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cassette.go
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cassette.go
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// Copyright (c) 2015 Marin Atanasov Nikolov <dnaeon@gmail.com>
// All rights reserved.
//
// Redistribution and use in source and binary forms, with or without
// modification, are permitted provided that the following conditions
// are met:
// 1. Redistributions of source code must retain the above copyright
// notice, this list of conditions and the following disclaimer
// in this position and unchanged.
// 2. Redistributions in binary form must reproduce the above copyright
// notice, this list of conditions and the following disclaimer in the
// documentation and/or other materials provided with the distribution.
//
// THIS SOFTWARE IS PROVIDED BY THE AUTHOR(S) ``AS IS'' AND ANY EXPRESS OR
// IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
// OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
// IN NO EVENT SHALL THE AUTHOR(S) BE LIABLE FOR ANY DIRECT, INDIRECT,
// INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
// NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
// THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
package cassette
import (
"errors"
"fmt"
"io/ioutil"
"net/http"
"net/url"
"os"
"path/filepath"
"sync"
"time"
"gopkg.in/yaml.v3"
)
// Cassette format versions
const (
cassetteFormatV1 = 1
)
var (
// ErrInteractionNotFound indicates that a requested
// interaction was not found in the cassette file
ErrInteractionNotFound = errors.New("requested interaction not found")
// ErrCassetteNotFound indicates that a requested
// casette doesn't exist (only in Replaying mode)
ErrCassetteNotFound = errors.New("requested cassette not found")
)
// Request represents a client request as recorded in the
// cassette file
type Request struct {
// Body of request
Body string `yaml:"body"`
// Form values
Form url.Values `yaml:"form"`
// Request headers
Headers http.Header `yaml:"headers"`
// Request URL
URL string `yaml:"url"`
// Request method
Method string `yaml:"method"`
}
// Response represents a server response as recorded in the
// cassette file
type Response struct {
// Body of response
Body string `yaml:"body"`
// Response headers
Headers http.Header `yaml:"headers"`
// Response status message
Status string `yaml:"status"`
// Response status code
Code int `yaml:"code"`
// Response duration (something like "100ms" or "10s")
Duration time.Duration `yaml:"duration"`
replayed bool
}
// Interaction type contains a pair of request/response for a
// single HTTP interaction between a client and a server
type Interaction struct {
Request `yaml:"request"`
Response `yaml:"response"`
}
// Matcher function returns true when the actual request matches
// a single HTTP interaction's request according to the function's
// own criteria.
type Matcher func(*http.Request, Request) bool
// DefaultMatcher is used when a custom matcher is not defined
// and compares only the method and URL.
func DefaultMatcher(r *http.Request, i Request) bool {
return r.Method == i.Method && r.URL.String() == i.URL
}
// Filter function allows modification of an interaction before saving.
type Filter func(*Interaction) error
// Cassette type
type Cassette struct {
// Name of the cassette
Name string `yaml:"-"`
// File name of the cassette as written on disk
File string `yaml:"-"`
// Cassette format version
Version int `yaml:"version"`
// Mutex to lock accessing Interactions. omitempty is set
// to prevent the mutex appearing in the recorded YAML.
Mu sync.RWMutex `yaml:"mu,omitempty"`
// Interactions between client and server
Interactions []*Interaction `yaml:"interactions"`
// ReplayableInteractions defines whether to allow interactions to be replayed or not
ReplayableInteractions bool `yaml:"-"`
// Matches actual request with interaction requests.
Matcher Matcher `yaml:"-"`
// Filters interactions before when they are captured.
Filters []Filter `yaml:"-"`
// SaveFilters are applied to interactions just before they are saved.
SaveFilters []Filter `yaml:"-"`
}
// New creates a new empty cassette
func New(name string) *Cassette {
c := &Cassette{
Name: name,
File: fmt.Sprintf("%s.yaml", name),
Version: cassetteFormatV1,
Interactions: make([]*Interaction, 0),
Matcher: DefaultMatcher,
Filters: make([]Filter, 0),
SaveFilters: make([]Filter, 0),
}
return c
}
// Load reads a cassette file from disk
func Load(name string) (*Cassette, error) {
c := New(name)
data, err := ioutil.ReadFile(c.File)
if err != nil {
return nil, err
}
err = yaml.Unmarshal(data, &c)
return c, err
}
// AddInteraction appends a new interaction to the cassette
func (c *Cassette) AddInteraction(i *Interaction) {
c.Mu.Lock()
c.Interactions = append(c.Interactions, i)
c.Mu.Unlock()
}
// GetInteraction retrieves a recorded request/response interaction
func (c *Cassette) GetInteraction(r *http.Request) (*Interaction, error) {
c.Mu.Lock()
defer c.Mu.Unlock()
for _, i := range c.Interactions {
if (c.ReplayableInteractions || !i.replayed) && c.Matcher(r, i.Request) {
i.replayed = true
return i, nil
}
}
return nil, ErrInteractionNotFound
}
// Save writes the cassette data on disk for future re-use
func (c *Cassette) Save() error {
c.Mu.RLock()
defer c.Mu.RUnlock()
// Save cassette file only if there were any interactions made
if len(c.Interactions) == 0 {
return nil
}
for _, interaction := range c.Interactions {
for _, filter := range c.SaveFilters {
if err := filter(interaction); err != nil {
return err
}
}
}
// Create directory for cassette if missing
cassetteDir := filepath.Dir(c.File)
if _, err := os.Stat(cassetteDir); os.IsNotExist(err) {
if err = os.MkdirAll(cassetteDir, 0755); err != nil {
return err
}
}
// Marshal to YAML and save interactions
data, err := yaml.Marshal(c)
if err != nil {
return err
}
f, err := os.Create(c.File)
if err != nil {
return err
}
defer f.Close()
// Honor the YAML structure specification
// http://www.yaml.org/spec/1.2/spec.html#id2760395
_, err = f.Write([]byte("---\n"))
if err != nil {
return err
}
_, err = f.Write(data)
if err != nil {
return err
}
return nil
}