//! Extract draw state from the Xenos register file at `PM4_DRAW_INDX` time.
//!
//! This is the "what are we drawing?" snapshot: primitive type, vertex count,
//! index buffer (if any), viewport, scissor, blend, depth state, and enough
//! handles for a future translator / uber-shader to pull fetch constants +
//! shader blobs. Ground truth: `xenia-canary/src/xenia/gpu/draw_util.h` and
//! the PM4 handler at `pm4_command_processor_implement.h:1128-1151`.
//!
//! We only extract what the P3 uber-shader actually consumes; the rest is
//! reserved for later phases.

use crate::register_file::RegisterFile;

/// Primitive type (Xenos `PrimitiveType` enum from `xenos.h`).
#[derive(Debug, Clone, Copy, PartialEq, Eq)]
pub enum PrimitiveType {
    None,
    PointList,
    LineList,
    LineStrip,
    TriangleList,
    TriangleFan,
    TriangleStrip,
    RectangleList,
    QuadList,
    Unknown(u8),
}

impl PrimitiveType {
    pub fn from_bits(b: u32) -> Self {
        match b & 0x3F {
            0 => PrimitiveType::None,
            1 => PrimitiveType::PointList,
            2 => PrimitiveType::LineList,
            3 => PrimitiveType::LineStrip,
            4 => PrimitiveType::TriangleList,
            5 => PrimitiveType::TriangleFan,
            6 => PrimitiveType::TriangleStrip,
            8 => PrimitiveType::RectangleList,
            13 => PrimitiveType::QuadList,
            other => PrimitiveType::Unknown(other as u8),
        }
    }
}

/// How the draw was issued per `VGT_DRAW_INITIATOR.source_select`:
/// 0=DMA, 1=Immediate (in-packet indices), 2=AutoIndex.
#[derive(Debug, Clone, Copy, PartialEq, Eq)]
pub enum IndexSource {
    /// Index buffer fetched from `VGT_DMA_BASE` / `VGT_DMA_SIZE`.
    Dma {
        base_address: u32,
        size_dwords: u32,
        index_size: IndexSize,
    },
    /// Indices follow the `DRAW_INDX_2` packet header inline.
    Immediate { index_size: IndexSize },
    /// No index buffer; generate `0..vertex_count - 1` on the host.
    AutoIndex,
}

#[derive(Debug, Clone, Copy, PartialEq, Eq)]
pub enum IndexSize {
    /// 16-bit indices.
    Sixteen,
    /// 32-bit indices.
    ThirtyTwo,
}

/// Snapshot of one draw call's state, sampled from the register file.
#[derive(Debug, Clone, Copy)]
pub struct DrawState {
    pub primitive: PrimitiveType,
    pub vertex_count: u32,
    pub index_source: IndexSource,
    pub viewport: Viewport,
    pub scissor: Scissor,
    /// RB_COLOR_INFO for each of the 4 possible color render targets; `None`
    /// where the target is not bound.
    pub color_info: [Option<ColorTargetInfo>; 4],
    pub depth_info: Option<DepthTargetInfo>,
    pub rb_modecontrol: u32,
    pub rb_colorcontrol: u32,
    pub rb_depthcontrol: u32,
    /// P4: per-color-target blend state. Index matches `color_info`.
    pub rb_blendcontrol: [u32; 4],
    /// P4: stencil state.
    pub rb_stencilrefmask: u32,
    pub rb_stencilrefmask_bf: u32,
    /// P4: pixel offset applied at rasterization.
    pub pa_sc_window_offset: u32,
    /// P4: resolve destination registers (`RB_COPY_*`). These are set by
    /// the guest just before triggering a TILE_FLUSH event and describe
    /// where an EDRAM→texture copy should land.
    pub rb_copy_control: u32,
    pub rb_copy_dest_base: u32,
    pub rb_copy_dest_pitch: u32,
    pub rb_copy_dest_info: u32,
    /// Key of the VS blob that was active at draw time (from
    /// `GpuSystem::active_vs_key`). `None` = no VS loaded yet; the draw is
    /// meaningless and will be rejected by the dispatcher.
    pub vs_blob_key: Option<u32>,
    /// Key of the PS blob that was active at draw time.
    pub ps_blob_key: Option<u32>,
}

#[derive(Debug, Clone, Copy, Default)]
pub struct Viewport {
    pub scale_x: f32,
    pub scale_y: f32,
    pub scale_z: f32,
    pub offset_x: f32,
    pub offset_y: f32,
    pub offset_z: f32,
}

#[derive(Debug, Clone, Copy, Default)]
pub struct Scissor {
    pub tl_x: u16,
    pub tl_y: u16,
    pub br_x: u16,
    pub br_y: u16,
}

#[derive(Debug, Clone, Copy)]
pub struct ColorTargetInfo {
    /// EDRAM tile base for this color target (`RB_COLOR_INFO.base_tiles`).
    pub base_tiles: u16,
    /// Color format (`RB_COLOR_INFO.color_format`).
    pub format: u8,
}

#[derive(Debug, Clone, Copy)]
pub struct DepthTargetInfo {
    /// EDRAM tile base for depth/stencil.
    pub base_tiles: u16,
    /// 0=D24S8, 1=D24FS8 (per `xenos.h:404-408`).
    pub format: u8,
}

/// Resolve source: either one of four color render targets or the depth RT.
/// Packed into `RB_COPY_CONTROL.copy_src_select` (bits [2:0]): 0..=3 pick
/// color0..3, 4 picks depth. Canary `registers.h:853`.
#[derive(Debug, Clone, Copy, PartialEq, Eq)]
pub enum ResolveSource {
    Color(u8),
    Depth,
}

/// Resolve rectangle in pixel coordinates at the destination resolution,
/// 8-pixel aligned per Canary's `kResolveAlignmentPixels = 8`. MSAA scaling
/// is kept separate — `sample_count_log2_x/y` tell the resolve how many
/// samples to step per destination pixel.
#[derive(Debug, Clone, Copy, Default, PartialEq, Eq)]
pub struct ResolveCoordinates {
    pub x0: u32,
    pub y0: u32,
    pub width: u32,
    pub height: u32,
    /// 1 iff 4x MSAA (samples laid out 2x wider than pixels).
    pub sample_count_log2_x: u32,
    /// 1 iff 2x+ MSAA (samples laid out 2x taller than pixels).
    pub sample_count_log2_y: u32,
}

/// Decoded resolve state — describes how a `TILE_FLUSH` event should copy
/// EDRAM bytes to a guest-memory tiled texture. Canary equivalent:
/// `draw_util::ResolveInfo` at `draw_util.h:627`. Bit-field layout in
/// `RB_COPY_CONTROL / RB_COPY_DEST_INFO / RB_COPY_DEST_PITCH` comes from
/// `registers.h:853-897`.
#[derive(Debug, Clone, Copy)]
pub struct ResolveInfo {
    /// Which source RT (0..=3=color, 4=depth). Raw register bits.
    pub copy_src_select: u8,
    /// Sample selector for MSAA sources. See `xenos::CopySampleSelect`.
    pub copy_sample_select: u8,
    /// Enable clear of the source render target after the copy.
    pub color_clear_enable: bool,
    pub depth_clear_enable: bool,
    /// 0 = raw tile copy (same format), 1 = convert to `copy_dest_format`.
    /// 2 = constantOne, 3 = null (no copy).
    pub copy_command: u8,
    /// Guest-memory destination address, already masked to the 29-bit
    /// Xenon physical range (`& 0x1FFF_FFFF`).
    pub dest_base: u32,
    /// Destination pitch in pixels (0..=16383). Byte pitch = pitch * bpp
    /// after the caller pitch-aligns to `kStoragePitchHeightAlignmentBlocks
    /// = 32`.
    pub dest_pitch_pixels: u32,
    pub dest_height_pixels: u32,
    /// Destination format (`xenos::ColorFormat`, 6 bits).
    pub dest_format: u8,
    /// Byte-swap mode applied before the write (`xenos::Endian128`, 0..=5).
    pub dest_endian: u8,
    /// Signed [-32, 31] exponent bias applied during conversion.
    pub dest_exp_bias: i8,
    /// Decoded resolve source (color0..3 or depth).
    pub source: ResolveSource,
    /// 8-pixel-aligned resolve rectangle.
    pub coords: ResolveCoordinates,
    /// Source format: `ColorRenderTargetFormat` when color,
    /// `DepthRenderTargetFormat` when depth.
    pub source_format: u8,
    /// EDRAM tile origin of the source RT (from `RB_COLOR_INFO.color_base`
    /// or `RB_DEPTH_INFO.depth_base`, 11-bit mod 2048).
    pub source_base_tiles: u16,
    /// `GetSurfacePitchTiles(surface_pitch, msaa, is_64bpp)` — how many
    /// 80-sample-wide tiles make up one EDRAM row.
    pub surface_pitch_tiles: u32,
    /// MSAA mode from `RB_SURFACE_INFO`.
    pub msaa: crate::render_target_cache::MsaaSamples,
    /// True iff the source color format is 64bpp (doubles EDRAM pitch/base).
    pub source_is_64bpp: bool,
    /// `RB_COLOR_CLEAR` — constant written into EDRAM when
    /// `color_clear_enable` is set.
    pub color_clear_value: u32,
    /// `RB_COLOR_CLEAR_LO` — second 32-bit lane for 64bpp clear.
    pub color_clear_value_lo: u32,
    /// `RB_DEPTH_CLEAR` — constant written into EDRAM depth tiles on
    /// `depth_clear_enable`.
    pub depth_clear_value: u32,
    /// `RB_COPY_DEST_INFO.copy_dest_array` — 2D (false) vs 3D/stacked (true).
    pub copy_dest_array: bool,
}

/// `GetSurfacePitchTiles(pitch_pixels, msaa, is_64bpp)` — ported from
/// `xenos.h:465-476`. Returns the number of 80-sample-wide EDRAM tiles
/// that make up one row of a surface with `pitch_pixels`-pixel pitch.
///
/// At 4x MSAA samples span twice the pixel width, so the sample pitch
/// doubles. 64bpp formats pack two EDRAM tiles per color value, so the
/// effective tile pitch doubles again.
#[inline]
pub fn surface_pitch_tiles(
    pitch_pixels: u32,
    msaa: crate::render_target_cache::MsaaSamples,
    is_64bpp: bool,
) -> u32 {
    use crate::render_target_cache::MsaaSamples;
    const EDRAM_TILE_WIDTH_SAMPLES: u32 = 80;
    let pitch_samples = pitch_pixels << u32::from(msaa == MsaaSamples::X4);
    let pitch_tiles = pitch_samples.div_ceil(EDRAM_TILE_WIDTH_SAMPLES);
    pitch_tiles << u32::from(is_64bpp)
}

/// Canary `ColorRenderTargetFormat` is 64bpp iff its numeric value is one
/// of {5, 7, 15} — i.e. `k_16_16_16_16`, `k_16_16_16_16_FLOAT`, or
/// `k_32_32_FLOAT`. `xenos.h:297-317` + the enum's `IsColorRenderTarget
/// Format64bpp` helper.
#[inline]
pub fn color_render_target_format_is_64bpp(fmt: u8) -> bool {
    matches!(fmt, 5 | 7 | 15)
}

/// `kResolveAlignmentPixels` from Canary (`draw_util.cc:925` area).
pub const RESOLVE_ALIGNMENT_PIXELS: u32 = 8;

/// Clamp a raw resolve rectangle to the `PA_SC_WINDOW_SCISSOR_*` registers
/// and align to the 8-pixel grid. Caller passes `i32` because the VF0
/// derivation can produce negative bounding-box values; this helper clamps
/// them to the non-negative window defined by the scissor.
///
/// Returns `(x0, y0, width, height)` in pixels, all non-negative, all
/// 8-pixel-aligned, `width`/`height` already `>= 0`. Width/height of 0
/// signals "empty resolve; skip".
pub fn resolve_rect_apply_scissor_and_align_8(
    rf: &RegisterFile,
    x0_in: i32,
    y0_in: i32,
    x1_in: i32,
    y1_in: i32,
) -> (u32, u32, u32, u32) {
    let tl = rf.read(reg::PA_SC_WINDOW_SCISSOR_TL);
    let br = rf.read(reg::PA_SC_WINDOW_SCISSOR_BR);
    let tl_x = (tl & 0x3FFF) as i32;
    let tl_y = ((tl >> 16) & 0x3FFF) as i32;
    let br_x = (br & 0x3FFF) as i32;
    let br_y = ((br >> 16) & 0x3FFF) as i32;

    // Clamp only when the scissor is a non-degenerate window; otherwise
    // leave the input rect alone (Canary's `kResolveAlignmentPixels` will
    // still 8-align it below).
    let (mut x0, mut y0, mut x1, mut y1) = (x0_in, y0_in, x1_in, y1_in);
    if br_x > tl_x && br_y > tl_y {
        let clamp = |v: i32, lo: i32, hi: i32| v.max(lo).min(hi);
        x0 = clamp(x0, tl_x, br_x);
        y0 = clamp(y0, tl_y, br_y);
        x1 = clamp(x1, tl_x, br_x);
        y1 = clamp(y1, tl_y, br_y);
    }
    if x1 < x0 {
        x1 = x0;
    }
    if y1 < y0 {
        y1 = y0;
    }

    // 8-pixel align. Floor top-left; ceil bottom-right.
    let align_mask = (RESOLVE_ALIGNMENT_PIXELS as i32) - 1;
    x0 &= !align_mask;
    y0 &= !align_mask;
    x1 = (x1 + align_mask) & !align_mask;
    y1 = (y1 + align_mask) & !align_mask;

    let x0u = x0.max(0) as u32;
    let y0u = y0.max(0) as u32;
    let x1u = x1.max(0) as u32;
    let y1u = y1.max(0) as u32;
    (
        x0u,
        y0u,
        x1u.saturating_sub(x0u),
        y1u.saturating_sub(y0u),
    )
}

/// Parse vertex fetch constant 0 (Canary `xe_gpu_vertex_fetch_t`,
/// `xenos.h:1158-1172`) and derive the resolve bounding-box in pixel units.
/// Returns `None` when the fetch isn't the 6-float vertex buffer the
/// resolve shader expects (type != kVertex or size != 6).
///
/// This mirrors `draw_util.cc:950-1014` minus window-offset and half-pixel
/// nudging — the pitfalls there are (a) handling endian via `GpuSwap` and
/// (b) Fixed16p8 top-left rounding `(v + 127) >> 8`. Both are replicated.
///
/// The returned rect is in *pixel* coordinates, *pre-scissor-clamp* and
/// *pre-alignment*. Caller feeds it through
/// [`resolve_rect_apply_scissor_and_align_8`].
pub fn vertex_fetch_0_rect(
    rf: &RegisterFile,
    mem: &dyn xenia_memory::access::MemoryAccess,
) -> Option<(i32, i32, i32, i32)> {
    const CONST_BASE_FETCH: u32 = 0x4800;
    let dword_0 = rf.read(CONST_BASE_FETCH);
    let dword_1 = rf.read(CONST_BASE_FETCH + 1);

    // type:2 at bits [1:0]; kVertex = 3 per xenos.h:1147-1152.
    let fetch_type = dword_0 & 0x3;
    if fetch_type != 3 {
        return None;
    }
    // size:24 at bits [25:2] of dword_1 — in dwords; expect 6 (3 × vec2).
    let size = (dword_1 >> 2) & 0x00FF_FFFF;
    if size != 6 {
        return None;
    }
    // address:30 at bits [31:2] of dword_0 — in dwords.
    let address_bytes = dword_0 & 0xFFFF_FFFC;
    // endian:2 at bits [1:0] of dword_1 — xenos::Endian (kNone/k8in16/k8in32/k16in32).
    let fetch_endian = (dword_1 & 0x3) as u8;

    // Read 6 floats from guest memory. `mem.read_u32` stores BE bytes as a
    // u32 value; to mirror Canary's "raw LE bytes → u32 → GpuSwap" we have
    // to re-interpret the memory as LE (flipping what `read_u32` did).
    let floats: [f32; 6] = std::array::from_fn(|i| {
        let be_u32 = mem.read_u32(address_bytes.wrapping_add(i as u32 * 4));
        // `be_u32` was composed from bytes `[b0,b1,b2,b3]` as
        // `(b0<<24)|...|b3`. Canary reads those same bytes in host-LE,
        // producing `(b3<<24)|...|b0`. That's `be_u32.swap_bytes()`.
        let canary_le = be_u32.swap_bytes();
        let swapped = gpu_swap_u32(canary_le, fetch_endian);
        f32::from_bits(swapped)
    });

    // PA_SU_VTX_CNTL::pix_center: bit 0, 0 = kD3DZero (+0.5 half-pixel),
    // 1 = kOpenGL (no offset). Pre-fix the constant at this site read
    // 0x2083 (PA_SC_CLIPRECT_RULE), giving non-deterministic half-pixel
    // offsets that broke 3D camera matrices. Canary `register_table.inc`
    // line 1336 says PA_SU_VTX_CNTL is 0x2302. GPUBUG-105.
    const PA_SU_VTX_CNTL: u32 = 0x2302;
    let half_pixel_offset = if rf.read(PA_SU_VTX_CNTL) & 1 == 0 {
        0.5f32
    } else {
        0.0f32
    };

    // Convert each to Fixed16p8 (multiply by 256, round).
    let fixed: [i32; 6] = std::array::from_fn(|i| {
        ((floats[i] + half_pixel_offset) * 256.0).round() as i32
    });

    let x0 = fixed[0].min(fixed[2]).min(fixed[4]);
    let y0 = fixed[1].min(fixed[3]).min(fixed[5]);
    let x1 = fixed[0].max(fixed[2]).max(fixed[4]);
    let y1 = fixed[1].max(fixed[3]).max(fixed[5]);

    // Top-left rounding: `(v + 127) >> 8` for both corners.
    let round = |v: i32| (v + 127) >> 8;
    Some((round(x0), round(y0), round(x1), round(y1)))
}

/// Canary `GpuSwapInline` on a u32. Exposed here so the vertex-fetch path
/// can apply the same byte-order transform Canary's `GpuSwap<float>` applies
/// to vertex data. `xenos.h:1077-1114`.
#[inline]
fn gpu_swap_u32(value: u32, endian: u8) -> u32 {
    match endian & 0x3 {
        // kNone.
        0 => value,
        // k8in16: swap bytes within each 16-bit word.
        1 => ((value & 0xFF00FF00) >> 8) | ((value & 0x00FF00FF) << 8),
        // k8in32: full byte reversal.
        2 => value.swap_bytes(),
        // k16in32: swap 16-bit halves.
        _ => value.rotate_left(16),
    }
}

impl ResolveInfo {
    /// Legacy entrypoint used when the caller already has a `DrawState`. It
    /// fills only the narrow register bits that live in `DrawState` — the
    /// wider coordinate / EDRAM fields require the full register file.
    ///
    /// Kept for tests that construct resolve decoders from captured draw
    /// states. `from_register_file` is the canonical path.
    pub fn from_draw_state(ds: &DrawState) -> Self {
        use crate::render_target_cache::MsaaSamples;
        let c = ds.rb_copy_control;
        let p = ds.rb_copy_dest_pitch;
        let i = ds.rb_copy_dest_info;
        // Sign-extend the 6-bit exp_bias from `copy_dest_info[21:16]`.
        let exp_raw = (i >> 16) & 0x3F;
        let exp_sign = ((exp_raw & 0x20) != 0) as i8;
        let exp_bias = (exp_raw as i8) - (exp_sign * 64);
        let src_sel = (c & 0x7) as u8;
        let source = if src_sel >= 4 {
            ResolveSource::Depth
        } else {
            ResolveSource::Color(src_sel)
        };
        Self {
            copy_src_select: src_sel,
            copy_sample_select: ((c >> 4) & 0x7) as u8,
            color_clear_enable: ((c >> 8) & 1) != 0,
            depth_clear_enable: ((c >> 9) & 1) != 0,
            copy_command: ((c >> 20) & 0x3) as u8,
            dest_base: ds.rb_copy_dest_base & 0x1FFF_FFFF,
            dest_pitch_pixels: p & 0x3FFF,
            dest_height_pixels: (p >> 16) & 0x3FFF,
            dest_format: ((i >> 7) & 0x3F) as u8,
            dest_endian: (i & 0x7) as u8,
            dest_exp_bias: exp_bias,
            source,
            coords: ResolveCoordinates::default(),
            source_format: 0,
            source_base_tiles: 0,
            surface_pitch_tiles: 0,
            msaa: MsaaSamples::X1,
            source_is_64bpp: false,
            color_clear_value: 0,
            color_clear_value_lo: 0,
            depth_clear_value: 0,
            copy_dest_array: ((i >> 3) & 1) != 0,
        }
    }

    /// Canonical resolve decoder — reads live register values and derives the
    /// full rectangle / EDRAM layout. Mirrors canary `draw_util.cc:926-1318`
    /// `GetResolveInfo` with the following simplifications (all scoped in
    /// the landing plan and will be expanded as needs arise):
    ///
    /// * The rectangle is derived from the scissor window and
    ///   `RB_COPY_DEST_PITCH` rather than fetched from vertex fetch 0.
    ///   Sylpheed's splash uses a clear-resolve — there's no draw ahead
    ///   of it — so vertex-fetch-derived geometry is not available.
    /// * `copy_sample_select` is kept as-is; sample averaging for 2x/4x
    ///   MSAA is not yet applied on the read side.
    /// * `PA_SC_WINDOW_OFFSET` is not applied — not needed for Sylpheed
    ///   and canary only applies it when `PA_SU_SC_MODE_CNTL.vtx_window
    ///   _offset_enable` is set, which requires a live draw.
    pub fn from_register_file(rf: &RegisterFile) -> Self {
        use crate::render_target_cache::MsaaSamples;
        let c = rf.read(reg::RB_COPY_CONTROL);
        let i = rf.read(reg::RB_COPY_DEST_INFO);
        let p = rf.read(reg::RB_COPY_DEST_PITCH);
        let dest_base_raw = rf.read(reg::RB_COPY_DEST_BASE);

        // Sign-extend 6-bit exp_bias from copy_dest_info[21:16].
        let exp_raw = (i >> 16) & 0x3F;
        let exp_sign = ((exp_raw & 0x20) != 0) as i8;
        let exp_bias = (exp_raw as i8) - (exp_sign * 64);

        let src_sel = (c & 0x7) as u8;
        let source = if src_sel >= 4 {
            ResolveSource::Depth
        } else {
            ResolveSource::Color(src_sel & 0x3)
        };

        let rb_surface_info = rf.read(reg::RB_SURFACE_INFO);
        let surface_pitch_pixels = rb_surface_info & 0x3FFF;
        let msaa = MsaaSamples::from_raw((rb_surface_info >> 16) & 0x3);

        // Source format + base tiles depend on which RT we're reading.
        let (source_format, source_base_tiles, source_is_64bpp) = match source {
            ResolveSource::Color(idx) => {
                let rb = match idx {
                    0 => rf.read(reg::RB_COLOR_INFO_0),
                    1 => rf.read(reg::RB_COLOR_INFO_1),
                    2 => rf.read(reg::RB_COLOR_INFO_2),
                    _ => rf.read(reg::RB_COLOR_INFO_3),
                };
                let fmt = ((rb >> 16) & 0xF) as u8;
                let base = (rb & 0xFFF) as u16;
                (fmt, base, color_render_target_format_is_64bpp(fmt))
            }
            ResolveSource::Depth => {
                let rb = rf.read(reg::RB_DEPTH_INFO);
                let fmt = ((rb >> 16) & 0x1) as u8;
                let base = (rb & 0xFFF) as u16;
                (fmt, base, false)
            }
        };

        let pitch_tiles = surface_pitch_tiles(surface_pitch_pixels, msaa, source_is_64bpp);

        // --- Rectangle derivation ---
        // Default extent is (0, 0, dest_pitch, dest_height); subject to
        // scissor clamp + 8-pixel alignment.
        let dest_pitch = p & 0x3FFF;
        let dest_height = (p >> 16) & 0x3FFF;
        let coords_no_msaa = resolve_rect_apply_scissor_and_align_8(
            rf,
            0,
            0,
            dest_pitch as i32,
            dest_height as i32,
        );
        let coords = ResolveCoordinates {
            x0: coords_no_msaa.0,
            y0: coords_no_msaa.1,
            width: coords_no_msaa.2,
            height: coords_no_msaa.3,
            sample_count_log2_x: u32::from(msaa == MsaaSamples::X4),
            sample_count_log2_y: u32::from(msaa != MsaaSamples::X1),
        };

        Self {
            copy_src_select: src_sel,
            copy_sample_select: ((c >> 4) & 0x7) as u8,
            color_clear_enable: ((c >> 8) & 1) != 0,
            depth_clear_enable: ((c >> 9) & 1) != 0,
            copy_command: ((c >> 20) & 0x3) as u8,
            dest_base: dest_base_raw & 0x1FFF_FFFF,
            dest_pitch_pixels: dest_pitch,
            dest_height_pixels: dest_height,
            dest_format: ((i >> 7) & 0x3F) as u8,
            dest_endian: (i & 0x7) as u8,
            dest_exp_bias: exp_bias,
            source,
            coords,
            source_format,
            source_base_tiles,
            surface_pitch_tiles: pitch_tiles,
            msaa,
            source_is_64bpp,
            color_clear_value: rf.read(reg::RB_COLOR_CLEAR),
            color_clear_value_lo: rf.read(reg::RB_COLOR_CLEAR_LO),
            depth_clear_value: rf.read(reg::RB_DEPTH_CLEAR),
            copy_dest_array: ((i >> 3) & 1) != 0,
        }
    }

    /// Memory-aware variant: if vertex fetch 0 contains the D3D9-hack
    /// "resolve rectangle" vertices (3 vec2 floats, Canary `draw_util.cc
    /// :950-1014`), use its bounding box as the resolve extent. Falls back
    /// to the scissor + `RB_COPY_DEST_PITCH/HEIGHT` rect when VF0 isn't a
    /// 6-dword vertex buffer.
    ///
    /// Used from the live TILE_FLUSH path; tests can stick with
    /// `from_register_file` when they don't want to program VF0.
    pub fn from_register_file_and_memory(
        rf: &RegisterFile,
        mem: &dyn xenia_memory::access::MemoryAccess,
    ) -> Self {
        let mut info = Self::from_register_file(rf);
        if let Some((x0, y0, x1, y1)) = vertex_fetch_0_rect(rf, mem) {
            let (rx0, ry0, rw, rh) =
                resolve_rect_apply_scissor_and_align_8(rf, x0, y0, x1, y1);
            // Only override when the VF0 rect is non-empty — an empty VF0
            // means the game hasn't set one up yet and we should keep the
            // scissor+dest default.
            if rw > 0 && rh > 0 {
                info.coords.x0 = rx0;
                info.coords.y0 = ry0;
                info.coords.width = rw;
                info.coords.height = rh;
            }
        }
        info
    }
}

/// Register indices from `xenia-canary/src/xenia/gpu/register_table.inc`.
/// Only what the extractor reads is named here.
///
/// GPUBUG-103/104/105: 8 of these were previously off-by-many — pointing at
/// completely different registers. Each has been re-validated against
/// canary's `register_table.inc`.
pub mod reg {
    // VGT (vertex/geometry transform) — GPUBUG-103.
    pub const VGT_DRAW_INITIATOR: u32 = 0x21FC; // was 0x2281 (junk).
    pub const VGT_DMA_BASE: u32 = 0x21FA; // was 0x2282 (junk).
    pub const VGT_DMA_SIZE: u32 = 0x21FB; // was 0x2283 (junk).
    pub const PA_CL_VPORT_XSCALE: u32 = 0x210F;
    pub const PA_CL_VPORT_XOFFSET: u32 = 0x2110;
    pub const PA_CL_VPORT_YSCALE: u32 = 0x2111;
    pub const PA_CL_VPORT_YOFFSET: u32 = 0x2112;
    pub const PA_CL_VPORT_ZSCALE: u32 = 0x2113;
    pub const PA_CL_VPORT_ZOFFSET: u32 = 0x2114;
    // GPUBUG-104: pre-fix these read PA_SC_SCREEN_SCISSOR_{TL,BR} (the
    // global screen scissor) instead of the per-window scissor.
    pub const PA_SC_WINDOW_SCISSOR_TL: u32 = 0x2081; // was 0x200E (= SCREEN_SCISSOR_TL).
    pub const PA_SC_WINDOW_SCISSOR_BR: u32 = 0x2082; // was 0x200F (= SCREEN_SCISSOR_BR).
    pub const RB_MODECONTROL: u32 = 0x2208;
    pub const RB_SURFACE_INFO: u32 = 0x2000;
    pub const RB_COLOR_INFO_0: u32 = 0x2001;
    // GPUBUG-105: per-RT color info; pre-fix indexed COHER_DEST_BASE_*
    // instead. Canary names them RB_COLOR1/2/3_INFO.
    pub const RB_COLOR_INFO_1: u32 = 0x2003; // was 0x2010 (= COHER_DEST_BASE_10).
    pub const RB_COLOR_INFO_2: u32 = 0x2004; // was 0x2011.
    pub const RB_COLOR_INFO_3: u32 = 0x2005; // was 0x2012.
    pub const RB_DEPTH_INFO: u32 = 0x2002;
    pub const RB_COLORCONTROL: u32 = 0x2202;
    pub const RB_DEPTHCONTROL: u32 = 0x2200;
    // P4 additions — per-RT blend + stencil + window offset + resolve dst.
    pub const RB_BLENDCONTROL_0: u32 = 0x2201;
    pub const RB_BLENDCONTROL_1: u32 = 0x2209;
    pub const RB_BLENDCONTROL_2: u32 = 0x220A;
    pub const RB_BLENDCONTROL_3: u32 = 0x220B;
    pub const RB_STENCILREFMASK: u32 = 0x210D;
    pub const RB_STENCILREFMASK_BF: u32 = 0x210C;
    pub const PA_SC_WINDOW_OFFSET: u32 = 0x2080;
    pub const RB_COPY_CONTROL: u32 = 0x2318;
    pub const RB_COPY_DEST_BASE: u32 = 0x2319;
    pub const RB_COPY_DEST_PITCH: u32 = 0x231A;
    pub const RB_COPY_DEST_INFO: u32 = 0x231B;
    pub const RB_DEPTH_CLEAR: u32 = 0x231D;
    pub const RB_COLOR_CLEAR: u32 = 0x231E;
    pub const RB_COLOR_CLEAR_LO: u32 = 0x231F;
}

/// Build a [`DrawState`] from a `VGT_DRAW_INITIATOR` value + the current
/// register file. `extra_dma_base`/`extra_dma_size` can override the
/// DMA fields if the caller has them from the PM4 packet payload (canary
/// passes them inline with `DRAW_INDX`).
pub fn extract(
    register_file: &RegisterFile,
    vgt_draw_initiator: u32,
    dma_base: Option<u32>,
    dma_size: Option<u32>,
) -> DrawState {
    // `VGT_DRAW_INITIATOR` bit layout (per canary `registers.h:315-327`):
    //   [5:0]   prim_type (PrimitiveType)
    //   [7:6]   source_select (0=DMA, 1=immediate, 2=auto)
    //   [9:8]   major_mode
    //   [10]    _pad
    //   [11]    index_size (0=16-bit, 1=32-bit)   ← GPUBUG-103
    //   [12]    not_eop
    //   [15:13] _pad
    //   [31:16] num_indices
    let prim_bits = vgt_draw_initiator & 0x3F;
    let source_select = (vgt_draw_initiator >> 6) & 0x3;
    let index_size_bit = (vgt_draw_initiator >> 11) & 0x1;
    let num_indices = (vgt_draw_initiator >> 16) & 0xFFFF;
    let index_size = if index_size_bit == 0 {
        IndexSize::Sixteen
    } else {
        IndexSize::ThirtyTwo
    };

    let index_source = match source_select {
        0 => IndexSource::Dma {
            base_address: dma_base.unwrap_or_else(|| register_file.read(reg::VGT_DMA_BASE)),
            size_dwords: dma_size.unwrap_or_else(|| register_file.read(reg::VGT_DMA_SIZE)),
            index_size,
        },
        1 => IndexSource::Immediate { index_size },
        _ => IndexSource::AutoIndex,
    };

    let f = |r: u32| f32::from_bits(register_file.read(r));
    let viewport = Viewport {
        scale_x: f(reg::PA_CL_VPORT_XSCALE),
        scale_y: f(reg::PA_CL_VPORT_YSCALE),
        scale_z: f(reg::PA_CL_VPORT_ZSCALE),
        offset_x: f(reg::PA_CL_VPORT_XOFFSET),
        offset_y: f(reg::PA_CL_VPORT_YOFFSET),
        offset_z: f(reg::PA_CL_VPORT_ZOFFSET),
    };

    let tl = register_file.read(reg::PA_SC_WINDOW_SCISSOR_TL);
    let br = register_file.read(reg::PA_SC_WINDOW_SCISSOR_BR);
    let scissor = Scissor {
        tl_x: (tl & 0x7FFF) as u16,
        tl_y: ((tl >> 16) & 0x7FFF) as u16,
        br_x: (br & 0x7FFF) as u16,
        br_y: ((br >> 16) & 0x7FFF) as u16,
    };

    let rb_modecontrol = register_file.read(reg::RB_MODECONTROL);
    let color_mask = rb_modecontrol & 0xF;
    let ci = |reg: u32, present: bool| {
        if !present {
            return None;
        }
        let raw = register_file.read(reg);
        Some(ColorTargetInfo {
            base_tiles: (raw & 0xFFF) as u16,
            format: ((raw >> 16) & 0xF) as u8,
        })
    };
    let color_info = [
        ci(reg::RB_COLOR_INFO_0, (color_mask & 0x1) != 0),
        ci(reg::RB_COLOR_INFO_1, (color_mask & 0x2) != 0),
        ci(reg::RB_COLOR_INFO_2, (color_mask & 0x4) != 0),
        ci(reg::RB_COLOR_INFO_3, (color_mask & 0x8) != 0),
    ];
    let depth_raw = register_file.read(reg::RB_DEPTH_INFO);
    // Depth-surface "present" = the RB_MODECONTROL depth-enable bit at bit 4.
    let depth_present = (rb_modecontrol & 0x10) != 0;
    let depth_info = if depth_present {
        Some(DepthTargetInfo {
            base_tiles: (depth_raw & 0xFFF) as u16,
            format: ((depth_raw >> 16) & 0x1) as u8,
        })
    } else {
        None
    };

    DrawState {
        primitive: PrimitiveType::from_bits(prim_bits),
        vertex_count: num_indices,
        index_source,
        viewport,
        scissor,
        color_info,
        depth_info,
        rb_modecontrol,
        rb_colorcontrol: register_file.read(reg::RB_COLORCONTROL),
        rb_depthcontrol: register_file.read(reg::RB_DEPTHCONTROL),
        rb_blendcontrol: [
            register_file.read(reg::RB_BLENDCONTROL_0),
            register_file.read(reg::RB_BLENDCONTROL_1),
            register_file.read(reg::RB_BLENDCONTROL_2),
            register_file.read(reg::RB_BLENDCONTROL_3),
        ],
        rb_stencilrefmask: register_file.read(reg::RB_STENCILREFMASK),
        rb_stencilrefmask_bf: register_file.read(reg::RB_STENCILREFMASK_BF),
        pa_sc_window_offset: register_file.read(reg::PA_SC_WINDOW_OFFSET),
        rb_copy_control: register_file.read(reg::RB_COPY_CONTROL),
        rb_copy_dest_base: register_file.read(reg::RB_COPY_DEST_BASE),
        rb_copy_dest_pitch: register_file.read(reg::RB_COPY_DEST_PITCH),
        rb_copy_dest_info: register_file.read(reg::RB_COPY_DEST_INFO),
        // P3b M1: the kernel-side caller is expected to populate these
        // via `DrawState { ..extract(...), vs_blob_key, ps_blob_key }` so
        // the pure-register extraction stays decoupled from `GpuSystem`
        // state. Default to None so a bare `extract()` stays valid for
        // unit tests.
        vs_blob_key: None,
        ps_blob_key: None,
    }
}

#[cfg(test)]
mod tests {
    use super::*;

    fn rf() -> RegisterFile {
        RegisterFile::new()
    }

    #[test]
    fn extract_basic_triangle_list_no_rt() {
        let rf = rf();
        // prim_type=4 (TriangleList), source=2 (auto), num_indices=6
        let vgt = (6u32 << 16) | (2 << 6) | 4;
        let ds = extract(&rf, vgt, None, None);
        assert_eq!(ds.primitive, PrimitiveType::TriangleList);
        assert_eq!(ds.vertex_count, 6);
        assert!(matches!(ds.index_source, IndexSource::AutoIndex));
        assert!(ds.color_info.iter().all(|c| c.is_none()));
        assert!(ds.depth_info.is_none());
    }

    #[test]
    fn extract_dma_indices_uses_override() {
        let rf = rf();
        let vgt = (3u32 << 16) | (0 << 6) | 4; // prim=TriList, source=DMA
        let ds = extract(&rf, vgt, Some(0xDEAD_0000), Some(6));
        match ds.index_source {
            IndexSource::Dma {
                base_address,
                size_dwords,
                index_size,
            } => {
                assert_eq!(base_address, 0xDEAD_0000);
                assert_eq!(size_dwords, 6);
                assert_eq!(index_size, IndexSize::Sixteen);
            }
            other => panic!("expected Dma, got {other:?}"),
        }
    }

    #[test]
    fn color_and_depth_enabled_bits_are_honored() {
        let mut rf = rf();
        // rb_modecontrol: color0 + depth enabled (bit0 + bit4)
        rf.write(reg::RB_MODECONTROL, 0x11);
        rf.write(reg::RB_COLOR_INFO_0, (2 << 16) | 0x64); // format=2, tile=0x64
        rf.write(reg::RB_DEPTH_INFO, (1 << 16) | 0x32);
        let ds = extract(&rf, 4, None, None);
        let c = ds.color_info[0].unwrap();
        assert_eq!(c.format, 2);
        assert_eq!(c.base_tiles, 0x64);
        let d = ds.depth_info.unwrap();
        assert_eq!(d.format, 1);
        assert_eq!(d.base_tiles, 0x32);
    }

    /// `RB_COPY_DEST_BASE` is a raw 32-bit register, but a Xenon physical
    /// address is 29-bit (`& 0x1FFF_FFFF`). `ResolveInfo::from_register_file`
    /// must mask before writes to prevent out-of-range memory accesses.
    #[test]
    fn resolve_info_masks_dest_base_to_physical() {
        let mut rf = rf();
        rf.write(reg::RB_COPY_DEST_BASE, 0xDEAD_BEEF);
        let info = ResolveInfo::from_register_file(&rf);
        assert_eq!(info.dest_base, 0x1EAD_BEEF);
    }

    /// Scissor ∩ (0, 0, dest_pitch, dest_height), then 8-pixel-aligned per
    /// Canary `kResolveAlignmentPixels`. Verify that the scissor actually
    /// tightens the rect (not just degenerates it).
    #[test]
    fn resolve_info_derives_8px_aligned_rect_from_scissor_and_dest_pitch() {
        let mut rf = rf();
        // Dest pitch/height 1280×720; scissor (5, 5) -> (1000, 717).
        rf.write(reg::RB_COPY_DEST_PITCH, (720u32 << 16) | 1280u32);
        rf.write(reg::PA_SC_WINDOW_SCISSOR_TL, (5u32 << 16) | 5u32);
        rf.write(reg::PA_SC_WINDOW_SCISSOR_BR, (717u32 << 16) | 1000u32);
        let info = ResolveInfo::from_register_file(&rf);
        // x0 floors to 0 (was 5 -> &!7 = 0), y0 same.
        // x1 = min(1280, 1000) = 1000; ceil-to-8 = 1000. y1 = min(720, 717) = 717, ceil = 720.
        assert_eq!(info.coords.x0, 0);
        assert_eq!(info.coords.y0, 0);
        assert_eq!(info.coords.width, 1000);
        assert_eq!(info.coords.height, 720);
    }

    /// Non-degenerate scissor outside `dest_pitch/height` clamps to the
    /// destination extent.
    #[test]
    fn resolve_info_scissor_cannot_widen_past_dest() {
        let mut rf = rf();
        rf.write(reg::RB_COPY_DEST_PITCH, (16u32 << 16) | 16u32);
        rf.write(reg::PA_SC_WINDOW_SCISSOR_BR, (1000u32 << 16) | 1000u32);
        let info = ResolveInfo::from_register_file(&rf);
        assert_eq!(info.coords.width, 16);
        assert_eq!(info.coords.height, 16);
    }

    /// Source decoding: `copy_src_select >= 4` → depth; otherwise Color(idx).
    #[test]
    fn resolve_info_decodes_source_select() {
        let mut rf = rf();
        rf.write(reg::RB_COPY_CONTROL, 2); // src_select = 2 (color2)
        let info = ResolveInfo::from_register_file(&rf);
        assert_eq!(info.source, ResolveSource::Color(2));
        assert_eq!(info.copy_src_select, 2);

        rf.write(reg::RB_COPY_CONTROL, 4); // src_select = 4 -> depth
        let info = ResolveInfo::from_register_file(&rf);
        assert_eq!(info.source, ResolveSource::Depth);
    }

    /// `copy_dest_info` fields: endian (bits 2:0), format (bits 12:7),
    /// exp_bias (bits 21:16, signed 6-bit), array (bit 3).
    #[test]
    fn resolve_info_decodes_copy_dest_info_fields() {
        let mut rf = rf();
        // endian=2 (k8in32), format=6 (k_8_8_8_8), exp_bias=-1 (0x3F), array=1
        let val = 2u32 | (1u32 << 3) | (6u32 << 7) | (0x3Fu32 << 16);
        rf.write(reg::RB_COPY_DEST_INFO, val);
        let info = ResolveInfo::from_register_file(&rf);
        assert_eq!(info.dest_endian, 2);
        assert_eq!(info.dest_format, 6);
        assert_eq!(info.dest_exp_bias, -1);
        assert!(info.copy_dest_array);
    }

    /// Positive and negative exp_bias round-trip through the 6-bit
    /// sign-extension.
    #[test]
    fn resolve_info_exp_bias_sign_extends() {
        let mut rf = rf();
        rf.write(reg::RB_COPY_DEST_INFO, 1u32 << 16); // exp_bias = +1
        assert_eq!(ResolveInfo::from_register_file(&rf).dest_exp_bias, 1);
        rf.write(reg::RB_COPY_DEST_INFO, 0x20u32 << 16); // exp_bias = -32
        assert_eq!(ResolveInfo::from_register_file(&rf).dest_exp_bias, -32);
        rf.write(reg::RB_COPY_DEST_INFO, 0x1Fu32 << 16); // exp_bias = +31
        assert_eq!(ResolveInfo::from_register_file(&rf).dest_exp_bias, 31);
    }

    /// `RB_SURFACE_INFO`: surface_pitch (bits 13:0) and msaa_samples (bits 17:16)
    /// feed `surface_pitch_tiles`. 1280 px divides by 80 exactly → 16 tiles
    /// at 1x MSAA / 32bpp; 4x MSAA doubles the sample pitch.
    #[test]
    fn resolve_info_computes_surface_pitch_tiles() {
        let mut rf = rf();
        rf.write(reg::RB_COPY_CONTROL, 0); // color0
        rf.write(reg::RB_COLOR_INFO_0, 0u32 << 16); // k_8_8_8_8 -> 32bpp
        rf.write(reg::RB_SURFACE_INFO, 1280); // msaa=1x, pitch=1280
        let info = ResolveInfo::from_register_file(&rf);
        assert_eq!(info.surface_pitch_tiles, 16);
        assert!(!info.source_is_64bpp);

        // 4x MSAA widens the sample pitch by 2x.
        rf.write(reg::RB_SURFACE_INFO, 1280 | (2u32 << 16));
        let info = ResolveInfo::from_register_file(&rf);
        assert_eq!(info.surface_pitch_tiles, 32);

        // Non-aligned pitch rounds up.
        rf.write(reg::RB_SURFACE_INFO, 1281);
        let info = ResolveInfo::from_register_file(&rf);
        assert_eq!(info.surface_pitch_tiles, 17);
    }

    /// `color_render_target_format_is_64bpp` matches the 64bpp enum values
    /// in `xenos::ColorRenderTargetFormat`: k_16_16_16_16 (5),
    /// k_16_16_16_16_FLOAT (7), k_32_32_FLOAT (15).
    #[test]
    fn color_format_64bpp_table_is_correct() {
        assert!(!color_render_target_format_is_64bpp(0));
        assert!(!color_render_target_format_is_64bpp(4));
        assert!(color_render_target_format_is_64bpp(5));
        assert!(!color_render_target_format_is_64bpp(6));
        assert!(color_render_target_format_is_64bpp(7));
        assert!(!color_render_target_format_is_64bpp(14));
        assert!(color_render_target_format_is_64bpp(15));
    }

    /// `surface_pitch_tiles` helper: exact arithmetic including the 64bpp
    /// doubling. `xenos.h:465-476`.
    #[test]
    fn surface_pitch_tiles_matches_canary_helper() {
        use crate::render_target_cache::MsaaSamples;
        // 80 px, 1x, 32bpp -> 1 tile exactly.
        assert_eq!(surface_pitch_tiles(80, MsaaSamples::X1, false), 1);
        // 81 px, 1x, 32bpp -> 2 tiles (round up).
        assert_eq!(surface_pitch_tiles(81, MsaaSamples::X1, false), 2);
        // 80 px, 1x, 64bpp -> 2 tiles (64bpp doubles).
        assert_eq!(surface_pitch_tiles(80, MsaaSamples::X1, true), 2);
        // 80 px, 2x, 32bpp -> 1 tile (2x MSAA doesn't widen X).
        assert_eq!(surface_pitch_tiles(80, MsaaSamples::X2, false), 1);
        // 80 px, 4x, 32bpp -> 2 tiles (4x MSAA widens X 2x).
        assert_eq!(surface_pitch_tiles(80, MsaaSamples::X4, false), 2);
        // 80 px, 4x, 64bpp -> 4 tiles.
        assert_eq!(surface_pitch_tiles(80, MsaaSamples::X4, true), 4);
    }

    /// The color-source branch reads from `RB_COLOR_INFO_<idx>` based on
    /// `copy_src_select`. Verify that index-3 color targets are addressed.
    #[test]
    fn resolve_info_color_source_selects_correct_color_info() {
        let mut rf = rf();
        rf.write(reg::RB_COPY_CONTROL, 3); // color3
        rf.write(reg::RB_COLOR_INFO_3, (5u32 << 16) | 0x123); // k_16_16_16_16, base=0x123
        let info = ResolveInfo::from_register_file(&rf);
        assert_eq!(info.source, ResolveSource::Color(3));
        assert_eq!(info.source_format, 5);
        assert_eq!(info.source_base_tiles, 0x123);
        assert!(info.source_is_64bpp);
    }

    /// Depth-source branch reads from `RB_DEPTH_INFO` and parses its
    /// 1-bit format.
    #[test]
    fn resolve_info_depth_source_reads_depth_info() {
        let mut rf = rf();
        rf.write(reg::RB_COPY_CONTROL, 4); // depth
        rf.write(reg::RB_DEPTH_INFO, (1u32 << 16) | 0x55); // kD24FS8, base=0x55
        let info = ResolveInfo::from_register_file(&rf);
        assert_eq!(info.source, ResolveSource::Depth);
        assert_eq!(info.source_format, 1);
        assert_eq!(info.source_base_tiles, 0x55);
        assert!(!info.source_is_64bpp); // depth always 32bpp
    }

    // ---- Vertex fetch 0 rectangle tests -------------------------------

    /// Helper: seed a triangle covering the rectangle `(x0, y0) → (x1, y1)`
    /// into guest memory at `vb_addr` and program VF0 to read 6 dwords
    /// from it with endian = k8in32 (the standard D3D-vertex-buffer case).
    fn seed_vertex_fetch_0(
        rf: &mut RegisterFile,
        mem: &xenia_memory::GuestMemory,
        vb_addr: u32,
        x0: f32,
        y0: f32,
        x1: f32,
        y1: f32,
    ) {
        use xenia_memory::MemoryAccess;
        // Three (x, y) float pairs covering the rect — exactly the D3D9
        // resolve triangle layout Canary expects.
        //   (x0, y0), (x1, y0), (x0, y1)
        let floats = [x0, y0, x1, y0, x0, y1];
        for (i, f) in floats.iter().enumerate() {
            // Write float as BE (PPC `stfs` semantics). `mem.write_u32`
            // already stores BE bytes; pass the raw u32 bit pattern.
            mem.write_u32(
                vb_addr + i as u32 * 4,
                f.to_bits(),
            );
        }

        // VF0 dword 0: address (bits 31:2, in dwords) + type (bits 1:0 = 3).
        let addr_dwords = vb_addr / 4;
        let dword_0 = (addr_dwords << 2) | 3;
        // VF0 dword 1: size (bits 25:2 = 6) + endian (bits 1:0 = 2 = k8in32).
        let dword_1 = (6u32 << 2) | 2;
        rf.write(0x4800, dword_0);
        rf.write(0x4801, dword_1);
    }

    fn fresh_mem_for_vf0() -> xenia_memory::GuestMemory {
        use xenia_memory::page_table::MemoryProtect;
        let mut mem = xenia_memory::GuestMemory::new().expect("guest memory");
        mem.alloc(
            0x5000_0000,
            0x1_0000,
            MemoryProtect::READ | MemoryProtect::WRITE,
        )
        .expect("alloc");
        mem
    }

    #[test]
    fn vf0_rect_returns_none_when_no_vertex_buffer() {
        let rf = rf();
        let mem = fresh_mem_for_vf0();
        assert!(vertex_fetch_0_rect(&rf, &mem).is_none());
    }

    #[test]
    fn vf0_rect_returns_none_for_wrong_size() {
        let mut rf = rf();
        let mem = fresh_mem_for_vf0();
        // type=3 (kVertex), size=4 (wrong — should be 6), endian=2.
        rf.write(0x4800, (0x5000_0000u32) | 3);
        rf.write(0x4801, (4u32 << 2) | 2);
        assert!(vertex_fetch_0_rect(&rf, &mem).is_none());
    }

    #[test]
    fn vf0_rect_derives_rectangle_from_three_vertices() {
        let mut rf = rf();
        let mut mem = fresh_mem_for_vf0();
        // D3D9 pixel center: +0.5 half-pixel offset applied before Fixed16p8.
        // Leave PA_SU_VTX_CNTL at 0 (kD3DZero).
        // Triangle at (0, 0) → (100, 50) → vertex 2 = (0, 50).
        seed_vertex_fetch_0(&mut rf, &mut mem, 0x5000_0000, 0.0, 0.0, 100.0, 50.0);

        let (x0, y0, x1, y1) = vertex_fetch_0_rect(&rf, &mem).expect("VF0 present");
        // (0 + 0.5) * 256 = 128. (128 + 127) >> 8 = 0. So x0/y0 = 0.
        // (100 + 0.5) * 256 = 25728. (25728 + 127) >> 8 = 100.
        // (50 + 0.5) * 256 = 12928. (12928 + 127) >> 8 = 50.
        assert_eq!(x0, 0);
        assert_eq!(y0, 0);
        assert_eq!(x1, 100);
        assert_eq!(y1, 50);
    }

    #[test]
    fn from_register_file_and_memory_prefers_vf0_rect() {
        let mut rf = rf();
        let mut mem = fresh_mem_for_vf0();
        // Without VF0: dest_pitch/height defaults produce (0, 0, 1280, 720).
        rf.write(reg::RB_COPY_DEST_PITCH, (720u32 << 16) | 1280u32);
        // With VF0 pointing at a 256×128 triangle, override to that.
        seed_vertex_fetch_0(&mut rf, &mut mem, 0x5000_0000, 0.0, 0.0, 256.0, 128.0);

        let info = ResolveInfo::from_register_file_and_memory(&rf, &mem);
        assert_eq!(info.coords.x0, 0);
        assert_eq!(info.coords.y0, 0);
        assert_eq!(info.coords.width, 256);
        assert_eq!(info.coords.height, 128);
    }

    /// If VF0 is absent, fall back to the scissor+dest default.
    #[test]
    fn from_register_file_and_memory_falls_back_without_vf0() {
        let mut rf = rf();
        let mem = fresh_mem_for_vf0();
        rf.write(reg::RB_COPY_DEST_PITCH, (720u32 << 16) | 1280u32);
        let info = ResolveInfo::from_register_file_and_memory(&rf, &mem);
        assert_eq!(info.coords.width, 1280);
        assert_eq!(info.coords.height, 720);
    }

    /// `resolve_rect_apply_scissor_and_align_8` with no scissor just
    /// 8-aligns.
    #[test]
    fn scissor_helper_8_aligns_with_no_scissor() {
        let rf = rf();
        let (x0, y0, w, h) = resolve_rect_apply_scissor_and_align_8(&rf, 5, 5, 1001, 17);
        assert_eq!(x0, 0);
        assert_eq!(y0, 0);
        // 1001 ceil-to-8 = 1008; 17 ceil-to-8 = 24.
        assert_eq!(w, 1008);
        assert_eq!(h, 24);
    }

    /// Negative bounding-box (VF0 can produce these) clamps to the scissor
    /// top-left without going below zero.
    #[test]
    fn scissor_helper_clamps_negative_to_zero() {
        let mut rf = rf();
        // Small scissor at (0,0)..(128, 64).
        rf.write(reg::PA_SC_WINDOW_SCISSOR_BR, (64u32 << 16) | 128u32);
        let (x0, y0, w, h) = resolve_rect_apply_scissor_and_align_8(&rf, -50, -50, 80, 32);
        assert_eq!(x0, 0);
        assert_eq!(y0, 0);
        // x1 clamped from 80 -> 80, ceil8 -> 80. y1 32 -> 32.
        assert_eq!(w, 80);
        assert_eq!(h, 32);
    }
}