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package pkg
import (
"fmt"
"io"
"net/http"
"path"
"unique"
)
// An httpArtifact is an [Artifact] backed by a [http] url string. The method is
// hardcoded as [http.MethodGet]. Request body is not allowed because it cannot
// be deterministically represented by Params.
type httpArtifact struct {
// Caller-supplied url string.
url string
// Caller-supplied checksum of the response body. This is validated when
// closing the [io.ReadCloser] returned by Cure.
checksum unique.Handle[Checksum]
// doFunc is the Do method of [http.Client] supplied by the caller.
doFunc func(req *http.Request) (*http.Response, error)
}
var _ KnownChecksum = new(httpArtifact)
var _ fmt.Stringer = new(httpArtifact)
// NewHTTPGet returns a new [FileArtifact] backed by the supplied client. A GET
// request is set up for url. If c is nil, [http.DefaultClient] is used instead.
func NewHTTPGet(
c *http.Client,
url string,
checksum Checksum,
) FileArtifact {
if c == nil {
c = http.DefaultClient
}
return &httpArtifact{url: url, checksum: unique.Make(checksum), doFunc: c.Do}
}
// Kind returns the hardcoded [Kind] constant.
func (a *httpArtifact) Kind() Kind { return KindHTTPGet }
// Params writes the backing url string. Client is not represented as it does
// not affect [Cache.Cure] outcome.
func (a *httpArtifact) Params(ctx *IContext) {
ctx.GetHash().Write([]byte(a.url))
}
// Dependencies returns a nil slice.
func (a *httpArtifact) Dependencies() []Artifact { return nil }
// Checksum returns the caller-supplied checksum.
func (a *httpArtifact) Checksum() Checksum { return a.checksum.Value() }
// String returns [path.Base] over the backing url.
func (a *httpArtifact) String() string { return path.Base(a.url) }
// ResponseStatusError is returned for a response returned by an [http.Client]
// with a status code other than [http.StatusOK].
type ResponseStatusError int
func (e ResponseStatusError) Error() string {
return "the requested URL returned non-OK status: " + http.StatusText(int(e))
}
// Cure sends the http request and returns the resulting response body reader
// wrapped to perform checksum validation. It is valid but not encouraged to
// close the resulting [io.ReadCloser] before it is read to EOF, as that causes
// Close to block until all remaining data is consumed and validated.
func (a *httpArtifact) Cure(r *RContext) (rc io.ReadCloser, err error) {
var req *http.Request
req, err = http.NewRequestWithContext(r.Unwrap(), http.MethodGet, a.url, nil)
if err != nil {
return
}
var resp *http.Response
if resp, err = a.doFunc(req); err != nil {
return
}
if resp.StatusCode != http.StatusOK {
_ = resp.Body.Close()
return nil, ResponseStatusError(resp.StatusCode)
}
rc = r.NewMeasuredReader(resp.Body, a.checksum)
return
}
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