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amfora/renderer/page.go

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package renderer
import (
"errors"
"io/ioutil"
"mime"
"strings"
"github.com/makeworld-the-better-one/amfora/structs"
"github.com/makeworld-the-better-one/go-gemini"
"golang.org/x/text/encoding/ianaindex"
)
// isUTF8 returns true for charsets that are compatible with UTF-8 and don't need to be decoded.
func isUTF8(charset string) bool {
utfCharsets := []string{"", "utf-8", "us-ascii"}
for i := range utfCharsets {
if strings.ToLower(charset) == utfCharsets[i] {
return true
}
}
return false
}
// CanDisplay returns true if the response is supported by Amfora
// for displaying on the screen.
// It also doubles as a function to detect whether something can be stored in a Page struct.
func CanDisplay(res *gemini.Response) bool {
if gemini.SimplifyStatus(res.Status) != 20 {
// No content
return false
}
mediatype, params, err := mime.ParseMediaType(res.Meta)
if err != nil {
return false
}
if !strings.HasPrefix(mediatype, "text/") {
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// Amfora doesn't support other filetypes
return false
}
if isUTF8(params["charset"]) {
return true
}
enc, err := ianaindex.MIME.Encoding(params["charset"]) // Lowercasing is done inside
// Encoding sometimes returns nil, see #3 on this repo and golang/go#19421
return err == nil && enc != nil
}
func MakePage(url string, res *gemini.Response, width int) (*structs.Page, error) {
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if !CanDisplay(res) {
return nil, errors.New("not valid content for a Page")
}
rawText, err := ioutil.ReadAll(res.Body) // TODO: Don't use all memory on large pages
if err != nil {
return nil, err
}
res.Body.Close()
mediatype, params, _ := mime.ParseMediaType(res.Meta)
// Convert content first
var utfText string
if isUTF8(params["charset"]) {
utfText = string(rawText)
} else {
encoding, err := ianaindex.MIME.Encoding(params["charset"])
if encoding == nil || err != nil {
// Some encoding doesn't exist and wasn't caught in CanDisplay()
return nil, errors.New("unsupported encoding")
}
utfText, err = encoding.NewDecoder().String(string(rawText))
if err != nil {
return nil, err
}
}
if mediatype == "text/gemini" {
rendered, links := RenderGemini(utfText, width)
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return &structs.Page{
Url: url,
Content: rendered,
Links: links,
}, nil
} else if strings.HasPrefix(mediatype, "text/") {
return &structs.Page{
Url: url,
Content: utfText,
Links: []string{}, // Non-gemini links are not supported
}, nil
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}
return nil, errors.New("displayable mediatype is not handled in the code, implementation error")
}