//! Rotated log sink for the chat bot's PTY output.
//!
//! The chat bot runs Claude Code CLI in a PTY (see
//! [`crate::llm::providers::claude_code`]) and previously logged every raw
//! PTY line — spawn commands, reader-thread lifecycle, and truncated
//! passthrough of each NDJSON line — via [`crate::slog!`], which meant this
//! high-volume, low-signal output shared the bounded operational ring buffer
//! and `server.log` with everything else, displacing genuinely operational
//! lines. This sink gives that PTY output its own daily-rotated file
//! (`chatbot-YYYY-MM-DD.log`) instead.

use std::fs::OpenOptions;
use std::io::Write;
use std::path::{Path, PathBuf};
use std::sync::{Mutex, OnceLock};

/// Number of daily log files to keep on disk before pruning older ones.
const KEEP_DAYS: u64 = 7;

/// Internal state for the on-disk log: directory and last-written date.
struct ChatBotLogState {
    dir: Option<PathBuf>,
    /// `YYYY-MM-DD` of the last written entry — used to detect day rollover.
    last_date: String,
}

/// Daily-rotated on-disk sink for the chat bot's PTY output.
pub struct ChatBotLog {
    state: Mutex<ChatBotLogState>,
}

impl ChatBotLog {
    fn new() -> Self {
        Self {
            state: Mutex::new(ChatBotLogState {
                dir: None,
                last_date: String::new(),
            }),
        }
    }

    /// Set the directory for daily-rotated chat bot log files.
    ///
    /// Files are written as `chatbot-YYYY-MM-DD.log` inside `dir`. Files
    /// older than [`KEEP_DAYS`] are pruned immediately and again on each day
    /// rollover. Call once at startup after the project root is known.
    pub fn set_log_dir(&self, dir: PathBuf) {
        prune_old_logs(&dir, KEEP_DAYS);
        if let Ok(mut state) = self.state.lock() {
            state.dir = Some(dir);
        }
    }

    /// Append a line to today's chat bot log file, prefixed with an ISO 8601
    /// UTC timestamp. No-ops silently until [`set_log_dir`] has been called.
    pub fn push_line(&self, message: &str) {
        let (log_path, prune_dir) = match self.state.lock() {
            Ok(mut state) => {
                if let Some(dir) = state.dir.clone() {
                    let today = chrono::Utc::now().format("%Y-%m-%d").to_string();
                    let path = dir.join(format!("chatbot-{today}.log"));
                    let maybe_prune = if state.last_date != today {
                        state.last_date = today;
                        Some(dir)
                    } else {
                        None
                    };
                    (Some(path), maybe_prune)
                } else {
                    (None, None)
                }
            }
            Err(_) => (None, None),
        };

        if let Some(ref dir) = prune_dir {
            prune_old_logs(dir, KEEP_DAYS);
        }

        if let Some(ref path) = log_path {
            let timestamp = chrono::Utc::now().format("%Y-%m-%dT%H:%M:%SZ").to_string();
            if let Ok(mut file) = OpenOptions::new().create(true).append(true).open(path) {
                let _ = writeln!(file, "{timestamp} [pty-debug] {message}");
            }
        }
    }
}

static GLOBAL: OnceLock<ChatBotLog> = OnceLock::new();

/// Access the process-wide chat bot PTY log sink.
pub fn global() -> &'static ChatBotLog {
    GLOBAL.get_or_init(ChatBotLog::new)
}

/// Delete daily `chatbot-*.log` files older than `keep_days` from `dir`.
fn prune_old_logs(dir: &Path, keep_days: u64) {
    let cutoff = chrono::Utc::now()
        .checked_sub_signed(chrono::Duration::days(keep_days as i64))
        .map(|t| t.format("%Y-%m-%d").to_string())
        .unwrap_or_default();

    let Ok(entries) = std::fs::read_dir(dir) else {
        return;
    };
    for entry in entries.filter_map(|e| e.ok()) {
        let path = entry.path();
        let Some(name) = path.file_name().and_then(|n| n.to_str()) else {
            continue;
        };
        // Match "chatbot-YYYY-MM-DD.log"
        if name.starts_with("chatbot-") && name.ends_with(".log") && name.len() == 22 {
            // SAFETY: "chatbot-" is 8 ASCII bytes, ".log" is 4, total 22 chars
            // means the middle 10 bytes are the date "YYYY-MM-DD" — all
            // ASCII, safe to slice.
            if let Some(date_part) = name.get(8..18)
                && date_part < cutoff.as_str()
            {
                let _ = std::fs::remove_file(&path);
            }
        }
    }
}

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

    fn fresh_sink() -> ChatBotLog {
        ChatBotLog::new()
    }

    #[test]
    fn push_line_before_set_log_dir_is_a_noop() {
        let sink = fresh_sink();
        // Must not panic when no directory has been configured yet.
        sink.push_line("hello");
    }

    #[test]
    fn push_line_writes_to_rotated_file() {
        let tmp = std::env::temp_dir().join(format!(
            "huskies_chatbot_log_test_{}",
            std::time::SystemTime::now()
                .duration_since(std::time::UNIX_EPOCH)
                .unwrap_or_default()
                .as_nanos()
        ));
        std::fs::create_dir_all(&tmp).unwrap();

        let sink = fresh_sink();
        sink.set_log_dir(tmp.clone());
        sink.push_line("raw line: {\"type\":\"assistant\"}");

        let today = chrono::Utc::now().format("%Y-%m-%d").to_string();
        let path = tmp.join(format!("chatbot-{today}.log"));
        let contents = std::fs::read_to_string(&path).unwrap();

        let _ = std::fs::remove_dir_all(&tmp);

        assert!(contents.contains("[pty-debug]"));
        assert!(contents.contains("raw line: {\"type\":\"assistant\"}"));
    }

    #[test]
    fn does_not_write_into_shared_ring_buffer() {
        let tmp = std::env::temp_dir().join(format!(
            "huskies_chatbot_log_isolation_test_{}",
            std::time::SystemTime::now()
                .duration_since(std::time::UNIX_EPOCH)
                .unwrap_or_default()
                .as_nanos()
        ));
        std::fs::create_dir_all(&tmp).unwrap();

        let sink = fresh_sink();
        sink.set_log_dir(tmp.clone());
        let marker = "chatbot_isolation_marker_9f31a";
        sink.push_line(marker);

        let _ = std::fs::remove_dir_all(&tmp);

        let ring_hits = crate::log_buffer::global().get_recent(1000, Some(marker), None);
        assert!(
            ring_hits.is_empty(),
            "chat bot PTY output must not land in the shared server log ring buffer"
        );
    }
}