sglang/sgl-router/src/tool_parser/parsers/llama_parser.rs

use async_trait::async_trait;

use super::json_parser::JsonParser;
use crate::tool_parser::{
    errors::ToolParserResult,
    state::ParseState,
    traits::ToolParser,
    types::{StreamResult, TokenConfig, ToolCall},
};

/// Llama 3.2 format parser for tool calls
///
/// Handles the Llama 3.2 specific format:
/// `<|python_tag|>{"name": "func", "arguments": {...}}`
///
/// Also supports plain JSON without the python_tag prefix
pub struct LlamaParser {
    /// Underlying JSON parser with Llama-specific configuration
    json_parser: JsonParser,
}

impl LlamaParser {
    /// Create a new Llama parser
    pub fn new() -> Self {
        // Configure JSON parser with Llama's python_tag token
        // Note: No end token for python_tag format
        let json_parser = JsonParser::with_config(TokenConfig {
            start_tokens: vec!["<|python_tag|>".to_string()],
            end_tokens: vec!["".to_string()], // Empty end token
            separator: ";".to_string(), // Llama uses semicolon for multiple calls (though not well supported)
        });

        Self { json_parser }
    }
}

impl Default for LlamaParser {
    fn default() -> Self {
        Self::new()
    }
}

#[async_trait]
impl ToolParser for LlamaParser {
    async fn parse_complete(&self, text: &str) -> ToolParserResult<Vec<ToolCall>> {
        // First try with the configured python_tag parser
        let result = self.json_parser.parse_complete(text).await?;

        if !result.is_empty() {
            return Ok(result);
        }

        // If no results and text starts with '{', try plain JSON
        if text.trim_start().starts_with('{') {
            // Create a temporary plain JSON parser
            let plain_parser = JsonParser::new();
            return plain_parser.parse_complete(text).await;
        }

        Ok(vec![])
    }

    async fn parse_incremental(
        &self,
        chunk: &str,
        state: &mut ParseState,
    ) -> ToolParserResult<StreamResult> {
        // Try with the python_tag parser first
        let result = self.json_parser.parse_incremental(chunk, state).await?;

        // If we get Incomplete and buffer starts with '{', might be plain JSON
        if matches!(result, StreamResult::Incomplete) && state.buffer.trim_start().starts_with('{')
        {
            // Check if we have python_tag in the buffer
            if !state.buffer.contains("<|python_tag|>") {
                // Likely plain JSON, create temporary parser
                let plain_parser = JsonParser::new();
                return plain_parser.parse_incremental("", state).await;
            }
        }

        Ok(result)
    }

    fn detect_format(&self, text: &str) -> bool {
        // Llama format if contains python_tag or starts with JSON object
        text.contains("<|python_tag|>")
            || (text.trim_start().starts_with('{')
                && (text.contains(r#""name""#) || text.contains(r#""function""#)))
    }
}

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

    #[tokio::test]
    async fn test_parse_with_python_tag() {
        let parser = LlamaParser::new();
        let input = r#"<|python_tag|>{"name": "search", "arguments": {"query": "weather"}}"#;

        let result = parser.parse_complete(input).await.unwrap();
        assert_eq!(result.len(), 1);
        assert_eq!(result[0].function.name, "search");
        assert!(result[0].function.arguments.contains("weather"));
    }

    #[tokio::test]
    async fn test_parse_plain_json() {
        let parser = LlamaParser::new();
        let input = r#"{"name": "calculate", "arguments": {"x": 5, "y": 10}}"#;

        let result = parser.parse_complete(input).await.unwrap();
        assert_eq!(result.len(), 1);
        assert_eq!(result[0].function.name, "calculate");
    }

    #[tokio::test]
    async fn test_parse_with_text_before() {
        let parser = LlamaParser::new();
        let input = r#"Let me help you with that. <|python_tag|>{"name": "get_time", "arguments": {"timezone": "UTC"}}"#;

        let result = parser.parse_complete(input).await.unwrap();
        assert_eq!(result.len(), 1);
        assert_eq!(result[0].function.name, "get_time");
    }

    #[test]
    fn test_detect_format() {
        let parser = LlamaParser::new();

        assert!(parser.detect_format(r#"<|python_tag|>{"name": "test"}"#));
        assert!(parser.detect_format(r#"{"name": "test", "arguments": {}}"#));
        assert!(!parser.detect_format("plain text"));
        assert!(!parser.detect_format(r#"{"key": "value"}"#)); // No name field
    }

    #[tokio::test]
    async fn test_single_call_with_semicolon() {
        let parser = LlamaParser::new();
        // Note: Llama 3.2 doesn't handle multiple calls well
        // Test that we can at least parse a single call followed by semicolon
        let input = r#"<|python_tag|>{"name": "func1", "arguments": {"x": 1}};"#;

        let result = parser.parse_complete(input).await.unwrap();

        // We expect this to either parse the first JSON object or fail gracefully
        // Since the semicolon makes it invalid JSON, it will likely return empty
        // This is acceptable as Llama 3.2 doesn't reliably support parallel calls

        // If it parses anything, it should be func1
        if !result.is_empty() {
            assert_eq!(result[0].function.name, "func1");
        }
    }
}