error) {
	buf, err := ioutil.ReadFile(path)
	if err != nil {
		return "", err
	}
	return string(buf), nil
}

// manifestFiles parses a manifest, returning a list of the files in the manifest.
func manifestFiles(manifest string) ([]string, error) {
	f, err := os.Open(manifest)
	if err != nil {
		return nil, fmt.Errorf("could not read manifest %s: %s", manifest, err)
	}
	defer f.Close()
	return manifestFilesFromReader(f)
}

// manifestFilesFromReader is a helper for manifestFiles, split out for testing.
func manifestFilesFromReader(r io.Reader) ([]string, error) {
	var lines []string
	s := bufio.NewScanner(r)
	for s.Scan() {
		path := s.Text()
		if path == "" {
			continue
		}
		lines = append(lines, path)
	}
	if err := s.Err(); err != nil {
		return nil, err
	}

	return lines, nil
}