// Copyright 2013 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.

package web

import (
	"log"
	"net/http"
	"net/url"
	"path"
	"strings"

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

// docServer serves a package doc tree (/cmd or /pkg).
type docServer struct {
	p *Site
	d *pkgdoc.Docs
}

func (h *docServer) ServeHTTP(w http.ResponseWriter, r *http.Request) {
	if maybeRedirect(w, r) {
		return
	}

	// TODO(rsc): URL should be clean already.
	relpath := path.Clean(strings.TrimPrefix(r.URL.Path, "/pkg"))
	relpath = strings.TrimPrefix(relpath, "/")

	mode := pkgdoc.ParseMode(r.FormValue("m"))

	// Redirect to pkg.go.dev.
	// We provide two overrides for the redirect.
	// First, the request can set ?m=old to get the old pages.
	// Second, the request can come from China:
	// since pkg.go.dev is not available in China, we serve the docs directly.
	if mode&pkgdoc.ModeOld == 0 && !GoogleCN(r) {
		if relpath == "" {
			relpath = "std"
		}
		suffix := ""
		if r.Host == "tip.golang.org" {
			suffix = "@master"
		}
		if goos, goarch := r.FormValue("GOOS"), r.FormValue("GOARCH"); goos != "" || goarch != "" {
			suffix += "?"
			if goos != "" {
				suffix += "GOOS=" + url.QueryEscape(goos)
			}
			if goarch != "" {
				if goos != "" {
					suffix += "&"
				}
				suffix += "GOARCH=" + url.QueryEscape(goarch)
			}
		}
		http.Redirect(w, r, "https://pkg.go.dev/"+relpath+suffix, http.StatusTemporaryRedirect)
		return
	}

	if relpath == "builtin" {
		// The fake built-in package contains unexported identifiers,
		// but we want to show them. Also, disable type association,
		// since it's not helpful for this fake package (see issue 6645).
		mode |= pkgdoc.ModeAll | pkgdoc.ModeBuiltin
	}
	info := pkgdoc.Doc(h.d, "src/"+relpath, mode, r.FormValue("GOOS"), r.FormValue("GOARCH"))
	if info.Err != nil {
		log.Print(info.Err)
		h.p.ServeError(w, r, info.Err)
		return
	}

	var tabtitle, title, subtitle string
	switch {
	case info.PDoc != nil:
		tabtitle = info.PDoc.Name
	default:
		tabtitle = info.Dirname
		title = "Directory "
	}
	if title == "" {
		if info.IsMain {
			// assume that the directory name is the command name
			_, tabtitle = path.Split(relpath)
			title = "Command "
		} else {
			title = "Package "
		}
	}
	title += tabtitle

	// special cases for top-level package/command directories
	switch tabtitle {
	case "/src":
		title = "Packages"
		tabtitle = "Packages"
	case "/src/cmd":
		title = "Commands"
		tabtitle = "Commands"
	}

	name := "package.html"
	if info.Dirname == "src" {
		name = "packageroot.html"
	}
	h.p.ServePage(w, r, Page{
		Title:    title,
		TabTitle: tabtitle,
		Subtitle: subtitle,
		Template: name,
		Data:     info,
		OldDocs:  mode&pkgdoc.ModeOld != 0,
	})
}

// ModeQuery returns the "?m=..." query for the current page.
// The page's Data must be a *pkgdoc.Page (to find the mode).
func (p *Page) ModeQuery() string {
	m := p.Data.(*pkgdoc.Page).Mode
	s := m.String()
	if s == "" {
		return ""
	}
	return "?m=" + s
}