// Copyright 2009 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.

// golangorg: The Go Website (golang.org)

// Web server tree:
//
//	https://golang.org/			main landing page
//	https://golang.org/doc/	serve from content/doc, then $GOROOT/doc. spec, mem, etc.
//	https://golang.org/src/	serve files from $GOROOT/src; .go gets pretty-printed
//	https://golang.org/cmd/	serve documentation about commands
//	https://golang.org/pkg/	serve documentation about packages
//				(idea is if you say import "compress/zlib", you go to
//				https://golang.org/pkg/compress/zlib)
//

//go:build go1.16
// +build go1.16

package main

import (
	"flag"
	"fmt"
	"io/fs"
	"log"
	"net/http"
	"os"
	"runtime"

	"golang.org/x/website"
	"golang.org/x/website/internal/godoc"
)

var (
	httpAddr    = flag.String("http", "localhost:6060", "HTTP service address")
	verbose     = flag.Bool("v", false, "verbose mode")
	goroot      = flag.String("goroot", runtime.GOROOT(), "Go root directory")
	templateDir = flag.String("templates", "", "load templates/JS/CSS from disk in this directory (usually /path-to-website/content)")
)

func usage() {
	fmt.Fprintf(os.Stderr, "usage: golangorg\n")
	flag.PrintDefaults()
	os.Exit(2)
}

func loggingHandler(h http.Handler) http.Handler {
	return http.HandlerFunc(func(w http.ResponseWriter, req *http.Request) {
		log.Printf("%s\t%s", req.RemoteAddr, req.URL)
		h.ServeHTTP(w, req)
	})
}

func main() {
	earlySetup()

	flag.Usage = usage
	flag.Parse()

	// Check usage.
	if flag.NArg() > 0 {
		fmt.Fprintln(os.Stderr, "Unexpected arguments.")
		usage()
	}
	if *httpAddr == "" {
		fmt.Fprintln(os.Stderr, "-http must be set")
		usage()
	}

	// Serve files from _content, falling back to GOROOT.
	var content fs.FS
	if *templateDir != "" {
		content = os.DirFS(*templateDir)
	} else {
		content = website.Content
	}
	fsys = unionFS{content, os.DirFS(*goroot)}

	var err error
	pres, err = godoc.NewPresentation(fsys)
	if err != nil {
		log.Fatal(err)
	}
	pres.GoogleCN = googleCN

	readTemplates(pres)
	mux := registerHandlers(pres)
	lateSetup(mux)

	var handler http.Handler = http.DefaultServeMux
	if *verbose {
		log.Printf("golang.org server:")
		log.Printf("\tversion = %s", runtime.Version())
		log.Printf("\taddress = %s", *httpAddr)
		log.Printf("\tgoroot = %s", *goroot)
		handler = loggingHandler(handler)
	}

	// Start http server.
	fmt.Fprintf(os.Stderr, "serving http://%s\n", *httpAddr)
	if err := http.ListenAndServe(*httpAddr, handler); err != nil {
		log.Fatalf("ListenAndServe %s: %v", *httpAddr, err)
	}
}

var _ fs.ReadDirFS = unionFS{}

// A unionFS is an FS presenting the union of the file systems in the slice.
// If multiple file systems provide a particular file, Open uses the FS listed earlier in the slice.
// If multiple file systems provide a particular directory, ReadDir presents the
// concatenation of all the directories listed in the slice (with duplicates removed).
type unionFS []fs.FS

func (fsys unionFS) Open(name string) (fs.File, error) {
	var errOut error
	for _, sub := range fsys {
		f, err := sub.Open(name)
		if err == nil {
			// Note: Should technically check for directory
			// and return a synthetic directory that merges
			// reads from all the matching directories,
			// but all the directory reads in internal/godoc
			// come from fsys.ReadDir, which does that for us.
			// So we can ignore direct f.ReadDir calls.
			return f, nil
		}
		if errOut == nil {
			errOut = err
		}
	}
	return nil, errOut
}

func (fsys unionFS) ReadDir(name string) ([]fs.DirEntry, error) {
	var all []fs.DirEntry
	var seen map[string]bool // seen[name] is true if name is listed in all; lazily initialized
	var errOut error
	for _, sub := range fsys {
		list, err := fs.ReadDir(sub, toFS(name))
		if err != nil {
			errOut = err
		}
		if len(all) == 0 {
			all = append(all, list...)
		} else {
			if seen == nil {
				// Initialize seen only after we get two different directory listings.
				seen = make(map[string]bool)
				for _, d := range all {
					seen[d.Name()] = true
				}
			}
			for _, d := range list {
				name := d.Name()
				if !seen[name] {
					seen[name] = true
					all = append(all, d)
				}
			}
		}
	}
	if len(all) > 0 {
		return all, nil
	}
	return nil, errOut
}