Create Interface for Backend AI Providers (#2572)

Created an interface in aiusechat for the backend providers. Use that
interface throughout the usechat code. Isolate the backend
implementations to only the new file usechat-backend.go.

Author: sawka

pkg/aiusechat/aiutil/aiutil.go

@@ -0,0 +1,182 @@
+// Copyright 2025, Command Line Inc.
+// SPDX-License-Identifier: Apache-2.0
+
+package aiutil
+
+import (
+	"bytes"
+	"crypto/sha256"
+	"encoding/base64"
+	"encoding/hex"
+	"encoding/json"
+	"fmt"
+	"strconv"
+	"strings"
+
+	"github.com/wavetermdev/waveterm/pkg/aiusechat/uctypes"
+	"github.com/wavetermdev/waveterm/pkg/util/utilfn"
+)
+
+// ExtractXmlAttribute extracts an attribute value from an XML-like tag.
+// Expects double-quoted strings where internal quotes are encoded as ".
+// Returns the unquoted value and true if found, or empty string and false if not found or invalid.
+func ExtractXmlAttribute(tag, attrName string) (string, bool) {
+	attrStart := strings.Index(tag, attrName+"=")
+	if attrStart == -1 {
+		return "", false
+	}
+
+	pos := attrStart + len(attrName+"=")
+	start := strings.Index(tag[pos:], `"`)
+	if start == -1 {
+		return "", false
+	}
+	start += pos
+
+	end := strings.Index(tag[start+1:], `"`)
+	if end == -1 {
+		return "", false
+	}
+	end += start + 1
+
+	quotedValue := tag[start : end+1]
+	value, err := strconv.Unquote(quotedValue)
+	if err != nil {
+		return "", false
+	}
+
+	value = strings.ReplaceAll(value, """, `"`)
+	return value, true
+}
+
+// GenerateDeterministicSuffix creates an 8-character hash from input strings
+func GenerateDeterministicSuffix(inputs ...string) string {
+	hasher := sha256.New()
+	for _, input := range inputs {
+		hasher.Write([]byte(input))
+	}
+	hash := hasher.Sum(nil)
+	return hex.EncodeToString(hash)[:8]
+}
+
+// ExtractImageUrl extracts an image URL from either URL field (http/https/data) or raw Data
+func ExtractImageUrl(data []byte, url, mimeType string) (string, error) {
+	if url != "" {
+		if !strings.HasPrefix(url, "data:") &&
+			!strings.HasPrefix(url, "http://") &&
+			!strings.HasPrefix(url, "https://") {
+			return "", fmt.Errorf("unsupported URL protocol in file part: %s", url)
+		}
+		return url, nil
+	}
+	if len(data) > 0 {
+		base64Data := base64.StdEncoding.EncodeToString(data)
+		return fmt.Sprintf("data:%s;base64,%s", mimeType, base64Data), nil
+	}
+	return "", fmt.Errorf("file part missing both url and data")
+}
+
+// ExtractTextData extracts text data from either Data field or URL field (data: URLs only)
+func ExtractTextData(data []byte, url string) ([]byte, error) {
+	if len(data) > 0 {
+		return data, nil
+	}
+	if url != "" {
+		if strings.HasPrefix(url, "data:") {
+			_, decodedData, err := utilfn.DecodeDataURL(url)
+			if err != nil {
+				return nil, fmt.Errorf("failed to decode data URL for text/plain file: %w", err)
+			}
+			return decodedData, nil
+		}
+		return nil, fmt.Errorf("dropping text/plain file with URL (must be fetched and converted to data)")
+	}
+	return nil, fmt.Errorf("text/plain file part missing data")
+}
+
+// FormatAttachedTextFile formats a text file attachment with proper encoding and deterministic suffix
+func FormatAttachedTextFile(fileName string, textContent []byte) string {
+	if fileName == "" {
+		fileName = "untitled.txt"
+	}
+
+	encodedFileName := strings.ReplaceAll(fileName, `"`, """)
+	quotedFileName := strconv.Quote(encodedFileName)
+
+	textStr := string(textContent)
+	deterministicSuffix := GenerateDeterministicSuffix(textStr, fileName)
+	return fmt.Sprintf("<AttachedTextFile_%s file_name=%s>\n%s\n</AttachedTextFile_%s>", deterministicSuffix, quotedFileName, textStr, deterministicSuffix)
+}
+
+// FormatAttachedDirectoryListing formats a directory listing attachment with proper encoding and deterministic suffix
+func FormatAttachedDirectoryListing(directoryName, jsonContent string) string {
+	if directoryName == "" {
+		directoryName = "unnamed-directory"
+	}
+
+	encodedDirName := strings.ReplaceAll(directoryName, `"`, "&quot;")
+	quotedDirName := strconv.Quote(encodedDirName)
+
+	deterministicSuffix := GenerateDeterministicSuffix(jsonContent, directoryName)
+	return fmt.Sprintf("<AttachedDirectoryListing_%s directory_name=%s>\n%s\n</AttachedDirectoryListing_%s>", deterministicSuffix, quotedDirName, jsonContent, deterministicSuffix)
+}
+
+// ConvertDataUserFile converts OpenAI attached file/directory blocks to UIMessagePart
+// Returns (found, part) where found indicates if the prefix was matched,
+// and part is the converted UIMessagePart (can be nil if parsing failed)
+func ConvertDataUserFile(blockText string) (bool, *uctypes.UIMessagePart) {
+	if strings.HasPrefix(blockText, "<AttachedTextFile_") {
+		openTagEnd := strings.Index(blockText, "\n")
+		if openTagEnd == -1 || blockText[openTagEnd-1] != '>' {
+			return true, nil
+		}
+
+		openTag := blockText[:openTagEnd]
+		fileName, ok := ExtractXmlAttribute(openTag, "file_name")
+		if !ok {
+			return true, nil
+		}
+
+		return true, &uctypes.UIMessagePart{
+			Type: "data-userfile",
+			Data: uctypes.UIMessageDataUserFile{
+				FileName: fileName,
+				MimeType: "text/plain",
+			},
+		}
+	}
+
+	if strings.HasPrefix(blockText, "<AttachedDirectoryListing_") {
+		openTagEnd := strings.Index(blockText, "\n")
+		if openTagEnd == -1 || blockText[openTagEnd-1] != '>' {
+			return true, nil
+		}
+
+		openTag := blockText[:openTagEnd]
+		directoryName, ok := ExtractXmlAttribute(openTag, "directory_name")
+		if !ok {
+			return true, nil
+		}
+
+		return true, &uctypes.UIMessagePart{
+			Type: "data-userfile",
+			Data: uctypes.UIMessageDataUserFile{
+				FileName: directoryName,
+				MimeType: "directory",
+			},
+		}
+	}
+
+	return false, nil
+}
+
+func JsonEncodeRequestBody(reqBody any) (bytes.Buffer, error) {
+	var buf bytes.Buffer
+	encoder := json.NewEncoder(&buf)
+	encoder.SetEscapeHTML(false)
+	err := encoder.Encode(reqBody)
+	if err != nil {
+		return buf, err
+	}
+	return buf, nil
+}

pkg/aiusechat/anthropic/anthropic-backend.go

@@ -480,16 +480,14 @@ func RunAnthropicChatStep(
 			if rateLimitInfo.PReq == 0 && rateLimitInfo.Req > 0 {
 				// Premium requests exhausted, but regular requests available
 				stopReason := &uctypes.WaveStopReason{
-					Kind:          uctypes.StopKindPremiumRateLimit,
-					RateLimitInfo: rateLimitInfo,
+					Kind: uctypes.StopKindPremiumRateLimit,
 				}
 				return stopReason, nil, rateLimitInfo, nil
 			}
 			if rateLimitInfo.Req == 0 {
 				// All requests exhausted
 				stopReason := &uctypes.WaveStopReason{
-					Kind:          uctypes.StopKindRateLimit,
-					RateLimitInfo: rateLimitInfo,
+					Kind: uctypes.StopKindRateLimit,
 				}
 				return stopReason, nil, rateLimitInfo, nil
 			}
@@ -590,8 +588,6 @@ func handleAnthropicStreamingResp(
 	rtnStopReason = &uctypes.WaveStopReason{
 		Kind:      uctypes.StopKindDone,
 		RawReason: state.stopFromDelta,
-		MessageID: state.msgID,
-		Model:     state.model,
 	}
 	return rtnStopReason, state.rtnMessage
 }
@@ -849,41 +845,30 @@ func handleAnthropicEvent(
 		switch reason {
 		case "tool_use":
 			return nil, &uctypes.WaveStopReason{
-				Kind:       uctypes.StopKindToolUse,
-				RawReason:  reason,
-				MessageID:  state.msgID,
-				Model:      state.model,
-				ToolCalls:  state.toolCalls,
-				FinishStep: true,
+				Kind:      uctypes.StopKindToolUse,
+				RawReason: reason,
+				ToolCalls: state.toolCalls,
 			}
 		case "max_tokens":
 			return nil, &uctypes.WaveStopReason{
 				Kind:      uctypes.StopKindMaxTokens,
 				RawReason: reason,
-				MessageID: state.msgID,
-				Model:     state.model,
 			}
 		case "refusal":
 			return nil, &uctypes.WaveStopReason{
 				Kind:      uctypes.StopKindContent,
 				RawReason: reason,
-				MessageID: state.msgID,
-				Model:     state.model,
 			}
 		case "pause_turn":
 			return nil, &uctypes.WaveStopReason{
 				Kind:      uctypes.StopKindPauseTurn,
 				RawReason: reason,
-				MessageID: state.msgID,
-				Model:     state.model,
 			}
 		default:
 			// end_turn, stop_sequence (treat as end of this call)
 			return nil, &uctypes.WaveStopReason{
 				Kind:      uctypes.StopKindDone,
 				RawReason: reason,
-				MessageID: state.msgID,
-				Model:     state.model,
 			}
 		}