// session.rs — Session state and transcript info
//
// Session: per-session state (seen set, state directory) across hook
// invocations. Created from hook JSON input or POC_SESSION_ID env var.
//
// TranscriptInfo: cached metadata about the current session's transcript
// file — size, path, compaction offset. Read once, used by all callers.

use std::collections::HashSet;
use std::fs;
use std::path::PathBuf;

pub struct HookSession {
    pub session_id: String,
    pub transcript_path: String,
    pub hook_event: String,
    pub state_dir: PathBuf,
}

impl HookSession {
    fn sessions_dir() -> PathBuf {
        let dir = dirs::home_dir().unwrap_or_default().join(".consciousness/sessions");
        fs::create_dir_all(&dir).ok();
        dir
    }

    pub fn from_json(input: &str) -> Option<Self> {
        let state_dir = Self::sessions_dir();

        let json: serde_json::Value = serde_json::from_str(input).ok()?;
        let session_id = json["session_id"].as_str().unwrap_or("").to_string();
        if session_id.is_empty() { return None; }
        let transcript_path = json["transcript_path"].as_str().unwrap_or("").to_string();
        let hook_event = json["hook_event_name"].as_str().unwrap_or("").to_string();

        Some(HookSession { session_id, transcript_path, hook_event, state_dir })
    }

    pub fn path(&self, prefix: &str) -> PathBuf {
        self.state_dir.join(format!("{}-{}", prefix, self.session_id))
    }

    /// Construct directly from fields.
    pub fn from_fields(session_id: String, transcript_path: String, hook_event: String) -> Self {
        HookSession {
            state_dir: Self::sessions_dir(),
            session_id,
            transcript_path,
            hook_event,
        }
    }

    /// Load from a session ID string
    pub fn from_id(session_id: String) -> Option<Self> {
        if session_id.is_empty() { return None; }
        let state_dir = Self::sessions_dir();
        Some(HookSession {
            session_id,
            transcript_path: String::new(),
            hook_event: String::new(),
            state_dir,
        })
    }

    /// Load from POC_SESSION_ID environment variable
    pub fn from_env() -> Option<Self> {
        Self::from_id(std::env::var("POC_SESSION_ID").ok()?)
    }

    /// Get the seen set for this session
    pub fn seen(&self) -> HashSet<String> {
        super::claude::hook::load_seen(&self.state_dir, &self.session_id)
    }

    /// Get transcript metadata, resolving the path if needed.
    pub fn transcript(&self) -> TranscriptInfo {
        if !self.transcript_path.is_empty() {
            return TranscriptInfo::from_path(&self.transcript_path);
        }

        // Find transcript by session ID in projects dir
        let projects = crate::config::get().projects_dir.clone();
        if let Ok(dirs) = fs::read_dir(&projects) {
            for dir in dirs.filter_map(|e| e.ok()) {
                let path = dir.path().join(format!("{}.jsonl", self.session_id));
                if path.exists() {
                    return TranscriptInfo::from_path(&path.to_string_lossy());
                }
            }
        }

        TranscriptInfo::empty()
    }
}

/// Cached transcript metadata — read once, use everywhere.
pub struct TranscriptInfo {
    pub path: String,
    pub size: u64,
}

impl TranscriptInfo {
    pub fn from_path(path: &str) -> Self {
        let size = fs::metadata(path).map(|m| m.len()).unwrap_or(0);
        TranscriptInfo {
            path: path.to_string(),
            size,
        }
    }

    pub fn empty() -> Self {
        TranscriptInfo {
            path: String::new(),
            size: 0,
        }
    }

    pub fn exists(&self) -> bool {
        !self.path.is_empty() && self.size > 0
    }
}