const std = @import("std");
const builtin = @import("builtin");

const vk = @import("vk");
const c = @import("c.zig");

pub fn uploadData(
    comptime T: type,
    pdev: vk.PhysicalDevice,
    vki: Instance.Wrapper,
    dev: vk.Device,
    vkd: Device.Wrapper,
    queue: vk.Queue,
    pool: vk.CommandPool,
    buffer: vk.Buffer,
    source: []const T,
) !void {
    // if (@typeInfo(T) == .Struct and @typeInfo(T).Struct.layout == .auto) @compileError("Requires defined T layout");

    const size = @sizeOf(T) * source.len;

    const staging_buffer = try vkd.createBuffer(dev, &.{
        .size = size,
        .usage = .{ .transfer_src_bit = true },
        .sharing_mode = .exclusive,
    }, null);
    defer vkd.destroyBuffer(dev, staging_buffer, null);

    const vally = VkAllocator.init(pdev, vki);

    const mem_reqs = vkd.getBufferMemoryRequirements(dev, staging_buffer);
    const staging_memory = try vally.alloc(dev, vkd, mem_reqs, .{ .host_visible_bit = true, .host_coherent_bit = true });
    // const staging_memory = try allocate(pdev, vki, dev, vkd, mem_reqs, .{
    //     .host_visible_bit = true,
    //     .host_coherent_bit = true,
    // });
    defer vkd.freeMemory(dev, staging_memory, null);

    try vkd.bindBufferMemory(dev, staging_buffer, staging_memory, 0);

    {
        const data = try vkd.mapMemory(dev, staging_memory, 0, vk.WHOLE_SIZE, .{});
        defer vkd.unmapMemory(dev, staging_memory);

        const dest: [*]T = @ptrCast(@alignCast(data));
        @memcpy(dest, source);
    }

    try copyBuffer(dev, queue, pool, buffer, staging_buffer, size, vkd);
}

pub fn copyBuffer(
    dev: vk.Device,
    queue: vk.Queue,
    pool: vk.CommandPool,
    dst: vk.Buffer,
    src: vk.Buffer,
    size: vk.DeviceSize,
    vkd: Device.Wrapper,
) !void {
    var cmdbuf: vk.CommandBuffer = undefined;
    try vkd.allocateCommandBuffers(dev, &.{
        .command_pool = pool,
        .level = .primary,
        .command_buffer_count = 1,
    }, @ptrCast(&cmdbuf));
    defer vkd.freeCommandBuffers(dev, pool, 1, @ptrCast(&cmdbuf));

    try vkd.beginCommandBuffer(cmdbuf, &.{
        .flags = .{ .one_time_submit_bit = true },
    });

    const region = vk.BufferCopy{
        .src_offset = 0,
        .dst_offset = 0,
        .size = size,
    };
    vkd.cmdCopyBuffer(cmdbuf, src, dst, 1, @ptrCast(&region));

    try vkd.endCommandBuffer(cmdbuf);

    const si = vk.SubmitInfo{
        .command_buffer_count = 1,
        .p_command_buffers = @ptrCast(&cmdbuf),
        .p_wait_dst_stage_mask = undefined,
    };

    // creating and submitting a queue for every copy operation seems a bad idea for "streamed" data
    // gonna want a way to send a copy operation WITH SYNCHRONIZATION PRIMITIVES on a particular queue
    // see https://stackoverflow.com/a/62183243
    //
    // this may be a misunderstanding on how submission works...

    try vkd.queueSubmit(queue, 1, @ptrCast(&si), .null_handle);
    try vkd.queueWaitIdle(queue);
}

pub const VkAllocator = struct {
    memory_types: [vk.MAX_MEMORY_TYPES]vk.MemoryType,
    memory_type_count: u32,

    pub fn init(
        pdev: vk.PhysicalDevice,
        vki: Instance.Wrapper,
    ) VkAllocator {
        const props = vki.getPhysicalDeviceMemoryProperties(pdev);

        return VkAllocator{
            .memory_types = props.memory_types,
            .memory_type_count = props.memory_type_count,
        };
    }

    pub fn alloc(
        self: VkAllocator,
        dev: vk.Device,
        vkd: Device.Wrapper,
        reqs: vk.MemoryRequirements,
        flags: vk.MemoryPropertyFlags,
    ) !vk.DeviceMemory {
        const memory_type_bits = reqs.memory_type_bits;

        for (self.memory_types[0..self.memory_type_count], 0..) |mem_type, idx| {
            if (memory_type_bits & (@as(u32, 1) << @truncate(idx)) != 0 and mem_type.property_flags.contains(flags)) {
                return try vkd.allocateMemory(dev, &.{
                    .allocation_size = reqs.size,
                    .memory_type_index = @intCast(idx),
                }, null);
            }
        }

        return error.NoSuitableMemoryType;
    }
};