// massive_game_server/server/src/systems/physics/collision.rs
// This file might be new or you might integrate this function into an existing collision system.

use crate::core::types::{EntityId, GameEvent, Projectile, Vec2, Wall}; // Assuming GameEvent and Vec2 are in types
use crate::systems::respawn::WallRespawnManager; // To call wall_destroyed
use tracing::{debug, warn}; // For logging

// Placeholder for other collision functions you might have or add
// pub fn handle_player_projectile_collision(...) { ... }
// pub fn handle_player_player_collision(...) { ... }

/// Handles the collision between a projectile and a wall.
///
/// # Arguments
/// * `projectile` - A reference to the projectile involved in the collision.
/// * `wall_id` - The ID of the wall that was hit.
/// * `walls_map` - A DashMap or similar structure to get/update wall state.
///   Using a generic approach here; you'll need to adapt it to how you store walls.
///   For this example, assuming it's a DashMap<EntityId, Wall>.
/// * `respawn_manager` - A reference to the WallRespawnManager to handle wall destruction.
///
/// # Returns
/// * `Option<GameEvent>` - An event to be broadcasted if the wall was impacted or destroyed.
///
/// Note: This function needs mutable access to the wall's state.
/// The way you get this mutable access (e.g., directly from a DashMap entry,
/// or by sending a command to a wall-managing system) depends on your architecture.
/// For this example, we'll assume direct mutable access for simplicity.
/// In a real system, you'd likely pass a mutable reference to the specific Wall instance.
pub fn handle_projectile_wall_collision(
    projectile: &Projectile,
    wall_id: EntityId,
    // Instead of a generic map, let's assume we get a mutable reference to the wall directly
    // This is often how it's done if the collision system iterates through walls or has direct access.
    // If walls are managed by partitions, the partition would call this with its wall.
    wall_mut_ref: &mut Wall, // Pass a mutable reference to the specific wall
    respawn_manager: &WallRespawnManager,
) -> Option<GameEvent> {
    // Check if the wall is destructible and still has health.
    // The `wall_mut_ref.id` should match `wall_id` passed in.
    if wall_id != wall_mut_ref.id {
        warn!(
            "Wall ID mismatch in collision: projectile hit wall_id {}, but got ref to wall_id {}",
            wall_id, wall_mut_ref.id
        );
        return None; // ID mismatch, something is wrong.
    }

    if wall_mut_ref.is_destructible && wall_mut_ref.current_health > 0 {
        let damage_to_apply = projectile.damage; // Assuming projectile has a damage field

        // Apply damage, ensuring health doesn't go below zero.
        let old_health = wall_mut_ref.current_health;
        wall_mut_ref.current_health = (wall_mut_ref.current_health - damage_to_apply).max(0);

        debug!(
            "Wall ID {} hit by projectile ID {}. Health: {} -> {}.",
            wall_mut_ref.id, projectile.id, old_health, wall_mut_ref.current_health
        );

        // If wall health reaches zero, mark it as destroyed.
        if wall_mut_ref.current_health == 0 && old_health > 0 {
            // Ensure it was just destroyed
            respawn_manager.wall_destroyed(wall_mut_ref.id);
            // Return a WallDestroyed event
            return Some(GameEvent::WallDestroyed {
                wall_id: wall_mut_ref.id,
                position: Vec2::new(
                    wall_mut_ref.x + wall_mut_ref.width / 2.0,
                    wall_mut_ref.y + wall_mut_ref.height / 2.0,
                ),
                // instigator_id: Some(projectile.owner_id.clone()), // Optional: if GameEvent supports it
            });
        } else {
            // Wall was damaged but not destroyed, return a WallImpact event
            return Some(GameEvent::WallImpact {
                wall_id: wall_mut_ref.id,
                position: Vec2::new(
                    wall_mut_ref.x + wall_mut_ref.width / 2.0,
                    wall_mut_ref.y + wall_mut_ref.height / 2.0,
                ),
                damage: damage_to_apply,
                // instigator_id: Some(projectile.owner_id.clone()), // Optional
            });
        }
    } else if !wall_mut_ref.is_destructible {
        // Projectile hit an indestructible wall.
        // You might still want an event for visual/audio feedback.
        return Some(GameEvent::WallImpact {
            wall_id: wall_mut_ref.id,
            position: Vec2::new(
                // Or projectile impact position
                wall_mut_ref.x + wall_mut_ref.width / 2.0,
                wall_mut_ref.y + wall_mut_ref.height / 2.0,
            ),
            damage: 0, // No damage to indestructible wall
        });
    }
    // Projectile hit an already destroyed wall or a non-destructible wall with no impact event configured.
    None
}

// Example of how this might be called within a broader collision processing loop:
/*
pub fn process_all_collisions(
    projectiles: &mut Vec<Projectile>, // Or however you store projectiles
    world_partitions: &WorldPartitionManager, // To get walls
    player_manager: &PlayerManager, // For player-projectile collisions
    respawn_manager: &WallRespawnManager,
    game_events_queue: &PriorityEventQueue, // To push generated events
) {
    let mut projectiles_to_remove_indices = Vec::new();

    for (proj_idx, projectile) in projectiles.iter().enumerate() {
        let mut projectile_collided_this_tick = false;

        // 1. Check projectile-wall collisions
        // This is a simplified check; a real system would use spatial indexing (e.g., query partition for walls near projectile)
        let projectile_partition_idx = world_partitions.get_partition_index_for_point(projectile.x, projectile.y);
        if let Some(partition) = world_partitions.get_partition(projectile_partition_idx) {
            // Need mutable access to walls if their state changes (health)
            // This part is tricky with DashMap directly. Often, a copy of wall data is made for the tick,
            // or changes are queued. For simplicity, let's imagine the partition provides a way
            // to get mutable access or apply damage.
            //
            // A more realistic approach for DashMap:
            // partition.all_walls_in_partition.iter_mut().for_each(|mut wall_entry| { ... });
            // However, iter_mut() on DashMap is tricky.
            //
            // Let's assume the partition has a method that handles this internally or we fetch a mutable wall.
            // This part needs to be adapted to your actual wall storage and access patterns.
            //
            // For this example, we'll iterate IDs and then try to get a mutable ref.
            // This is not efficient for a real game loop.
            let wall_ids_in_partition: Vec<EntityId> = partition.all_walls_in_partition.iter()
                                                                .map(|entry| *entry.key())
                                                                .collect();

            for wall_id_in_partition in wall_ids_in_partition {
                if let Some(mut wall_entry) = partition.all_walls_in_partition.get_mut(&wall_id_in_partition) {
                    let wall = wall_entry.value_mut(); // Get mutable reference

                    // Basic AABB check for projectile center vs wall bounds
                    if projectile.x >= wall.x && projectile.x <= wall.x + wall.width &&
                       projectile.y >= wall.y && projectile.y <= wall.y + wall.height {

                        if let Some(event) = handle_projectile_wall_collision(projectile, wall.id, wall, respawn_manager) {
                            game_events_queue.push(event, crate::core::types::EventPriority::Normal);
                        }
                        projectiles_to_remove_indices.push(proj_idx);
                        projectile_collided_this_tick = true;
                        break; // Projectile hits one wall and is removed
                    }
                }
            }
        }
        if projectile_collided_this_tick { continue; }

        // 2. Check projectile-player collisions (pseudo-code)
        // player_manager.for_each_player_mut(|_player_id, player_state| {
        //     if player_state.alive && /* collision check (e.g. distance < PLAYER_RADIUS) */ {
        //         // Apply damage to player_state
        //         // Create PlayerDamaged event
        //         // projectiles_to_remove_indices.push(proj_idx);
        //         // projectile_collided_this_tick = true;
        //         // return; // Exit player loop for this projectile
        //     }
        // });
        // if projectile_collided_this_tick { continue; }

        // 3. Check projectile lifetime / bounds
        // if projectile.should_remove() || projectile_out_of_bounds(projectile) {
        //     projectiles_to_remove_indices.push(proj_idx);
        // }
    }

    // Remove collided/expired projectiles (iterate in reverse to handle indices correctly)
    // projectiles_to_remove_indices.sort_unstable();
    // projectiles_to_remove_indices.dedup();
    // for i in projectiles_to_remove_indices.iter().rev() {
    //     projectiles.swap_remove(*i);
    // }
}
*/
