//! Pure domain entity for the edit log — an append-only log of file mutations.
//!
//! Records every file mutation made by any tool, enabling audit trails
//! and potential undo operations. Each entry captures the tool name,
//! target path, reason, content hash, and byte delta.
//!
//! # Architecture
//! This is a pure data structure with **no I/O logic**. Load/save
//! responsibilities live in `EditLogRepository` (domain::repository).
//!
//! ## Data Flow
//! 1. Tools call `EditLog::push()` to record each mutation
//! 2. The in-memory `EditLog` is periodically flushed to disk by the repo
//! 3. Oldest entries are evicted from the in-memory cache when
//!    `MAX_MEMORY_ENTRIES` is exceeded (prevents unbounded growth)

use serde::{Deserialize, Serialize};

/// A single recorded file edit event.
///
/// ## Fields
/// - `ts` — Unix timestamp (seconds) when the edit occurred
/// - `tool` — name of the tool that performed the edit (e.g. "Bash", "Edit")
/// - `path` — absolute file path that was modified
/// - `reason` — human-readable explanation of why the edit was made
/// - `content_sha256` — SHA-256 hex digest of the content *after* the edit
/// - `bytes_delta` — signed byte count change (+added, -removed)
/// - `origin` — origin identifier (which agent / session context)
/// - `session_id` — session in which this edit was performed
#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct EditLogEntry {
    pub ts: i64,
    pub tool: String,
    pub path: String,
    pub reason: String,
    pub content_sha256: String,
    pub bytes_delta: i64,
    pub origin: String,
    pub session_id: String,
}

/// Maximum number of edit entries held in memory at once.
///
/// Beyond this limit, old entries are dropped from the in-memory cache
/// to prevent unbounded memory growth in long-running sessions.
pub const MAX_MEMORY_ENTRIES: usize = 10_000;

/// In-memory view of a session's edit log.
///
/// Wraps a `Vec<EditLogEntry>` and provides basic query helpers.
#[derive(Debug, Clone)]
pub struct EditLog {
    /// Ordered list of edit entries (newest appended last).
    pub entries: Vec<EditLogEntry>,
}

impl EditLog {
    /// Create an empty edit log with no entries.
    pub fn new() -> Self {
        Self {
            entries: Vec::new(),
        }
    }

    /// Return the number of in-memory entries.
    pub fn len(&self) -> usize {
        self.entries.len()
    }

    /// Return `true` if the log contains no entries.
    pub fn is_empty(&self) -> bool {
        self.entries.is_empty()
    }
}

impl Default for EditLog {
    /// Returns an empty `EditLog` via `EditLog::new()`.
    fn default() -> Self {
        Self::new()
    }
}