Send the Telegram replies as rich messages

[onechat] / telegram.go

diff --git a/telegram.go b/telegram.go
index 9a24a4e861d7436bcd0a109480b50fbbb538377e..dd62ef0221db72fc88a1893b1421ce301cab0cff 100644 (file)
--- a/telegram.go
+++ b/telegram.go
@@ -14,6 +14,7 @@ import (
        "strings"
        "sync"
        "time"
        "strings"
        "sync"
        "time"

+       "unicode/utf8"

 )
 
 const (
 )
 
 const (


@@ -33,6 +34,12 @@ const (
        // messageUnits is the most UTF-16 code units of one Telegram message.
        messageUnits = 4096
 
        // messageUnits is the most UTF-16 code units of one Telegram message.
        messageUnits = 4096
 

+       // richMessageBytes is the most bytes of the Markdown of one rich
+       // message. The Bot API allows 32768 characters of rendered text, and
+       // the Markdown of a text has at least as many bytes as the text has
+       // characters.
+       richMessageBytes = 32768
+

        // typingInterval is how often the bot shows the typing action while a
        // turn runs. Telegram shows the action for about five seconds.
        typingInterval = 4 * time.Second
        // typingInterval is how often the bot shows the typing action while a
        // turn runs. Telegram shows the action for about five seconds.
        typingInterval = 4 * time.Second


@@ -53,8 +60,9 @@ type botConfig struct {
 // agent. It ignores every other update. Its sender sends the replies, the
 // errors, the notices of the bot, and the user messages of the other clients to
 // the chat, and shows the typing action while a turn runs. Only the replies
 // agent. It ignores every other update. Its sender sends the replies, the
 // errors, the notices of the bot, and the user messages of the other clients to
 // the chat, and shows the typing action while a turn runs. Only the replies

-// have a format: their Markdown goes as message entities. The rest is plain
-// text. Tool calls do not go to the chat.
+// have a format: their Markdown goes as rich messages, which Telegram renders
+// itself, and as message entities only when Telegram refuses a rich message.
+// The rest is plain text. Tool calls do not go to the chat.

 //
 // The offset file holds the ID of the next update. It moves past an update
 // only after the message of the update is durable in the log, so a restart
 //
 // The offset file holds the ID of the next update. It moves past an update
 // only after the message of the update is durable in the log, so a restart


@@ -237,9 +245,7 @@ func (b *telegramBot) send(ctx context.Context) {
                case "idle":
                        busy = false
                default:
                case "idle":
                        busy = false
                default:

-                       for _, part := range botParts(event) {
-                               b.deliver(ctx, part)
-                       }
+                       b.post(ctx, event)

 
                        if busy {
                                b.typing(ctx)
 
                        if busy {
                                b.typing(ctx)


@@ -269,6 +275,57 @@ func (b *telegramBot) typing(ctx context.Context) {
        _ = b.api.SendTyping(ctx, b.owner)
 }
 
        _ = b.api.SendTyping(ctx, b.owner)
 }
 

+// post sends event to the chat. A reply goes as rich messages of its Markdown,
+// split with splitRich. Every other event goes as plain text, split with
+// splitMessage.
+func (b *telegramBot) post(ctx context.Context, event Event) {
+       if event.Kind != "reply" {
+               for _, text := range splitMessage(botText(event), messageUnits) {
+                       b.deliver(ctx, botPart{
+                               text: text,
+                       })
+               }
+
+               return
+       }
+
+       for _, markdown := range splitRich(event.Text, richMessageBytes) {
+               b.deliverRich(ctx, markdown)
+       }
+}
+
+// deliverRich sends markdown to the chat as a rich message. When the Bot API
+// refuses it with HTTP 400 or 404, the message was not sent, so deliverRich
+// sends the same Markdown once with message entities, and the reply is not
+// lost and does not repeat. It tries again after each failure that a later try
+// can fix, until ctx ends. It drops the message after any other failure.
+func (b *telegramBot) deliverRich(ctx context.Context, markdown string) {
+       wait := b.minWait
+       for {
+               err := b.api.SendRichMessage(ctx, b.owner, markdown)
+               if err == nil || ctx.Err() != nil {
+                       return
+               }
+
+               if rejected(err) {
+                       b.logger.Printf("rich message refused, the reply goes with entities: %v", err)
+                       for _, part := range replyParts(markdown) {
+                               b.deliver(ctx, part)
+                       }
+
+                       return
+               }
+
+               retry, asked := retryable(err)
+               if !retry {
+                       b.logger.Printf("message dropped: %v", err)
+                       return
+               }
+
+               wait = b.pause(ctx, err, wait, asked)
+       }
+}
+

 // deliver sends part to the chat. When Telegram refuses a part with entities
 // (HTTP 400), it sends the text of the part again once with no entities, so a
 // reply is not lost to a bad entity. It tries again after each failure that a
 // deliver sends part to the chat. When Telegram refuses a part with entities
 // (HTTP 400), it sends the text of the part again once with no entities, so a
 // reply is not lost to a bad entity. It tries again after each failure that a


@@ -441,23 +498,6 @@ func saveOffset(path string, offset int64) error {
        return nil
 }
 
        return nil
 }
 

-// botParts returns the messages of event for the chat. The Markdown of a reply
-// becomes text with entities. Every other event is plain text. A reply that has
-// no text left after the conversion, such as an empty code block, goes as its
-// Markdown.
-func botParts(event Event) []botPart {
-       text, entities := botText(event), []botEntity(nil)
-       if event.Kind == "reply" {
-               text, entities = markdownEntities(event.Text)
-       }
-
-       if strings.TrimSpace(text) == "" {
-               text, entities = event.Text, nil
-       }
-
-       return splitEntities(text, entities, messageUnits)
-}
-

 // botText returns the text of event for the chat. A user message of another
 // client has its source as a mark.
 func botText(event Event) string {
 // botText returns the text of event for the chat. A user message of another
 // client has its source as a mark.
 func botText(event Event) string {


@@ -471,38 +511,6 @@ func botText(event Event) string {
        }
 }
 
        }
 }
 

-// splitEntities cuts text into parts with splitMessage, and gives each part the
-// entities in it, with offsets from the start of the part. An entity that
-// crosses a cut becomes one entity in each part.
-func splitEntities(text string, entities []botEntity, limit int) []botPart {
-       var parts []botPart
-       start := 0
-       for _, part := range splitMessage(text, limit) {
-               end := start + utf16Units(part)
-               var kept []botEntity
-               for _, entity := range entities {
-                       from := max(entity.Offset, start)
-                       to := min(entity.Offset+entity.Length, end)
-                       if to <= from {
-                               continue
-                       }
-
-                       entity.Offset = from - start
-                       entity.Length = to - from
-                       kept = append(kept, entity)
-               }
-
-               parts = append(parts, botPart{
-                       text:     part,
-                       entities: kept,
-               })
-
-               start = end
-       }
-
-       return parts
-}
-

 // splitMessage cuts text into parts of at most limit UTF-16 code units, the
 // unit of the Telegram message limit. It cuts after the last line break or
 // space of a part when one is in its second half, and else at the limit. It
 // splitMessage cuts text into parts of at most limit UTF-16 code units, the
 // unit of the Telegram message limit. It cuts after the last line break or
 // space of a part when one is in its second half, and else at the limit. It


@@ -548,3 +556,127 @@ func prefixEnd(text string, limit int) int {
 
        return len(text)
 }
 
        return len(text)
 }

+
+// splitRich cuts the Markdown of a reply into parts of at most limit bytes. It
+// cuts after a blank line outside a code block, so a table, a code block, or a
+// paragraph stays whole. When no such cut fits in a part, it cuts after the
+// last line break outside a code block, then after the last line break in a
+// code block, which it closes at the end of the part and opens again in the
+// next part with the same fence line. A line longer than limit is cut at the
+// limit. It never cuts a character.
+func splitRich(markdown string, limit int) []string {
+       var parts []string
+       for len(markdown) > limit {
+               cut, fence, opening := richCut(markdown, limit)
+               if fence == "" {
+                       parts = append(parts, markdown[:cut])
+                       markdown = markdown[cut:]
+
+                       continue
+               }
+
+               parts = append(parts, markdown[:cut]+fence+"\n")
+               markdown = opening + "\n" + markdown[cut:]
+       }
+
+       return append(parts, markdown)
+}
+
+// richCut returns where splitRich cuts markdown, which is longer than limit.
+// For a cut in a code block, it also returns the fence that closes the block
+// and the line that opens it. Each part before a cut holds text other than
+// space, and a cut in a code block leaves room for the fence, so each cut makes
+// the rest shorter.
+func richCut(markdown string, limit int) (int, string, string) {
+       blank, line, code := 0, 0, 0
+       var fence, opening, inFence, inOpening string
+       for start := 0; start < limit; {
+               end := strings.IndexByte(markdown[start:], '\n')
+               if end < 0 || start+end+1 > limit {
+                       break
+               }
+
+               end += start + 1
+               text := strings.TrimRight(markdown[start:end], "\r\n")
+               _, opens := codeFence(text)
+               switch {
+               case fence != "":
+                       if closesFence(text, fence) {
+                               fence = ""
+                       } else if end > len(opening)+1 && end+len(fence)+1 <= limit {
+                               code, inFence, inOpening = end, fence, opening
+                       }
+               case opens != "":
+                       fence, opening = opens, text
+               case strings.TrimSpace(markdown[:end]) == "":
+               case strings.TrimSpace(text) == "":
+                       blank = end
+               }
+
+               if fence == "" && strings.TrimSpace(markdown[:end]) != "" {
+                       line = end
+               }
+
+               start = end
+       }
+
+       switch {
+       case blank > 0:
+               return blank, "", ""
+       case line > 0:
+               return line, "", ""
+       case code > 0:
+               return code, inFence, inOpening
+       }
+
+       cut := limit
+       for !utf8.RuneStart(markdown[cut]) {
+               cut--
+       }
+
+       return cut, "", ""
+}
+
+// replyParts returns the messages of the Markdown of a reply with message
+// entities. A reply that has no text left after the conversion, such as an
+// empty code block, goes as its Markdown.
+func replyParts(markdown string) []botPart {
+       text, entities := markdownEntities(markdown)
+       if strings.TrimSpace(text) == "" {
+               text, entities = markdown, nil
+       }
+
+       return splitEntities(text, entities, messageUnits)
+}
+
+// splitEntities cuts text into parts with splitMessage, and gives each part the
+// entities in it, with offsets from the start of the part. An entity that
+// crosses a cut becomes one entity in each part.
+func splitEntities(text string, entities []botEntity, limit int) []botPart {
+       var parts []botPart
+       start := 0
+       for _, part := range splitMessage(text, limit) {
+               end := start + utf16Units(part)
+               var kept []botEntity
+               for _, entity := range entities {
+                       from := max(entity.Offset, start)
+                       to := min(entity.Offset+entity.Length, end)
+                       if to <= from {
+                               continue
+                       }
+
+                       entity.Offset = from - start
+                       entity.Length = to - from
+                       kept = append(kept, entity)
+               }
+
+               parts = append(parts, botPart{
+                       text:     part,
+                       entities: kept,
+               })
+
+               start = end
+       }
+
+       return parts
+}