/* This file is part of DarkFi (https://dark.fi)
 *
 * Copyright (C) 2026-2026 Dyne.org foundation
 *
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU Affero General Public License as
 * published by the Free Software Foundation, either version 3 of the
 * License, or (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU Affero General Public License for more details.
 *
 * You should have received a copy of the GNU Affero General Public License
 * along with this program.  If not, see <https://www.gnu.org/licenses/>.
 */

//! Simulate the creation of a [`DatabaseOverlay`] on top of an entire
//! [`Database`] instance, and perform writes to verify overlay's cache
//! functionality.

use kvdb_overlay::{Database, DatabaseOverlay, Result};

const TREE_1: &str = "_tree1";
const TREE_2: &str = "_tree2";

#[test]
fn database_overlay() -> Result<()> {
    // Initialize database
    let (db, _folder) = Database::open_temp()?;

    // Initialize overlay
    let mut overlay = DatabaseOverlay::new(&db, vec![])?;

    // Open trees in the overlay
    overlay.open_tree_default(TREE_1, false)?;
    overlay.open_tree_default(TREE_2, false)?;

    // Check overlay trees are empty
    assert!(overlay.is_empty(TREE_1)?);
    assert!(overlay.is_empty(TREE_2)?);

    // Check last value is `None`
    assert_eq!(overlay.last(TREE_1)?, None);
    assert_eq!(overlay.last(TREE_2)?, None);

    // We keep seperate trees for validation
    let tree_1 = db.open_tree_default(TREE_1)?;
    let tree_2 = db.open_tree_default(TREE_2)?;

    // Insert some values to the overlay
    overlay.insert(TREE_1, b"key_a", b"val_a")?;
    overlay.insert(TREE_1, b"key_b", b"val_b")?;
    overlay.insert(TREE_1, b"key_c", b"val_c")?;

    overlay.insert(TREE_2, b"key_d", b"val_d")?;
    overlay.insert(TREE_2, b"key_e", b"val_e")?;
    overlay.insert(TREE_2, b"key_f", b"val_f")?;

    // Verify they are in the overlay
    assert_eq!(overlay.get(TREE_1, b"key_a")?, Some(b"val_a".into()));
    assert_eq!(overlay.get(TREE_1, b"key_b")?, Some(b"val_b".into()));
    assert_eq!(overlay.get(TREE_1, b"key_c")?, Some(b"val_c".into()));

    assert_eq!(overlay.get(TREE_2, b"key_d")?, Some(b"val_d".into()));
    assert_eq!(overlay.get(TREE_2, b"key_e")?, Some(b"val_e".into()));
    assert_eq!(overlay.get(TREE_2, b"key_f")?, Some(b"val_f".into()));

    // Check overlay trees are not empty
    assert!(!overlay.is_empty(TREE_1)?);
    assert!(!overlay.is_empty(TREE_2)?);

    // Check their last values
    assert_eq!(
        overlay.last(TREE_1)?,
        Some((b"key_c".into(), b"val_c".into()))
    );
    assert_eq!(
        overlay.last(TREE_2)?,
        Some((b"key_f".into(), b"val_f".into()))
    );

    // Verify they are not in the database
    assert_eq!(tree_1.get(b"key_a")?, None);
    assert_eq!(tree_1.get(b"key_b")?, None);
    assert_eq!(tree_1.get(b"key_c")?, None);

    assert_eq!(tree_2.get(b"key_d")?, None);
    assert_eq!(tree_2.get(b"key_e")?, None);
    assert_eq!(tree_2.get(b"key_f")?, None);

    // Now execute all tree batches in the overlay
    overlay.apply()?;

    // Don't forget to flush
    db.flush_default_mode()?;

    // Verify the database contains keys
    assert_eq!(tree_1.get(b"key_a")?, Some(b"val_a".into()));
    assert_eq!(tree_1.get(b"key_b")?, Some(b"val_b".into()));
    assert_eq!(tree_1.get(b"key_c")?, Some(b"val_c".into()));

    assert_eq!(tree_2.get(b"key_d")?, Some(b"val_d".into()));
    assert_eq!(tree_2.get(b"key_e")?, Some(b"val_e".into()));
    assert_eq!(tree_2.get(b"key_f")?, Some(b"val_f".into()));

    Ok(())
}

#[test]
fn database_overlay_iteration() -> Result<()> {
    // Initialize database
    let (db, _folder) = Database::open_temp()?;

    // Initialize tree
    let tree = db.open_tree_default(TREE_1)?;
    tree.insert(b"key_a", b"val_a")?;
    tree.insert(b"key_c", b"val_c")?;
    tree.insert(b"key_e", b"val_e")?;

    // Initialize overlay
    let mut overlay = DatabaseOverlay::new(&db, vec![])?;

    // Open tree in the overlay
    overlay.open_tree_default(TREE_1, false)?;

    // Insert some values to the overlay
    overlay.insert(TREE_1, b"key_b", b"val_b")?;
    overlay.insert(TREE_1, b"key_d", b"val_d")?;
    overlay.insert(TREE_1, b"key_e", b"val_ee")?;
    overlay.insert(TREE_1, b"key_f", b"val_f")?;

    // Remove some values from the overlay
    overlay.remove(TREE_1, b"key_c")?;
    overlay.remove(TREE_1, b"key_d")?;

    // Iterate overlay to verify sequence
    let expected_sequence = [
        (b"key_a".to_vec(), b"val_a".to_vec()),
        (b"key_b".to_vec(), b"val_b".to_vec()),
        (b"key_e".to_vec(), b"val_ee".to_vec()),
        (b"key_f".to_vec(), b"val_f".to_vec()),
    ];
    for (index, record) in overlay.iter(TREE_1)?.enumerate() {
        assert_eq!(record?, expected_sequence[index]);
    }

    Ok(())
}