ds2api/internal/adapter/openai/history_split.go

package openai

import (
	"context"
	"errors"
	"fmt"
	"strings"

	"ds2api/internal/auth"
	"ds2api/internal/deepseek"
	"ds2api/internal/util"
)

const (
	historySplitFilename    = "HISTORY.txt"
	historySplitContentType = "text/plain; charset=utf-8"
	historySplitPurpose     = "assistants"
)

func (h *Handler) applyHistorySplit(ctx context.Context, a *auth.RequestAuth, stdReq util.StandardRequest) (util.StandardRequest, error) {
	if h == nil || h.DS == nil || h.Store == nil || a == nil {
		return stdReq, nil
	}
	if !h.Store.HistorySplitEnabled() {
		return stdReq, nil
	}

	promptMessages, historyMessages := splitOpenAIHistoryMessages(stdReq.Messages, h.Store.HistorySplitTriggerAfterTurns())
	if len(historyMessages) == 0 {
		return stdReq, nil
	}

	historyText := buildOpenAIHistoryTranscript(historyMessages)
	if strings.TrimSpace(historyText) == "" {
		return stdReq, errors.New("history split produced empty transcript")
	}

	result, err := h.DS.UploadFile(ctx, a, deepseek.UploadFileRequest{
		Filename:    historySplitFilename,
		ContentType: historySplitContentType,
		Purpose:     historySplitPurpose,
		Data:        []byte(historyText),
	}, 3)
	if err != nil {
		return stdReq, fmt.Errorf("upload history file: %w", err)
	}
	fileID := strings.TrimSpace(result.ID)
	if fileID == "" {
		return stdReq, errors.New("upload history file returned empty file id")
	}

	stdReq.Messages = promptMessages
	stdReq.RefFileIDs = prependUniqueRefFileID(stdReq.RefFileIDs, fileID)
	stdReq.FinalPrompt, stdReq.ToolNames = buildHistorySplitPrompt(promptMessages, stdReq.ToolsRaw, stdReq.ToolChoice, stdReq.Thinking)
	return stdReq, nil
}

func buildHistorySplitPrompt(messages []any, toolsRaw any, toolPolicy util.ToolChoicePolicy, thinkingEnabled bool) (string, []string) {
	if len(messages) == 0 {
		return "", nil
	}
	instruction := historySplitPromptInstruction()
	withInstruction := make([]any, 0, len(messages)+1)
	withInstruction = append(withInstruction, map[string]any{
		"role":    "system",
		"content": instruction,
	})
	withInstruction = append(withInstruction, messages...)
	return buildOpenAIFinalPromptWithPolicy(withInstruction, toolsRaw, "", toolPolicy, thinkingEnabled)
}

func historySplitPromptInstruction() string {
	return "An attached HISTORY.txt file contains prior conversation history and tool progress. Read it first, then answer the latest user request using that history as context."
}

func splitOpenAIHistoryMessages(messages []any, triggerAfterTurns int) ([]any, []any) {
	if triggerAfterTurns <= 0 {
		triggerAfterTurns = 1
	}
	lastUserIndex := -1
	userTurns := 0
	for i, raw := range messages {
		msg, ok := raw.(map[string]any)
		if !ok {
			continue
		}
		role := strings.ToLower(strings.TrimSpace(asString(msg["role"])))
		if role != "user" {
			continue
		}
		userTurns++
		lastUserIndex = i
	}
	if userTurns <= triggerAfterTurns || lastUserIndex < 0 {
		return messages, nil
	}

	promptMessages := make([]any, 0, len(messages)-lastUserIndex)
	historyMessages := make([]any, 0, lastUserIndex)
	for i, raw := range messages {
		msg, ok := raw.(map[string]any)
		if !ok {
			if i >= lastUserIndex {
				promptMessages = append(promptMessages, raw)
			} else {
				historyMessages = append(historyMessages, raw)
			}
			continue
		}
		role := strings.ToLower(strings.TrimSpace(asString(msg["role"])))
		switch role {
		case "system", "developer":
			promptMessages = append(promptMessages, raw)
		default:
			if i >= lastUserIndex {
				promptMessages = append(promptMessages, raw)
			} else {
				historyMessages = append(historyMessages, raw)
			}
		}
	}
	if len(promptMessages) == 0 {
		return messages, nil
	}
	return promptMessages, historyMessages
}

func buildOpenAIHistoryTranscript(messages []any) string {
	var b strings.Builder
	b.WriteString("# HISTORY.txt\n")
	b.WriteString("Prior conversation history and tool progress.\n\n")

	entry := 0
	for _, raw := range messages {
		msg, ok := raw.(map[string]any)
		if !ok {
			continue
		}
		role := strings.ToLower(strings.TrimSpace(asString(msg["role"])))
		content := buildOpenAIHistoryEntry(role, msg)
		if strings.TrimSpace(content) == "" {
			continue
		}
		entry++
		fmt.Fprintf(&b, "=== %d. %s ===\n%s\n\n", entry, strings.ToUpper(roleLabelForHistory(role)), content)
	}
	return strings.TrimSpace(b.String()) + "\n"
}

func buildOpenAIHistoryEntry(role string, msg map[string]any) string {
	switch role {
	case "assistant":
		return strings.TrimSpace(buildAssistantContentForPrompt(msg))
	case "tool", "function":
		return strings.TrimSpace(buildToolHistoryContent(msg))
	case "user":
		return strings.TrimSpace(normalizeOpenAIContentForPrompt(msg["content"]))
	default:
		return strings.TrimSpace(normalizeOpenAIContentForPrompt(msg["content"]))
	}
}

func buildToolHistoryContent(msg map[string]any) string {
	content := strings.TrimSpace(normalizeOpenAIContentForPrompt(msg["content"]))
	parts := make([]string, 0, 2)
	if name := strings.TrimSpace(asString(msg["name"])); name != "" {
		parts = append(parts, "name="+name)
	}
	if callID := strings.TrimSpace(asString(msg["tool_call_id"])); callID != "" {
		parts = append(parts, "tool_call_id="+callID)
	}
	header := ""
	if len(parts) > 0 {
		header = "[" + strings.Join(parts, " ") + "]"
	}
	switch {
	case header != "" && content != "":
		return header + "\n" + content
	case header != "":
		return header
	default:
		return content
	}
}

func roleLabelForHistory(role string) string {
	role = strings.ToLower(strings.TrimSpace(role))
	switch role {
	case "function":
		return "tool"
	case "":
		return "unknown"
	default:
		return role
	}
}

func prependUniqueRefFileID(existing []string, fileID string) []string {
	fileID = strings.TrimSpace(fileID)
	if fileID == "" {
		return existing
	}
	out := make([]string, 0, len(existing)+1)
	out = append(out, fileID)
	for _, id := range existing {
		trimmed := strings.TrimSpace(id)
		if trimmed == "" || strings.EqualFold(trimmed, fileID) {
			continue
		}
		out = append(out, trimmed)
	}
	return out
}