auts/isotest/geom.v

module main

import math

// TODO: add world_to_cell_pos, cell_to_world_pos (as an extra to screen versions)

// World pos to screen pos
fn world_to_screen_pos(x, y int) (int, int) {

	sx := x + -game.viewport.shx
	sy := y + -game.viewport.shy

	return sx, sy
}

fn screen_to_world_pos(sx, sy int) (int, int) {
	wx := sx + game.viewport.shx
	wy := sy + game.viewport.shy

	return wx, wy
}

// XXX returned value is top-left corner of cell
// use center version for cell's center
fn cell_to_world_pos(cx, cy int) (int, int) {
	//wx := cx * c_cell_w
	//wy := cy * c_cell_h

	cell_size_z := 0
	cz := 0
	
	wx := (c_cell_w * cx) + ((cy&1) * (c_cell_w / 2))
	wy := (c_cell_h * cy / 2) - cell_size_z * cz

	return wx, wy
}

// XXX get center position of cell at cx, cy in world-space
fn cell_to_world_pos_center(cx, cy int) (int, int) {
	wx, wy := cell_to_world_pos(cx, cy)

	center_wx := wx + c_cell_w / 2
	center_wy := wy + c_cell_h / 2

	return center_wx, center_wy
}

fn cell_to_screen_pos(cx, cy int) (int, int) {
	pan_x := 0
	pan_y := 0
	cell_size_z := 0
	cz := 0
	
	sx := pan_x + (c_cell_w * cx) + ((cy&1) * (c_cell_w / 2))
	sy := pan_y + (c_cell_h * cy / 2) - cell_size_z * cz

	return sx, sy
}

// XXX bad
fn cell_to_screen_pos2(cx, cy int) (int, int) {
			scale_ := f32(1.0)

			width_ := f32(c_cell_w)
			height_ := f32(c_cell_h)

			//width_ := f32(game.field.w * c_cell_w)
			//height_ := f32(game.field.h * c_cell_h)
			
            sw := scale_ * width_/2.0
            sh := scale_ * height_/2.0

            rx, ry := (cx - cy + f32(int(cy)&1)/2.0) * sw,
                      (cx + cy + f32(int(cy)&1)/2.0) * sh

            rxi, ryi := int(rx), int(ry)

            return rxi, ryi
}

/*
fn screen_to_cell_pos(sx, sy int) (int, int) {
	pan_x := 0
	pan_y := 0
	cell_size_z := 0

	mut cy := (2 * (sy - pan_y)) / c_cell_h
    mut cx := (sx - pan_x - ((cy&1) * (c_cell_w / 2))) / c_cell_w
    mut cz := 0

    // Correction?

    //mut xx, mut yy := cell_to_screen_pos(cx, cy, cz)
    mut xx, mut yy := cell_to_screen_pos(cx, cy)

    xx = sx - xx
    mx0 := cx
    yy = sy - yy
    my0 := cy
    
    if xx <= (c_cell_w / 2) {
    	if yy > xx * c_cell_h/c_cell_w {
    	    cy++
    	    if int(cy&1) != 0 {
    	    	cx--
  			}
    	}
    } else {
    	if yy > (c_cell_w - xx) * c_cell_h/c_cell_w {
    		cy++
    		if int(cy&1) == 0 {
    			cx++
    		}
    	}
    }

    return cx, cy
}
*/

// XXX bad
fn screen_to_cell_pos2(sx, sy int) (int, int) {
	px := f32(sx)
	py := f32(sy)

	//width := game.field.w * c_cell_w
	//height := game.field.h * c_cell_h

	//width := game.field.w
	//height := game.field.h

	width := c_cell_w
	height := c_cell_h

    mx := int(math.floor(px / width))
    my := int(math.floor(py / height) * 2)

    return mx, my
}

fn screen_to_cell_pos3(sx, sy int) (int, int) {
	wx, wy := screen_to_world_pos(sx, sy)
	return world_to_cell_pos3(wx, wy)
}

// XXX
// x is accurate +/-
// y is not very
//fn screen_to_cell_pos3(sx, sy int) (int, int) {
fn world_to_cell_pos3(wx, wy int) (int, int) {

	// XXX name alias for world version
	sx := wx
	sy := wy

	//y := f32(game.field.h) - 1.0 - f32(sy) * 2.0 / f32(c_cell_h) 
	//sy_ := ctx.vars.res_y - sy
	//sy_ := game.field.height_px() - (f32(c_cell_h) * 1.5) - sy
	//sy_ := sy
	//sy_ := 1.0
	//sy_ := f32(0.0)
	//println("sy_: $sy_")
	//y := f32(game.field.h) - f32(sy_) * 2.0 / f32(c_cell_h) 
	//y := f32(game.field.h) - 1.0 - f32(sy_) * 2.0 / f32(c_cell_h) 
	//mut y := f32(sy) / f32(c_cell_h)
	//mut y := 0.0  - 1.0 - f32(sy_) * 2.0 / f32(c_cell_h) 
	mut y := f32(sy) * 2.0 / f32(c_cell_h) + 1.0
	//mut y := f32(sy) * 2.0 / f32(c_cell_h)
	mut x := f32(0.0)

	y = (2 * (sy)) / c_cell_h

	if int(y) % 2 == 0 {
		x = f32(sx) / f32(c_cell_w)
	} else {
		//x = f32(sx) / f32(c_cell_w)
		//x = (f32(sx) / f32(c_cell_w)) / 2.0
		//x = (f32(sx) + f32(c_cell_w / 2)) / f32(c_cell_w)
		x = ((f32(sx) / f32(c_cell_w))) - f32(0.5) // 0.5 is float rounding correction to the lower number
	}

	yi, xi := int(y), int(x)

	return xi, yi
}

// XXX inaccurate
fn mouse_to_cell_pos(mx, my int) (int, int) {
	// https://gamedev.stackexchange.com/questions/45103/staggered-isometric-map-calculate-map-coordinates-for-point-on-screen

	px := f32(mx) - (c_cell_w / 2.0)
	py := f32(my) - (c_cell_h / 2.0)

	x := math.floor((px + (py - (c_cell_h / 2.0)) * 2.0) / c_cell_w)
	y := math.floor((py - (px - (c_cell_w / 2.0)) * 0.5) / c_cell_h)

	
	tx := math.floor((x - y) / 2.0) + 1.0 //+ this.camera.x;
	ty := y + x + 2.0 //+ this.camera.y;
	

	/*
	tx := math.floor((x - y) / 2) + 1 + -(game.viewport.shx / c_tile_w)
	ty := y + x + 2 + -(game.viewport.shy / c_tile_h)
	*/

	// XXX rounding errors?
	mut txi := int(tx)
	mut tyi := int(ty)

	// XXX correct y by shift, fixme?
	tyi = tyi - 1

	/*
	vp_shx_tiles := game.viewport.shx / c_tile_w
	vp_shy_tiles := game.viewport.shy / c_tile_h

	txi = txi + vp_shx_tiles
	tyi = tyi + (vp_shy_tiles * 2)
	*/

	return txi, tyi
}