ambi 0.3.1

A flexible, multi-backend, customizable AI agent framework, entirely based on Rust.
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
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

// src/agent/core/formatter.rs

use crate::types::StreamFormatter;

/// A passthrough formatter that performs zero modifications to the text.
pub struct PassThroughFormatter;
impl StreamFormatter for PassThroughFormatter {
    fn push(&mut self, token: &str) -> String {
        token.to_string()
    }
    fn flush(&mut self) -> String {
        String::new()
    }
}

/// The framework's default standard stream formatter.
pub struct StandardStreamFormatter {
    buffer: String,
    in_tool_call: bool,
    started: bool,

    tool_start_tag: String,
    tool_end_tag: String,

    think_start_tag: String,
    think_end_tag: String,

    max_buffer_size: usize,
}

impl StandardStreamFormatter {
    /// Initializes the formatter with tags to intercept and hide.
    pub fn new(tool_start: &str, tool_end: &str, think_start: &str, think_end: &str) -> Self {
        Self {
            buffer: String::new(),
            in_tool_call: false,
            started: false,
            tool_start_tag: tool_start.to_string(),
            tool_end_tag: tool_end.to_string(),

            think_start_tag: if think_start.is_empty() {
                "<think>".to_string()
            } else {
                think_start.to_string()
            },
            think_end_tag: if think_end.is_empty() {
                "</think>".to_string()
            } else {
                think_end.to_string()
            },
            max_buffer_size: 8192,
        }
    }

    /// Defines a maximum buffer limit to prevent Out-Of-Memory exploits on stream chunks.
    pub fn set_max_buffer_size(mut self, max_buffer_size: usize) -> Self {
        self.max_buffer_size = max_buffer_size;
        self
    }

    fn process_text(&self, text: &str) -> String {
        text.replace(&self.think_end_tag, "\n\n[Content]: ")
    }

    fn suffix_matches_tag_prefix(&self, text: &str, tag: &str) -> bool {
        if tag.is_empty() {
            return false;
        }
        for len in 1..=tag.len() {
            let prefix = &tag[..len];
            if text.ends_with(prefix) {
                return true;
            }
        }
        false
    }
}

impl StreamFormatter for StandardStreamFormatter {
    fn push(&mut self, token: &str) -> String {
        self.buffer.push_str(token);

        if self.buffer.len() > self.max_buffer_size {
            self.buffer.clear();
            self.in_tool_call = false;
            self.started = true;

            log::error!(
                "Formatter buffer overflow (>{}). Discarding buffered data to prevent OOM.",
                self.max_buffer_size
            );
            return String::new();
        }

        let mut output = String::new();

        loop {
            if !self.started {
                let trimmed = self.buffer.trim_start();
                if let Some(idx) = self.buffer.find(&self.think_start_tag) {
                    let before = &self.buffer[..idx];
                    output.push_str(before);
                    output.push_str("[Thinking]:\n");
                    self.buffer = self.buffer[idx + self.think_start_tag.len()..].to_string();
                    self.started = true;
                    continue;
                } else if self.buffer.contains(&self.tool_start_tag) {
                    self.started = true;
                } else if self.suffix_matches_tag_prefix(&self.buffer, &self.think_start_tag) {
                    break;
                } else if self.suffix_matches_tag_prefix(&self.buffer, &self.tool_start_tag) {
                    if !trimmed.is_empty() {
                        output.push_str("[Content]: ");
                        self.started = true;
                    }
                    break;
                } else if !trimmed.is_empty() {
                    output.push_str("[Content]: ");
                    self.started = true;
                } else {
                    break;
                }
            }

            if self.in_tool_call {
                if let Some(end_idx) = self.buffer.find(&self.tool_end_tag) {
                    self.buffer = self.buffer[end_idx + self.tool_end_tag.len()..].to_string();
                    self.in_tool_call = false;
                    continue;
                }
                break;
            } else {
                if let Some(start_idx) = self.buffer.find(&self.tool_start_tag) {
                    let before = self.buffer[..start_idx].to_string();
                    output.push_str(&self.process_text(&before));
                    self.buffer = self.buffer[start_idx + self.tool_start_tag.len()..].to_string();
                    self.in_tool_call = true;
                    continue;
                }
                if self.suffix_matches_tag_prefix(&self.buffer, &self.tool_start_tag)
                    || self.suffix_matches_tag_prefix(&self.buffer, &self.think_end_tag)
                    || self.suffix_matches_tag_prefix(&self.buffer, &self.think_start_tag)
                {
                    break;
                }
                let safe_text = self.buffer.clone();
                output.push_str(&self.process_text(&safe_text));
                self.buffer.clear();
                break;
            }
        }
        output
    }

    fn flush(&mut self) -> String {
        let res = self.process_text(&self.buffer);
        self.buffer.clear();
        res
    }
}