implement New* routines for fetching and creating new feeds/pages.

Also includes routines for fetching gemini, http, and gopher resources.

TODO: add Update* routines to update existing feeds/pages.

6 files changed, 408 insertions, 0 deletions

diff --git a/fetch/fetch.go b/fetch/fetch.go
new file mode 100644
index 0000000..5c6809a
--- /dev/null
+++ b/fetch/fetch.go
@@ -0,0 +1,54 @@
+// Copyright (C) 2021 nytpu
+// SPDX-License-Identifier: AGPL-3.0-or-later
+// For more license details, see LICENSE or <https://www.gnu.org/licenses/agpl-3.0.html>.
+
+// package fetch implements routines for fetching gemini, gopher, and http
+// resources and parsing feed formats
+package fetch
+
+import (
+	"fmt"
+	"net/url"
+
+	"golang.nytpu.com/comitium/core"
+)
+
+// NewFeed will fetch and create a new core.Feed given any url
+func NewFeed(remoteURL *url.URL, title string) (*core.Feed, error) {
+	switch remoteURL.Scheme {
+	case "gemini":
+		return newGeminiFeed(remoteURL, title)
+	case "http", "https":
+		return newHTTPFeed(remoteURL, title)
+	case "gopher", "gophers":
+		return newGopherFeed(remoteURL, title)
+	default:
+		return nil, fmt.Errorf("Unsupported protocol '%s'", remoteURL.Scheme)
+	}
+}
+
+// NewPage will fetch and create a new core.Page given any url
+func NewPage(remoteURL *url.URL, title string) (*core.Page, error) {
+	switch remoteURL.Scheme {
+	case "gemini":
+		return newGeminiPage(remoteURL, title)
+	case "http", "https":
+		return newHTTPPage(remoteURL, title)
+	case "gopher", "gophers":
+		return newGopherPage(remoteURL, title)
+	default:
+		return nil, fmt.Errorf("Unsupported protocol '%s'", remoteURL.Scheme)
+	}
+}
+
+// UpdateFeed will check an existing core.Feed for updates
+func UpdateFeed(feed *core.Feed) error {
+	// TODO
+	return nil
+}
+
+// UpdatePage will check an existing core.Page for updages
+func UpdatePage(page *core.Page) error {
+	// TODO
+	return nil
+}
diff --git a/fetch/gemini.go b/fetch/gemini.go
new file mode 100644
index 0000000..d32d093
--- /dev/null
+++ b/fetch/gemini.go
@@ -0,0 +1,133 @@
+// Copyright (C) 2021 nytpu
+// SPDX-License-Identifier: AGPL-3.0-or-later
+// For more license details, see LICENSE or <https://www.gnu.org/licenses/agpl-3.0.html>.
+
+// This file incorporates code from Drew DeVault's gemreader:
+// https://git.sr.ht/~sircmpwn/gemreader/tree/master/item/feeds/fetch.go
+// Original source is Copyright 2021 Drew DeVault and is licensed under the
+// terms of the GNU Affero General Public License Version 3.0.
+// https://www.gnu.org/licenses/agpl-3.0-standalone.html
+
+package fetch
+
+import (
+	"context"
+	"crypto/sha256"
+	"fmt"
+	"io"
+	"mime"
+	"net/url"
+	"strings"
+	"time"
+
+	"git.sr.ht/~adnano/go-gemini"
+	"github.com/mmcdole/gofeed"
+
+	"golang.nytpu.com/comitium/core"
+)
+
+// fetchGemini will make a request for a gemini resource
+func fetchGemini(remoteURL *url.URL) (*gemini.Response, error) {
+	client := &gemini.Client{}
+	resp, err := client.Get(context.Background(), remoteURL.String())
+	if err != nil {
+		return nil, err
+	}
+	if resp.Status != gemini.StatusSuccess {
+		return nil, fmt.Errorf("Unexpected Gemini response: %d %s", resp.Status, resp.Meta)
+	}
+
+	return resp, nil
+}
+
+// newGeminiFeed will fetch and create a new core.Feed given a gemini url
+func newGeminiFeed(remoteURL *url.URL, title string) (*core.Feed, error) {
+	resp, err := fetchGemini(remoteURL)
+	if err != nil {
+		return nil, err
+	}
+	defer resp.Body.Close()
+
+	mimetype, _, err := mime.ParseMediaType(resp.Meta)
+	if err != nil {
+		return nil, fmt.Errorf("Unintelligible content type: %s", resp.Meta)
+	}
+
+	reader := io.LimitReader(resp.Body, 1073741824) // 1 GiB
+
+	switch mimetype {
+	case "text/gemini":
+		var feed core.Feed
+		feed.Title = title // will be set later if given title is ""
+		feed.Link = remoteURL
+		text, err := gemini.ParseText(resp.Body)
+		if err != nil {
+			return nil, err
+		}
+		for _, line := range text {
+			switch line := line.(type) {
+			case gemini.LineHeading1:
+				if feed.Title == "" {
+					feed.Title = strings.TrimLeft(line.String(), "# ")
+				}
+			case gemini.LineLink:
+				if line.Name == "" || len(line.Name) < 10 {
+					continue
+				}
+				name := strings.TrimLeft(line.Name[:10], " -—")
+				date, err := time.Parse("2006-01-02", name)
+				if err != nil {
+					continue
+				}
+				link, err := url.Parse(line.URL)
+				if err != nil {
+					continue
+				}
+				link = remoteURL.ResolveReference(link)
+				item := &core.Item{}
+				item.Title = strings.TrimLeft(line.Name[10:], ": ")
+				item.Published = date
+				item.Link = link
+				feed.Items = append(feed.Items, item)
+			}
+		}
+		return &feed, nil
+	case "text/xml",
+		"application/rss+xml",
+		"application/atom+xml",
+		"application/xml",
+		"application/json":
+		gofeed, err := gofeed.NewParser().Parse(reader)
+		if err != nil {
+			return nil, err
+		}
+		feed, err := core.GofeedConvert(gofeed, title)
+		return feed, err
+	default:
+		return nil, fmt.Errorf("Cannot interpret %s as a feed", resp.Meta)
+	}
+}
+
+// newGeminiPage will create a new core.Page given a gemini url
+func newGeminiPage(remoteURL *url.URL, title string) (*core.Page, error) {
+	resp, err := fetchGemini(remoteURL)
+	if err != nil {
+		return nil, err
+	}
+	defer resp.Body.Close()
+
+	reader := io.LimitReader(resp.Body, 1073741824) // 1 GiB
+
+	var page core.Page
+	page.Title = title
+	page.Link = remoteURL
+	page.Updated = time.Now()
+
+	h := sha256.New()
+	if _, err := io.Copy(h, reader); err != nil {
+		return nil, err
+	}
+	page.Hash = fmt.Sprintf("%x", h.Sum(nil))
+
+	return &page, nil
+}
diff --git a/fetch/gopher.go b/fetch/gopher.go
new file mode 100644
index 0000000..5750fad
--- /dev/null
+++ b/fetch/gopher.go
@@ -0,0 +1,67 @@
+// Copyright (C) 2021 nytpu
+// SPDX-License-Identifier: AGPL-3.0-or-later
+// For more license details, see LICENSE or <https://www.gnu.org/licenses/agpl-3.0.html>.
+
+package fetch
+
+import (
+	"bytes"
+	"crypto/sha256"
+	"fmt"
+	"io"
+	"net/url"
+	"time"
+
+	//"github.com/mmcdole/gofeed"
+	"github.com/prologic/go-gopher"
+
+	"golang.nytpu.com/comitium/core"
+)
+
+// fetchGopher will make a request for a gopher resource
+func fetchGopher(remoteURL *url.URL) (*gopher.Response, error) {
+	resp, err := gopher.Get(remoteURL.String())
+	if err != nil {
+		return nil, err
+	}
+	return resp, nil
+}
+
+// newGopherFeed will fetch and create a new core.Feed given a gopher url
+func newGopherFeed(remoteURL *url.URL, title string) (*core.Feed, error) {
+	// TODO
+	return nil, fmt.Errorf("Feeds served over gopher are currently unsupported.")
+}
+
+// newGopherPage will create a new core.Page given a gopher url
+func newGopherPage(remoteURL *url.URL, title string) (*core.Page, error) {
+	resp, err := fetchGopher(remoteURL)
+	if err != nil {
+		return nil, err
+	}
+	defer resp.Body.Close()
+
+	var reader io.Reader
+	if len(resp.Dir.Items) > 0 {
+		text, err := resp.Dir.ToText()
+		if err != nil {
+			return nil, err
+		}
+		reader = io.LimitReader(bytes.NewReader(text), 1073741824) // 1 GiB
+	} else {
+		reader = io.LimitReader(resp.Body, 1073741824) // 1 GiB
+	}
+
+	var page core.Page
+	page.Title = title
+	page.Link = remoteURL
+	page.Updated = time.Now()
+
+	h := sha256.New()
+	if _, err := io.Copy(h, reader); err != nil {
+		return nil, err
+	}
+	page.Hash = fmt.Sprintf("%x", h.Sum(nil))
+
+	return &page, nil
+}
diff --git a/fetch/http.go b/fetch/http.go
new file mode 100644
index 0000000..fb373e6
--- /dev/null
+++ b/fetch/http.go
@@ -0,0 +1,99 @@
+// Copyright (C) 2021 nytpu
+// SPDX-License-Identifier: AGPL-3.0-or-later
+// For more license details, see LICENSE or <https://www.gnu.org/licenses/agpl-3.0.html>.
+
+// This file incorporates code from Drew DeVault's gemreader:
+// https://git.sr.ht/~sircmpwn/gemreader/tree/master/item/feeds/fetch.go
+// Original source is Copyright 2021 Drew DeVault and is licensed under the
+// terms of the GNU Affero General Public License Version 3.0.
+// https://www.gnu.org/licenses/agpl-3.0-standalone.html
+
+package fetch
+
+import (
+	"context"
+	"crypto/sha256"
+	"fmt"
+	"io"
+	"net/http"
+	"net/url"
+	"time"
+
+	"github.com/mmcdole/gofeed"
+
+	"golang.nytpu.com/comitium/core"
+)
+
+// fetchHTTP will make a request for an http resource
+func fetchHTTP(remoteURL *url.URL) (*http.Response, error) {
+	client := &http.Client{
+		Timeout: 10 * time.Second,
+	}
+
+	req, err := http.NewRequestWithContext(context.Background(), "GET", remoteURL.String(), nil)
+	req.Header.Add("User-Agent", "comitium (https://git.nytpu.com/comitium/)")
+	if err != nil {
+		return nil, err
+	}
+
+	resp, err := client.Do(req)
+	if err != nil {
+		return nil, err
+	}
+
+	if resp.StatusCode != 200 {
+		resp.Body.Close()
+		return nil, fmt.Errorf("Unexpected HTTP response %s", resp.Status)
+	}
+	return resp, nil
+}
+
+// newHTTPFeed will fetch and create a new core.Feed given an http url
+func newHTTPFeed(remoteURL *url.URL, title string) (*core.Feed, error) {
+	resp, err := fetchHTTP(remoteURL)
+	if err != nil {
+		return nil, err
+	}
+	defer resp.Body.Close()
+
+	if resp.Header.Get("Content-Type") == "text/html" {
+		// TODO
+		return nil, fmt.Errorf("Extracting feed from HTML pages is unimplemented")
+	}
+
+	reader := io.LimitReader(resp.Body, 1073741824) // 1 GiB
+	data, err := io.ReadAll(reader)
+	if err != nil {
+		return nil, err
+	}
+	gofeed, err := gofeed.NewParser().Parse(reader)
+	if err != nil {
+		return nil, err
+	}
+	feed, err := core.GofeedConvert(gofeed, title)
+	return feed, err
+}
+
+// newHTTPPage will create a new core.Page given an http url
+func newHTTPPage(remoteURL *url.URL, title string) (*core.Page, error) {
+	resp, err := fetchHTTP(remoteURL)
+	if err != nil {
+		return nil, err
+	}
+	defer resp.Body.Close()
+
+	reader := io.LimitReader(resp.Body, 1073741824) // 1 GiB
+
+	var page core.Page
+	page.Title = title
+	page.Link = remoteURL
+	page.Updated = time.Now()
+
+	h := sha256.New()
+	if _, err := io.Copy(h, reader); err != nil {
+		return nil, err
+	}
+	page.Hash = fmt.Sprintf("%x", h.Sum(nil))
+
+	return &page, nil
+}
diff --git a/go.mod b/go.mod
index 337d9c1..8940067 100644
--- a/go.mod
+++ b/go.mod
@@ -3,6 +3,9 @@ module golang.nytpu.com/comitium
 go 1.16
 
 require (
+	git.sr.ht/~adnano/go-gemini v0.1.21
 	github.com/mitchellh/go-homedir v1.1.0
+	github.com/mmcdole/gofeed v1.1.0
+	github.com/prologic/go-gopher v0.0.0-20210114215941-1859ade2470b
 	github.com/spf13/pflag v1.0.5
 )
diff --git a/go.sum b/go.sum
index 8635e51..a22438e 100644
--- a/go.sum
+++ b/go.sum
@@ -1,4 +1,56 @@
+git.sr.ht/~adnano/go-gemini v0.1.21 h1:qpCtFYgHGeW0Jf+0A5MeUtZ4/hAnfSeS7LkOTJnpKwQ=
+git.sr.ht/~adnano/go-gemini v0.1.21/go.mod h1:kmWT0aLnjkuzAMouxNT6Bqv756HYHSe56HE7yoF5P7Y=
+github.com/BurntSushi/toml v0.3.1/go.mod h1:xHWCNGjB5oqiDr8zfno3MHue2Ht5sIBksp03qcyfWMU=
+github.com/PuerkitoBio/goquery v1.5.1 h1:PSPBGne8NIUWw+/7vFBV+kG2J/5MOjbzc7154OaKCSE=
+github.com/PuerkitoBio/goquery v1.5.1/go.mod h1:GsLWisAFVj4WgDibEWF4pvYnkVQBpKBKeU+7zCJoLcc=
+github.com/andybalholm/cascadia v1.1.0 h1:BuuO6sSfQNFRu1LppgbD25Hr2vLYW25JvxHs5zzsLTo=
+github.com/andybalholm/cascadia v1.1.0/go.mod h1:GsXiBklL0woXo1j/WYWtSYYC4ouU9PqHO0sqidkEA4Y=
+github.com/cpuguy83/go-md2man/v2 v2.0.0-20190314233015-f79a8a8ca69d/go.mod h1:maD7wRr/U5Z6m/iR4s+kqSMx2CaBsrgA7czyZG/E6dU=
+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=
+github.com/google/gofuzz v1.0.0/go.mod h1:dBl0BpW6vV/+mYPU4Po3pmUjxk6FQPldtuIdl/M65Eg=
+github.com/json-iterator/go v1.1.10 h1:Kz6Cvnvv2wGdaG/V8yMvfkmNiXq9Ya2KUv4rouJJr68=
+github.com/json-iterator/go v1.1.10/go.mod h1:KdQUCv79m/52Kvf8AW2vK1V8akMuk1QjK/uOdHXbAo4=
 github.com/mitchellh/go-homedir v1.1.0 h1:lukF9ziXFxDFPkA1vsr5zpc1XuPDn/wFntq5mG+4E0Y=
 github.com/mitchellh/go-homedir v1.1.0/go.mod h1:SfyaCUpYCn1Vlf4IUYiD9fPX4A5wJrkLzIz1N1q0pr0=
+github.com/mmcdole/gofeed v1.1.0 h1:T2WrGLVJRV04PY2qwhEJLHCt9JiCtBhb6SmC8ZvJH08=
+github.com/mmcdole/gofeed v1.1.0/go.mod h1:PPiVwgDXLlz2N83KB4TrIim2lyYM5Zn7ZWH9Pi4oHUk=
+github.com/mmcdole/goxpp v0.0.0-20181012175147-0068e33feabf h1:sWGE2v+hO0Nd4yFU/S/mDBM5plIU8v/Qhfz41hkDIAI=
+github.com/mmcdole/goxpp v0.0.0-20181012175147-0068e33feabf/go.mod h1:pasqhqstspkosTneA62Nc+2p9SOBBYAPbnmRRWPQ0V8=
+github.com/modern-go/concurrent v0.0.0-20180228061459-e0a39a4cb421 h1:ZqeYNhU3OHLH3mGKHDcjJRFFRrJa6eAM5H+CtDdOsPc=
+github.com/modern-go/concurrent v0.0.0-20180228061459-e0a39a4cb421/go.mod h1:6dJC0mAP4ikYIbvyc7fijjWJddQyLn8Ig3JB5CqoB9Q=
+github.com/modern-go/reflect2 v0.0.0-20180701023420-4b7aa43c6742 h1:Esafd1046DLDQ0W1YjYsBW+p8U2u7vzgW2SQVmlNazg=
+github.com/modern-go/reflect2 v0.0.0-20180701023420-4b7aa43c6742/go.mod h1:bx2lNnkwVCuqBIxFjflWJWanXIb3RllmbCylyMrvgv0=
+github.com/pmezard/go-difflib v1.0.0 h1:4DBwDE0NGyQoBHbLQYPwSUPoCMWR5BEzIk/f1lZbAQM=
+github.com/pmezard/go-difflib v1.0.0/go.mod h1:iKH77koFhYxTK1pcRnkKkqfTogsbg7gZNVY4sRDYZ/4=
+github.com/prologic/go-gopher v0.0.0-20210114215941-1859ade2470b h1:bOYTIzro9GwU+OV5RJnFXCUW7fVnzY+wGDaL2ceFvn4=
+github.com/prologic/go-gopher v0.0.0-20210114215941-1859ade2470b/go.mod h1:ypKOIAVSaX4/TBkLcXhjcpSZKrBOmOd/sufqKUyM6Xc=
+github.com/russross/blackfriday/v2 v2.0.1/go.mod h1:+Rmxgy9KzJVeS9/2gXHxylqXiyQDYRxCVz55jmeOWTM=
+github.com/shurcooL/sanitized_anchor_name v1.0.0/go.mod h1:1NzhyTcUVG4SuEtjjoZeVRXNmyL/1OwPU0+IJeTBvfc=
 github.com/spf13/pflag v1.0.5 h1:iy+VFUOCP1a+8yFto/drg2CJ5u0yRoB7fZw3DKv/JXA=
 github.com/spf13/pflag v1.0.5/go.mod h1:McXfInJRrz4CZXVZOBLb0bTZqETkiAhM9Iw0y3An2Bg=
+github.com/stretchr/objx v0.1.0/go.mod h1:HFkY916IF+rwdDfMAkV7OtwuqBVzrE8GR6GFx+wExME=
+github.com/stretchr/testify v1.3.0/go.mod h1:M5WIy9Dh21IEIfnGCwXGc5bZfKNJtfHm1UVUgZn+9EI=
+github.com/stretchr/testify v1.7.0 h1:nwc3DEeHmmLAfoZucVR881uASk0Mfjw8xYJ99tb5CcY=
+github.com/stretchr/testify v1.7.0/go.mod h1:6Fq8oRcR53rry900zMqJjRRixrwX3KX962/h/Wwjteg=
+github.com/urfave/cli v1.22.3/go.mod h1:Gos4lmkARVdJ6EkW0WaNv/tZAAMe9V7XWyB60NtXRu0=
+golang.org/x/crypto v0.0.0-20190308221718-c2843e01d9a2/go.mod h1:djNgcEr1/C05ACkg1iLfiJU5Ep61QUkGW8qpdssI0+w=
+golang.org/x/net v0.0.0-20180218175443-cbe0f9307d01/go.mod h1:mL1N/T3taQHkDXs73rZJwtUhF3w3ftmwwsq0BUmARs4=
+golang.org/x/net v0.0.0-20181220203305-927f97764cc3/go.mod h1:mL1N/T3taQHkDXs73rZJwtUhF3w3ftmwwsq0BUmARs4=
+golang.org/x/net v0.0.0-20200202094626-16171245cfb2/go.mod h1:z5CRVTTTmAJ677TzLLGU+0bjPO0LkuOLi4/5GtJWs/s=
+golang.org/x/net v0.0.0-20200301022130-244492dfa37a/go.mod h1:z5CRVTTTmAJ677TzLLGU+0bjPO0LkuOLi4/5GtJWs/s=
+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 v0.0.0-20190215142949-d0b11bdaac8a/go.mod h1:STP8DvDyc/dI5b8T5hshtkjS+E42TnysNCUPdjciGhY=
+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 v0.3.0/go.mod h1:NqM8EUOU14njkJ3fqMW+pc6Ldnwhi/IjpwHt7yyuwOQ=
+golang.org/x/text v0.3.2/go.mod h1:bEr9sfX3Q8Zfm5fL9x+3itogRgK3+ptLWKqgva+5dAk=
+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.v2 v2.2.2/go.mod h1:hI93XBmqTisBFMUTm0b8Fm+jr3Dg1NNxqwp+5A1VGuI=
+gopkg.in/yaml.v3 v3.0.0-20200313102051-9f266ea9e77c h1:dUUwHk2QECo/6vqA44rthZ8ie2QXMNeKRTHCNY2nXvo=
+gopkg.in/yaml.v3 v3.0.0-20200313102051-9f266ea9e77c/go.mod h1:K4uyk7z7BCEPqu6E+C64Yfv1cQ7kz7rIZviUmN+EgEM=