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use super::*;

/// "Blend Control".
///
/// Allows the configuration of hardware color blending.
#[cfg(feature = "unsafe_addresses")]
pub const BLDCNT: SimpleVolAddr<BlendControlValue> =
  unsafe { SimpleVolAddr::new(0x0400_0050) };

/// This lets you configure hardware color blending.
///
/// There's three possible [`ColorSpecialEffect`] options you can enable: alpha
/// blending, increase brightness, and decrease brightness. You can also set no
/// effect to occur.
///
/// When selecting an effect, it uses the topmost pixel from all layers among
/// those enabled as a "1st target". If the effect is for alpha blending then it
/// will also then select a pixel to blend with from the topmost pixel among
/// those selected for "2nd target". However, the second pixel to alpha blend
/// _must_ be in the next lower priority layer from the first pixel.
#[repr(transparent)]
#[derive(Debug, Clone, Copy, Default, PartialEq, Eq)]
pub struct BlendControlValue(u16);

#[rustfmt::skip]
#[allow(missing_docs)]
impl BlendControlValue {
  pub_const_fn_new_zero!();
  bool_bit_u16!(0, bg0_1st_target, with_bg0_1st_target, set_bg0_1st_target);
  bool_bit_u16!(1, bg1_1st_target, with_bg1_1st_target, set_bg1_1st_target);
  bool_bit_u16!(2, bg2_1st_target, with_bg2_1st_target, set_bg2_1st_target);
  bool_bit_u16!(3, bg3_1st_target, with_bg3_1st_target, set_bg3_1st_target);
  bool_bit_u16!(4, obj_1st_target, with_obj_1st_target, set_obj_1st_target);
  bool_bit_u16!(5, backdrop_1st_target, with_backdrop_1st_target, set_backdrop_1st_target);
  //
  const_enum_bits_u16!(ColorSpecialEffect, 0b1100_0000, effect, with_effect, set_effect);
  //
  bool_bit_u16!(8, bg0_2nd_target, with_bg0_2nd_target, set_bg0_2nd_target);
  bool_bit_u16!(9, bg1_2nd_target, with_bg1_2nd_target, set_bg1_2nd_target);
  bool_bit_u16!(10, bg2_2nd_target, with_bg2_2nd_target, set_bg2_2nd_target);
  bool_bit_u16!(11, bg3_2nd_target, with_bg3_2nd_target, set_bg3_2nd_target);
  bool_bit_u16!(12, obj_2nd_target, with_obj_2nd_target, set_obj_2nd_target);
  bool_bit_u16!(13, backdrop_2nd_target, with_backdrop_2nd_target, set_backdrop_2nd_target);
}

/// The color special effects available via hardware on the GBA.
///
/// * `NoEffect`: Does nothing, obviously.
/// * `AlphaBlend`: Alpha blend between the two pixels targeted, see
///   [`AlphaBlendValue`].
/// * `IncreaseBrightness` / `DecreaseBrightness`: Make the color brighter or
///   darker, see [`BLDBRIGHT`].
#[repr(transparent)]
#[derive(Debug, Clone, Copy, Default, PartialEq, Eq)]
pub struct ColorSpecialEffect(u16);

#[rustfmt::skip]
#[allow(missing_docs)]
impl ColorSpecialEffect {
  pub const NoEffect: Self = Self(0);
  pub const AlphaBlend: Self = Self(1);
  pub const IncreaseBrightness: Self = Self(2);
  pub const DecreaseBrightness: Self = Self(3);
}

//

/// "Alpha Blend Control".
///
/// Only useful if [`BLDCNT`] is set for alpha blending.
///
/// Adjusts alpha blending coefficients.
#[cfg(feature = "unsafe_addresses")]
pub const BLDALPHA: SimpleVolAddr<AlphaBlendValue> =
  unsafe { SimpleVolAddr::new(0x0400_0050) };

/// Coefficients for the alpha blending special effect.
///
/// For two pixels, "1st target" and "2nd target" the blending (per channel) is
/// as follows:
///
/// ```txt
/// Intensity = min(31, Intensity_1st * eva + Intensity_2nd * evb)
/// ```
///
/// The `eva` and `evb` values are specified in increments of 1/16ths, in the
/// range `0..=16`.
///
/// How the target pixels are selected is described in [`BlendControlValue`].
///
/// If alpha blending is selected but there aren't two pixels to target then
/// only the topmost pixel is displayed, and at normal intensity.
#[repr(transparent)]
#[derive(Debug, Clone, Copy, Default, PartialEq, Eq)]
pub struct AlphaBlendValue(u16);

#[rustfmt::skip]
#[allow(missing_docs)]
impl AlphaBlendValue {
  pub_const_fn_new_zero!();
  unsigned_bits_u16!(0..=4, eva, with_eva, set_eva);
  unsigned_bits_u16!(8..=12, evb, with_evb, set_evb);
}

//

/// "Brightness Blend Control".
///
/// Only useful if [`BLDCNT`] is set for increase or decrease brightness.
///
/// Performs a per-channel adjustment to the intensity of a color.
///
/// Increasing:
/// ```txt
/// Output = Initial + (31 - Initial) * BLDBRIGHT
/// ```
///
/// Decreasing:
/// ```txt
/// Output = Initial - Initial * BLDBRIGHT
/// ```
///
/// The `BLDBRIGHT` value is in terms of 1/16th increments, in the range
/// `0..=16`
///
/// How the target pixels is selected is described in [`BlendControlValue`].
#[cfg(feature = "unsafe_addresses")]
pub const BLDBRIGHT: WriteOnlyVolAddr<u32> =
  unsafe { WriteOnlyVolAddr::new(0x0400_0054) };