//! Memory snapshot — export/import core memories as human-readable Markdown.
//!
//! **Atomic Soul Export**: dumps `MemoryCategory::Core` from SQLite into
//! `MEMORY_SNAPSHOT.md` so the agent's "soul" is always Git-visible.
//!
//! **Auto-Hydration**: if `brain.db` is missing but `MEMORY_SNAPSHOT.md` exists,
//! re-indexes all entries back into a fresh SQLite database.

use anyhow::Result;
use chrono::Local;
use rusqlite::{Connection, params};
use std::fmt::Write;
use std::fs;
use std::path::{Path, PathBuf};

/// Filename for the snapshot (lives at workspace root for Git visibility).
pub const SNAPSHOT_FILENAME: &str = "MEMORY_SNAPSHOT.md";

/// Header written at the top of every snapshot file.
const SNAPSHOT_HEADER: &str = "# 🧠 KylinBot Memory Snapshot\n\n\
    > Auto-generated by KylinBot. Do not edit manually unless you know what you're doing.\n\
    > This file is the \"soul\" of your agent — if `brain.db` is lost, start the agent\n\
    > in this workspace and it will auto-hydrate from this file.\n\n";

/// Export all `Core` memories from SQLite → `MEMORY_SNAPSHOT.md`.
///
/// Returns the number of entries exported.
pub fn export_snapshot(workspace_dir: &Path) -> Result<usize> {
    let db_path = workspace_dir.join("memory").join("brain.db");
    if !db_path.exists() {
        tracing::debug!("snapshot export skipped: brain.db does not exist");
        return Ok(0);
    }

    let conn = Connection::open(&db_path)?;
    conn.execute_batch("PRAGMA journal_mode = WAL; PRAGMA synchronous = NORMAL;")?;

    let mut stmt = conn.prepare(
        "SELECT key, content, category, created_at, updated_at
         FROM memories
         WHERE category = 'core'
         ORDER BY updated_at DESC",
    )?;

    let rows: Vec<(String, String, String, String, String)> = stmt
        .query_map([], |row| {
            Ok((
                row.get(0)?,
                row.get(1)?,
                row.get(2)?,
                row.get(3)?,
                row.get(4)?,
            ))
        })?
        .filter_map(|r| r.ok())
        .collect();

    if rows.is_empty() {
        tracing::debug!("snapshot export: no core memories to export");
        return Ok(0);
    }

    let mut output = String::with_capacity(rows.len() * 200);
    output.push_str(SNAPSHOT_HEADER);

    let now = Local::now().format("%Y-%m-%d %H:%M:%S").to_string();
    write!(output, "**Last exported:** {now}\n\n").unwrap();
    write!(output, "**Total core memories:** {}\n\n---\n\n", rows.len()).unwrap();

    for (key, content, _category, created_at, updated_at) in &rows {
        write!(output, "### 🔑 `{key}`\n\n").unwrap();
        write!(output, "{content}\n\n").unwrap();
        write!(
            output,
            "*Created: {created_at} | Updated: {updated_at}*\n\n---\n\n"
        )
        .unwrap();
    }

    let snapshot_path = snapshot_path(workspace_dir);
    fs::write(&snapshot_path, output)?;

    tracing::info!(
        "📸 Memory snapshot exported: {} core memories → {}",
        rows.len(),
        snapshot_path.display()
    );

    Ok(rows.len())
}

/// Import memories from `MEMORY_SNAPSHOT.md` into SQLite.
///
/// Called during cold-boot when `brain.db` doesn't exist but the snapshot does.
/// Returns the number of entries hydrated.
pub fn hydrate_from_snapshot(workspace_dir: &Path) -> Result<usize> {
    let snapshot = snapshot_path(workspace_dir);
    if !snapshot.exists() {
        return Ok(0);
    }

    let content = fs::read_to_string(&snapshot)?;
    let entries = parse_snapshot(&content);

    if entries.is_empty() {
        return Ok(0);
    }

    // Ensure the memory directory exists
    let db_dir = workspace_dir.join("memory");
    fs::create_dir_all(&db_dir)?;

    let db_path = db_dir.join("brain.db");
    let conn = Connection::open(&db_path)?;
    conn.execute_batch("PRAGMA journal_mode = WAL; PRAGMA synchronous = NORMAL;")?;

    // Initialize schema (same as SqliteMemory::init_schema)
    conn.execute_batch(
        "CREATE TABLE IF NOT EXISTS memories (
            id         TEXT PRIMARY KEY,
            key        TEXT NOT NULL UNIQUE,
            content    TEXT NOT NULL,
            category   TEXT NOT NULL DEFAULT 'core',
            embedding  BLOB,
            created_at TEXT NOT NULL,
            updated_at TEXT NOT NULL
        );
        CREATE INDEX IF NOT EXISTS idx_mem_key ON memories(key);
        CREATE INDEX IF NOT EXISTS idx_mem_cat ON memories(category);
        CREATE INDEX IF NOT EXISTS idx_mem_updated ON memories(updated_at);

        CREATE VIRTUAL TABLE IF NOT EXISTS memories_fts
            USING fts5(key, content, content='memories', content_rowid='rowid');

        CREATE TABLE IF NOT EXISTS embedding_cache (
            content_hash TEXT PRIMARY KEY,
            embedding    BLOB NOT NULL,
            created_at   TEXT NOT NULL
        );",
    )?;

    let now = Local::now().to_rfc3339();
    let mut hydrated = 0;

    for (key, content) in &entries {
        let id = uuid::Uuid::new_v4().to_string();
        let result = conn.execute(
            "INSERT OR IGNORE INTO memories (id, key, content, category, created_at, updated_at)
             VALUES (?1, ?2, ?3, 'core', ?4, ?5)",
            params![id, key, content, now, now],
        );

        match result {
            Ok(changed) if changed > 0 => {
                // Populate FTS5
                let _ = conn.execute(
                    "INSERT INTO memories_fts(key, content) VALUES (?1, ?2)",
                    params![key, content],
                );
                hydrated += 1;
            }
            Ok(_) => {
                tracing::debug!("hydrate: key '{key}' already exists, skipping");
            }
            Err(e) => {
                tracing::warn!("hydrate: failed to insert key '{key}': {e}");
            }
        }
    }

    tracing::info!(
        "🧬 Memory hydration complete: {} entries restored from {}",
        hydrated,
        snapshot.display()
    );

    Ok(hydrated)
}

/// Check if we should auto-hydrate on startup.
///
/// Returns `true` if:
/// 1. `brain.db` does NOT exist (or is empty)
/// 2. `MEMORY_SNAPSHOT.md` DOES exist
pub fn should_hydrate(workspace_dir: &Path) -> bool {
    let db_path = workspace_dir.join("memory").join("brain.db");
    let snapshot = snapshot_path(workspace_dir);

    let db_missing_or_empty = if db_path.exists() {
        // DB exists but might be empty (freshly created)
        fs::metadata(&db_path)
            .map(|m| m.len() < 4096) // SQLite header is ~4096 bytes minimum
            .unwrap_or(true)
    } else {
        true
    };

    db_missing_or_empty && snapshot.exists()
}

/// Path to the snapshot file.
fn snapshot_path(workspace_dir: &Path) -> PathBuf {
    workspace_dir.join(SNAPSHOT_FILENAME)
}

/// Parse the structured markdown snapshot back into (key, content) pairs.
fn parse_snapshot(input: &str) -> Vec<(String, String)> {
    let mut entries = Vec::new();
    let mut current_key: Option<String> = None;
    let mut current_content = String::new();

    for line in input.lines() {
        let trimmed = line.trim();

        // Match: ### 🔑 `key_name`
        if trimmed.starts_with("### 🔑 `") && trimmed.ends_with('`') {
            // Save previous entry
            if let Some(key) = current_key.take() {
                let content = current_content.trim().to_string();
                if !content.is_empty() {
                    entries.push((key, content));
                }
            }

            // Extract new key
            let key = trimmed
                .strip_prefix("### 🔑 `")
                .and_then(|s| s.strip_suffix('`'))
                .unwrap_or("")
                .to_string();

            if !key.is_empty() {
                current_key = Some(key);
                current_content = String::new();
            }
        } else if current_key.is_some() {
            // Skip metadata lines and separators
            if trimmed.starts_with("*Created:") || trimmed == "---" {
                continue;
            }
            // Accumulate content
            if !current_content.is_empty() || !trimmed.is_empty() {
                if !current_content.is_empty() {
                    current_content.push('\n');
                }
                current_content.push_str(line);
            }
        }
    }

    // Don't forget the last entry
    if let Some(key) = current_key {
        let content = current_content.trim().to_string();
        if !content.is_empty() {
            entries.push((key, content));
        }
    }

    entries
}

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

    #[test]
    fn parse_snapshot_basic() {
        let input = r#"# 🧠 KylinBot Memory Snapshot

> Auto-generated by KylinBot.

**Last exported:** 2025-01-15 14:30:00

**Total core memories:** 2

---

### 🔑 `identity`

I am KylinBot, a self-preserving AI agent.

*Created: 2025-01-15 | Updated: 2025-01-15*

---

### 🔑 `preference_lang`

The user prefers Rust for systems programming.

*Created: 2025-01-14 | Updated: 2025-01-15*

---
"#;

        let entries = parse_snapshot(input);
        assert_eq!(entries.len(), 2);
        assert_eq!(entries[0].0, "identity");
        assert!(entries[0].1.contains("self-preserving"));
        assert_eq!(entries[1].0, "preference_lang");
        assert!(entries[1].1.contains("Rust"));
    }

    #[test]
    fn parse_snapshot_empty() {
        let input = "# 🧠 KylinBot Memory Snapshot\n\n> Nothing here.\n";
        let entries = parse_snapshot(input);
        assert!(entries.is_empty());
    }

    #[test]
    fn parse_snapshot_multiline_content() {
        let input = r#"### 🔑 `rules`

Rule 1: Always be helpful.
Rule 2: Never lie.
Rule 3: Protect the user.

*Created: 2025-01-15 | Updated: 2025-01-15*

---
"#;

        let entries = parse_snapshot(input);
        assert_eq!(entries.len(), 1);
        assert!(entries[0].1.contains("Rule 1"));
        assert!(entries[0].1.contains("Rule 3"));
    }

    #[test]
    fn export_no_db_returns_zero() {
        let tmp = TempDir::new().unwrap();
        let count = export_snapshot(tmp.path()).unwrap();
        assert_eq!(count, 0);
    }

    #[test]
    fn export_and_hydrate_roundtrip() {
        let tmp = TempDir::new().unwrap();
        let workspace = tmp.path();

        // Create a brain.db manually with some core memories
        let db_dir = workspace.join("memory");
        fs::create_dir_all(&db_dir).unwrap();
        let db_path = db_dir.join("brain.db");

        let conn = Connection::open(&db_path).unwrap();
        conn.execute_batch(
            "PRAGMA journal_mode = WAL;
             CREATE TABLE IF NOT EXISTS memories (
                id TEXT PRIMARY KEY,
                key TEXT NOT NULL UNIQUE,
                content TEXT NOT NULL,
                category TEXT NOT NULL DEFAULT 'core',
                embedding BLOB,
                created_at TEXT NOT NULL,
                updated_at TEXT NOT NULL
             );
             CREATE INDEX IF NOT EXISTS idx_mem_key ON memories(key);",
        )
        .unwrap();

        let now = Local::now().to_rfc3339();
        conn.execute(
            "INSERT INTO memories (id, key, content, category, created_at, updated_at)
             VALUES ('id1', 'identity', 'I am a test agent', 'core', ?1, ?2)",
            params![now, now],
        )
        .unwrap();
        conn.execute(
            "INSERT INTO memories (id, key, content, category, created_at, updated_at)
             VALUES ('id2', 'preference', 'User likes Rust', 'core', ?1, ?2)",
            params![now, now],
        )
        .unwrap();
        // Non-core entry (should NOT be exported)
        conn.execute(
            "INSERT INTO memories (id, key, content, category, created_at, updated_at)
             VALUES ('id3', 'conv1', 'Random convo', 'conversation', ?1, ?2)",
            params![now, now],
        )
        .unwrap();
        drop(conn);

        // Export snapshot
        let exported = export_snapshot(workspace).unwrap();
        assert_eq!(exported, 2, "Should export only core memories");

        // Verify the file exists and is readable
        let snapshot = workspace.join(SNAPSHOT_FILENAME);
        assert!(snapshot.exists());
        let content = fs::read_to_string(&snapshot).unwrap();
        assert!(content.contains("identity"));
        assert!(content.contains("I am a test agent"));
        assert!(content.contains("preference"));
        assert!(!content.contains("Random convo"));

        // Simulate catastrophic failure: delete brain.db
        fs::remove_file(&db_path).unwrap();
        assert!(!db_path.exists());

        // Verify should_hydrate detects the scenario
        assert!(should_hydrate(workspace));

        // Hydrate from snapshot
        let hydrated = hydrate_from_snapshot(workspace).unwrap();
        assert_eq!(hydrated, 2, "Should hydrate both core memories");

        // Verify brain.db was recreated
        assert!(db_path.exists());

        // Verify the data is actually in the new database
        let conn = Connection::open(&db_path).unwrap();
        let count: i64 = conn
            .query_row("SELECT COUNT(*) FROM memories", [], |row| row.get(0))
            .unwrap();
        assert_eq!(count, 2);

        let identity: String = conn
            .query_row(
                "SELECT content FROM memories WHERE key = 'identity'",
                [],
                |row| row.get(0),
            )
            .unwrap();
        assert_eq!(identity, "I am a test agent");
    }

    #[test]
    fn should_hydrate_only_when_needed() {
        let tmp = TempDir::new().unwrap();
        let workspace = tmp.path();

        // No DB, no snapshot → false
        assert!(!should_hydrate(workspace));

        // Create snapshot but no DB → true
        let snapshot = workspace.join(SNAPSHOT_FILENAME);
        fs::write(&snapshot, "### 🔑 `test`\n\nHello\n").unwrap();
        assert!(should_hydrate(workspace));

        // Create a real DB → false
        let db_dir = workspace.join("memory");
        fs::create_dir_all(&db_dir).unwrap();
        let db_path = db_dir.join("brain.db");
        let conn = Connection::open(&db_path).unwrap();
        conn.execute_batch(
            "CREATE TABLE IF NOT EXISTS memories (
                id TEXT PRIMARY KEY,
                key TEXT NOT NULL UNIQUE,
                content TEXT NOT NULL,
                category TEXT NOT NULL DEFAULT 'core',
                embedding BLOB,
                created_at TEXT NOT NULL,
                updated_at TEXT NOT NULL
             );
             INSERT INTO memories VALUES('x','x','x','core',NULL,'2025-01-01','2025-01-01');",
        )
        .unwrap();
        drop(conn);
        assert!(!should_hydrate(workspace));
    }

    #[test]
    fn hydrate_no_snapshot_returns_zero() {
        let tmp = TempDir::new().unwrap();
        let count = hydrate_from_snapshot(tmp.path()).unwrap();
        assert_eq!(count, 0);
    }
}
