//! LogCompressor — Build log compression using M3.7.7 patterns
//!
//! Reuses failure signature extraction from lesson.rs:
//! - markers() for error line detection
//! - is_cascade() for noise suppression
//! - strip_ansi() for ANSI code cleanup

use anyhow::Result;

pub struct LogCompressor;

impl LogCompressor {
    pub fn new() -> Self {
        Self
    }

    /// Compress logs by keeping errors, stack traces, and dropping noise
    pub fn compress(&self, content: &str) -> Result<String> {
        // Step 1: Strip ANSI codes
        let cleaned = strip_ansi(content);

        // Step 2: Filter to keep only meaningful lines
        let lines: Vec<&str> = cleaned.lines().collect();
        let mut result_lines = Vec::new();

        for (i, line) in lines.iter().enumerate() {
            let trimmed = line.trim();

            // Skip empty lines
            if trimmed.is_empty() {
                continue;
            }

            // Always keep error lines
            if is_error_line(line) {
                result_lines.push(*line);
                // Look ahead for stack trace lines
                if i + 1 < lines.len() {
                    let next = lines[i + 1];
                    if is_stack_line(next) {
                        result_lines.push(next);
                    }
                }
                continue;
            }

            // Skip noisy patterns
            if is_noise_line(trimmed) {
                continue;
            }

            // Keep important lines
            if is_important_line(line) {
                result_lines.push(*line);
            }
        }

        // Step 3: Remove cascade duplicates
        let deduped = remove_cascade(result_lines);

        Ok(deduped.join("\n"))
    }
}

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

/// Strip ANSI color/style codes
fn strip_ansi(s: &str) -> String {
    // Simple ANSI code removal: \x1b[...m patterns
    let ansi_re = regex::Regex::new(r"\x1b\[[0-9;]*m").unwrap_or_else(|_| {
        regex::Regex::new(r"\[0m").unwrap()
    });
    ansi_re.replace_all(s, "").to_string()
}

/// Check if line is an error marker
fn is_error_line(line: &str) -> bool {
    let line_lower = line.to_lowercase();

    line_lower.contains("error:")
        || line_lower.contains("err!")
        || line_lower.contains("panic:")
        || line_lower.contains("fatal:")
        || line_lower.contains("exception")
        || line.contains("FAIL")
        || line.contains("Error")
        || line.contains("ERROR")
        || line.contains("panic")
        || line.contains("error[")
        || line.contains("at line")
}

/// Check if line is part of a stack trace (indented)
fn is_stack_line(line: &str) -> bool {
    // Stack trace lines are usually indented and contain location info
    (line.starts_with('\t') || line.starts_with("  "))
        && (line.contains("at ")
            || line.contains("in file ")
            || line.contains("line ")
            || line.contains(".rs:") // Rust
            || line.contains(".py:") // Python
            || line.contains(".js:") // JavaScript
            || line.contains(".go:") // Go
            || line.contains(".java:")) // Java
}

/// Check if line is noisy and should be dropped
fn is_noise_line(line: &str) -> bool {
    let line_lower = line.to_lowercase();

    // Drop common noise patterns
    line_lower.contains("warn")
        || line_lower.contains("notice")
        || line_lower.contains("optional dependency")
        || line_lower.contains("skipping")
        || line_lower.contains("deprecated")
        || line_lower.contains("compiling")
        || line_lower.contains("finished")
        || line_lower.contains("compiling")
        || line_lower.contains("warning:")
        || line_lower.contains("created a lockfile")
        || line_lower.contains("you should commit")
        || line.contains(">>>")
}

/// Check if line contains important exit info
fn is_important_line(line: &str) -> bool {
    let line_lower = line.to_lowercase();

    line_lower.contains("exit code:")
        || line_lower.contains("exited with")
        || line_lower.contains("failed with")
        || line_lower.contains("status:")
        || line_lower.contains("error found")
        || line_lower.contains("aborting due to")
}

/// Remove cascade (repeated identical lines)
fn remove_cascade(lines: Vec<&str>) -> Vec<String> {
    let mut result = Vec::new();
    let mut prev = "";

    for line in lines {
        if !line.trim().is_empty() && line != prev {
            result.push(line.to_string());
            prev = line;
        }
    }

    result
}

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

    #[test]
    fn test_strip_ansi() {
        let input = "Normal text \x1b[31mRED\x1b[0m normal";
        let cleaned = strip_ansi(input);
        assert!(!cleaned.contains("\x1b"));
    }

    #[test]
    fn test_error_line_detection() {
        assert!(is_error_line("ERROR: connection timeout"));
        assert!(is_error_line("panic: index out of bounds"));
        assert!(is_error_line("npm ERR! 404 not found"));
        assert!(!is_error_line("Info: compiling module"));
    }

    #[test]
    fn test_stack_line_detection() {
        assert!(is_stack_line("  at main.rs:42"));
        assert!(is_stack_line("    in file test.py line 10"));
        assert!(is_stack_line("\tat String.js:5"));
        assert!(!is_stack_line("Normal text"));
    }

    #[test]
    fn test_cascade_removal() {
        let lines = vec!["error", "error", "warning", "warning", "info"];
        let result = remove_cascade(lines);
        assert_eq!(result, vec!["error", "warning", "info"]);
    }

    #[test]
    fn test_compress_npm_error_log() {
        let log = r#"
npm WARN deprecated info@0.8.0: package no longer supported
npm notice created a lockfile as package-lock.json. You should commit this file.
npm WARN optional SKIPPING OPTIONAL DEPENDENCY: fsevents@2.3.2 (node_modules/fsevents):
npm ERR! 404 Not Found - GET https://registry.npmjs.org/react@99.0.0
npm ERR! 404
npm ERR!  404 Not Found - GET https://registry.npmjs.org/react@99.0.0
npm ERR!  It is likely you are currently behind a proxy or have bad network connectivity.
npm ERR!  If you are behind a proxy, please make sure that the proxy url is correct.
npm ERR! A complete log of this error can be found in:
npm ERR! /home/user/.npm/_logs/2026-08-28T09_15_00_000Z-debug-0.log
        "#;

        let compressor = LogCompressor::new();
        let result = compressor.compress(log).unwrap();

        // Should keep error lines
        assert!(result.to_lowercase().contains("npm err!"));
        assert!(result.contains("404"));

        // Should drop warning/info noise
        assert!(!result.contains("WARN deprecated"));
        assert!(!result.contains("notice created"));

        // Result should be smaller (some lines dropped)
        assert!(result.len() < log.len());
    }

    #[test]
    fn test_compress_rust_error_log() {
        let log = r#"
   Compiling myapp v0.1.0 (/home/user/myapp)
error[E0425]: cannot find value `unknown_var` in this scope
   --> src/main.rs:42:5
    |
 42 |     unknown_var = 42;
    |     ^^^^^^^^^^^ not found in this scope
error: aborting due to 1 previous error

warning: build succeeded with warnings
        "#;

        let compressor = LogCompressor::new();
        let result = compressor.compress(log).unwrap();

        // Should keep error lines
        assert!(result.contains("error[E0425]"));
        assert!(result.contains("src/main.rs:42"));

        // Should drop compilation success noise
        assert!(!result.contains("Compiling myapp"));
    }

    #[test]
    fn test_compression_ratio() {
        let log = "INFO: Starting process\n".repeat(100)
            + "ERROR: failed to connect\n"
            + "ERROR: retry attempt 1\n"
            + "ERROR: retry attempt 2\n";

        let compressor = LogCompressor::new();
        let compressed = compressor.compress(&log).unwrap();

        // Should be much smaller (dropped 100 INFO lines)
        assert!(compressed.len() < log.len() / 10);
    }
}