// Copyright 2019 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 frontend

import (
	"context"
	"net/http"
	"strings"

	"golang.org/x/pkgsite/internal"
	"golang.org/x/pkgsite/internal/derrors"
	"golang.org/x/pkgsite/internal/postgres"
	"golang.org/x/pkgsite/internal/stdlib"
)

// handlePackageDetailsRedirect redirects all redirects to "/pkg" to "/".
func (s *Server) handlePackageDetailsRedirect(w http.ResponseWriter, r *http.Request) {
	urlPath := strings.TrimPrefix(r.URL.Path, "/pkg")
	http.Redirect(w, r, urlPath, http.StatusMovedPermanently)
}

// handleModuleDetailsRedirect redirects all redirects to "/mod" to "/".
func (s *Server) handleModuleDetailsRedirect(w http.ResponseWriter, r *http.Request) {
	urlPath := strings.TrimPrefix(r.URL.Path, "/mod")
	http.Redirect(w, r, urlPath, http.StatusMovedPermanently)
}

// stdlibPathForShortcut returns a path in the stdlib that shortcut should redirect to,
// or the empty string if there is no such path.
func stdlibPathForShortcut(ctx context.Context, ds internal.DataSource, shortcut string) (path string, err error) {
	defer derrors.Wrap(&err, "stdlibPathForShortcut(ctx, %q)", shortcut)
	if !stdlib.Contains(shortcut) {
		return "", nil
	}
	db, ok := ds.(*postgres.DB)
	if !ok {
		return "", proxydatasourceNotSupportedErr()
	}
	matches, err := db.GetStdlibPathsWithSuffix(ctx, shortcut)
	if err != nil {
		return "", err
	}
	if len(matches) == 1 {
		return matches[0], nil
	}
	// No matches, or ambiguous.
	return "", nil
}