// TODO:
// - handle textures better with texture atlas
// - handle adding and removing triangles and quads better

const std = @import("std");
const mach = @import("mach");
const core = mach.core;
const ft = @import("freetype");
const zigimg = @import("zigimg");
const assets = @import("assets");
const draw = @import("draw.zig");
const Label = @import("label.zig");
const ResizableLabel = @import("resizable_label.zig");
const gpu = mach.gpu;
const Atlas = mach.gfx.Atlas;

pub const App = @This();

pipeline: *gpu.RenderPipeline,
vertex_buffer: *gpu.Buffer,
vertices: std.ArrayList(draw.Vertex),
update_vertex_buffer: bool,
vertex_uniform_buffer: *gpu.Buffer,
update_vertex_uniform_buffer: bool,
frag_uniform_buffer: *gpu.Buffer,
fragment_uniform_list: std.ArrayList(draw.FragUniform),
update_frag_uniform_buffer: bool,
bind_group: *gpu.BindGroup,
texture_atlas_data: Atlas,

pub fn init(app: *App) !void {
    try core.init(.{});

    // TODO: Refactor texture atlas size number
    app.texture_atlas_data = try Atlas.init(
        core.allocator,
        1280,
        .rgba,
    );
    const atlas_size = gpu.Extent3D{ .width = app.texture_atlas_data.size, .height = app.texture_atlas_data.size };

    const texture = core.device.createTexture(&.{
        .size = atlas_size,
        .format = .rgba8_unorm,
        .usage = .{
            .texture_binding = true,
            .copy_dst = true,
            .render_attachment = true,
        },
    });
    const data_layout = gpu.Texture.DataLayout{
        .bytes_per_row = @as(u32, @intCast(atlas_size.width * 4)),
        .rows_per_image = @as(u32, @intCast(atlas_size.height)),
    };

    var img = try zigimg.Image.fromMemory(core.allocator, assets.gotta_go_fast_png);
    defer img.deinit();

    const atlas_img_region = try app.texture_atlas_data.reserve(core.allocator, @as(u32, @truncate(img.width)), @as(u32, @truncate(img.height)));
    const img_uv_data = atlas_img_region.calculateUV(app.texture_atlas_data.size);

    switch (img.pixels) {
        .rgba32 => |pixels| app.texture_atlas_data.set(
            atlas_img_region,
            @as([*]const u8, @ptrCast(pixels.ptr))[0 .. pixels.len * 4],
        ),
        .rgb24 => |pixels| {
            const data = try rgb24ToRgba32(core.allocator, pixels);
            defer data.deinit(core.allocator);
            app.texture_atlas_data.set(
                atlas_img_region,
                @as([*]const u8, @ptrCast(data.rgba32.ptr))[0 .. data.rgba32.len * 4],
            );
        },
        else => @panic("unsupported image color format"),
    }

    const white_tex_scale = 80;
    var atlas_white_region = try app.texture_atlas_data.reserve(core.allocator, white_tex_scale, white_tex_scale);
    atlas_white_region.x += 1;
    atlas_white_region.y += 1;
    atlas_white_region.width -= 2;
    atlas_white_region.height -= 2;
    const white_texture_uv_data = atlas_white_region.calculateUV(app.texture_atlas_data.size);
    const white_tex_data = try core.allocator.alloc(zigimg.color.Rgba32, white_tex_scale * white_tex_scale);
    defer core.allocator.free(white_tex_data);
    @memset(white_tex_data, zigimg.color.Rgba32.initRgb(0xff, 0xff, 0xff));
    app.texture_atlas_data.set(atlas_white_region, @as([*]const u8, @ptrCast(white_tex_data.ptr))[0 .. white_tex_data.len * 4]);

    app.vertices = try std.ArrayList(draw.Vertex).initCapacity(core.allocator, 9);
    app.fragment_uniform_list = try std.ArrayList(draw.FragUniform).initCapacity(core.allocator, 3);

    // Quick test for using freetype
    const lib = try ft.Library.init();
    defer lib.deinit();

    const DemoMode = enum {
        gkurves,
        bitmap_text, // TODO: broken
        text,
        quad,
        circle,
    };
    const demo_mode: DemoMode = .gkurves;

    core.queue.writeTexture(
        &.{ .texture = texture },
        &data_layout,
        &.{ .width = app.texture_atlas_data.size, .height = app.texture_atlas_data.size },
        app.texture_atlas_data.data,
    );

    const wsize = core.size();
    const window_width = @as(f32, @floatFromInt(wsize.width));
    const window_height = @as(f32, @floatFromInt(wsize.height));
    const triangle_scale = 250;
    switch (demo_mode) {
        .gkurves => {
            try draw.equilateralTriangle(app, .{ window_width / 2, window_height / 1.9 }, triangle_scale, .{}, img_uv_data, 1.0);
            try draw.equilateralTriangle(app, .{ window_width / 2, window_height / 1.9 - triangle_scale }, triangle_scale, .{ .type = .quadratic_concave }, img_uv_data, 1.0);
            try draw.equilateralTriangle(app, .{ window_width / 2 - triangle_scale, window_height / 1.9 }, triangle_scale, .{ .type = .quadratic_convex }, white_texture_uv_data, 1.0);
            try draw.equilateralTriangle(app, .{ window_width / 2 - triangle_scale, window_height / 1.9 - triangle_scale }, triangle_scale, .{ .type = .quadratic_convex }, white_texture_uv_data, 0.5);
        },
        else => @panic("disabled for now"),
        // TODO: disabled for now because these rely on a Label API that expects a font filepath,
        // rather than bytes. This gkurve example / experiment test bed should probably be moved
        // elsewhere anyway.
        //
        // .bitmap_text => {
        //     // const character = "Gotta-go-fast!\n0123456789\n~!@#$%^&*()_+è\n:\"<>?`-=[];',./";
        //     // const character = "ABCDEFGHIJ\nKLMNOPQRST\nUVWXYZ";
        //     const size_multiplier = 5;
        //     var label = try Label.init(lib, assets.roboto_medium_ttf.path, 0, 110 * size_multiplier, core.allocator);
        //     defer label.deinit();
        //     try label.print(app, "All your game's bases are belong to us èçòà", .{}, @Vector(2, f32){ 0, 420 }, @Vector(4, f32){ 1, 1, 1, 1 });
        //     try label.print(app, "wow!", .{}, @Vector(2, f32){ 70 * size_multiplier, 70 }, @Vector(4, f32){ 1, 1, 1, 1 });
        // },
        // .text => {
        //     const character = "Gotta-go-fast!\n0123456789\n~!@#$%^&*()_+è\n:\"<>?`-=[];',./";
        //     const size_multiplier = 5;

        //     var resizable_label: ResizableLabel = undefined;
        //     try resizable_label.init(lib, assets.roboto_medium_ttf.path, 0, core.allocator, white_texture_uv_data);
        //     defer resizable_label.deinit();
        //     try resizable_label.print(app, character, .{}, @Vector(4, f32){ 20, 300, 0, 0 }, @Vector(4, f32){ 1, 1, 1, 1 }, 20 * size_multiplier);
        //     // try resizable_label.print(app, "@", .{}, @Vector(4, f32){ 20, 150, 0, 0 }, @Vector(4, f32){ 1, 1, 1, 1 }, 130 * size_multiplier);
        // },
        .quad => {
            try draw.quad(app, .{ 0, 0 }, .{ 480, 480 }, .{}, .{ .x = 0, .y = 0, .width = 1, .height = 1 });
        },
        .circle => {
            try draw.circle(app, .{ window_width / 2, window_height / 2 }, window_height / 2 - 10, .{ 0, 0.5, 0.75, 1.0 }, white_texture_uv_data);
        },
    }

    const vs_module = core.device.createShaderModuleWGSL("vert", @embedFile("vert.wgsl"));
    const fs_module = core.device.createShaderModuleWGSL("frag", @embedFile("frag.wgsl"));

    const blend = gpu.BlendState{
        .color = .{
            .operation = .add,
            .src_factor = .src_alpha,
            .dst_factor = .one_minus_src_alpha,
        },
        .alpha = .{
            .operation = .add,
            .src_factor = .one,
            .dst_factor = .zero,
        },
    };

    const color_target = gpu.ColorTargetState{
        .format = core.descriptor.format,
        .blend = &blend,
        .write_mask = gpu.ColorWriteMaskFlags.all,
    };
    const fragment = gpu.FragmentState.init(.{
        .module = fs_module,
        .entry_point = "main",
        .targets = &.{color_target},
    });

    const vbgle = gpu.BindGroupLayout.Entry.buffer(0, .{ .vertex = true }, .uniform, true, 0);
    const fbgle = gpu.BindGroupLayout.Entry.buffer(1, .{ .fragment = true }, .read_only_storage, true, 0);
    const sbgle = gpu.BindGroupLayout.Entry.sampler(2, .{ .fragment = true }, .filtering);
    const tbgle = gpu.BindGroupLayout.Entry.texture(3, .{ .fragment = true }, .float, .dimension_2d, false);
    const bgl = core.device.createBindGroupLayout(
        &gpu.BindGroupLayout.Descriptor.init(.{
            .entries = &.{ vbgle, fbgle, sbgle, tbgle },
        }),
    );
    const bind_group_layouts = [_]*gpu.BindGroupLayout{bgl};
    const pipeline_layout = core.device.createPipelineLayout(&gpu.PipelineLayout.Descriptor.init(.{
        .bind_group_layouts = &bind_group_layouts,
    }));

    const pipeline_descriptor = gpu.RenderPipeline.Descriptor{
        .fragment = &fragment,
        .layout = pipeline_layout,
        .vertex = gpu.VertexState.init(.{
            .module = vs_module,
            .entry_point = "main",
            .buffers = &.{draw.VERTEX_BUFFER_LAYOUT},
        }),
    };

    const vertex_buffer = core.device.createBuffer(&.{
        .usage = .{ .copy_dst = true, .vertex = true },
        .size = @sizeOf(draw.Vertex) * app.vertices.items.len,
        .mapped_at_creation = .false,
    });

    const vertex_uniform_buffer = core.device.createBuffer(&.{
        .usage = .{ .copy_dst = true, .uniform = true },
        .size = @sizeOf(draw.VertexUniform),
        .mapped_at_creation = .false,
    });

    const frag_uniform_buffer = core.device.createBuffer(&.{
        .usage = .{ .copy_dst = true, .storage = true },
        .size = @sizeOf(draw.FragUniform) * app.fragment_uniform_list.items.len,
        .mapped_at_creation = .false,
    });

    const sampler = core.device.createSampler(&.{
        // .mag_filter = .linear,
        // .min_filter = .linear,
    });

    std.debug.assert((app.vertices.items.len / 3) == app.fragment_uniform_list.items.len);
    const bind_group = core.device.createBindGroup(
        &gpu.BindGroup.Descriptor.init(.{
            .layout = bgl,
            .entries = &.{
                gpu.BindGroup.Entry.buffer(0, vertex_uniform_buffer, 0, @sizeOf(draw.VertexUniform)),
                gpu.BindGroup.Entry.buffer(1, frag_uniform_buffer, 0, @sizeOf(draw.FragUniform) * app.fragment_uniform_list.items.len),
                gpu.BindGroup.Entry.sampler(2, sampler),
                gpu.BindGroup.Entry.textureView(3, texture.createView(&gpu.TextureView.Descriptor{ .dimension = .dimension_2d })),
            },
        }),
    );

    app.pipeline = core.device.createRenderPipeline(&pipeline_descriptor);
    app.vertex_buffer = vertex_buffer;
    app.vertex_uniform_buffer = vertex_uniform_buffer;
    app.frag_uniform_buffer = frag_uniform_buffer;
    app.bind_group = bind_group;
    app.update_vertex_buffer = true;
    app.update_vertex_uniform_buffer = true;
    app.update_frag_uniform_buffer = true;

    vs_module.release();
    fs_module.release();
    pipeline_layout.release();
    bgl.release();
}

pub fn deinit(app: *App) void {
    defer core.deinit();

    app.vertex_buffer.release();
    app.vertex_uniform_buffer.release();
    app.frag_uniform_buffer.release();
    app.bind_group.release();
    app.vertices.deinit();
    app.fragment_uniform_list.deinit();
    app.texture_atlas_data.deinit(core.allocator);
}

pub fn update(app: *App) !bool {
    var iter = core.pollEvents();
    while (iter.next()) |event| {
        switch (event) {
            .key_press => |ev| {
                if (ev.key == .space) return true;
            },
            .framebuffer_resize => {
                app.update_vertex_uniform_buffer = true;
            },
            .close => return true,
            else => {},
        }
    }

    const back_buffer_view = core.swap_chain.getCurrentTextureView().?;
    const color_attachment = gpu.RenderPassColorAttachment{
        .view = back_buffer_view,
        .clear_value = std.mem.zeroes(gpu.Color),
        .load_op = .clear,
        .store_op = .store,
    };

    const encoder = core.device.createCommandEncoder(null);
    const render_pass_info = gpu.RenderPassDescriptor.init(.{
        .color_attachments = &.{color_attachment},
    });

    {
        if (app.update_vertex_buffer) {
            encoder.writeBuffer(app.vertex_buffer, 0, app.vertices.items);
            app.update_vertex_buffer = false;
        }
        if (app.update_frag_uniform_buffer) {
            encoder.writeBuffer(app.frag_uniform_buffer, 0, app.fragment_uniform_list.items);
            app.update_frag_uniform_buffer = false;
        }
        if (app.update_vertex_uniform_buffer) {
            encoder.writeBuffer(app.vertex_uniform_buffer, 0, &[_]draw.VertexUniform{try draw.getVertexUniformBufferObject()});
            app.update_vertex_uniform_buffer = false;
        }
    }

    const pass = encoder.beginRenderPass(&render_pass_info);
    pass.setPipeline(app.pipeline);
    pass.setVertexBuffer(0, app.vertex_buffer, 0, @sizeOf(draw.Vertex) * app.vertices.items.len);
    pass.setBindGroup(0, app.bind_group, &.{ 0, 0 });
    pass.draw(@as(u32, @truncate(app.vertices.items.len)), 1, 0, 0);
    pass.end();
    pass.release();

    var command = encoder.finish(null);
    encoder.release();

    core.queue.submit(&[_]*gpu.CommandBuffer{command});
    command.release();
    core.swap_chain.present();
    back_buffer_view.release();

    return false;
}

fn rgb24ToRgba32(allocator: std.mem.Allocator, in: []zigimg.color.Rgb24) !zigimg.color.PixelStorage {
    const out = try zigimg.color.PixelStorage.init(allocator, .rgba32, in.len);
    var i: usize = 0;
    while (i < in.len) : (i += 1) {
        out.rgba32[i] = zigimg.color.Rgba32{ .r = in[i].r, .g = in[i].g, .b = in[i].b, .a = 255 };
    }
    return out;
}