// Copyright (c) 2019-2020 Alexander Medvednikov. All rights reserved.
// Use of this source code is governed by an MIT license that can be found in the LICENSE file.
module gg

import os
import gx
import sokol
import sokol.sapp
import sokol.sgl
import sokol.gfx
import math

// import time
pub type FNCb = fn (x voidptr)

pub type FNEvent = fn (e voidptr, x voidptr)

pub type FNFail = fn (msg string, x voidptr)

pub type FNKeyDown = fn (c sapp.KeyCode, m sapp.Modifier, x voidptr)

pub type FNMove = fn (x f32, y f32, z voidptr)

pub type FNChar = fn (c u32, x voidptr)

pub struct Config {
pub:
	width                 int
	height                int
	use_ortho             bool
	retina                bool
	resizable             bool
	user_data             voidptr
	font_size             int
	create_window         bool
	// window_user_ptr voidptr
	window_title          string
	borderless_window     bool
	always_on_top         bool
	bg_color              gx.Color
	init_fn               FNCb      = voidptr(0)
	frame_fn              FNCb      = voidptr(0)
	cleanup_fn            FNCb      = voidptr(0)
	fail_fn               FNFail    = voidptr(0)
	event_fn              FNEvent   = voidptr(0)
	keydown_fn            FNKeyDown = voidptr(0)
	// special case of event_fn
	char_fn               FNChar = voidptr(0)
	// special case of event_fn
	move_fn               FNMove = voidptr(0)
	// special case of event_fn
	click_fn              FNMove = voidptr(0)
	// special case of event_fn
	// wait_events       bool // set this to true for UIs, to save power
	fullscreen            bool
	scale                 f32 = 1.0
	sample_count          int
	// vid needs this
	// init_text bool
	font_path             string
	custom_bold_font_path string
	ui_mode               bool // refreshes only on events to save CPU usage
}

pub struct Context {
	render_text   bool
mut:
	// a cache with all images created by the user. used for sokol image init and to save space
	// (so that the user can store image ids, not entire Image objects)
	image_cache   []Image
	needs_refresh bool = true
	ticks         int
pub mut:
	scale         f32 = 1.0
	// will get set to 2.0 for retina, will remain 1.0 for normal
	width         int
	height        int
	clear_pass    C.sg_pass_action
	window        C.sapp_desc
	timage_pip    C.sgl_pipeline
	config        Config
	ft            &FT
	font_inited   bool
	ui_mode       bool // do not redraw everything 60 times/second, but only when the user requests
}

pub struct Size {
pub:
	width  int
	height int
}

fn gg_init_sokol_window(user_data voidptr) {
	mut g := unsafe { &Context(user_data) }
	desc := sapp.create_desc()
	/*
	desc := C.sg_desc{
		mtl_device: sapp.metal_get_device()
		mtl_renderpass_descriptor_cb: sapp.metal_get_renderpass_descriptor
		mtl_drawable_cb: sapp.metal_get_drawable
		d3d11_device: sapp.d3d11_get_device()
		d3d11_device_context: sapp.d3d11_get_device_context()
		d3d11_render_target_view_cb: sapp.d3d11_get_render_target_view
		d3d11_depth_stencil_view_cb: sapp.d3d11_get_depth_stencil_view
	}
	*/
	gfx.setup(&desc)
	sgl_desc := C.sgl_desc_t{}
	sgl.setup(&sgl_desc)
	g.scale = sapp.dpi_scale()
	// NB: on older X11, `Xft.dpi` from ~/.Xresources, that sokol uses,
	// may not be set which leads to sapp.dpi_scale reporting incorrectly 0.0
	if g.scale < 0.1 {
		g.scale = 1.0
	}
	// is_high_dpi := sapp.high_dpi()
	// fb_w := sapp.width()
	// fb_h := sapp.height()
	// println('g.scale=$g.scale is_high_dpi=$is_high_dpi fb_w=$fb_w fb_h=$fb_h')
	// if g.config.init_text {
	// `os.is_file()` won't work on Android if the font file is embedded into the APK
	exists := $if !android { os.is_file(g.config.font_path) } $else { true }
	if g.config.font_path != '' && exists {
		// t := time.ticks()
		g.ft = new_ft(
			font_path: g.config.font_path
			custom_bold_font_path: g.config.custom_bold_font_path
			scale: sapp.dpi_scale()
		) or { panic(err) }
		// println('FT took ${time.ticks()-t} ms')
		g.font_inited = true
	} else {
		if !exists {
			sfont := system_font_path()
			eprintln('font file "$g.config.font_path" does not exist, the system font was used instead.')
			g.ft = new_ft(
				font_path: sfont
				custom_bold_font_path: g.config.custom_bold_font_path
				scale: sapp.dpi_scale()
			) or { panic(err) }
			g.font_inited = true
		}
	}
	//
	mut pipdesc := C.sg_pipeline_desc{}
	unsafe { C.memset(&pipdesc, 0, sizeof(pipdesc)) }
	pipdesc.blend.enabled = true
	pipdesc.blend.src_factor_rgb = C.SG_BLENDFACTOR_SRC_ALPHA
	pipdesc.blend.dst_factor_rgb = C.SG_BLENDFACTOR_ONE_MINUS_SRC_ALPHA
	g.timage_pip = sgl.make_pipeline(&pipdesc)
	//
	if g.config.init_fn != voidptr(0) {
		g.config.init_fn(g.config.user_data)
	}
	// Create images now that we can do that after sg is inited
	for i in 0 .. g.image_cache.len {
		g.image_cache[i].init_sokol_image()
	}
}

fn gg_frame_fn(user_data voidptr) {
	mut ctx := unsafe { &Context(user_data) }
	if ctx.config.frame_fn == voidptr(0) {
		return
	}
	if ctx.ui_mode && !ctx.needs_refresh {
		// Draw 3 more frames after the "stop refresh" command
		ctx.ticks++
		if ctx.ticks > 3 {
			return
		}
	}
	ctx.config.frame_fn(ctx.config.user_data)
	ctx.needs_refresh = false
}

pub fn (mut ctx Context) refresh_ui() {
	ctx.needs_refresh = true
	ctx.ticks = 0
}

fn gg_event_fn(ce &C.sapp_event, user_data voidptr) {
	e := unsafe { &sapp.Event(ce) }
	mut g := unsafe { &Context(user_data) }
	if g.config.event_fn != voidptr(0) {
		g.config.event_fn(e, g.config.user_data)
	}
	match e.typ {
		.key_down {
			if g.config.keydown_fn != voidptr(0) {
				kdfn := g.config.keydown_fn
				kdfn(e.key_code, e.modifiers, g.config.user_data)
			}
		}
		.char {
			if g.config.char_fn != voidptr(0) {
				cfn := g.config.char_fn
				cfn(e.char_code, g.config.user_data)
			}
		}
		.mouse_move {
			if g.config.move_fn != voidptr(0) {
				cfn := g.config.move_fn
				cfn(e.mouse_x / g.scale, e.mouse_y / g.scale, g.config.user_data)
			}
		}
		.mouse_down {
			if g.config.click_fn != voidptr(0) {
				cfn := g.config.click_fn
				cfn(e.mouse_x / g.scale, e.mouse_y / g.scale, g.config.user_data)
			}
		}
		else {}
	}
}

fn gg_cleanup_fn(user_data voidptr) {
	mut g := unsafe { &Context(user_data) }
	if g.config.cleanup_fn != voidptr(0) {
		g.config.cleanup_fn(g.config.user_data)
	}
}

fn gg_fail_fn(msg charptr, user_data voidptr) {
	mut g := unsafe { &Context(user_data) }
	vmsg := tos3(msg)
	if g.config.fail_fn != voidptr(0) {
		g.config.fail_fn(vmsg, g.config.user_data)
	} else {
		eprintln('gg error: $vmsg')
	}
}

//
pub fn new_context(cfg Config) &Context {
	mut g := &Context{
		width: cfg.width
		height: cfg.height
		config: cfg
		render_text: cfg.font_path != ''
		ft: 0
		ui_mode: cfg.ui_mode
	}
	g.set_bg_color(cfg.bg_color)
	// C.printf('new_context() %p\n', cfg.user_data)
	window := C.sapp_desc{
		user_data: g
		init_userdata_cb: gg_init_sokol_window
		frame_userdata_cb: gg_frame_fn
		event_userdata_cb: gg_event_fn
		fail_userdata_cb: gg_fail_fn
		cleanup_userdata_cb: gg_cleanup_fn
		window_title: cfg.window_title.str
		html5_canvas_name: cfg.window_title.str
		width: cfg.width
		height: cfg.height
		sample_count: cfg.sample_count
		high_dpi: true
		fullscreen: cfg.fullscreen
	}
	if cfg.use_ortho {
	} else {
	}
	g.window = window
	return g
}

pub fn (gg &Context) run() {
	sapp.run(&gg.window)
}

pub fn (mut ctx Context) set_bg_color(c gx.Color) {
	ctx.clear_pass = gfx.create_clear_pass(f32(c.r) / 255.0, f32(c.g) / 255.0, f32(c.b) / 255.0,
		f32(c.a) / 255.0)
}

// TODO: Fix alpha
pub fn (ctx &Context) draw_rect(x f32, y f32, w f32, h f32, c gx.Color) {
	if c.a != 255 {
		sgl.load_pipeline(ctx.timage_pip)
	}
	sgl.c4b(c.r, c.g, c.b, c.a)
	sgl.begin_quads()
	sgl.v2f(x * ctx.scale, y * ctx.scale)
	sgl.v2f((x + w) * ctx.scale, y * ctx.scale)
	sgl.v2f((x + w) * ctx.scale, (y + h) * ctx.scale)
	sgl.v2f(x * ctx.scale, (y + h) * ctx.scale)
	sgl.end()
}

pub fn (ctx &Context) draw_triangle(x f32, y f32, x2 f32, y2 f32, x3 f32, y3 f32, c gx.Color) {
	if c.a != 255 {
		sgl.load_pipeline(ctx.timage_pip)
	}
	sgl.c4b(c.r, c.g, c.b, c.a)
	sgl.begin_quads()
	sgl.v2f(x * ctx.scale, y * ctx.scale)
	sgl.v2f(x2 * ctx.scale, y2 * ctx.scale)
	sgl.v2f(x3 * ctx.scale, y3 * ctx.scale)
	sgl.end()
}

pub fn (ctx &Context) draw_empty_rect(x f32, y f32, w f32, h f32, c gx.Color) {
	if c.a != 255 {
		sgl.load_pipeline(ctx.timage_pip)
	}
	sgl.c4b(c.r, c.g, c.b, c.a)
	sgl.begin_line_strip()
	if ctx.scale == 1 {
		sgl.v2f(x, y)
		sgl.v2f(x + w, y)
		sgl.v2f(x + w, y + h)
		sgl.v2f(x, y + h)
		sgl.v2f(x, y)
	} else {
		sgl.v2f(x * ctx.scale, y * ctx.scale)
		sgl.v2f((x + w) * ctx.scale, y * ctx.scale)
		sgl.v2f((x + w) * ctx.scale, (y + h) * ctx.scale)
		sgl.v2f(x * ctx.scale, (y + h) * ctx.scale)
		sgl.v2f(x * ctx.scale, y * ctx.scale)
	}
	sgl.end()
}

pub fn (ctx &Context) draw_circle_line(x f32, y f32, r int, segments int, c gx.Color) {
	if c.a != 255 {
		sgl.load_pipeline(ctx.timage_pip)
	}
	sgl.c4b(c.r, c.g, c.b, c.a)
	mut theta := f32(0)
	mut xx := f32(0)
	mut yy := f32(0)
	sgl.begin_line_strip()
	for i := 0; i < segments + 1; i++ {
		theta = 2.0 * f32(math.pi) * f32(i) / f32(segments)
		xx = r * math.cosf(theta)
		yy = r * math.sinf(theta)
		sgl.v2f(xx + x, yy + y)
	}
	sgl.end()
}

pub fn (ctx &Context) draw_circle(x f32, y f32, r f32, c gx.Color) {
	if ctx.scale == 1 {
		ctx.draw_circle_with_segments(x, y, r, 10, c)
	} else {
		ctx.draw_circle_with_segments(x * f32(ctx.scale), y * f32(ctx.scale), r * ctx.scale,
			10, c)
	}
}

pub fn (ctx &Context) draw_circle_with_segments(x f32, y f32, r f32, segments int, c gx.Color) {
	if c.a != 255 {
		sgl.load_pipeline(ctx.timage_pip)
	}
	sgl.c4b(c.r, c.g, c.b, c.a)
	mut theta := f32(0)
	mut xx := f32(0)
	mut yy := f32(0)
	sgl.begin_triangle_strip()
	for i := 0; i < segments + 1; i++ {
		theta = 2.0 * f32(math.pi) * f32(i) / f32(segments)
		xx = r * math.cosf(theta)
		yy = r * math.sinf(theta)
		sgl.v2f(xx + x, yy + y)
		sgl.v2f(x, y)
	}
	sgl.end()
}

pub fn (ctx &Context) draw_arc_line(x f32, y f32, r int, start_angle f32, arc_angle f32, segments int, c gx.Color) {
	if c.a != 255 {
		sgl.load_pipeline(ctx.timage_pip)
	}
	sgl.c4b(c.r, c.g, c.b, c.a)
	theta := f32(arc_angle / f32(segments))
	tan_factor := math.tanf(theta)
	rad_factor := math.cosf(theta)
	mut xx := f32(r * math.cosf(start_angle))
	mut yy := f32(r * math.sinf(start_angle))
	sgl.begin_line_strip()
	for i := 0; i < segments + 1; i++ {
		sgl.v2f(xx + x, yy + y)
		tx := -yy
		ty := xx
		xx += tx * tan_factor
		yy += ty * tan_factor
		xx *= rad_factor
		yy *= rad_factor
	}
	sgl.end()
}

pub fn (ctx &Context) draw_arc(x f32, y f32, r int, start_angle f32, arc_angle f32, segments int, c gx.Color) {
	if c.a != 255 {
		sgl.load_pipeline(ctx.timage_pip)
	}
	sgl.c4b(c.r, c.g, c.b, c.a)
	theta := f32(arc_angle / f32(segments))
	tan_factor := math.tanf(theta)
	rad_factor := math.cosf(theta)
	mut xx := f32(r * math.cosf(start_angle))
	mut yy := f32(r * math.sinf(start_angle))
	sgl.begin_triangle_strip()
	for i := 0; i < segments + 1; i++ {
		sgl.v2f(xx + x, yy + y)
		sgl.v2f(x, y)
		tx := -yy
		ty := xx
		xx += tx * tan_factor
		yy += ty * tan_factor
		xx *= rad_factor
		yy *= rad_factor
	}
	sgl.end()
}

pub fn (gg &Context) begin() {
	if gg.render_text && gg.font_inited {
		gg.ft.flush()
	}
	sgl.defaults()
	sgl.matrix_mode_projection()
	sgl.ortho(0.0, f32(sapp.width()), f32(sapp.height()), 0.0, -1.0, 1.0)
}

pub fn (gg &Context) end() {
	gfx.begin_default_pass(gg.clear_pass, sapp.width(), sapp.height())
	sgl.draw()
	gfx.end_pass()
	gfx.commit()
	/*
	if gg.config.wait_events {
		// println('gg: waiting')
		wait_events()
	}
	*/
}

fn abs(a f32) f32 {
	if a >= 0 {
		return a
	}
	return -a
}

pub fn (ctx &Context) draw_line(x f32, y f32, x2 f32, y2 f32, c gx.Color) {
	if c.a != 255 {
		sgl.load_pipeline(ctx.timage_pip)
	}
	if ctx.scale > 1 {
		// Make the line more clear on hi dpi screens: draw a rectangle
		mut width := abs(x2 - x)
		mut height := abs(y2 - y)
		if width == 0 {
			width = 1
		} else if height == 0 {
			height = 1
		}
		ctx.draw_rect(x, y, width, height, c)
		return
	}
	sgl.c4b(c.r, c.g, c.b, c.a)
	sgl.begin_line_strip()
	sgl.v2f(x * ctx.scale, y * ctx.scale)
	sgl.v2f(x2 * ctx.scale, y2 * ctx.scale)
	sgl.end()
}

pub fn (ctx &Context) draw_rounded_rect(x f32, y f32, w f32, h f32, radius f32, color gx.Color) {
	sgl.c4b(color.r, color.g, color.b, color.a)
	sgl.begin_triangle_strip()
	mut theta := f32(0)
	mut xx := f32(0)
	mut yy := f32(0)
	r := radius * f32(ctx.scale)
	nx := x * f32(ctx.scale)
	ny := y * f32(ctx.scale)
	width := w * f32(ctx.scale)
	height := h * f32(ctx.scale)
	segments := 2 * math.pi * r
	segdiv := segments / 4
	rb := 0
	lb := int(rb + segdiv)
	lt := int(lb + segdiv)
	rt := int(lt + segdiv)
	// left top
	lx := nx + r
	ly := ny + r
	for i in lt .. rt {
		theta = 2 * f32(math.pi) * f32(i) / segments
		xx = r * math.cosf(theta)
		yy = r * math.sinf(theta)
		sgl.v2f(xx + lx, yy + ly)
		sgl.v2f(lx, ly)
	}
	// right top
	mut rx := nx + 2 * width - r
	mut ry := ny + r
	for i in rt .. int(segments) {
		theta = 2 * f32(math.pi) * f32(i) / segments
		xx = r * math.cosf(theta)
		yy = r * math.sinf(theta)
		sgl.v2f(xx + rx, yy + ry)
		sgl.v2f(rx, ry)
	}
	// right bottom
	mut rbx := rx
	mut rby := ny + 2 * height - r
	for i in rb .. lb {
		theta = 2 * f32(math.pi) * f32(i) / segments
		xx = r * math.cosf(theta)
		yy = r * math.sinf(theta)
		sgl.v2f(xx + rbx, yy + rby)
		sgl.v2f(rbx, rby)
	}
	// left bottom
	mut lbx := lx
	mut lby := ny + 2 * height - r
	for i in lb .. lt {
		theta = 2 * f32(math.pi) * f32(i) / segments
		xx = r * math.cosf(theta)
		yy = r * math.sinf(theta)
		sgl.v2f(xx + lbx, yy + lby)
		sgl.v2f(lbx, lby)
	}
	sgl.v2f(lx + xx, ly)
	sgl.v2f(lx, ly)
	sgl.end()
	sgl.begin_quads()
	sgl.v2f(lx, ly)
	sgl.v2f(rx, ry)
	sgl.v2f(rbx, rby)
	sgl.v2f(lbx, lby)
	sgl.end()
}

pub fn (ctx &Context) draw_empty_rounded_rect(x f32, y f32, w f32, h f32, radius f32, border_color gx.Color) {
	mut theta := f32(0)
	mut xx := f32(0)
	mut yy := f32(0)
	r := radius * f32(ctx.scale)
	nx := x * f32(ctx.scale)
	ny := y * f32(ctx.scale)
	width := w * f32(ctx.scale)
	height := h * f32(ctx.scale)
	segments := 2 * math.pi * r
	segdiv := segments / 4
	rb := 0
	lb := int(rb + segdiv)
	lt := int(lb + segdiv)
	rt := int(lt + segdiv)
	sgl.c4b(border_color.r, border_color.g, border_color.b, border_color.a)
	sgl.begin_line_strip()
	// left top
	lx := nx + r
	ly := ny + r
	for i in lt .. rt {
		theta = 2 * f32(math.pi) * f32(i) / segments
		xx = r * math.cosf(theta)
		yy = r * math.sinf(theta)
		sgl.v2f(xx + lx, yy + ly)
	}
	// right top
	mut rx := nx + 2 * width - r
	mut ry := ny + r
	for i in rt .. int(segments) {
		theta = 2 * f32(math.pi) * f32(i) / segments
		xx = r * math.cosf(theta)
		yy = r * math.sinf(theta)
		sgl.v2f(xx + rx, yy + ry)
	}
	// right bottom
	mut rbx := rx
	mut rby := ny + 2 * height - r
	for i in rb .. lb {
		theta = 2 * f32(math.pi) * f32(i) / segments
		xx = r * math.cosf(theta)
		yy = r * math.sinf(theta)
		sgl.v2f(xx + rbx, yy + rby)
	}
	// left bottom
	mut lbx := lx
	mut lby := ny + 2 * height - r
	for i in lb .. lt {
		theta = 2 * f32(math.pi) * f32(i) / segments
		xx = r * math.cosf(theta)
		yy = r * math.sinf(theta)
		sgl.v2f(xx + lbx, yy + lby)
	}
	sgl.v2f(lx + xx, ly)
	sgl.end()
}

pub fn screen_size() Size {
	$if macos {
		return C.gg_get_screen_size()
	}
	// TODO windows, linux, etc
	return Size{}
}

fn C.WaitMessage()

/*
pub fn wait_events() {
	unsafe {
		$if macos {
			#NSEvent *event = [NSApp nextEventMatchingMask:NSEventMaskAny
			#untilDate:[NSDate distantFuture]
			#inMode:NSDefaultRunLoopMode
			#dequeue:YES];
			#[NSApp sendEvent:event];
		}
		$if windows {
			C.WaitMessage()
		}
	}
}
*/