//! Content Router — regex-based content type detection

use anyhow::Result;

use super::ContentType;

pub struct ContentRouter {
    _confidence_threshold: f32,
}

impl ContentRouter {
    /// Create router with regex-only detection
    pub fn new() -> Result<Self> {
        Ok(Self {
            _confidence_threshold: 0.7,
        })
    }

    /// Detect content type using regex heuristics
    pub fn detect(&self, content: &str) -> Result<ContentType> {
        Ok(self.regex_fallback(content))
    }

    /// Regex-based detection
    fn regex_fallback(&self, content: &str) -> ContentType {
        if is_json(content) {
            return ContentType::Json;
        }
        if is_log(content) {
            return ContentType::Log;
        }
        if is_diff(content) {
            return ContentType::Diff;
        }
        if is_code(content) {
            return ContentType::Code;
        }
        ContentType::Text
    }
}

/// Check if content is valid JSON
fn is_json(content: &str) -> bool {
    let trimmed = content.trim();
    if !((trimmed.starts_with('{') || trimmed.starts_with('['))) {
        return false;
    }
    serde_json::from_str::<serde_json::Value>(trimmed).is_ok()
}

/// Check if content looks like logs (timestamps, log levels, errors)
fn is_log(content: &str) -> bool {
    let content_lower = content.to_lowercase();

    let has_log_level = content_lower.contains("error:")
        || content_lower.contains("warn:")
        || content_lower.contains("info:")
        || content_lower.contains("debug:")
        || content_lower.contains("err!")
        || content.contains("ERROR")
        || content.contains("WARN")
        || content.contains("INFO")
        || content.contains("FAIL");

    let has_timestamp = regex_contains(
        content,
        r"\d{4}-\d{2}-\d{2}T\d{2}:\d{2}:\d{2}",
    );

    let has_error_markers = content_lower.contains("exception")
        || content_lower.contains("stack trace")
        || content_lower.contains("at line")
        || content.contains("npm ERR!")
        || content.contains("error[")
        || content.contains("panic:");

    has_log_level || (has_timestamp && has_error_markers)
}

/// Check if content looks like a unified diff
fn is_diff(content: &str) -> bool {
    let has_diff_markers = content.contains("---") && content.contains("+++")
        || content.contains("@@");

    has_diff_markers && (content.contains("+") || content.contains("-"))
}

/// Check if content looks like source code
fn is_code(content: &str) -> bool {
    let lines: Vec<&str> = content.lines().collect();

    let import_use_pattern =
        regex_contains(content, r"^(import|use|require|include|from|package|class|def|fn|public|private|const|let|var|function)\b");
    let has_brackets =
        content.contains('{') && content.contains('}') || content.contains('[') && content.contains(']');
    let has_indentation = lines.iter().any(|line| line.starts_with('\t') || line.starts_with("  "));

    (import_use_pattern || has_brackets) && has_indentation
}

/// Helper to check if text contains a regex pattern
fn regex_contains(text: &str, pattern: &str) -> bool {
    if let Ok(re) = regex::Regex::new(pattern) {
        re.is_match(text)
    } else {
        false
    }
}

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

    #[test]
    fn test_json_detection() {
        let json = r#"{"key": "value", "number": 42}"#;
        assert!(is_json(json));
    }

    #[test]
    fn test_json_array_detection() {
        let json = r#"[1, 2, 3, {"nested": true}]"#;
        assert!(is_json(json));
    }

    #[test]
    fn test_invalid_json_rejected() {
        let not_json = r#"{"key": "value", invalid}"#;
        assert!(!is_json(not_json));
    }

    #[test]
    fn test_log_detection_with_error_level() {
        let log = "2026-08-28T09:15:00Z ERROR: connection timeout";
        assert!(is_log(log));
    }

    #[test]
    fn test_log_detection_with_npm_err() {
        let log = "npm ERR! 404 Not Found - react@18.2.5";
        assert!(is_log(log));
    }

    #[test]
    fn test_diff_detection() {
        let diff = "--- a/file.txt\n+++ b/file.txt\n@@ -1,3 +1,3 @@\n-old\n+new";
        assert!(is_diff(diff));
    }

    #[test]
    fn test_code_detection() {
        let code = r#"
fn main() {
    println!("hello");
}
        "#;
        assert!(is_code(code));
    }

    #[test]
    fn test_text_detection_fallback() {
        let router = ContentRouter::new().unwrap();
        assert_eq!(router.detect("This is just plain English text without any special structure.").unwrap(), ContentType::Text);
    }

    #[test]
    fn test_router_json() {
        let router = ContentRouter::new().unwrap();
        assert_eq!(router.detect(r#"{"key": "value"}"#).unwrap(), ContentType::Json);
    }
}