class_name WeaponFireHelper extends Node


## Compute bullet properties for a standard shot.
## Returns a Dictionary with: position, angle, fire_time, time_offset, index_from_center, animation_offset
func compute_standard_props(weapon_data: WeaponShot, projectile_index: int, spawn_position: Vector2, current_time: float) -> Dictionary:
	var total_projectiles: int = weapon_data.projectiles
	var center_index: float = (total_projectiles - 1) / 2.0

	var index_from_center: float = projectile_index - center_index

	# Horizontal offset (symmetrical: left=-ve, right=+ve)
	var bullet_horizontal_offset: float = index_from_center * weapon_data.horizontal_offset

	# Timing: center-first, pairs outward
	var time_offset: float = abs(index_from_center) * weapon_data.stagger_offset

	# Angle (only when projectiles >= 3, division-by-zero guard)
	# Moved before vertical offset to support compensation
	var bullet_angle: float = 0.0
	if total_projectiles >= 3:
		bullet_angle = (index_from_center / center_index) * (weapon_data.spread_angle / 2.0)

	# Vertical spacing creates the ^ (inverted-V) geometry: outer projectiles fire lower
	# (higher Y values, further from the player) than the center projectile, which sits
	# higher on screen (lower Y values). This creates a ^ pattern relative to the origin.
	# When compensate_spawn_geometry is enabled and spread_angle > 0, compute vertical
	# offsets to align the geometric spread with velocity vectors.
	var vertical_offset: float
	if weapon_data.compensate_spawn_geometry and weapon_data.spread_angle > 0 and total_projectiles >= 3:
		var velocity_angle_rad: float = abs(bullet_angle) * PI / 180.0
		if index_from_center == 0:
			# Center bullet in compensated mode: use full projectile_vertical_spacing
			# so the V-shape stays visually smooth (center = 35, outer ≈ 75)
			# instead of a broken gap (center = 8.75, outer ≈ 75).
			vertical_offset = weapon_data.projectile_vertical_spacing
		elif velocity_angle_rad > 0.1:  # Guard against division by zero for very small angles
			vertical_offset = abs(bullet_horizontal_offset) / tan(velocity_angle_rad)
		else:
			# Very small angle: fall back to full spacing
			vertical_offset = weapon_data.projectile_vertical_spacing
	else:
		vertical_offset = (abs(index_from_center) * weapon_data.projectile_vertical_spacing) / 2.0
	var position: Vector2 = spawn_position + Vector2(bullet_horizontal_offset, +vertical_offset)

	# Fire time
	var fire_time: float = current_time + time_offset

	# Animation offset (if staggered animation is enabled)
	var animation_offset: float = index_from_center * weapon_data.stagger_offset

	return {
		"position": position,
		"angle": bullet_angle,
		"fire_time": fire_time,
		"time_offset": time_offset,
		"index_from_center": index_from_center,
		"animation_offset": animation_offset,
	}


## Compute bullet properties for a grouped shot, with optional mirroring.
## Returns a Dictionary with: position, angle, fire_time, time_offset, index_from_center, animation_offset
func compute_grouped_props(group: WeaponProjectileGroup, weapon_data: WeaponShot,
						   bullet_index: int, spawn_position: Vector2, current_time: float,
						   mirror: bool = false) -> Dictionary:
	var center_index: float = (group.bullet_count - 1) / 2.0
	var index_from_center: float = bullet_index - center_index

	# Horizontal offset: group offset + within-group spread
	var bullet_horizontal_offset: float = group.horizontal_offset + index_from_center * group.horizontal_spacing
	if mirror:
		bullet_horizontal_offset = -bullet_horizontal_offset

	# Base angle: group angle (negated when mirrored) + within-group spread
	var bullet_angle: float = group.angle_offset
	if mirror:
		bullet_angle = -group.angle_offset

	# Symmetrical spread (guard against < 3 bullets)
	var spread_contribution: float = 0.0
	if group.bullet_count >= 3:
		spread_contribution = (index_from_center / center_index) * (group.spread_angle / 2.0)
		if mirror:
			bullet_angle -= spread_contribution
		else:
			bullet_angle += spread_contribution

	# Vertical spacing creates the ^ (inverted-V) geometry: outer projectiles fire lower
	# (higher Y values, further from the player) than the center projectile, which sits
	# higher on screen (lower Y values). This creates a ^ pattern relative to the origin.
	# When compensate_spawn_geometry is enabled and group.spread_angle > 0, compute
	# vertical offsets to preserve the within-group V-shape independently of
	# angle_offset, which handles global tilt.
	#
	# angle_offset tilts the entire group — mixing it into the compensation formula
	# breaks the V-shape because the formula assumes velocity vectors converge at the
	# origin, but with angle_offset > 0 they fan out from an offset line instead.
	# Solution: calculate compensation using only within-group parameters.
	var vertical_offset: float
	if weapon_data.compensate_spawn_geometry and group.spread_angle > 0 and group.bullet_count >= 3 and index_from_center != 0:
		var within_group_angle: float = abs(spread_contribution)  # exclude angle_offset
		var within_group_angle_rad: float = within_group_angle * PI / 180.0
		var within_group_horizontal: float = abs(index_from_center * group.horizontal_spacing)  # exclude group.horizontal_offset
		if within_group_angle_rad > 0.1:  # Guard against division by zero for very small angles
			vertical_offset = within_group_horizontal / tan(within_group_angle_rad)
		else:
			vertical_offset = (abs(index_from_center) * weapon_data.projectile_vertical_spacing) / 2.0
	else:
		vertical_offset = (abs(index_from_center) * weapon_data.projectile_vertical_spacing) / 2.0
	var position: Vector2 = spawn_position + Vector2(bullet_horizontal_offset, +vertical_offset)

	# Timing: group delay + within-group stagger
	var time_offset: float = group.group_delay + abs(index_from_center) * group.stagger_offset

	# Fire time
	var fire_time: float = current_time + time_offset

	# Animation offset (if staggered animation is enabled)
	var animation_offset: float = index_from_center * weapon_data.stagger_offset

	return {
		"position": position,
		"angle": bullet_angle,
		"fire_time": fire_time,
		"time_offset": time_offset,
		"index_from_center": index_from_center,
		"animation_offset": animation_offset,
	}