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package service
import (
"context"
"encoding/json"
"fmt"
"regexp"
"sort"
"strings"
"time"
agenttools "github.com/Tencent/WeKnora/internal/agent/tools"
"github.com/Tencent/WeKnora/internal/models/chat"
"github.com/Tencent/WeKnora/internal/types"
"github.com/Tencent/WeKnora/internal/types/interfaces"
)
// agentHistoryFetchMultiplier controls how many raw DB messages to fetch
// when assembling history. Each turn contributes ~2 rows (user + assistant);
// we ask for a generous multiple so we never under-fetch when some pairs are
// incomplete (e.g. an in-flight turn).
const agentHistoryFetchMultiplier = 4
// agentHistoryFetchMin is the floor for the DB fetch limit, used when
// maxRounds is small or unset.
const agentHistoryFetchMin = 50
var agentHistoryThinkTagRegex = regexp.MustCompile(`(?s)<think>.*?</think>`)
// LoadAgentHistory rebuilds the multi-turn LLM context for an Agent-mode
// session directly from the persistent messages table. The result is a
// chronologically ordered list of chat.Message entries suitable for prepending
// to the current turn (without system prompt; the engine adds that itself).
//
// For each historical turn it emits:
// 1. A user message (RenderedContent if present, else Content, plus any
// image captions appended).
// 2. For each AgentStep with non-terminal tool calls (i.e. excluding
// final_answer), an assistant message carrying the step's thought and
// tool_calls, followed by one tool message per tool result.
// 3. A final assistant message with the canonical answer (msg.Content with
// <think> blocks stripped).
//
// Turns lacking either user or assistant content are skipped. The newest
// maxRounds turns are returned in chronological order.
//
// DB is treated as the single source of truth — there is no Redis/in-memory
// cache layer above this function. Callers are expected to invoke it once
// per turn before handing the messages to the agent engine.
func LoadAgentHistory(
ctx context.Context,
messageRepo interfaces.MessageRepository,
sessionID string,
maxRounds int,
) ([]chat.Message, error) {
if maxRounds <= 0 {
return []chat.Message{}, nil
}
fetchLimit := maxRounds * agentHistoryFetchMultiplier
if fetchLimit < agentHistoryFetchMin {
fetchLimit = agentHistoryFetchMin
}
rows, err := messageRepo.GetRecentMessagesBySession(ctx, sessionID, fetchLimit)
if err != nil {
return nil, fmt.Errorf("load agent history: %w", err)
}
if len(rows) == 0 {
return []chat.Message{}, nil
}
type pair struct {
user *types.Message
assistant *types.Message
createdAt time.Time
}
pairs := make(map[string]*pair)
for _, msg := range rows {
p, ok := pairs[msg.RequestID]
if !ok {
p = &pair{}
pairs[msg.RequestID] = p
}
switch msg.Role {
case "user":
p.user = msg
if p.createdAt.IsZero() || msg.CreatedAt.Before(p.createdAt) {
p.createdAt = msg.CreatedAt
}
case "assistant":
p.assistant = msg
}
}
completePairs := make([]*pair, 0, len(pairs))
for _, p := range pairs {
if p.user != nil && p.assistant != nil && p.assistant.IsCompleted {
completePairs = append(completePairs, p)
}
}
sort.Slice(completePairs, func(i, j int) bool {
return completePairs[i].createdAt.Before(completePairs[j].createdAt)
})
if len(completePairs) > maxRounds {
completePairs = completePairs[len(completePairs)-maxRounds:]
}
out := make([]chat.Message, 0, len(completePairs)*4)
for _, p := range completePairs {
out = append(out, buildUserHistoryMessage(p.user))
out = append(out, buildAssistantHistoryMessages(p.assistant)...)
}
return out, nil
}
// buildUserHistoryMessage converts a stored user message into the chat.Message
// form that should appear in LLM history. It deliberately ignores
// RenderedContent: that field is a snapshot of the old prompt and retrieval
// context format, which must not be mixed into the current request protocol.
// Image captions and attachments are reconstructed from their canonical DB
// columns so useful user-provided context is retained without stale RAG data.
func buildUserHistoryMessage(m *types.Message) chat.Message {
content := m.Content
if captions := extractImageCaptionsFromMessage(m.Images); captions != "" {
content += "\n\n[用户上传图片内容]\n" + captions
}
if len(m.Attachments) > 0 {
content += m.Attachments.BuildPrompt()
}
return chat.Message{Role: "user", Content: content}
}
// buildAssistantHistoryMessages reconstructs the assistant side of one
// historical turn. It walks AgentSteps to expand intermediate tool calls into
// proper OpenAI-shaped assistant + tool messages, then emits the canonical
// final answer as a trailing assistant message.
//
// AgentSteps from KnowledgeQA-mode turns are empty, in which case the result
// is just the single final-answer assistant message — exactly mirroring how
// the KnowledgeQA pipeline replays history today.
func buildAssistantHistoryMessages(m *types.Message) []chat.Message {
msgs := make([]chat.Message, 0, len(m.AgentSteps)*2+1)
for _, step := range m.AgentSteps {
nonTerminalCalls := filterNonTerminalToolCalls(step.ToolCalls)
if len(nonTerminalCalls) == 0 {
continue
}
assistantMsg := chat.Message{
Role: "assistant",
Content: step.Thought,
ReasoningContent: step.ReasoningContent,
ToolCalls: make([]chat.ToolCall, 0, len(nonTerminalCalls)),
}
for _, tc := range nonTerminalCalls {
argsJSON, _ := json.Marshal(tc.Args)
assistantMsg.ToolCalls = append(assistantMsg.ToolCalls, chat.ToolCall{
ID: tc.ID,
Type: "function",
ProviderMetadata: tc.ProviderMetadata,
Function: chat.FunctionCall{
Name: tc.Name,
Arguments: string(argsJSON),
},
})
}
msgs = append(msgs, assistantMsg)
for _, tc := range nonTerminalCalls {
msgs = append(msgs, chat.Message{
Role: "tool",
Content: toolCallOutput(tc),
ToolCallID: tc.ID,
Name: tc.Name,
})
}
}
finalContent := agentHistoryThinkTagRegex.ReplaceAllString(m.Content, "")
finalContent = strings.TrimSpace(finalContent)
if finalContent != "" {
msgs = append(msgs, chat.Message{Role: "assistant", Content: finalContent})
}
return msgs
}
// legacyFinalAnswerToolName is the name of the now-removed final_answer tool.
// It is retained here only to filter such calls out of OLD persisted agent
// histories: pre-existing conversations recorded a final_answer tool call as
// the terminal step, and the canonical answer text is replayed via the
// trailing assistant message instead. Re-injecting it would duplicate the
// answer or confuse the model into thinking the previous turn is mid-flight.
const legacyFinalAnswerToolName = "final_answer"
// filterNonTerminalToolCalls drops legacy final_answer entries from historical
// tool calls (see legacyFinalAnswerToolName), plus the pipeline stages a
// fast-answer turn records for its own timeline (see
// types.PipelineToolCallIDPrefix): the model never issued those, so replaying
// them would attribute calls to it that it cannot answer for.
func filterNonTerminalToolCalls(calls []types.ToolCall) []types.ToolCall {
out := make([]types.ToolCall, 0, len(calls))
for _, tc := range calls {
if tc.Name == legacyFinalAnswerToolName || types.IsPipelineToolCallID(tc.ID) {
continue
}
out = append(out, tc)
}
return out
}
// toolCallOutput returns the textual content to use for a historical tool
// message. Failures still go through CompactToolOutputForHistory so stdout
// from a crashed skill script is not dropped in favor of a one-line exit code.
func toolCallOutput(tc types.ToolCall) string {
if tc.Result == nil {
return ""
}
return agenttools.CompactToolOutputForHistory(tc.Name, tc.Result)
}
// extractImageCaptionsFromMessage concatenates non-empty Caption fields from
// stored message images. Mirrors the helper used in chat_pipeline so both
// modes surface previous-turn image descriptions identically.
func extractImageCaptionsFromMessage(images types.MessageImages) string {
var parts []string
for _, img := range images {
if img.Caption != "" {
parts = append(parts, img.Caption)
}
}
return strings.Join(parts, "\n")
}