use std::fmt;
use std::fs;
use std::path::Path;

use tracing_subscriber::EnvFilter;
use tracing_subscriber::fmt::format::{FormatEvent, FormatFields};
use tracing_subscriber::registry::LookupSpan;

/// Compact stderr formatter: `HH:MM:SS LEVEL  message key=value`
///
/// No span context, no full timestamps, no target — just the essentials.
/// The JSON file log is unaffected (it uses its own layer).
pub struct CompactHumanFormat;

impl<S, N> FormatEvent<S, N> for CompactHumanFormat
where
    S: tracing::Subscriber + for<'a> LookupSpan<'a>,
    N: for<'a> FormatFields<'a> + 'static,
{
    fn format_event(
        &self,
        ctx: &tracing_subscriber::fmt::FmtContext<'_, S, N>,
        mut writer: tracing_subscriber::fmt::format::Writer<'_>,
        event: &tracing::Event<'_>,
    ) -> fmt::Result {
        let now = chrono::Local::now();
        let time = now.format("%H:%M:%S");

        let level = *event.metadata().level();
        let styled = match level {
            tracing::Level::ERROR => console::style("ERROR").red().bold(),
            tracing::Level::WARN => console::style(" WARN").yellow(),
            tracing::Level::INFO => console::style(" INFO").green(),
            tracing::Level::DEBUG => console::style("DEBUG").dim(),
            tracing::Level::TRACE => console::style("TRACE").dim(),
        };

        write!(writer, "{time} {styled}  ")?;
        ctx.format_fields(writer.by_ref(), event)?;
        writeln!(writer)
    }
}

pub fn build_stderr_filter(verbose: u8, quiet: bool) -> EnvFilter {
    if std::env::var("RUST_LOG").is_ok() {
        return EnvFilter::from_default_env();
    }

    if quiet {
        return EnvFilter::new("lore=warn,error");
    }

    let directives = match verbose {
        0 => "lore=warn",
        1 => "lore=info,warn",
        2 => "lore=debug,info",
        _ => "lore=trace,debug",
    };

    EnvFilter::new(directives)
}

pub fn build_file_filter() -> EnvFilter {
    if std::env::var("RUST_LOG").is_ok() {
        return EnvFilter::from_default_env();
    }

    EnvFilter::new("lore=debug,warn")
}

pub fn cleanup_old_logs(log_dir: &Path, retention_days: u32) -> usize {
    if retention_days == 0 || !log_dir.exists() {
        return 0;
    }

    let cutoff = chrono::Utc::now() - chrono::Duration::days(i64::from(retention_days));
    let cutoff_date = cutoff.format("%Y-%m-%d").to_string();
    let mut deleted = 0;

    let entries = match fs::read_dir(log_dir) {
        Ok(entries) => entries,
        Err(_) => return 0,
    };

    for entry in entries.flatten() {
        let file_name = entry.file_name();
        let name = file_name.to_string_lossy();

        if let Some(date_str) = extract_log_date(&name)
            && date_str < cutoff_date
            && fs::remove_file(entry.path()).is_ok()
        {
            deleted += 1;
        }
    }

    deleted
}

fn extract_log_date(filename: &str) -> Option<String> {
    let rest = filename.strip_prefix("lore.")?;

    let date_part = rest.get(..10)?;

    let parts: Vec<&str> = date_part.split('-').collect();
    if parts.len() != 3 || parts[0].len() != 4 || parts[1].len() != 2 || parts[2].len() != 2 {
        return None;
    }

    if !parts.iter().all(|p| p.chars().all(|c| c.is_ascii_digit())) {
        return None;
    }

    let suffix = rest.get(10..)?;
    if suffix.is_empty() || suffix == ".log" {
        Some(date_part.to_string())
    } else {
        None
    }
}

#[cfg(test)]
mod tests {
    use super::*;
    use std::fs::File;
    use tempfile::TempDir;

    #[test]
    fn test_extract_log_date_with_extension() {
        assert_eq!(
            extract_log_date("lore.2026-02-04.log"),
            Some("2026-02-04".to_string())
        );
    }

    #[test]
    fn test_extract_log_date_without_extension() {
        assert_eq!(
            extract_log_date("lore.2026-02-04"),
            Some("2026-02-04".to_string())
        );
    }

    #[test]
    fn test_extract_log_date_rejects_non_log_files() {
        assert_eq!(extract_log_date("other.txt"), None);
        assert_eq!(extract_log_date("lore.config.json"), None);
        assert_eq!(extract_log_date("lore.db"), None);
    }

    #[test]
    fn test_extract_log_date_rejects_invalid_dates() {
        assert_eq!(extract_log_date("lore.not-a-date.log"), None);
        assert_eq!(extract_log_date("lore.20260204.log"), None);
    }

    #[test]
    fn test_cleanup_old_logs_deletes_old_files() {
        let dir = TempDir::new().unwrap();

        File::create(dir.path().join("lore.2020-01-01.log")).unwrap();
        File::create(dir.path().join("lore.2020-01-15.log")).unwrap();

        let today = chrono::Utc::now().format("%Y-%m-%d").to_string();
        let recent_name = format!("lore.{today}.log");
        File::create(dir.path().join(&recent_name)).unwrap();

        File::create(dir.path().join("other.txt")).unwrap();

        let deleted = cleanup_old_logs(dir.path(), 7);

        assert_eq!(deleted, 2);
        assert!(!dir.path().join("lore.2020-01-01.log").exists());
        assert!(!dir.path().join("lore.2020-01-15.log").exists());
        assert!(dir.path().join(&recent_name).exists());
        assert!(dir.path().join("other.txt").exists());
    }

    #[test]
    fn test_cleanup_old_logs_zero_retention_is_noop() {
        let dir = TempDir::new().unwrap();
        File::create(dir.path().join("lore.2020-01-01.log")).unwrap();

        let deleted = cleanup_old_logs(dir.path(), 0);
        assert_eq!(deleted, 0);
        assert!(dir.path().join("lore.2020-01-01.log").exists());
    }

    #[test]
    fn test_cleanup_old_logs_nonexistent_dir() {
        let deleted = cleanup_old_logs(Path::new("/nonexistent/dir"), 7);
        assert_eq!(deleted, 0);
    }

    #[test]
    fn test_build_stderr_filter_default() {
        let _filter = build_stderr_filter(0, false);
    }

    #[test]
    fn test_build_stderr_filter_verbose_levels() {
        let _f0 = build_stderr_filter(0, false);
        let _f1 = build_stderr_filter(1, false);
        let _f2 = build_stderr_filter(2, false);
        let _f3 = build_stderr_filter(3, false);
    }

    #[test]
    fn test_build_stderr_filter_quiet_overrides_verbose() {
        let _filter = build_stderr_filter(3, true);
    }

    #[test]
    fn test_build_file_filter() {
        let _filter = build_file_filter();
    }
}