Implement basic Client which supports the gemini protocol

client.go

@@ -0,0 +1,140 @@
+package deadlinks
+
+import (
+	"context"
+	"errors"
+	"fmt"
+	"io"
+
+	"git.sr.ht/~adnano/go-gemini"
+)
+
+// Client is a thread-safe type which fetches a resource at the given URL,
+// returning its MIME type and body. If the MIME type is not known then empty
+// string should be returned.
+type Client interface {
+	Get(context.Context, URL) (string, io.ReadCloser, error)
+}
+
+// ClientOpts are optional fields which can be provided to NewClient. A nil
+// ClientOpts is equivalent to an empty one.
+type ClientOpts struct {
+	// GeminiClient will be used for retrieving resources via the gemini
+	// protocol.
+	//
+	// Defaults to `new(gemini.Client)`.
+	GeminiClient interface {
+		Do(context.Context, *gemini.Request) (*gemini.Response, error)
+	}
+
+	// MaxRedirects indicates the maximum number of redirects which will be
+	// allowed when resolving a resource. A negative value indicates no
+	// redirects are allowed.
+	//
+	// Default: 10.
+	MaxRedirects int
+}
+
+func (o *ClientOpts) withDefaults() *ClientOpts {
+	if o == nil {
+		o = new(ClientOpts)
+	}
+
+	if o.GeminiClient == nil {
+		o.GeminiClient = new(gemini.Client)
+	}
+
+	if o.MaxRedirects == 0 {
+		o.MaxRedirects = 10
+	}
+
+	return o
+}
+
+type client struct {
+	opts ClientOpts
+}
+
+// NewClient initializes and returns a Client which supports commonly used
+// transport protocols. The returned Client will error when it encounters an
+// unfamiliar protocol.
+//
+// Supported URL schemas:
+// - gemini
+// - http/https (TODO)
+func NewClient(opts *ClientOpts) Client {
+	return &client{*opts.withDefaults()}
+}
+
+func (c *client) getGemini(
+	ctx context.Context, url URL, redirectDepth int,
+) (
+	string, io.ReadCloser, error,
+) {
+	req, err := gemini.NewRequest(string(url))
+	if err != nil {
+		return "", nil, fmt.Errorf("building request: %w", err)
+	}
+
+	// TODO allow specifying client cert
+
+	res, err := c.opts.GeminiClient.Do(ctx, req)
+	if err != nil {
+		return "", nil, fmt.Errorf("performing request: %w", err)
+	}
+
+	// all status numbers are grouped by their first digit, and actions taken
+	// can be entirely based on that.
+	switch res.Status / 10 {
+
+	case 1: // input required
+		// Assume that input required is fine, even though we don't know the
+		// MIME type.
+		return "", res.Body, nil
+
+	case 2: // success
+		return res.Meta, res.Body, nil
+
+	case 3: // redirect
+		defer res.Body.Close()
+		if redirectDepth >= c.opts.MaxRedirects {
+			return "", nil, errors.New("too many redirects")
+		}
+
+		newURL, err := url.ResolveReference(res.Meta)
+		if err != nil {
+			return "", nil, fmt.Errorf("resolving redirect URL %q: %w", res.Meta, err)
+		}
+
+		return c.get(ctx, newURL, redirectDepth+1)
+
+	default:
+		defer res.Body.Close()
+		return "", nil, fmt.Errorf(
+			"response code %d (%v): %q", res.Status, res.Status, res.Meta,
+		)
+	}
+}
+
+func (c *client) get(
+	ctx context.Context, url URL, redirectDepth int,
+) (
+	string, io.ReadCloser, error,
+) {
+
+	scheme := url.toStd().Scheme
+	switch scheme {
+	case "gemini":
+		return c.getGemini(ctx, url, redirectDepth)
+	default:
+		return "", nil, fmt.Errorf("unsupported scheme %q", scheme)
+	}
+}
+
+func (c *client) Get(
+	ctx context.Context, url URL,
+) (
+	string, io.ReadCloser, error,
+) {
+	return c.get(ctx, url, 0)
+}

deadlinks.go

@@ -50,6 +50,23 @@ func parseURLs(urlStrs []string) ([]URL, error) {
 	return res, errors.Join(errs...)
 }
 
+func (u URL) toStd() *url.URL {
+	uu, err := url.Parse(string(u))
+	if err != nil {
+		panic(fmt.Sprintf("parsing URL %q: %v", u, err))
+	}
+	return uu
+}
+
+// ResolveReference is equivalend to the method of the same name in `net/url`.
+func (u URL) ResolveReference(u2Str string) (URL, error) {
+	u2, err := url.Parse(u2Str)
+	if err != nil {
+		return "", err
+	}
+	return URL(u.toStd().ResolveReference(u2).String()), nil
+}
+
 // ResourceStatus describes what state a particular Resource is in.
 type ResourceStatus int
 

go.mod

@@ -4,6 +4,7 @@ go 1.20
 
 require (
 	code.betamike.com/mediocregopher/mediocre-go-lib v0.0.0-20231226160338-0b5bdf3dfb03 // indirect
+	git.sr.ht/~adnano/go-gemini v0.2.3 // indirect
 	github.com/davecgh/go-spew v1.1.1 // indirect
 	github.com/go-gorp/gorp/v3 v3.1.0 // indirect
 	github.com/mattn/go-sqlite3 v1.14.19 // indirect
@@ -11,5 +12,7 @@ require (
 	github.com/rubenv/sql-migrate v1.6.0 // indirect
 	github.com/stretchr/objx v0.5.0 // indirect
 	github.com/stretchr/testify v1.8.4 // indirect
+	golang.org/x/net v0.0.0-20210119194325-5f4716e94777 // indirect
+	golang.org/x/text v0.3.3 // indirect
 	gopkg.in/yaml.v3 v3.0.1 // indirect
 )

go.sum

@@ -2,6 +2,8 @@ code.betamike.com/mediocregopher/mediocre-go-lib v0.0.0-20231226155808-e8376ef26
 code.betamike.com/mediocregopher/mediocre-go-lib v0.0.0-20231226155808-e8376ef263a7/go.mod h1:GJhpoMNnN/OT6O9NmeQBV02yq9kQP8zPyY1IvsslHak=
 code.betamike.com/mediocregopher/mediocre-go-lib v0.0.0-20231226160338-0b5bdf3dfb03 h1:wJ6X1vc289RpHVGClD1P33yijPoNIdgCXbTn7DjVWYs=
 code.betamike.com/mediocregopher/mediocre-go-lib v0.0.0-20231226160338-0b5bdf3dfb03/go.mod h1:GJhpoMNnN/OT6O9NmeQBV02yq9kQP8zPyY1IvsslHak=
+git.sr.ht/~adnano/go-gemini v0.2.3 h1:oJ+Y0/mheZ4Vg0ABjtf5dlmvq1yoONStiaQvmWWkofc=
+git.sr.ht/~adnano/go-gemini v0.2.3/go.mod h1:hQ75Y0i5jSFL+FQ7AzWVAYr5LQsaFC7v3ZviNyj46dY=
 github.com/davecgh/go-spew v1.1.0/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
 github.com/davecgh/go-spew v1.1.1 h1:vj9j/u1bqnvCEfJOwUhtlOARqs3+rkHYY13jYWTU97c=
 github.com/davecgh/go-spew v1.1.1/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
@@ -21,6 +23,13 @@ github.com/stretchr/testify v1.7.1/go.mod h1:6Fq8oRcR53rry900zMqJjRRixrwX3KX962/
 github.com/stretchr/testify v1.8.0/go.mod h1:yNjHg4UonilssWZ8iaSj1OCr/vHnekPRkoO+kdMU+MU=
 github.com/stretchr/testify v1.8.4 h1:CcVxjf3Q8PM0mHUKJCdn+eZZtm5yQwehR5yeSVQQcUk=
 github.com/stretchr/testify v1.8.4/go.mod h1:sz/lmYIOXD/1dqDmKjjqLyZ2RngseejIcXlSw2iwfAo=
+golang.org/x/net v0.0.0-20210119194325-5f4716e94777 h1:003p0dJM77cxMSyCPFphvZf/Y5/NXf5fzg6ufd1/Oew=
+golang.org/x/net v0.0.0-20210119194325-5f4716e94777/go.mod h1:m0MpNAwzfU5UDzcl9v0D8zg8gWTRqZa9RBIspLL5mdg=
+golang.org/x/sys v0.0.0-20201119102817-f84b799fce68/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
+golang.org/x/term v0.0.0-20201126162022-7de9c90e9dd1/go.mod h1:bj7SfCRtBDWHUb9snDiAeCFNEtKQo2Wmx5Cou7ajbmo=
+golang.org/x/text v0.3.3 h1:cokOdA+Jmi5PJGXLlLllQSgYigAEfHXJAERHVMaCc2k=
+golang.org/x/text v0.3.3/go.mod h1:5Zoc/QRtKVWzQhOtBMvqHzDpF6irO9z98xDceosuGiQ=
+golang.org/x/tools v0.0.0-20180917221912-90fa682c2a6e/go.mod h1:n7NCudcB/nEzxVGmLbDWY5pfWTLqBcC2KZ6jyYvM4mQ=
 gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405/go.mod h1:Co6ibVJAznAaIkqp8huTwlJQCZ016jof/cbN4VW5Yz0=
 gopkg.in/yaml.v3 v3.0.0-20200313102051-9f266ea9e77c/go.mod h1:K4uyk7z7BCEPqu6E+C64Yfv1cQ7kz7rIZviUmN+EgEM=
 gopkg.in/yaml.v3 v3.0.1 h1:fxVm/GzAzEWqLHuvctI91KS9hhNmmWOoWu0XTYJS7CA=

store.go

@@ -80,8 +80,8 @@ var migrations = &migrate.MemoryMigrationSource{Migrations: []*migrate.Migration
 	},
 }}
 
-// SQLiteSQLiteStoreOpts are optional fields which can be provided to NewSQLiteStore.
-// A nil SQLiteSQLiteStoreOpts is equivalent to an empty one.
+// SQLiteSQLiteStoreOpts are optional fields which can be provided to
+// NewSQLiteStore. A nil SQLiteSQLiteStoreOpts is equivalent to an empty one.
 type SQLiteStoreOpts struct {
 	// Path to the database file to use.
 	//