Space-Game/apps/game/src/camera.rs

use bevy::input::mouse::MouseButton;
use bevy::prelude::*;
use bevy::window::PrimaryWindow;

use crate::ui::util::cursor_over_ui;

#[derive(Component)]
pub struct MainCamera;

/// Camera mode determines how the camera behaves.
/// - Orbit: Free-look inspection around a target (Galaxy view, docked inspection)
/// - Follow: Tracks behind a moving entity (player ship during flight)
/// - Cinematic: Fixed cinematic shot (docked view, cutscenes)
#[derive(Debug, Clone, Copy, PartialEq, Default)]
pub enum CameraMode {
    #[default]
    Orbit,
    Follow,
    Cinematic,
}

impl CameraMode {
    pub fn is_orbit(&self) -> bool {
        matches!(self, Self::Orbit)
    }

    pub fn is_follow(&self) -> bool {
        matches!(self, Self::Follow)
    }

    pub fn is_cinematic(&self) -> bool {
        matches!(self, Self::Cinematic)
    }
}

/// Global camera state resource. Controls which camera mode is active
/// and which entity the camera should follow (if any).
#[derive(Resource, Default, Debug)]
pub struct CameraState {
    pub mode: CameraMode,
    pub target_entity: Option<Entity>,
    pub follow_distance: f32,
    pub follow_height: f32,
}

/// Follow camera component. Attached to the MainCamera when in Follow mode,
/// this configures how the camera tracks its target.
#[derive(Component, Debug, Clone)]
pub struct FollowCamera {
    pub target: Entity,
    pub distance: f32,
    pub height: f32,
    pub stiffness: f32,
    pub damping: f32,
}

/// Orbit-style camera: rotates around `target` at `distance`, controlled by mouse.
/// Used for inspection scenes like Galaxy where there is no player to follow.
///
/// Orientation is stored as a quaternion (`rotation`) to allow true 360° motion
/// with no gimbal lock. The base orientation is camera at `target + (0, 0, distance)`
/// looking toward `target` with up `+Y`. The quaternion rotates this base around
/// `target`. Mouse drag applies incremental rotations:
///   - horizontal delta → rotate around world `+Y` (yaw)
///   - vertical delta   → rotate around the camera's local `+X` (its right vector)
///
/// This yaw-around-world / pitch-around-local split is the standard free-look
/// construction; it never produces a degenerate "up" vector at the poles.
#[derive(Component, Debug, Clone, Copy)]
pub struct OrbitCamera {
    pub target: Vec3,
    pub distance: f32,
    pub rotation: Quat,
}

impl OrbitCamera {
    /// Reset to default orientation (camera at the canonical "starting" view).
    pub fn reset(&mut self) {
        *self = Self::default();
    }
}

impl Default for OrbitCamera {
    fn default() -> Self {
        // ~36° above horizontal, slightly rotated, roughly matching the docs
        // GalaxyScene opening shot. Built as yaw * pitch so the angles compose
        // the same way the incremental drag rotations do.
        let yaw = Quat::from_rotation_y(0.15);
        let pitch = Quat::from_rotation_x(0.625);
        Self {
            target: Vec3::ZERO,
            distance: 420.0,
            rotation: yaw * pitch,
        }
    }
}

/// Initial camera spawn. The same entity is reused across states; control systems
/// decide how it moves depending on which state is active.
pub fn spawn_camera(mut commands: Commands) {
    let orbit = OrbitCamera::default();
    let offset = orbit.rotation * Vec3::new(0.0, 0.0, orbit.distance);
    commands.spawn((
        Camera3d::default(),
        Transform::from_translation(orbit.target + offset)
            .with_rotation(orbit.rotation)
            .looking_at(orbit.target, Vec3::Y),
        MainCamera,
        orbit,
        Camera {
            // Customize clear color for space background
            clear_color: ClearColorConfig::Custom(Color::srgb(0.02, 0.02, 0.05)),
            ..default()
        },
    ));
}

const ORBIT_ROTATE_SENSITIVITY: f32 = 0.005;
const ORBIT_ZOOM_SENSITIVITY: f32 = 0.1;
const ORBIT_MIN_DISTANCE: f32 = 40.0;
const ORBIT_MAX_DISTANCE: f32 = 1500.0;

/// Left-drag rotates around the orbit target; scroll wheel zooms.
/// No pitch clamping — the camera can tumble a full 360°.
///
/// Drag is suppressed when the cursor is over any UI node — otherwise clicking
/// buttons or panels would also rotate the camera.
///
/// Only runs when camera mode is Orbit or Follow (for tactical repositioning).
pub fn orbit_camera_control(
    camera_state: Res<CameraState>,
    mouse_input: Res<ButtonInput<MouseButton>>,
    primary_window: Query<&Window, With<PrimaryWindow>>,
    mut mouse_motion: EventReader<bevy::input::mouse::MouseMotion>,
    mut scroll_events: EventReader<bevy::input::mouse::MouseWheel>,
    mut query: Query<(&mut Transform, &mut OrbitCamera), With<MainCamera>>,
    ui_nodes: Query<(&bevy::ui::ComputedNode, &GlobalTransform)>,
) {
    // Only run orbit controls in Orbit or Follow mode (not Cinematic)
    if !camera_state.mode.is_orbit() && !camera_state.mode.is_follow() {
        mouse_motion.clear();
        scroll_events.clear();
        return;
    }
    let Ok((mut transform, mut orbit)) = query.single_mut() else {
        // Drain pending input to avoid stale buildup when there's no camera.
        mouse_motion.clear();
        scroll_events.clear();
        return;
    };

    let cursor_over_ui = primary_window
        .single()
        .ok()
        .map(|w| cursor_over_ui(w, &ui_nodes))
        .unwrap_or(false);

    if mouse_input.pressed(MouseButton::Left) && !cursor_over_ui {
        for event in mouse_motion.read() {
            // iPhone-style: content follows the finger horizontally.
            let yaw = Quat::from_rotation_y(-event.delta.x * ORBIT_ROTATE_SENSITIVITY);
            // Vertical: drag down raises the camera so the scene appears to
            // shift down with the cursor.
            let pitch = Quat::from_rotation_x(event.delta.y * ORBIT_ROTATE_SENSITIVITY);
            // Pre-multiply yaw (world-axis rotation), post-multiply pitch
            // (local-axis rotation) — this preserves a stable horizon line as
            // long as `rotation` doesn't already pitch past 90°.
            orbit.rotation = yaw * orbit.rotation * pitch;

            // Re-normalize to counteract floating-point drift from repeated
            // multiplications. Without this the quaternion gradually loses unit
            // length, introducing an implicit scale that manifests as visual
            // stretching / skewing of the scene.
            orbit.rotation = orbit.rotation.normalize();
        }
    } else {
        mouse_motion.clear();
    }

    for event in scroll_events.read() {
        if cursor_over_ui {
            continue;
        }
        // Scroll up (positive y) → decrease distance (zoom in).
        orbit.distance *= 1.0 - event.y * ORBIT_ZOOM_SENSITIVITY;
    }

    orbit.distance = orbit.distance.clamp(ORBIT_MIN_DISTANCE, ORBIT_MAX_DISTANCE);

    // Position = target + rotation * (camera-forward * distance).
    // In the base orientation the camera sits on +Z looking at the origin, so
    // the offset is `rotation * +Z * distance`.
    let offset = orbit.rotation * Vec3::new(0.0, 0.0, orbit.distance);
    let position = orbit.target + offset;

    // Use `orbit.rotation` directly — it already encodes the correct look
    // direction (rotation * -Z points toward the target). Do NOT call
    // `looking_at` then `with_rotation`; that computes a correct rotation
    // only to discard it, and hides the fact that the raw quaternion is the
    // sole source of truth.
    *transform = Transform::from_translation(position).with_rotation(orbit.rotation);
}

/// Resource: set by UI buttons (e.g. "Center View") to request the orbit camera
/// be reset to its default orientation on the next frame. Consumed by
/// [`apply_orbit_reset`].
#[derive(Resource, Default, Debug)]
pub struct ResetOrbitCamera;

/// If [`ResetOrbitCamera`] is present, snap the orbit camera back to default
/// and consume the resource. Lives in `Update` so UI button presses (which
/// insert the resource via `Commands`) take effect on the following frame.
pub fn apply_orbit_reset(
    mut commands: Commands,
    flag: Option<Res<ResetOrbitCamera>>,
    mut query: Query<&mut OrbitCamera, With<MainCamera>>,
) {
    let Some(_flag) = flag else { return };
    let Ok(mut orbit) = query.single_mut() else {
        commands.remove_resource::<ResetOrbitCamera>();
        return;
    };
    orbit.reset();
    commands.remove_resource::<ResetOrbitCamera>();
}

/// Follow camera system. Tracks behind the target entity (player ship) during flight.
/// The camera maintains a fixed distance and height behind the target, smoothly
/// interpolating to the ideal position each frame.
pub fn follow_camera_system(
    time: Res<Time>,
    camera_state: Res<CameraState>,
    mut camera_query: Query<&mut Transform, With<MainCamera>>,
    target_query: Query<&GlobalTransform>,
    follow_cam_query: Query<&FollowCamera, With<MainCamera>>,
) {
    // Only run when in follow mode
    if camera_state.mode != CameraMode::Follow {
        return;
    }

    let Some(target_entity) = camera_state.target_entity else {
        return;
    };

    let Ok(mut camera_transform) = camera_query.single_mut() else {
        return;
    };

    let Ok(target_transform) = target_query.get(target_entity) else {
        return;
    };

    let dt = time.delta_secs();

    // Get target's forward direction (negative Z is forward in Bevy)
    let target_rotation = target_transform.rotation();
    let target_forward = target_rotation * Vec3::NEG_Z;
    let target_up = target_rotation * Vec3::Y;

    // Calculate ideal camera position: behind and above the target
    let follow_distance = camera_state.follow_distance;
    let follow_height = camera_state.follow_height;

    // Position behind the ship: target position - forward * distance + up * height
    let target_pos = target_transform.translation();
    let ideal_position = target_pos - target_forward * follow_distance + target_up * follow_height;

    // Get stiffness from FollowCamera component if it exists, otherwise use default
    let stiffness = follow_cam_query
        .single()
        .map(|fc| fc.stiffness)
        .unwrap_or(3.0);

    // Smoothly interpolate current position to ideal position
    // Using exponential lerp: current = current + (ideal - current) * stiffness * dt
    let lerp_factor = (stiffness * dt).min(1.0);
    camera_transform.translation = camera_transform.translation
        .lerp(ideal_position, lerp_factor);

    // Look at the target (slightly above center to look at ship body, not feet)
    let look_target = target_pos + target_up * (follow_height * 0.5);
    let look_dir = (look_target - camera_transform.translation).normalize();

    // Smoothly rotate to look at target
    let ideal_look = Transform::IDENTITY.looking_to(look_dir, Vec3::Y);
    camera_transform.rotation = camera_transform.rotation
        .slerp(ideal_look.rotation, lerp_factor);
}

/// Initialize the follow camera when transitioning to follow mode.
/// This system adds the FollowCamera component to the MainCamera entity.
pub fn setup_follow_camera(
    mut commands: Commands,
    camera_state: Res<CameraState>,
    camera_query: Query<Entity, With<MainCamera>>,
    follow_cam_query: Query<&FollowCamera, With<MainCamera>>,
) {
    // Only run when we just switched to follow mode and don't have FollowCamera component yet
    if camera_state.mode != CameraMode::Follow {
        return;
    }

    let Some(target_entity) = camera_state.target_entity else {
        return;
    };

    let Ok(camera_entity) = camera_query.single() else {
        return;
    };

    // Check if FollowCamera already exists, if so don't add it again
    if follow_cam_query.single().is_ok() {
        return;
    }

    commands.entity(camera_entity).insert(FollowCamera {
        target: target_entity,
        distance: camera_state.follow_distance,
        height: camera_state.follow_height,
        stiffness: 3.0,
        damping: 0.5,
    });
}