// channel_log.rs — Per-channel message history
//
// Shared by all channel daemon implementations. Tracks messages
// with consumed/unread semantics for the recv protocol.

use std::collections::VecDeque;

const DEFAULT_CAPACITY: usize = 200;

/// Per-channel message history with consumed/unread tracking.
pub struct ChannelLog {
    messages: VecDeque<String>,
    consumed: usize,
    total: usize,
    /// Messages we sent (don't count as unread)
    own: usize,
}

impl ChannelLog {
    pub fn new() -> Self {
        Self {
            messages: VecDeque::with_capacity(DEFAULT_CAPACITY),
            consumed: 0,
            total: 0,
            own: 0,
        }
    }

    pub fn push(&mut self, line: String) {
        if self.messages.len() >= DEFAULT_CAPACITY {
            self.messages.pop_front();
            if self.consumed > 0 {
                self.consumed -= 1;
            }
        }
        self.messages.push_back(line);
        self.total += 1;
    }

    pub fn unread(&self) -> u32 {
        (self.total - self.consumed - self.own) as u32
    }

    /// Push a message that we sent (doesn't count as unread).
    pub fn push_own(&mut self, line: String) {
        self.push(line);
        self.own += 1;
    }

    /// Return all unconsumed messages (marks consumed), plus scrollback
    /// to reach at least min_count total.
    pub fn recv_new(&mut self, min_count: usize) -> String {
        let buf_len = self.messages.len();
        let unconsumed_start = buf_len.saturating_sub(self.total - self.consumed);

        let new_msgs: Vec<&str> = self.messages.iter()
            .skip(unconsumed_start)
            .map(|s| s.as_str())
            .collect();

        let need_extra = min_count.saturating_sub(new_msgs.len());
        let scroll_start = unconsumed_start.saturating_sub(need_extra);
        let scrollback: Vec<&str> = self.messages.iter()
            .skip(scroll_start)
            .take(unconsumed_start - scroll_start)
            .map(|s| s.as_str())
            .collect();

        self.consumed = self.total;
        self.own = 0;

        let mut result = scrollback;
        result.extend(new_msgs);
        result.join("\n")
    }

    /// Return last N lines without consuming.
    pub fn recv_history(&self, count: usize) -> String {
        self.messages.iter()
            .rev().take(count)
            .collect::<Vec<_>>().into_iter().rev()
            .map(|s| s.as_str())
            .collect::<Vec<_>>()
            .join("\n")
    }
}

// ── Disk logging ───────────────────────────────────────────────

use std::path::PathBuf;

/// Append a timestamped message to a per-channel log file.
///
/// Log path: `{log_dir}/{channel}.log`
/// Format: `{unix_secs} <{nick}> {text}`
pub fn append_disk_log(log_dir: &std::path::Path, channel: &str, nick: &str, text: &str) {
    use std::io::Write;
    let filename = format!("{}.log", channel.trim_start_matches('#').to_lowercase());
    let _ = std::fs::create_dir_all(log_dir);
    if let Ok(mut f) = std::fs::OpenOptions::new()
        .create(true)
        .append(true)
        .open(log_dir.join(&filename))
    {
        let secs = std::time::SystemTime::now()
            .duration_since(std::time::UNIX_EPOCH)
            .unwrap_or_default()
            .as_secs();
        let _ = writeln!(f, "{secs} <{nick}> {text}");
    }
}

/// Load a ChannelLog from a disk log file, populating with the last N lines.
pub fn load_disk_log(log_dir: &std::path::Path, channel: &str) -> ChannelLog {
    use std::io::{BufRead, BufReader};
    let filename = format!("{}.log", channel.trim_start_matches('#').to_lowercase());
    let path = log_dir.join(&filename);

    let mut log = ChannelLog::new();
    let Ok(file) = std::fs::File::open(&path) else { return log };
    let reader = BufReader::new(file);

    // Read all lines, keep only the last DEFAULT_CAPACITY
    let lines: Vec<String> = reader.lines().flatten().collect();
    for line in lines.into_iter().rev().take(DEFAULT_CAPACITY).collect::<Vec<_>>().into_iter().rev() {
        log.push(line);
    }
    // Mark all loaded lines as consumed (they're history, not new)
    log.consumed = log.total;
    log
}

/// Standard log directory for a channel daemon.
pub fn log_dir(daemon_name: &str) -> PathBuf {
    dirs::home_dir()
        .unwrap_or_default()
        .join(format!(".consciousness/channels/{}.logs", daemon_name))
}