143 lines
4.5 KiB
Go
143 lines
4.5 KiB
Go
// gomuks - A terminal Matrix client written in Go.
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// Copyright (C) 2018 Tulir Asokan
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//
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// This program is free software: you can redistribute it and/or modify
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// it under the terms of the GNU General Public License as published by
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// the Free Software Foundation, either version 3 of the License, or
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// (at your option) any later version.
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//
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// This program is distributed in the hope that it will be useful,
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// but WITHOUT ANY WARRANTY; without even the implied warranty of
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// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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// GNU General Public License for more details.
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//
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// You should have received a copy of the GNU General Public License
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// along with this program. If not, see <http://www.gnu.org/licenses/>.
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package htmlparser
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import (
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"io"
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"strings"
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"golang.org/x/net/html"
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)
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// HTMLProcessor contains the functions to process parsed HTML data.
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type HTMLProcessor interface {
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// Preprocess is called before the parsing is started.
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Preprocess()
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// HandleStartTag is called with the tag name and attributes when
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// the parser encounters a StartTagToken, except if the tag is
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// always self-closing.
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HandleStartTag(tagName string, attrs map[string]string)
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// HandleSelfClosingTag is called with the tag name and attributes
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// when the parser encounters a SelfClosingTagToken OR a StartTagToken
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// with a tag that's always self-closing.
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HandleSelfClosingTag(tagName string, attrs map[string]string)
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// HandleText is called with the text when the parser encounters
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// a TextToken.
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HandleText(text string)
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// HandleEndTag is called with the tag name when the parser encounters
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// an EndTagToken.
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HandleEndTag(tagName string)
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// ReceiveError is called with the error when the parser encounters
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// an ErrorToken that IS NOT io.EOF.
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ReceiveError(err error)
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// Postprocess is called after parsing is completed successfully.
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// An unsuccessful parsing will trigger a ReceiveError() call.
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Postprocess()
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}
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// HTMLParser wraps a net/html.Tokenizer and a HTMLProcessor to call
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// the HTMLProcessor with data from the Tokenizer.
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type HTMLParser struct {
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*html.Tokenizer
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processor HTMLProcessor
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}
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// NewHTMLParserFromTokenizer creates a new HTMLParser from an existing html Tokenizer.
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func NewHTMLParserFromTokenizer(z *html.Tokenizer, processor HTMLProcessor) HTMLParser {
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return HTMLParser{
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z,
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processor,
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}
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}
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// NewHTMLParserFromReader creates a Tokenizer with the given io.Reader and
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// then uses that to create a new HTMLParser.
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func NewHTMLParserFromReader(reader io.Reader, processor HTMLProcessor) HTMLParser {
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return NewHTMLParserFromTokenizer(html.NewTokenizer(reader), processor)
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}
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// NewHTMLParserFromString creates a Tokenizer with a reader of the given
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// string and then uses that to create a new HTMLParser.
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func NewHTMLParserFromString(html string, processor HTMLProcessor) HTMLParser {
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return NewHTMLParserFromReader(strings.NewReader(html), processor)
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}
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// SelfClosingTags is the list of tags that always call
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// HTMLProcessor.HandleSelfClosingTag() even if it is encountered
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// as a html.StartTagToken rather than html.SelfClosingTagToken.
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var SelfClosingTags = []string{"img", "br", "hr", "area", "base", "basefont", "input", "link", "meta"}
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func (parser HTMLParser) mapAttrs() map[string]string {
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attrs := make(map[string]string)
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hasMore := true
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for hasMore {
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var key, val []byte
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key, val, hasMore = parser.TagAttr()
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attrs[string(key)] = string(val)
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}
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return attrs
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}
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func (parser HTMLParser) isSelfClosing(tag string) bool {
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for _, selfClosingTag := range SelfClosingTags {
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if tag == selfClosingTag {
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return true
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}
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}
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return false
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}
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// Process parses the HTML using the tokenizer in this parser and
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// calls the appropriate functions of the HTML processor.
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func (parser HTMLParser) Process() {
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parser.processor.Preprocess()
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Loop:
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for {
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tt := parser.Next()
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switch tt {
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case html.ErrorToken:
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if parser.Err() != io.EOF {
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parser.processor.ReceiveError(parser.Err())
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return
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}
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break Loop
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case html.TextToken:
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parser.processor.HandleText(string(parser.Text()))
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case html.StartTagToken, html.SelfClosingTagToken:
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tagb, _ := parser.TagName()
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attrs := parser.mapAttrs()
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tag := string(tagb)
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selfClosing := tt == html.SelfClosingTagToken || parser.isSelfClosing(tag)
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if selfClosing {
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parser.processor.HandleSelfClosingTag(tag, attrs)
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} else {
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parser.processor.HandleStartTag(tag, attrs)
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}
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case html.EndTagToken:
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tagb, _ := parser.TagName()
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parser.processor.HandleEndTag(string(tagb))
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}
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}
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parser.processor.Postprocess()
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}
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