Keep the README for the user

[onechat] / markdown.go

diff --git a/markdown.go b/markdown.go
index 1a2f4feb1343723a704a874c2c586e78a0fee8d6..0f5f941575e6625db71c60cb70ccb8eeaeba63fd 100644 (file)
--- a/markdown.go
+++ b/markdown.go
@@ -1,7 +1,6 @@
 package main
 
 import (
 package main
 
 import (

-       "slices"

        "strings"
        "unicode"
        "unicode/utf8"
        "strings"
        "unicode"
        "unicode/utf8"


@@ -10,141 +9,18 @@ import (
 // markdownPunctuation holds the ASCII characters that a backslash makes plain.
 const markdownPunctuation = "!\"#$%&'()*+,-./:;<=>?@[\\]^_`{|}~"
 
 // markdownPunctuation holds the ASCII characters that a backslash makes plain.
 const markdownPunctuation = "!\"#$%&'()*+,-./:;<=>?@[\\]^_`{|}~"
 

-// markdownText is the plain text of a Markdown reply and its Telegram entities,
-// while the conversion builds it. Units counts the UTF-16 code units of text,
-// the unit of the entity offsets and lengths.
-type markdownText struct {
-       text     strings.Builder
-       units    int
-       entities []botEntity
-}
-
-// markdownSpan is an inline mark of a line: the entity type, the content inside
+// MarkdownSpan is an inline mark of a line: the mark kind, the content inside

 // the marks, the index after the closing mark, and the URL of a link.
 // the marks, the index after the closing mark, and the URL of a link.

-type markdownSpan struct {
+type MarkdownSpan struct {

        kind    string
        content string
        end     int
        url     string
 }
 
        kind    string
        content string
        end     int
        url     string
 }
 

-// markdownEntities converts the Markdown of a reply to plain text and Telegram
-// message entities. It knows bold (** and __), italic (* and _),
-// strikethrough (~~), inline code, fenced code blocks with an optional
-// language, links [text](url), and ATX headings, which become bold. Lists,
-// quotes, and tables stay as their text. A mark that does not close stays as
-// text with no entity, and code holds no entity.
-//
-// Inline marks do not cross a line break, so a mark that does not close cannot
-// change the rest of the reply.
-func markdownEntities(markdown string) (string, []botEntity) {
-       var out markdownText
-       lines := strings.Split(markdown, "\n")
-       for index := 0; index < len(lines); index++ {
-               if index > 0 {
-                       out.add("\n")
-               }
-
-               line := lines[index]
-               language, fence := codeFence(line)
-               end := closingFence(lines, index, fence)
-               heading := headingText(line)
-               switch {
-               case end > index:
-                       start := out.units
-                       out.add(strings.Join(lines[index+1:end], "\n"))
-                       out.entity(botEntity{
-                               Type:     "pre",
-                               Offset:   start,
-                               Length:   out.units - start,
-                               Language: language,
-                       })
-
-                       index = end
-               case heading != "":
-                       start := out.units
-                       out.inline(heading)
-                       out.entity(botEntity{
-                               Type:   "bold",
-                               Offset: start,
-                               Length: out.units - start,
-                       })
-               default:
-                       out.inline(line)
-               }
-       }
-
-       slices.SortStableFunc(out.entities, func(a, b botEntity) int {
-               if a.Offset != b.Offset {
-                       return a.Offset - b.Offset
-               }
-
-               return b.Length - a.Length
-       })
-
-       return out.text.String(), out.entities
-}
-
-// add appends text.
-func (m *markdownText) add(text string) {
-       m.text.WriteString(text)
-       m.units += utf16Units(text)
-}
-
-// entity keeps entity, unless it is empty, because Telegram refuses an entity
-// of length 0.
-func (m *markdownText) entity(entity botEntity) {
-       if entity.Length > 0 {
-               m.entities = append(m.entities, entity)
-       }
-}
-
-// inline appends one line of Markdown with its inline marks as entities. A
-// backslash before an ASCII punctuation character makes the character plain
-// text.
-func (m *markdownText) inline(line string) {
-       plain := 0
-       index := 0
-       for index < len(line) {
-               if line[index] == '\\' && index+1 < len(line) && strings.IndexByte(markdownPunctuation, line[index+1]) >= 0 {
-                       m.add(line[plain:index])
-                       plain = index + 1
-                       index += 2
-
-                       continue
-               }
-
-               span, found := markSpan(line, index)
-               if !found {
-                       index++
-                       continue
-               }
-
-               m.add(line[plain:index])
-               start := m.units
-               if span.kind == "code" {
-                       m.add(span.content)
-               } else {
-                       m.inline(span.content)
-               }
-
-               m.entity(botEntity{
-                       Type:   span.kind,
-                       Offset: start,
-                       Length: m.units - start,
-                       URL:    span.url,
-               })
-
-               index = span.end
-               plain = span.end
-       }
-
-       m.add(line[plain:])
-}
-
-// codeFence returns the language of a line that opens a fenced code block, and
-// the fence. The fence is "" when line does not open a block.
-func codeFence(line string) (string, string) {
+// markdownCodeFence returns the language of a line that opens a fenced code
+// block, and the fence. The fence is "" when line does not open a block.
+func markdownCodeFence(line string) (string, string) {

        trimmed := strings.TrimLeft(line, " ")
        if len(line)-len(trimmed) > 3 || !strings.HasPrefix(trimmed, "```") {
                return "", ""
        trimmed := strings.TrimLeft(line, " ")
        if len(line)-len(trimmed) > 3 || !strings.HasPrefix(trimmed, "```") {
                return "", ""


@@ -161,15 +37,15 @@ func codeFence(line string) (string, string) {
        return language, trimmed[:run]
 }
 
        return language, trimmed[:run]
 }
 

-// closingFence returns the index of the line after index that closes the code
-// block of fence, or -1 when fence is "" or no line closes it.
-func closingFence(lines []string, index int, fence string) int {
+// markdownClosingFence returns the index of the line after index that closes
+// the code block of fence, or -1 when fence is "" or no line closes it.
+func markdownClosingFence(lines []string, index int, fence string) int {

        if fence == "" {
                return -1
        }
 
        for end := index + 1; end < len(lines); end++ {
        if fence == "" {
                return -1
        }
 
        for end := index + 1; end < len(lines); end++ {

-               if closesFence(lines[end], fence) {
+               if markdownClosesFence(lines[end], fence) {

                        return end
                }
        }
                        return end
                }
        }


@@ -177,15 +53,15 @@ func closingFence(lines []string, index int, fence string) int {
        return -1
 }
 
        return -1
 }
 

-// closesFence tells if line closes the code block of fence.
-func closesFence(line, fence string) bool {
+// markdownClosesFence tells if line closes the code block of fence.
+func markdownClosesFence(line, fence string) bool {

        trimmed := strings.TrimSpace(line)
        return strings.HasPrefix(trimmed, fence) && strings.Trim(trimmed, "`") == ""
 }
 
        trimmed := strings.TrimSpace(line)
        return strings.HasPrefix(trimmed, fence) && strings.Trim(trimmed, "`") == ""
 }
 

-// headingText returns the text of an ATX heading line without its marks, or ""
-// when line is not a heading or has no text.
-func headingText(line string) string {
+// markdownHeadingText returns the text of an ATX heading line without its
+// marks, or "" when line is not a heading or has no text.
+func markdownHeadingText(line string) string {

        trimmed := strings.TrimLeft(line, " ")
        if len(line)-len(trimmed) > 3 {
                return ""
        trimmed := strings.TrimLeft(line, " ")
        if len(line)-len(trimmed) > 3 {
                return ""


@@ -210,48 +86,36 @@ func headingText(line string) string {
        return rest
 }
 
        return rest
 }
 

-// utf16Units returns the number of UTF-16 code units of text.
-func utf16Units(text string) int {
-       units := 0
-       for _, char := range text {
-               units++
-               if char > 0xFFFF {
-                       units++
-               }
-       }
-
-       return units
-}
-
-// markSpan returns the inline mark that starts at index of line and closes in
-// line. It returns false when no mark starts there or the mark does not close.
-func markSpan(line string, index int) (markdownSpan, bool) {
+// markdownMarkSpan returns the inline mark that starts at index of line and
+// closes in line. It returns false when no mark starts there or the mark does
+// not close.
+func markdownMarkSpan(line string, index int) (MarkdownSpan, bool) {

        switch line[index] {
        case '`':
        switch line[index] {
        case '`':

-               return codeSpan(line, index)
+               return markdownCodeSpan(line, index)

        case '[':
        case '[':

-               return linkSpan(line, index)
+               return markdownLinkSpan(line, index)

        case '~':
        case '~':

-               return delimited(line, index, "~~", "strikethrough")
+               return markdownDelimited(line, index, "~~", "strikethrough")

        case '*', '_':
                double := line[index : index+1]
                double += double
        case '*', '_':
                double := line[index : index+1]
                double += double

-               span, found := delimited(line, index, double, "bold")
+               span, found := markdownDelimited(line, index, double, "bold")

                if found {
                        return span, true
                }
 
                if found {
                        return span, true
                }
 

-               return delimited(line, index, line[index:index+1], "italic")
+               return markdownDelimited(line, index, line[index:index+1], "italic")

        default:
        default:

-               return markdownSpan{}, false
+               return MarkdownSpan{}, false

        }
 }
 
        }
 }
 

-// codeSpan returns the inline code that starts at index: a run of backticks,
-// the code, and a run of the same length. One space on each side of the code
-// is left out, as in Markdown.
-func codeSpan(line string, index int) (markdownSpan, bool) {
-       run := backticks(line[index:])
+// markdownCodeSpan returns the inline code that starts at index: a run of
+// backticks, the code, and a run of the same length. One space on each side of
+// the code is left out, as in Markdown.
+func markdownCodeSpan(line string, index int) (MarkdownSpan, bool) {
+       run := markdownBackticks(line[index:])

        for search := index + run; search < len(line); {
                next := strings.IndexByte(line[search:], '`')
                if next < 0 {
        for search := index + run; search < len(line); {
                next := strings.IndexByte(line[search:], '`')
                if next < 0 {


@@ -259,7 +123,7 @@ func codeSpan(line string, index int) (markdownSpan, bool) {
                }
 
                next += search
                }
 
                next += search

-               length := backticks(line[next:])
+               length := markdownBackticks(line[next:])

                if length != run {
                        search = next + length
                        continue
                if length != run {
                        search = next + length
                        continue


@@ -274,19 +138,19 @@ func codeSpan(line string, index int) (markdownSpan, bool) {
                        content = content[1 : len(content)-1]
                }
 
                        content = content[1 : len(content)-1]
                }
 

-               return markdownSpan{
+               return MarkdownSpan{

                        kind:    "code",
                        content: content,
                        end:     next + run,
                }, true
        }
 
                        kind:    "code",
                        content: content,
                        end:     next + run,
                }, true
        }
 

-       return markdownSpan{}, false
+       return MarkdownSpan{}, false

 }
 
 }
 

-// linkSpan returns the link [text](url) that starts at index. The text can
-// hold brackets in pairs, and the URL holds no space.
-func linkSpan(line string, index int) (markdownSpan, bool) {
+// markdownLinkSpan returns the link [text](url) that starts at index. The text
+// can hold brackets in pairs, and the URL holds no space.
+func markdownLinkSpan(line string, index int) (MarkdownSpan, bool) {

        depth := 0
        for closing := index; closing < len(line); closing++ {
                switch line[closing] {
        depth := 0
        for closing := index; closing < len(line); closing++ {
                switch line[closing] {


@@ -304,15 +168,15 @@ func linkSpan(line string, index int) (markdownSpan, bool) {
 
                rest := line[closing+1:]
                if closing == index+1 || !strings.HasPrefix(rest, "(") {
 
                rest := line[closing+1:]
                if closing == index+1 || !strings.HasPrefix(rest, "(") {

-                       return markdownSpan{}, false
+                       return MarkdownSpan{}, false

                }
 
                url, _, found := strings.Cut(rest[1:], ")")
                if !found || url == "" || strings.ContainsAny(url, " \t") {
                }
 
                url, _, found := strings.Cut(rest[1:], ")")
                if !found || url == "" || strings.ContainsAny(url, " \t") {

-                       return markdownSpan{}, false
+                       return MarkdownSpan{}, false

                }
 
                }
 

-               return markdownSpan{
+               return MarkdownSpan{

                        kind:    "text_link",
                        content: line[index+1 : closing],
                        end:     closing + 2 + len(url) + 1,
                        kind:    "text_link",
                        content: line[index+1 : closing],
                        end:     closing + 2 + len(url) + 1,


@@ -320,27 +184,27 @@ func linkSpan(line string, index int) (markdownSpan, bool) {
                }, true
        }
 
                }, true
        }
 

-       return markdownSpan{}, false
+       return MarkdownSpan{}, false

 }
 
 }
 

-// delimited returns the span of kind between the mark at index and the same
-// mark later in line. An opening mark is followed by a character that is not a
-// space, and a closing mark follows one. A single mark is not a part of a
+// markdownDelimited returns the span of kind between the mark at index and the
+// same mark later in line. An opening mark is followed by a character that is
+// not a space, and a closing mark follows one. A single mark is not a part of a

 // double one. A mark of underscores does not open or close inside a word, so
 // snake_case stays as text. A code span inside the content is skipped whole.
 // double one. A mark of underscores does not open or close inside a word, so
 // snake_case stays as text. A code span inside the content is skipped whole.

-func delimited(line string, index int, mark, kind string) (markdownSpan, bool) {
+func markdownDelimited(line string, index int, mark, kind string) (MarkdownSpan, bool) {

        char := mark[0]
        after := index + len(mark)
        char := mark[0]
        after := index + len(mark)

-       if !strings.HasPrefix(line[index:], mark) || after >= len(line) || isSpace(line[after]) {
-               return markdownSpan{}, false
+       if !strings.HasPrefix(line[index:], mark) || after >= len(line) || markdownIsSpace(line[after]) {
+               return MarkdownSpan{}, false

        }
 
        if len(mark) == 1 && (line[after] == char || index > 0 && line[index-1] == char) {
        }
 
        if len(mark) == 1 && (line[after] == char || index > 0 && line[index-1] == char) {

-               return markdownSpan{}, false
+               return MarkdownSpan{}, false

        }
 
        }
 

-       if char == '_' && index > 0 && wordCharBefore(line[:index]) {
-               return markdownSpan{}, false
+       if char == '_' && index > 0 && markdownWordCharBefore(line[:index]) {
+               return MarkdownSpan{}, false

        }
 
        for closing := after + 1; closing < len(line); closing++ {
        }
 
        for closing := after + 1; closing < len(line); closing++ {


@@ -349,13 +213,13 @@ func delimited(line string, index int, mark, kind string) (markdownSpan, bool) {
                        closing++
                        continue
                case line[closing] == '`':
                        closing++
                        continue
                case line[closing] == '`':

-                       span, found := codeSpan(line, closing)
+                       span, found := markdownCodeSpan(line, closing)

                        if found {
                                closing = span.end - 1
                        }
 
                        continue
                        if found {
                                closing = span.end - 1
                        }
 
                        continue

-               case !strings.HasPrefix(line[closing:], mark) || isSpace(line[closing-1]):
+               case !strings.HasPrefix(line[closing:], mark) || markdownIsSpace(line[closing-1]):

                        continue
                }
 
                        continue
                }
 


@@ -364,39 +228,41 @@ func delimited(line string, index int, mark, kind string) (markdownSpan, bool) {
                        continue
                }
 
                        continue
                }
 

-               if char == '_' && wordChar(line[end:]) {
+               if char == '_' && markdownWordChar(line[end:]) {

                        continue
                }
 
                        continue
                }
 

-               return markdownSpan{
+               return MarkdownSpan{

                        kind:    kind,
                        content: line[after:closing],
                        end:     end,
                }, true
        }
 
                        kind:    kind,
                        content: line[after:closing],
                        end:     end,
                }, true
        }
 

-       return markdownSpan{}, false
+       return MarkdownSpan{}, false

 }
 
 }
 

-// backticks returns the length of the run of backticks at the start of text.
-func backticks(text string) int {
+// markdownBackticks returns the length of the run of backticks at the start of
+// text.
+func markdownBackticks(text string) int {

        return len(text) - len(strings.TrimLeft(text, "`"))
 }
 
        return len(text) - len(strings.TrimLeft(text, "`"))
 }
 

-// isSpace tells if char is a space, a tab, or a line break.
-func isSpace(char byte) bool {
+// markdownIsSpace tells if char is a space, a tab, or a line break.
+func markdownIsSpace(char byte) bool {

        return char == ' ' || char == '\t' || char == '\n' || char == '\r'
 }
 
        return char == ' ' || char == '\t' || char == '\n' || char == '\r'
 }
 

-// wordCharBefore tells if the character that ends text is a letter or a digit.
-func wordCharBefore(text string) bool {
+// markdownWordCharBefore tells if the character that ends text is a letter or a
+// digit.
+func markdownWordCharBefore(text string) bool {

        char, _ := utf8.DecodeLastRuneInString(text)
        return text != "" && (unicode.IsLetter(char) || unicode.IsDigit(char))
 }
 
        char, _ := utf8.DecodeLastRuneInString(text)
        return text != "" && (unicode.IsLetter(char) || unicode.IsDigit(char))
 }
 

-// wordChar tells if the character that starts text is a letter or a digit. An
-// underscore next to one is a part of a word, such as in snake_case.
-func wordChar(text string) bool {
+// markdownWordChar tells if the character that starts text is a letter or a
+// digit. An underscore next to one is a part of a word, such as in snake_case.
+func markdownWordChar(text string) bool {

        char, _ := utf8.DecodeRuneInString(text)
        return text != "" && (unicode.IsLetter(char) || unicode.IsDigit(char))
 }
        char, _ := utf8.DecodeRuneInString(text)
        return text != "" && (unicode.IsLetter(char) || unicode.IsDigit(char))
 }