langgraph 0.1.0

A Rust implementation of LangGraph for building stateful, multi-actor applications with LLMs
Documentation 
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

use parking_lot::RwLock;
use serde_json::Value as JsonValue;
use langgraph_checkpoint::error::ChannelError;
use super::base::Channel;

/// PubSub topic channel.
///
/// Can accumulate values (`accumulate=true`) or clear each step.
/// Used for the TASKS channel (holds Send objects).
pub struct Topic {
    key: String,
    values: RwLock<Vec<JsonValue>>,
    accumulate: bool,
}

impl Topic {
    pub fn new(key: impl Into<String>, accumulate: bool) -> Self {
        Self {
            key: key.into(),
            values: RwLock::new(Vec::new()),
            accumulate,
        }
    }
}

impl Channel for Topic {
    fn checkpoint(&self) -> Option<JsonValue> {
        let vals = self.values.read();
        if vals.is_empty() {
            None
        } else {
            Some(JsonValue::Array(vals.clone()))
        }
    }

    fn from_checkpoint(&self, checkpoint: Option<&JsonValue>) -> Box<dyn Channel> {
        let values = match checkpoint {
            Some(JsonValue::Array(arr)) => arr.clone(),
            Some(other) => vec![other.clone()],
            None => Vec::new(),
        };
        Box::new(Self {
            key: self.key.clone(),
            values: RwLock::new(values),
            accumulate: self.accumulate,
        })
    }

    fn update(&self, values: &[JsonValue]) -> Result<bool, ChannelError> {
        if values.is_empty() {
            return Ok(false);
        }
        let mut guard = self.values.write();
        for val in values {
            match val {
                JsonValue::Array(arr) => guard.extend(arr.iter().cloned()),
                other => guard.push(other.clone()),
            }
        }
        Ok(true)
    }

    fn get(&self) -> Result<JsonValue, ChannelError> {
        let vals = self.values.read();
        if vals.is_empty() {
            Err(ChannelError::EmptyChannel)
        } else {
            Ok(JsonValue::Array(vals.clone()))
        }
    }

    fn consume(&self) -> bool {
        if !self.accumulate {
            let changed = !self.values.read().is_empty();
            self.values.write().clear();
            changed
        } else {
            false
        }
    }

    fn is_available(&self) -> bool {
        !self.values.read().is_empty()
    }

    fn clone_channel(&self) -> Box<dyn Channel> {
        Box::new(Self {
            key: self.key.clone(),
            values: RwLock::new(self.values.read().clone()),
            accumulate: self.accumulate,
        })
    }

    fn name(&self) -> &str {
        &self.key
    }
}

#[cfg(test)]
mod tests {
    use super::*;

    #[test]
    fn test_topic_accumulate() {
        let ch = Topic::new("tasks", true);
        ch.update(&[serde_json::json!("a")]).unwrap();
        ch.update(&[serde_json::json!("b")]).unwrap();
        assert_eq!(ch.get().unwrap(), serde_json::json!(["a", "b"]));
        // consume doesn't clear when accumulate=true
        ch.consume();
        assert!(ch.is_available());
    }

    #[test]
    fn test_topic_no_accumulate() {
        let ch = Topic::new("tasks", false);
        ch.update(&[serde_json::json!("a")]).unwrap();
        ch.update(&[serde_json::json!("b")]).unwrap();
        assert_eq!(ch.get().unwrap(), serde_json::json!(["a", "b"]));
        // consume clears when accumulate=false
        ch.consume();
        assert!(!ch.is_available());
    }

    #[test]
    fn test_topic_array_update() {
        let ch = Topic::new("tasks", true);
        ch.update(&[serde_json::json!(["a", "b"]), serde_json::json!(["c"])]).unwrap();
        assert_eq!(ch.get().unwrap(), serde_json::json!(["a", "b", "c"]));
    }
}