github.com/yorinasub17/go-cloud@v0.27.40/internal/openurl/openurl.go (about)

     1  // Copyright 2019 The Go Cloud Development Kit Authors
     2  //
     3  // Licensed under the Apache License, Version 2.0 (the "License");
     4  // you may not use this file except in compliance with the License.
     5  // You may obtain a copy of the License at
     6  //
     7  //     https://www.apache.org/licenses/LICENSE-2.0
     8  //
     9  // Unless required by applicable law or agreed to in writing, software
    10  // distributed under the License is distributed on an "AS IS" BASIS,
    11  // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    12  // See the License for the specific language governing permissions and
    13  // limitations under the License.
    14  
    15  // Package openurl provides helpers for URLMux and URLOpeners in portable APIs.
    16  package openurl // import "gocloud.dev/internal/openurl"
    17  
    18  import (
    19  	"fmt"
    20  	"net/url"
    21  	"sort"
    22  	"strings"
    23  )
    24  
    25  // SchemeMap maps URL schemes to values. The zero value is an empty map, ready for use.
    26  type SchemeMap struct {
    27  	api string
    28  	m   map[string]interface{}
    29  }
    30  
    31  // Register registers scheme for value; subsequent calls to FromString or
    32  // FromURL with scheme will return value.
    33  // api is the portable API name (e.g., "blob"); the same value should always
    34  // be passed. It should be in all lowercase.
    35  // typ is the portable type (e.g., "Bucket").
    36  // Register panics if scheme has already been registered.
    37  func (m *SchemeMap) Register(api, typ, scheme string, value interface{}) {
    38  	if m.m == nil {
    39  		m.m = map[string]interface{}{}
    40  	}
    41  	if api != strings.ToLower(api) {
    42  		panic(fmt.Errorf("api should be lowercase: %q", api))
    43  	}
    44  	if m.api == "" {
    45  		m.api = api
    46  	} else if m.api != api {
    47  		panic(fmt.Errorf("previously registered using api %q (now %q)", m.api, api))
    48  	}
    49  	if _, exists := m.m[scheme]; exists {
    50  		panic(fmt.Errorf("scheme %q already registered for %s.%s", scheme, api, typ))
    51  	}
    52  	m.m[scheme] = value
    53  }
    54  
    55  // FromString parses urlstr as an URL and looks up the value for the URL's scheme.
    56  func (m *SchemeMap) FromString(typ, urlstr string) (interface{}, *url.URL, error) {
    57  	u, err := url.Parse(urlstr)
    58  	if err != nil {
    59  		return nil, nil, fmt.Errorf("open %s.%s: %v", m.api, typ, err)
    60  	}
    61  	val, err := m.FromURL(typ, u)
    62  	if err != nil {
    63  		return nil, nil, err
    64  	}
    65  	return val, u, nil
    66  }
    67  
    68  // FromURL looks up the value for u's scheme.
    69  func (m *SchemeMap) FromURL(typ string, u *url.URL) (interface{}, error) {
    70  	scheme := u.Scheme
    71  	if scheme == "" {
    72  		return nil, fmt.Errorf("open %s.%s: no scheme in URL %q", m.api, typ, u)
    73  	}
    74  	for _, prefix := range []string{
    75  		fmt.Sprintf("%s+%s+", m.api, strings.ToLower(typ)),
    76  		fmt.Sprintf("%s+", m.api),
    77  	} {
    78  		scheme = strings.TrimPrefix(scheme, prefix)
    79  	}
    80  	v, ok := m.m[scheme]
    81  	if !ok {
    82  		return nil, fmt.Errorf("open %s.%s: no driver registered for %q for URL %q; available schemes: %v", m.api, typ, scheme, u, strings.Join(m.Schemes(), ", "))
    83  	}
    84  	return v, nil
    85  }
    86  
    87  // Schemes returns a sorted slice of the registered schemes.
    88  func (m *SchemeMap) Schemes() []string {
    89  	var schemes []string
    90  	for s := range m.m {
    91  		schemes = append(schemes, s)
    92  	}
    93  	sort.Strings(schemes)
    94  	return schemes
    95  }
    96  
    97  // ValidScheme returns true iff scheme has been registered.
    98  func (m *SchemeMap) ValidScheme(scheme string) bool {
    99  	for s := range m.m {
   100  		if scheme == s {
   101  			return true
   102  		}
   103  	}
   104  	return false
   105  }