//! 共享 JSON 工具函数
//! 从 LLM 返回的文本中提取 JSON 块

/// 从 LLM 返回文本中提取 JSON 块
/// 支持三种格式：```json...``` 围栏、```...``` 围栏、裸 {...}
/// 使用括号平衡算法找到第一个完整 JSON 块，避免误匹配
pub fn extract_json_block(text: &str) -> &str {
    // 尝试匹配 ```json ... ```
    if let Some(start) = text.find("```json") {
        let json_start = start + 7;
        if let Some(end) = text[json_start..].find("```") {
            return text[json_start..json_start + end].trim();
        }
    }
    // 尝试匹配 ``` ... ```
    if let Some(start) = text.find("```") {
        let json_start = start + 3;
        if let Some(end) = text[json_start..].find("```") {
            return text[json_start..json_start + end].trim();
        }
    }
    // 用括号平衡算法找第一个完整 {...} 块
    if let Some(slice) = find_balanced_json(text) {
        return slice;
    }
    text.trim()
}

/// 使用括号平衡计数找到第一个完整的 {...} JSON 块
/// 正确处理字符串字面量中的花括号
fn find_balanced_json(text: &str) -> Option<&str> {
    let start = text.find('{')?;
    let mut depth = 0i32;
    let mut in_string = false;
    let mut escape_next = false;

    for (i, c) in text[start..].char_indices() {
        if escape_next {
            escape_next = false;
            continue;
        }
        match c {
            '\\' if in_string => escape_next = true,
            '"' => in_string = !in_string,
            '{' if !in_string => {
                depth += 1;
            }
            '}' if !in_string => {
                depth -= 1;
                if depth == 0 {
                    return Some(&text[start..=start + i]);
                }
            }
            _ => {}
        }
    }
    None
}

/// 从 serde_json::Value 中提取字符串数组
/// 用于解析 LLM 返回 JSON 中的 triggers/tools 等字段
pub fn extract_string_array(raw: &serde_json::Value, key: &str) -> Vec<String> {
    raw.get(key)
        .and_then(|v| v.as_array())
        .map(|a| {
            a.iter()
                .filter_map(|v| v.as_str().map(String::from))
                .collect()
        })
        .unwrap_or_default()
}

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

    #[test]
    fn test_json_block_with_markdown() {
        let text = "Here is the result:\n```json\n{\"key\": \"value\"}\n```\nDone.";
        assert_eq!(extract_json_block(text), "{\"key\": \"value\"}");
    }

    #[test]
    fn test_json_block_bare() {
        let text = "{\"key\": \"value\"}";
        assert_eq!(extract_json_block(text), "{\"key\": \"value\"}");
    }

    #[test]
    fn test_json_block_plain_fences() {
        let text = "Result:\n```\n{\"a\": 1}\n```";
        assert_eq!(extract_json_block(text), "{\"a\": 1}");
    }

    #[test]
    fn test_json_block_nested_braces() {
        let text = r#"{"outer": {"inner": "val"}}"#;
        assert_eq!(extract_json_block(text), r#"{"outer": {"inner": "val"}}"#);
    }

    #[test]
    fn test_json_block_no_json() {
        let text = "no json here";
        assert_eq!(extract_json_block(text), "no json here");
    }

    #[test]
    fn test_balanced_json_skips_outer_text() {
        // 第一个 { 到最后一个 } 会包含多余文本，但平衡算法只取第一个完整块
        let text = "prefix {\"a\": 1} suffix {\"b\": 2}";
        assert_eq!(extract_json_block(text), "{\"a\": 1}");
    }

    #[test]
    fn test_balanced_json_handles_braces_in_strings() {
        let text = r#"{"body": "function() { return x; }", "name": "test"}"#;
        assert_eq!(
            extract_json_block(text),
            r#"{"body": "function() { return x; }", "name": "test"}"#
        );
    }

    #[test]
    fn test_balanced_json_handles_escaped_quotes() {
        let text = r#"{"msg": "He said \"hello {world}\""}"#;
        assert_eq!(
            extract_json_block(text),
            r#"{"msg": "He said \"hello {world}\""}"#
        );
    }

    #[test]
    fn test_extract_string_array() {
        let raw: serde_json::Value = serde_json::from_str(
            r#"{"triggers": ["报表", "日报"], "name": "test"}"#,
        )
        .unwrap();
        let arr = extract_string_array(&raw, "triggers");
        assert_eq!(arr, vec!["报表", "日报"]);
    }

    #[test]
    fn test_extract_string_array_missing_key() {
        let raw: serde_json::Value = serde_json::from_str(r#"{"name": "test"}"#).unwrap();
        let arr = extract_string_array(&raw, "triggers");
        assert!(arr.is_empty());
    }
}