langchainrust 0.2.15

A LangChain-inspired framework for building LLM applications in Rust. Supports OpenAI, Agents, Tools, Memory, Chains, RAG, BM25, Hybrid Retrieval, LangGraph, HyDE, Reranking, MultiQuery, and native Function Calling.
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222

use langchainrust::{
    StateGraph, START, END,
    AgentState, StateUpdate, MessageEntry,
    FunctionRouter,
};
use std::collections::HashMap;

// 示例: 智能问答处理流程
// 展示 LangGraph 的分支路由、状态流转、消息记录功能

#[tokio::test]
async fn example_smart_qa_pipeline() {
    let mut graph: StateGraph<AgentState> = StateGraph::new();
    
    // 节点1: 接收用户问题
    graph.add_node_fn("receive_question", |state: &AgentState| {
        let mut new_state = state.clone();
        new_state.add_message(MessageEntry::ai(format!("收到问题: {}", state.input)));
        Ok(StateUpdate::full(new_state))
    });
    
    // 节点2: 分析问题复杂度
    graph.add_node_fn("analyze_complexity", |state: &AgentState| {
        let is_complex = state.input.len() > 20;
        let mut new_state = state.clone();
        new_state.add_message(MessageEntry::ai(
            format!("分析完成 - 问题类型: {}", if is_complex { "复杂" } else { "简单" })
        ));
        Ok(StateUpdate::full(new_state))
    });
    
    // 节点3a: 简单问题快速回答
    graph.add_node_fn("simple_answer", |state: &AgentState| {
        let mut new_state = state.clone();
        let answer = format!("快速回答: {}", state.input);
        new_state.set_output(answer);
        Ok(StateUpdate::full(new_state))
    });
    
    // 节点3b: 复杂问题详细分析
    graph.add_node_fn("complex_answer", |state: &AgentState| {
        let mut new_state = state.clone();
        new_state.add_message(MessageEntry::ai("正在深度分析...".to_string()));
        let answer = format!("详细分析: {}", state.input);
        new_state.set_output(answer);
        Ok(StateUpdate::full(new_state))
    });
    
    // 节点4: 最终处理
    graph.add_node_fn("finalize", |state: &AgentState| {
        let mut new_state = state.clone();
        new_state.add_message(MessageEntry::ai(format!("处理完成，共 {} 条消息", state.messages.len())));
        Ok(StateUpdate::full(new_state))
    });
    
    // 构建边
    graph.add_edge(START, "receive_question");
    graph.add_edge("receive_question", "analyze_complexity");
    
    // 条件边: 根据复杂度选择路径
    let targets = HashMap::from([
        ("simple".to_string(), "simple_answer".to_string()),
        ("complex".to_string(), "complex_answer".to_string()),
    ]);
    graph.add_conditional_edges("analyze_complexity", "complexity_router", targets, None);
    
    graph.add_edge("simple_answer", "finalize");
    graph.add_edge("complex_answer", "finalize");
    graph.add_edge("finalize", END);
    
    // 路由器
    let router = FunctionRouter::new(|state: &AgentState| {
        if state.input.len() <= 20 { "simple" } else { "complex" }.to_string()
    });
    graph.set_conditional_router("complexity_router", router);
    
    let compiled = graph.compile().unwrap();
    
    // 测试简单问题
    let simple_result = compiled.invoke(AgentState::new("什么是 Rust?".to_string())).await.unwrap();
    assert_eq!(simple_result.recursion_count, 4);
    let output = simple_result.final_state.output.as_ref().unwrap();
    assert!(output.contains("快速回答"));
    println!("=== 简单问题 ===");
    println!("输出: {}", output);
    println!("消息数: {}", simple_result.final_state.messages.len());
    
    // 测试复杂问题
    let complex_result = compiled.invoke(AgentState::new("请详细解释所有权系统和生命周期概念?".to_string())).await.unwrap();
    let output2 = complex_result.final_state.output.as_ref().unwrap();
    assert!(output2.contains("详细分析"));
    println!("=== 复杂问题 ===");
    println!("输出: {}", output2);
}

// 示例: 三分支路由系统

#[tokio::test]
async fn example_multi_branch_routing() {
    let mut graph: StateGraph<AgentState> = StateGraph::new();
    
    graph.add_node_fn("classify_input", |state: &AgentState| {
        Ok(StateUpdate::full(state.clone()))
    });
    graph.add_node_fn("math_handler", |state: &AgentState| {
        let mut s = state.clone();
        s.set_output(format!("数学解答: {}", state.input));
        Ok(StateUpdate::full(s))
    });
    graph.add_node_fn("text_handler", |state: &AgentState| {
        let mut s = state.clone();
        s.set_output(format!("文本解答: {}", state.input));
        Ok(StateUpdate::full(s))
    });
    graph.add_node_fn("code_handler", |state: &AgentState| {
        let mut s = state.clone();
        s.set_output(format!("代码解答: {}", state.input));
        Ok(StateUpdate::full(s))
    });
    graph.add_node_fn("default_handler", |state: &AgentState| {
        let mut s = state.clone();
        s.set_output(format!("通用解答: {}", state.input));
        Ok(StateUpdate::full(s))
    });
    
    graph.add_edge(START, "classify_input");
    
    let targets = HashMap::from([
        ("math".to_string(), "math_handler".to_string()),
        ("text".to_string(), "text_handler".to_string()),
        ("code".to_string(), "code_handler".to_string()),
    ]);
    graph.add_conditional_edges("classify_input", "type_router", targets, Some("default_handler".to_string()));
    
    graph.add_edge("math_handler", END);
    graph.add_edge("text_handler", END);
    graph.add_edge("code_handler", END);
    graph.add_edge("default_handler", END);
    
    let router = FunctionRouter::new(|state: &AgentState| {
        let input = state.input.to_lowercase();
        if input.contains("计算") || input.contains("数学") { "math" }
        else if input.contains("翻译") || input.contains("写作") { "text" }
        else if input.contains("代码") || input.contains("编程") { "code" }
        else { "unknown" }
    }.to_string());
    graph.set_conditional_router("type_router", router);
    
    let compiled = graph.compile().unwrap();
    
    // 测试四种类型
    let math_result = compiled.invoke(AgentState::new("帮我计算 1+1".to_string())).await.unwrap();
    assert!(math_result.final_state.output.as_ref().unwrap().contains("数学解答"));
    
    let text_result = compiled.invoke(AgentState::new("请翻译这段文字".to_string())).await.unwrap();
    assert!(text_result.final_state.output.as_ref().unwrap().contains("文本解答"));
    
    let code_result = compiled.invoke(AgentState::new("写一段排序代码".to_string())).await.unwrap();
    assert!(code_result.final_state.output.as_ref().unwrap().contains("代码解答"));
    
    let default_result = compiled.invoke(AgentState::new("今天天气怎么样".to_string())).await.unwrap();
    assert!(default_result.final_state.output.as_ref().unwrap().contains("通用解答"));
    
    println!("=== 三分支路由 ===");
    println!("数学 -> {}", math_result.final_state.output.as_ref().unwrap());
    println!("文本 -> {}", text_result.final_state.output.as_ref().unwrap());
    println!("代码 -> {}", code_result.final_state.output.as_ref().unwrap());
    println!("未知 -> {}", default_result.final_state.output.as_ref().unwrap());
}

// 示例: 循环处理

#[tokio::test]
async fn example_loop_with_limit() {
    let mut graph: StateGraph<AgentState> = StateGraph::new();
    
    // 计数器
    graph.add_node_fn("increment_counter", |state: &AgentState| {
        let mut new_state = state.clone();
        let current: i32 = state.input.parse().unwrap_or(0);
        new_state.input = (current + 1).to_string();
        Ok(StateUpdate::full(new_state))
    });
    
    // 检查限制
    graph.add_node_fn("check_limit", |state: &AgentState| {
        Ok(StateUpdate::full(state.clone()))
    });
    
    // 完成
    graph.add_node_fn("finish", |state: &AgentState| {
        let mut s = state.clone();
        s.set_output(format!("最终计数: {}", state.input));
        Ok(StateUpdate::full(s))
    });
    
    graph.add_edge(START, "increment_counter");
    graph.add_edge("increment_counter", "check_limit");
    
    let targets = HashMap::from([
        ("continue".to_string(), "increment_counter".to_string()),
        ("done".to_string(), "finish".to_string()),
    ]);
    graph.add_conditional_edges("check_limit", "limit_router", targets, None);
    
    graph.add_edge("finish", END);
    
    let router = FunctionRouter::new(|state: &AgentState| {
        let current: i32 = state.input.parse().unwrap_or(0);
        if current >= 5 { "done" } else { "continue" }.to_string()
    });
    graph.set_conditional_router("limit_router", router);
    
    let compiled = graph.compile().unwrap().with_recursion_limit(20);
    
    let result = compiled.invoke(AgentState::new("0".to_string())).await.unwrap();
    assert!(result.final_state.output.as_ref().unwrap().contains("最终计数: 5"));
    
    println!("=== 循环处理 ===");
    println!("最终输出: {}", result.final_state.output.as_ref().unwrap());
    println!("执行节点数: {}", result.recursion_count);
}