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client.go
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client.go
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package api2
import (
"context"
"fmt"
"io"
"net/http"
"reflect"
)
// Client is used on client-side to call remote methods provided by the API.
type Client struct {
routeMap map[signature]Route
client HttpClient
baseURL string
errorf func(format string, args ...interface{})
authorization string
maxBody int64
human bool
}
type signature struct {
request reflect.Type
response reflect.Type
}
// NewClient creates new instance of client.
//
// The list of routes must provide all routes that this client is aware of.
// Paths from the table of routes are appended to baseURL to generate final
// URL used by HTTP client.
// All pairs of (request type, response type) must be unique in the table
// of routes.
func NewClient(routes []Route, baseURL string, opts ...Option) *Client {
var client HttpClient
client = &http.Client{
CheckRedirect: func(req *http.Request, via []*http.Request) error {
return http.ErrUseLastResponse
},
}
routeMap := make(map[signature]Route, len(routes))
for _, route := range routes {
handler := route.Handler
if m, ok := handler.(*interfaceMethod); ok {
handler = m.Func()
}
handlerType := reflect.TypeOf(handler)
validateHandler(handlerType, route.Path)
key := signature{
request: handlerType.In(1),
response: handlerType.Out(0),
}
if _, has := routeMap[key]; has {
panic(fmt.Sprintf("Already has a handler with signature %v.", key))
}
routeMap[key] = route
}
config := NewDefaultConfig()
for _, opt := range opts {
opt(config)
}
if config.client != nil {
client = config.client
}
return &Client{
routeMap: routeMap,
client: client,
baseURL: baseURL,
errorf: config.errorf,
authorization: config.authorization,
maxBody: config.maxBody,
human: config.human,
}
}
type bodyCloseNeeder interface {
BodyCloseNeeded(ctx context.Context, response, request interface{}) bool
}
type responseAndErrorDecoder interface {
DecodeResponseAndError(ctx context.Context, httpRes *http.Response, res interface{}) error
}
func bodyCloseNeeded(ctx context.Context, response, request interface{}, t Transport) bool {
n, ok := t.(bodyCloseNeeder)
if !ok {
// Backward-compatible mode. Old behaviour was to Close.
return true
}
return n.BodyCloseNeeded(ctx, response, request)
}
// Call calls remote method deduced by request and response types.
// Both request and response must be pointers to structs.
// The method must be called on exactly the same types as the
// corresponding method of a service.
func (c *Client) Call(ctx context.Context, response, request interface{}) error {
key := signature{
request: reflect.TypeOf(request),
response: reflect.TypeOf(response),
}
route, has := c.routeMap[key]
if !has {
panic(fmt.Sprintf("No registered method with signature %v %v.", key.request, key.response))
}
t := route.Transport
if t == nil {
t = DefaultTransport
}
url := c.baseURL + route.Path
if c.human {
url += "?human=on"
ctx = context.WithValue(ctx, humanType{}, true)
}
req, err := t.EncodeRequest(ctx, route.Method, url, request)
if err != nil {
return fmt.Errorf("failed to encode request: %w", err)
}
if c.authorization != "" {
req.Header.Set("Authorization", c.authorization)
}
res, err := c.client.Do(req)
if err != nil {
return fmt.Errorf("request failed: %w", err)
}
res.Body = http.MaxBytesReader(nil, res.Body, c.maxBody)
defer func() {
if !bodyCloseNeeded(ctx, response, request, t) {
return
}
if err := res.Body.Close(); err != nil {
c.errorf("failed to close resource: %v", err)
}
}()
if d, ok := t.(responseAndErrorDecoder); ok {
return d.DecodeResponseAndError(req.Context(), res, response)
} else if 200 <= res.StatusCode && res.StatusCode < 300 {
// Handle all 2xx responses as success.
return t.DecodeResponse(req.Context(), res, response)
} else {
return t.DecodeError(req.Context(), res)
}
}
func (c *Client) Close() error {
c.client.CloseIdleConnections()
if closer, ok := c.client.(io.Closer); ok {
if err := closer.Close(); err != nil {
return err
}
}
return nil
}