crabtalk-core 0.0.18

//! Session — conversation container with append-only JSONL persistence.
//!
//! Files are organized as `sessions/{YYYY-MM-DD}/{agent}_{sender}_{seq}.jsonl`.
//! After `set_title`, renamed to `{agent}_{sender}_{seq}_{title_slug}.jsonl`.
//!
//! Append-only. Compact markers (`{"compact":"..."}`) separate archived
//! history from the working context. Loading reads from the last compact
//! marker forward.

use crate::model::Message;
use serde::{Deserialize, Serialize};
use std::{
    fs::{self, OpenOptions},
    io::{BufRead, BufReader, Write},
    path::{Path, PathBuf},
    time::Instant,
};

/// Session metadata — first line of a JSONL session file.
#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct SessionMeta {
    pub agent: String,
    pub created_by: String,
    pub created_at: String,
    #[serde(default)]
    pub title: String,
    #[serde(default)]
    pub uptime_secs: u64,
}

/// A JSONL line that is either a message or a compact marker.
#[derive(Serialize, Deserialize)]
#[serde(untagged)]
enum SessionLine {
    Compact { compact: String },
    Message(Message),
}

/// A conversation session tied to a specific agent.
#[derive(Debug, Clone)]
pub struct Session {
    /// Unique session identifier (monotonic counter, runtime-only).
    pub id: u64,
    /// Name of the agent this session is bound to.
    pub agent: String,
    /// Conversation history (the working context for the LLM).
    pub history: Vec<Message>,
    /// Origin of this session (e.g. "user", "tg:12345").
    pub created_by: String,
    /// Conversation title (set by the `set_title` tool).
    pub title: String,
    /// Accumulated active time in seconds (persisted to meta).
    pub uptime_secs: u64,
    /// When this session was loaded/created in this process.
    pub created_at: Instant,
    /// Path to the JSONL persistence file.
    pub file_path: Option<PathBuf>,
}

impl Session {
    /// Create a new session with an empty history.
    pub fn new(id: u64, agent: impl Into<String>, created_by: impl Into<String>) -> Self {
        Self {
            id,
            agent: agent.into(),
            history: Vec::new(),
            created_by: created_by.into(),
            title: String::new(),
            uptime_secs: 0,
            created_at: Instant::now(),
            file_path: None,
        }
    }

    /// Initialize a new JSONL file in the flat sessions directory.
    ///
    /// Creates `{sessions_dir}/{agent}_{sender}_{seq}.jsonl` with
    /// seq auto-incremented globally per identity.
    pub fn init_file(&mut self, sessions_dir: &Path) {
        let _ = fs::create_dir_all(sessions_dir);

        let slug = sender_slug(&self.created_by);
        let prefix = format!("{}_{slug}_", self.agent);
        let seq = next_seq(sessions_dir, &prefix);
        let filename = format!("{prefix}{seq}.jsonl");
        let path = sessions_dir.join(filename);

        let meta = SessionMeta {
            agent: self.agent.clone(),
            created_by: self.created_by.clone(),
            created_at: chrono::Utc::now().to_rfc3339(),
            title: String::new(),
            uptime_secs: self.uptime_secs,
        };

        match OpenOptions::new()
            .create(true)
            .truncate(true)
            .write(true)
            .open(&path)
        {
            Ok(mut f) => {
                if let Ok(json) = serde_json::to_string(&meta) {
                    let _ = writeln!(f, "{json}");
                }
                self.file_path = Some(path);
            }
            Err(e) => tracing::warn!("failed to create session file: {e}"),
        }
    }

    /// Set the conversation title and rename the file to include the title slug.
    pub fn set_title(&mut self, title: &str) {
        self.title = title.to_string();

        let Some(ref old_path) = self.file_path else {
            return;
        };

        // Rewrite meta line with the title.
        self.rewrite_meta();

        // Rename file: insert title slug before `.jsonl`.
        let title_slug = sender_slug(title);
        if title_slug.is_empty() {
            return;
        }
        let old_name = old_path.file_stem().and_then(|s| s.to_str()).unwrap_or("");
        let new_name = format!("{old_name}_{title_slug}.jsonl");
        let new_path = old_path.with_file_name(new_name);
        if fs::rename(old_path, &new_path).is_ok() {
            self.file_path = Some(new_path);
        }
    }

    /// Rewrite the meta line (first line) of the JSONL file.
    pub fn rewrite_meta(&self) {
        let Some(ref path) = self.file_path else {
            return;
        };
        let Ok(content) = fs::read_to_string(path) else {
            return;
        };
        let meta = SessionMeta {
            agent: self.agent.clone(),
            created_by: self.created_by.clone(),
            created_at: chrono::Utc::now().to_rfc3339(),
            title: self.title.clone(),
            uptime_secs: self.uptime_secs,
        };
        let Ok(meta_json) = serde_json::to_string(&meta) else {
            return;
        };
        // Replace only the first line.
        let rest = content.find('\n').map(|i| &content[i..]).unwrap_or("");
        let new_content = format!("{meta_json}{rest}");
        let _ = fs::write(path, new_content);
    }

    /// Append messages to the JSONL file. Skips auto-injected messages.
    pub fn append_messages(&self, messages: &[Message]) {
        let Some(ref path) = self.file_path else {
            return;
        };
        let mut file = match OpenOptions::new().append(true).open(path) {
            Ok(f) => f,
            Err(e) => {
                tracing::warn!("failed to open session file for append: {e}");
                return;
            }
        };
        for msg in messages {
            if msg.auto_injected {
                continue;
            }
            if let Ok(json) = serde_json::to_string(msg) {
                let _ = writeln!(file, "{json}");
            }
        }
    }

    /// Append a compact marker to the JSONL file.
    pub fn append_compact(&self, summary: &str) {
        let Some(ref path) = self.file_path else {
            return;
        };
        let mut file = match OpenOptions::new().append(true).open(path) {
            Ok(f) => f,
            Err(e) => {
                tracing::warn!("failed to open session file for compact: {e}");
                return;
            }
        };
        let line = SessionLine::Compact {
            compact: summary.to_string(),
        };
        if let Ok(json) = serde_json::to_string(&line) {
            let _ = writeln!(file, "{json}");
        }
    }

    /// Load the working context from a JSONL session file.
    ///
    /// Reads from the last `{"compact":"..."}` marker forward. If no compact
    /// marker exists, loads all messages.
    pub fn load_context(path: &Path) -> anyhow::Result<(SessionMeta, Vec<Message>)> {
        let file = fs::File::open(path)?;
        let reader = BufReader::new(file);
        let mut lines = reader.lines();

        let meta_line = lines
            .next()
            .ok_or_else(|| anyhow::anyhow!("empty session file"))??;
        let meta: SessionMeta = serde_json::from_str(&meta_line)?;

        let mut all_lines: Vec<String> = Vec::new();
        let mut last_compact_idx: Option<usize> = None;

        for line in lines {
            let line = line?;
            if line.trim().is_empty() {
                continue;
            }
            if line.contains("\"compact\"")
                && let Ok(SessionLine::Compact { .. }) = serde_json::from_str(&line)
            {
                last_compact_idx = Some(all_lines.len());
            }
            all_lines.push(line);
        }

        let context_start = last_compact_idx.unwrap_or_default();

        let mut messages = Vec::new();
        for (i, line) in all_lines[context_start..].iter().enumerate() {
            if i == 0
                && last_compact_idx.is_some()
                && let Ok(SessionLine::Compact { compact }) = serde_json::from_str(line)
            {
                messages.push(Message::user(&compact));
                continue;
            }
            if let Ok(msg) = serde_json::from_str::<Message>(line) {
                messages.push(msg);
            }
        }

        Ok((meta, messages))
    }
}

/// Find the latest session file for an (agent, created_by) identity.
///
/// Scans the flat sessions directory for files matching the identity prefix
/// and returns the one with the highest seq number.
pub fn find_latest_session(sessions_dir: &Path, agent: &str, created_by: &str) -> Option<PathBuf> {
    let slug = sender_slug(created_by);
    let prefix = format!("{agent}_{slug}_");

    let mut best: Option<(u32, PathBuf)> = None;

    for entry in fs::read_dir(sessions_dir).ok()?.flatten() {
        let path = entry.path();
        if path.is_dir() {
            continue;
        }
        let name = path.file_name()?.to_str()?;
        if !name.starts_with(&prefix) || !name.ends_with(".jsonl") {
            continue;
        }
        let after_prefix = &name[prefix.len()..];
        let seq_str = after_prefix.split(|c: char| !c.is_ascii_digit()).next()?;
        let seq: u32 = seq_str.parse().ok()?;
        if best.as_ref().is_none_or(|(best_seq, _)| seq > *best_seq) {
            best = Some((seq, path));
        }
    }

    best.map(|(_, path)| path)
}

/// Compute the next seq number for a given prefix in a directory.
fn next_seq(dir: &Path, prefix: &str) -> u32 {
    let max = fs::read_dir(dir)
        .ok()
        .into_iter()
        .flatten()
        .flatten()
        .filter_map(|e| {
            let name = e.file_name();
            let name = name.to_str()?;
            if !name.starts_with(prefix) || !name.ends_with(".jsonl") {
                return None;
            }
            let after_prefix = &name[prefix.len()..];
            let seq_str = after_prefix.split(|c: char| !c.is_ascii_digit()).next()?;
            seq_str.parse::<u32>().ok()
        })
        .max()
        .unwrap_or(0);
    max + 1
}

/// Sanitize a string into a filesystem-safe slug.
pub fn sender_slug(s: &str) -> String {
    s.chars()
        .map(|c| {
            if c.is_alphanumeric() || c == '-' {
                c.to_ascii_lowercase()
            } else {
                '-'
            }
        })
        .collect::<String>()
        .split('-')
        .filter(|s| !s.is_empty())
        .collect::<Vec<_>>()
        .join("-")
}