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package pkg
import (
"context"
"crypto/sha512"
"errors"
"io"
"net/http"
"os"
"sync"
"hakurei.app/container/check"
)
// An httpArtifact is an [Artifact] backed by an [http] request.
type httpArtifact struct {
// Caller-supplied request.
req *http.Request
// Caller-supplied checksum of the response body, also used as the
// identifier. This is validated during curing.
id ID
// doFunc is the Do method of [http.Client] supplied by the caller.
doFunc func(req *http.Request) (*http.Response, error)
// Instance of [Cache] to submit the cured artifact to.
c *Cache
// Response body read to EOF.
data []byte
// Populated when submitting to or loading from [Cache].
pathname *check.Absolute
// Synchronises access to pathname and data.
mu sync.Mutex
}
// NewHTTP returns a new [File] backed by the supplied client and request. If
// c is nil, [http.DefaultClient] is used instead.
func (c *Cache) NewHTTP(hc *http.Client, req *http.Request, checksum Checksum) File {
if hc == nil {
hc = http.DefaultClient
}
return &httpArtifact{req: req, id: checksum, doFunc: hc.Do, c: c}
}
// NewHTTPGet returns a new [File] backed by the supplied client. A GET request
// is set up for url. If c is nil, [http.DefaultClient] is used instead.
func (c *Cache) NewHTTPGet(
ctx context.Context,
hc *http.Client,
url string,
checksum Checksum,
) (File, error) {
req, err := http.NewRequestWithContext(ctx, http.MethodGet, url, nil)
if err != nil {
return nil, err
}
return c.NewHTTP(hc, req, checksum), nil
}
// Kind returns the hardcoded [Kind] constant.
func (a *httpArtifact) Kind() Kind { return KindHTTP }
// ID returns the caller-supplied hash of the response body.
func (a *httpArtifact) ID() ID { return a.id }
// 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))
}
// do sends the caller-supplied request on the caller-supplied [http.Client]
// and reads its response body to EOF and returns the resulting bytes.
func (a *httpArtifact) do() (data []byte, err error) {
var resp *http.Response
if resp, err = a.doFunc(a.req); err != nil {
return
}
if resp.StatusCode != http.StatusOK {
_ = resp.Body.Close()
return nil, ResponseStatusError(resp.StatusCode)
}
if data, err = io.ReadAll(resp.Body); err != nil {
_ = resp.Body.Close()
return
}
err = resp.Body.Close()
return
}
// Hash cures the [Artifact] and returns its hash. The return value is always
// identical to that of the ID method.
func (a *httpArtifact) Hash() (Checksum, error) { _, err := a.Pathname(); return a.id, err }
// Pathname cures the [Artifact] and returns its pathname in the [Cache].
func (a *httpArtifact) Pathname() (pathname *check.Absolute, err error) {
a.mu.Lock()
defer a.mu.Unlock()
if a.pathname != nil {
return a.pathname, nil
}
if a.data != nil {
pathname, err = a.c.StoreFile(
a.id, a.data,
(*Checksum)(&a.id),
true,
)
if err == nil {
a.pathname = pathname
}
return
} else {
a.pathname, a.data, _, err = a.c.LoadOrStoreFile(
a.id, a.do,
(*Checksum)(&a.id),
true,
)
if err != nil {
a.pathname, a.data = nil, nil
}
return a.pathname, err
}
}
// Data completes the http request and returns the resulting response body read
// to EOF. Data does not write to the underlying [Cache].
func (a *httpArtifact) Data() (data []byte, err error) {
a.mu.Lock()
defer a.mu.Unlock()
if a.data != nil {
// validated by cache or a previous call to Data
return a.data, nil
}
if a.pathname, a.data, err = a.c.LoadFile(a.id); err == nil {
return a.data, nil
} else {
a.pathname, a.data = nil, nil
if !errors.Is(err, os.ErrNotExist) {
return
}
}
if data, err = a.do(); err != nil {
return
}
h := sha512.New384()
h.Write(data)
if got := (Checksum)(h.Sum(nil)); got != a.id {
return nil, &ChecksumMismatchError{got, a.id}
}
a.data = data
return
}
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