#import "modules/std.sx";
#import "build.sx";
#import "modules/compiler.sx";
#import "modules/opengl.sx";
#import "modules/sdl3.sx";
#import "modules/gpu/api.sx";
#import "modules/gpu/types.sx";
#import "modules/gpu/metal.sx";
#import "modules/platform/api.sx";
#import "modules/platform/sdl3.sx";
#import "modules/platform/uikit.sx";

#run configure_build();

g_plat : Platform = ---;
g_viewport_w : f32 = 800.0;
g_viewport_h : f32 = 600.0;

// iOS-only concrete handles kept alongside the boxed `g_plat` so the frame
// loop can reach the CAMetalLayer pointer / pixel dims without going through
// the protocol box.
g_uikit_plat : *UIKitPlatform = null;
g_metal_gpu  : *MetalGPU      = null;

// ── Render-path proof (P0.2) ─────────────────────────────────────────────
// Clear to a solid blue, then draw one centered orange quad covering the
// central 50%×50% of the drawable. Geometry is in NDC ([-0.5, 0.5]²) so the
// quad stays screen-size independent across simulator devices, which keeps
// the screenshot golden unambiguous. This is the GPU protocol's
// clear+quad path: an MSL pipeline state plus a 6-vertex (2-triangle)
// buffer, created lazily once the MTLDevice exists.
g_quad_shader : ShaderHandle = 0;
g_quad_vbuf   : BufferHandle = 0;

// ── Input-path proof (P0.3) ──────────────────────────────────────────────
// A tap toggles the quad between two distinct colors, proving a real touch
// reaches sx and changes the rendered frame. UIKit touchesBegan is mapped to
// a `mouse_down` Event in uikit.sx; the frame loop's poll flips
// `g_quad_flipped` and marks `g_quad_dirty`, which re-uploads the matching
// vertex colors before the next draw.
g_quad_flipped : bool = false;
g_quad_dirty   : bool = true;

BG_CLEAR :: ClearColor.{ r = 0.10, g = 0.20, b = 0.55, a = 1.0 };

// Vertex layout matches QUAD_MSL's `Vertex`: packed_float2 pos +
// packed_float4 color = 24 bytes. `packed_*` avoids the 16-byte alignment
// padding a plain `float4` would force. 6 vertices = 2 triangles. Two
// arrays share the same geometry and differ only in color so the buffer
// re-upload is a flat memcpy of the active palette.
QUAD_VERTS_ORANGE : [36]f32 = .[
    -0.5,  0.5,   1.0, 0.6, 0.0, 1.0,
     0.5,  0.5,   1.0, 0.6, 0.0, 1.0,
    -0.5, -0.5,   1.0, 0.6, 0.0, 1.0,
     0.5,  0.5,   1.0, 0.6, 0.0, 1.0,
     0.5, -0.5,   1.0, 0.6, 0.0, 1.0,
    -0.5, -0.5,   1.0, 0.6, 0.0, 1.0,
];

QUAD_VERTS_GREEN : [36]f32 = .[
    -0.5,  0.5,   0.15, 0.85, 0.35, 1.0,
     0.5,  0.5,   0.15, 0.85, 0.35, 1.0,
    -0.5, -0.5,   0.15, 0.85, 0.35, 1.0,
     0.5,  0.5,   0.15, 0.85, 0.35, 1.0,
     0.5, -0.5,   0.15, 0.85, 0.35, 1.0,
    -0.5, -0.5,   0.15, 0.85, 0.35, 1.0,
];

// Pass-through shader: the vertex stage emits NDC positions directly (no
// projection), the fragment stage returns the interpolated vertex color.
// Entry-point names vmain / fmain are what MetalGPU.create_shader looks up.
QUAD_MSL :: #string MSL
#include <metal_stdlib>
using namespace metal;

struct Vertex {
    packed_float2 pos;
    packed_float4 color;
};

struct RasterizerData {
    float4 position [[position]];
    float4 color;
};

vertex RasterizerData vmain(uint vid [[vertex_id]],
                            constant Vertex* vertices [[buffer(0)]]) {
    RasterizerData out;
    out.position = float4(vertices[vid].pos, 0.0, 1.0);
    out.color = float4(vertices[vid].color);
    return out;
}

fragment float4 fmain(RasterizerData in [[stage_in]]) {
    return in.color;
}
MSL;

frame :: () {
    fc := g_plat.begin_frame();
    g_viewport_w = fc.viewport_w;
    g_viewport_h = fc.viewport_h;

    for g_plat.poll_events(): (*ev) {
        if ev == {
            // Flip on the press only. A tap also produces mouse_up
            // (touchesEnded); toggling on both would net to no change.
            case .mouse_down: {
                g_quad_flipped = !g_quad_flipped;
                g_quad_dirty = true;
            }
        }
        inline if OS != .ios {
            if ev == {
                case .key_up: (e) {
                    if e.key == .escape { g_plat.stop(); }
                }
            }
        }
    }

    inline if OS == .ios {
        // Lazy-attach Metal once -[SxAppDelegate didFinishLaunching:] has
        // installed the SxMetalView and its bounds have been measured; both
        // can lag the first CADisplayLink tick, and a zero-sized drawable
        // aborts via XPC.
        if g_uikit_plat.gl_layer == null { return; }
        if g_uikit_plat.pixel_w <= 0 or g_uikit_plat.pixel_h <= 0 { return; }
        if g_metal_gpu.layer == null {
            g_metal_gpu.init(g_uikit_plat.gl_layer, g_uikit_plat.pixel_w, g_uikit_plat.pixel_h);
        } else if g_metal_gpu.pixel_w != g_uikit_plat.pixel_w or g_metal_gpu.pixel_h != g_uikit_plat.pixel_h {
            g_metal_gpu.resize(g_uikit_plat.pixel_w, g_uikit_plat.pixel_h);
        }
        // Compile the quad pipeline + upload its vertices once. The MTLDevice
        // was created eagerly in main(), so both only need a valid device.
        if g_quad_shader == 0 {
            g_quad_shader = g_metal_gpu.create_shader(QUAD_MSL, "");
            if g_quad_shader == 0 { return; }
        }
        if g_quad_vbuf == 0 {
            g_quad_vbuf = g_metal_gpu.create_buffer(size_of([36]f32));
            if g_quad_vbuf == 0 { return; }
        }
        if g_quad_dirty {
            verts := if g_quad_flipped then @QUAD_VERTS_GREEN else @QUAD_VERTS_ORANGE;
            g_metal_gpu.update_buffer(g_quad_vbuf, xx verts, size_of([36]f32));
            g_quad_dirty = false;
        }

        if !g_metal_gpu.begin_frame(BG_CLEAR) { return; }
        g_metal_gpu.set_shader(g_quad_shader);
        g_metal_gpu.set_vertex_buffer(g_quad_vbuf);
        g_metal_gpu.draw_triangles(0, 6);
        g_metal_gpu.end_frame(fc.target_present_time);
    } else {
        glViewport(0, 0, fc.pixel_w, fc.pixel_h);
        glClearColor(0.10, 0.20, 0.55, 1.0);
        glClear(GL_COLOR_BUFFER_BIT);
    }
    g_plat.end_frame();
}

main :: () -> void {
    inline if OS == .ios {
        u : *UIKitPlatform = xx context.allocator.alloc(size_of(UIKitPlatform));
        u.gpu_mode = .metal;
        if !u.init("m3te", 800, 600) { return; }
        g_plat = xx u;
        g_uikit_plat = u;

        // The CAMetalLayer doesn't exist until didFinishLaunching: runs after
        // we return into UIApplicationMain, so attach lazily on the first
        // frame. init(null, 0, 0) only needs the MTLDevice.
        g_metal_gpu = xx context.allocator.alloc(size_of(MetalGPU));
        // alloc returns uninitialized memory; struct field defaults are NOT
        // applied, so List caps/lens would be garbage without this memset.
        memset(xx g_metal_gpu, 0, size_of(MetalGPU));
        if !g_metal_gpu.init(null, 0, 0) { return; }
    } else {
        s : *SdlPlatform = xx context.allocator.alloc(size_of(SdlPlatform));
        if !s.init("m3te", 800, 600) { return; }
        g_plat = xx s;
    }

    fc := g_plat.begin_frame();
    g_viewport_w = fc.viewport_w;
    g_viewport_h = fc.viewport_h;

    g_plat.run_frame_loop(closure(frame));
    g_plat.shutdown();
}