/**********************************************************************
*
* Sokol 3d cube demo
*
* Copyright (c) 2021 Dario Deledda. All rights reserved.
* Use of this source code is governed by an MIT license
* that can be found in the LICENSE file.
*
* HOW TO COMPILE SHADERS:
* Run `v shader .` in this directory to compile the shaders.
* For more info and help with shader compilation see `docs.md` and `v help shader`.
*
* TODO:
* - frame counter
**********************************************************************/
import gg
import gg.m4
import gx
// import math
import sokol.sapp
import sokol.gfx
import sokol.sgl
import time

// GLSL Include and functions

#flag -I @VMODROOT/.
#include "rt_glsl.h" # Should be generated with `v shader .` (see the instructions at the top of this file)

fn C.rt_shader_desc(gfx.Backend) &gfx.ShaderDesc

const (
	win_width  = 800
	win_height = 800
	bg_color   = gx.white
)

struct App {
mut:
	gg          &gg.Context = unsafe { nil }
	texture     gfx.Image
	init_flag   bool
	frame_count int

	mouse_x int = -1
	mouse_y int = -1
	// glsl
	cube_pip_glsl gfx.Pipeline
	cube_bind     gfx.Bindings
	// time
	ticks i64
}

/******************************************************************************
* Texture functions
******************************************************************************/
fn create_texture(w int, h int, buf &byte) gfx.Image {
	sz := w * h * 4
	mut img_desc := gfx.ImageDesc{
		width: w
		height: h
		num_mipmaps: 0
		min_filter: .linear
		mag_filter: .linear
		// usage: .dynamic
		wrap_u: .clamp_to_edge
		wrap_v: .clamp_to_edge
		label: &u8(0)
		d3d11_texture: 0
	}
	// comment if .dynamic is enabled
	img_desc.data.subimage[0][0] = gfx.Range{
		ptr: buf
		size: usize(sz)
	}

	sg_img := gfx.make_image(&img_desc)
	return sg_img
}

fn destroy_texture(sg_img gfx.Image) {
	gfx.destroy_image(sg_img)
}

// Use only if usage: .dynamic is enabled
fn update_text_texture(sg_img gfx.Image, w int, h int, buf &byte) {
	sz := w * h * 4
	mut tmp_sbc := gfx.ImageData{}
	tmp_sbc.subimage[0][0] = gfx.Range{
		ptr: buf
		size: usize(sz)
	}
	gfx.update_image(sg_img, &tmp_sbc)
}

/******************************************************************************
* Draw functions
******************************************************************************
Cube vertex buffer with packed vertex formats for color and texture coords.
		Note that a vertex format which must be portable across all
		backends must only use the normalized integer formats
		(BYTE4N, UBYTE4N, SHORT2N, SHORT4N), which can be converted
		to floating point formats in the vertex shader inputs.
		The reason is that D3D11 cannot convert from non-normalized
		formats to floating point inputs (only to integer inputs),
		and WebGL2 / GLES2 don't support integer vertex shader inputs.
*/

struct Vertex_t {
	x     f32
	y     f32
	z     f32
	color u32
	u     f32
	v     f32
	// u u16   // for compatibility with D3D11
	// v u16   // for compatibility with D3D11
}

fn init_cube_glsl(mut app App) {
	// cube vertex buffer
	// d := u16(32767)     // for compatibility with D3D11, 32767 stand for 1
	d := f32(1.0)
	c := u32(0xFFFFFF_FF) // color RGBA8
	vertices := [
		// Face 0
		Vertex_t{-1.0, -1.0, -1.0, c,  0, 0},
		Vertex_t{ 1.0, -1.0, -1.0, c,  d, 0},
		Vertex_t{ 1.0,  1.0, -1.0, c,  d, d},
		Vertex_t{-1.0,  1.0, -1.0, c,  0, d},
		// Face 1
		Vertex_t{-1.0, -1.0,  1.0, c,  0, 0},
		Vertex_t{ 1.0, -1.0,  1.0, c,  d, 0},
		Vertex_t{ 1.0,  1.0,  1.0, c,  d, d},
		Vertex_t{-1.0,  1.0,  1.0, c,  0, d},
		// Face 2
		Vertex_t{-1.0, -1.0, -1.0, c,  0, 0},
		Vertex_t{-1.0,  1.0, -1.0, c,  d, 0},
		Vertex_t{-1.0,  1.0,  1.0, c,  d, d},
		Vertex_t{-1.0, -1.0,  1.0, c,  0, d},
		// Face 3
		Vertex_t{ 1.0, -1.0, -1.0, c,  0, 0},
		Vertex_t{ 1.0,  1.0, -1.0, c,  d, 0},
		Vertex_t{ 1.0,  1.0,  1.0, c,  d, d},
		Vertex_t{ 1.0, -1.0,  1.0, c,  0, d},
		// Face 4
		Vertex_t{-1.0, -1.0, -1.0, c,  0, 0},
		Vertex_t{-1.0, -1.0,  1.0, c,  d, 0},
		Vertex_t{ 1.0, -1.0,  1.0, c,  d, d},
		Vertex_t{ 1.0, -1.0, -1.0, c,  0, d},
		// Face 5
		Vertex_t{-1.0,  1.0, -1.0, c,  0, 0},
		Vertex_t{-1.0,  1.0,  1.0, c,  d, 0},
		Vertex_t{ 1.0,  1.0,  1.0, c,  d, d},
		Vertex_t{ 1.0,  1.0, -1.0, c,  0, d},
	]

	mut vert_buffer_desc := gfx.BufferDesc{label: c'cube-vertices'}
	unsafe { vmemset(&vert_buffer_desc, 0, int(sizeof(vert_buffer_desc))) }

	vert_buffer_desc.size = usize(vertices.len * int(sizeof(Vertex_t)))
	vert_buffer_desc.data = gfx.Range{
		ptr: vertices.data
		size: usize(vertices.len * int(sizeof(Vertex_t)))
	}

	vert_buffer_desc.@type = .vertexbuffer
	vbuf := gfx.make_buffer(&vert_buffer_desc)

	// create an index buffer for the cube
	indices := [
			u16(0),	1,	2,  	0, 	2, 	3,
			6, 	5,	4,		7,	6,	4,
			8,	9,	10,		8,	10,	11,
			14,	13,	12,		15,	14,	12,
			16,	17,	18,		16,	18,	19,
			22,	21,	20,		23,	22,	20,
	]

	mut index_buffer_desc := gfx.BufferDesc{label: c'cube-indices'}
	unsafe {vmemset(&index_buffer_desc, 0, int(sizeof(index_buffer_desc)))}

	index_buffer_desc.size = usize(indices.len * int(sizeof(u16)))
	index_buffer_desc.data = gfx.Range{
		ptr: indices.data
		size: usize(indices.len * int(sizeof(u16)))
	}

	index_buffer_desc.@type   = .indexbuffer
	ibuf := gfx.make_buffer(&index_buffer_desc)

	// create shader
	shader := gfx.make_shader(C.rt_shader_desc(C.sg_query_backend()))

	mut pipdesc := gfx.PipelineDesc{}
	unsafe { vmemset(&pipdesc, 0, int(sizeof(pipdesc))) }
	pipdesc.layout.buffers[0].stride = int(sizeof(Vertex_t))

	// the constants [C.ATTR_vs_pos, C.ATTR_vs_color0, C.ATTR_vs_texcoord0] are generated by sokol-shdc
	pipdesc.layout.attrs[C.ATTR_vs_pos      ].format = .float3  // x,y,z as f32
	pipdesc.layout.attrs[C.ATTR_vs_color0   ].format = .ubyte4n // color as u32
	pipdesc.layout.attrs[C.ATTR_vs_texcoord0].format = .float2  // u,v as f32
	// pipdesc.layout.attrs[C.ATTR_vs_texcoord0].format  = .short2n  // u,v as u16

	pipdesc.shader = shader
	pipdesc.index_type = .uint16

	pipdesc.depth = gfx.DepthState{
		write_enabled: true
		compare: .less_equal
	}
	pipdesc.cull_mode = .back

	pipdesc.label = 'glsl_shader pipeline'.str

	app.cube_bind.vertex_buffers[0] = vbuf
	app.cube_bind.index_buffer = ibuf
	app.cube_bind.fs_images[C.SLOT_tex] = app.texture
	app.cube_pip_glsl = gfx.make_pipeline(&pipdesc)
	println('GLSL init DONE!')
}

[inline]
fn vec4(x f32, y f32, z f32, w f32) m4.Vec4 {
	return m4.Vec4{e:[x, y, z, w]!}
}

fn calc_tr_matrices(w f32, h f32, rx f32, ry f32, in_scale f32) m4.Mat4 {
	proj := m4.perspective(60, w/h, 0.01, 10.0)
	view := m4.look_at(vec4(f32(0.0) ,0 , 6, 0), vec4(f32(0), 0, 0, 0), vec4(f32(0), 1, 0, 0))
	view_proj := view * proj

	rxm := m4.rotate(m4.rad(rx), vec4(f32(1), 0, 0, 0))
	rym := m4.rotate(m4.rad(ry), vec4(f32(0), 1, 0, 0))

	model :=  rym * rxm
	scale_m := m4.scale(vec4(in_scale, in_scale, in_scale, 1))

	res :=  (scale_m * model) * view_proj
	return res
}

fn draw_cube_glsl(app App) {
	if app.init_flag == false {
		return
	}

	ws := gg.window_size_real_pixels()
	ratio := f32(ws.width) / ws.height
	dw := f32(ws.width / 2)
	dh := f32(ws.height / 2)

	// use the following commented lines to rotate the 3d glsl cube
	// rot := [f32(app.mouse_y), f32(app.mouse_x)]
	// calc_tr_matrices(dw, dh, rot[0], rot[1] ,2.3)
	tr_matrix := calc_tr_matrices(dw, dh, 0, 0, 2.3)
	gfx.apply_viewport(0, 0, ws.width, ws.height, true)

	// apply the pipline and bindings
	gfx.apply_pipeline(app.cube_pip_glsl)
	gfx.apply_bindings(app.cube_bind)

	// Uniforms
	// *** vertex shadeer uniforms ***
	// passing the view matrix as uniform
	// res is a 4x4 matrix of f32 thus: 4*16 byte of size
	vs_uniforms_range := gfx.Range{
		ptr: &tr_matrix
		size: usize(4 * 16)
	}
	gfx.apply_uniforms(.vs, C.SLOT_vs_params, &vs_uniforms_range)

	// *** fragment shader uniforms ***
	time_ticks := f32(time.ticks() - app.ticks) / 1000
	mut tmp_fs_params := [
		f32(ws.width),
		ws.height * ratio,           // x,y resolution to pass to FS
		app.mouse_x,                 // mouse x
		ws.height - app.mouse_y * 2, // mouse y scaled
		time_ticks,                  // time as f32
		app.frame_count,             // frame count
		0,
		0 // padding bytes , see "fs_params" struct paddings in rt_glsl.h
	]!
	fs_uniforms_range := gfx.Range{
		ptr: unsafe { &tmp_fs_params }
		size: usize(sizeof(tmp_fs_params))
	}
	gfx.apply_uniforms(.fs, C.SLOT_fs_params, &fs_uniforms_range)

	// 3 vertices for triangle * 2 triangles per face * 6 faces = 36 vertices to draw
	gfx.draw(0, (3 * 2) * 6, 1)
	gfx.end_pass()
	gfx.commit()
}

fn frame(mut app App) {
	ws := gg.window_size_real_pixels()

	// clear
	mut color_action := gfx.ColorAttachmentAction{
		action: .clear
		value: gfx.Color{
			r: 0.0
			g: 0.0
			b: 0.0
			a: 1.0
		}
	}

	mut pass_action := gfx.PassAction{}
	pass_action.colors[0] = color_action
	gfx.begin_default_pass(&pass_action, ws.width, ws.height)

	// glsl cube
	draw_cube_glsl(app)
	app.frame_count++
}

/******************************************************************************
* Init / Cleanup
******************************************************************************/
fn my_init(mut app App) {
	// set max vertices,
	// for a large number of the same type of object it is better use the instances!!
	desc := sapp.create_desc()
	gfx.setup(&desc)
	sgl_desc := sgl.Desc{
		max_vertices: 50 * 65536
	}
	sgl.setup(&sgl_desc)

	// create chessboard texture 256*256 RGBA
	w := 256
	h := 256
	sz := w * h * 4
	tmp_txt := unsafe { malloc(sz) }
	mut i := 0
	for i < sz {
		unsafe {
			y := (i >> 0x8) >> 5 // 8 cell
			x := (i & 0xFF) >> 5 // 8 cell
			// upper left corner
			if x == 0 && y == 0 {
				tmp_txt[i + 0] = u8(0xFF)
				tmp_txt[i + 1] = u8(0)
				tmp_txt[i + 2] = u8(0)
				tmp_txt[i + 3] = u8(0xFF)
			}
			// low right corner
			else if x == 7 && y == 7 {
				tmp_txt[i + 0] = u8(0)
				tmp_txt[i + 1] = u8(0xFF)
				tmp_txt[i + 2] = u8(0)
				tmp_txt[i + 3] = u8(0xFF)
			} else {
				col := if ((x + y) & 1) == 1 { 0xFF } else { 128 }
				tmp_txt[i + 0] = u8(col)  // red
				tmp_txt[i + 1] = u8(col)  // green
				tmp_txt[i + 2] = u8(col)  // blue
				tmp_txt[i + 3] = u8(0xFF) // alpha
			}
			i += 4
		}
	}
	unsafe {
		app.texture = create_texture(w, h, tmp_txt)
		free(tmp_txt)
	}
	// glsl
	init_cube_glsl(mut app)
	app.init_flag = true
}

/******************************************************************************
* events handling
******************************************************************************/
fn my_event_manager(mut ev gg.Event, mut app App) {
	if ev.typ == .mouse_move {
		app.mouse_x = int(ev.mouse_x)
		app.mouse_y = int(ev.mouse_y)
	}
	if ev.typ == .touches_began || ev.typ == .touches_moved {
		if ev.num_touches > 0 {
			touch_point := ev.touches[0]
			app.mouse_x = int(touch_point.pos_x)
			app.mouse_y = int(touch_point.pos_y)
		}
	}
}

/******************************************************************************
* Main
******************************************************************************/
[console] // is needed for easier diagnostics on windows
fn main() {
	// App init
	mut app := &App{
		gg: 0
	}

	app.gg = gg.new_context(
		width: win_width
		height: win_height
		create_window: true
		window_title: '3D Ray Marching Cube'
		user_data: app
		bg_color: bg_color
		frame_fn: frame
		init_fn: my_init
		event_fn: my_event_manager
	)

	app.ticks = time.ticks()
	app.gg.run()
}