package main

import (
	"math/rand"
	"time"

	rl "github.com/gen2brain/raylib-go/raylib"
)

type Particle struct {
	Pos  rl.Vector2
	Vel  rl.Vector2
	Size float32
}

var particles []Particle
var topColor = rl.Color{R: 0x20, G: 0x0F, B: 0x3C, A: 0xFF}      // #200F3C top
var bottomColor = rl.Color{R: 0x3B, G: 0x0B, B: 0x42, A: 0xFF}   // #3B0B42 bottom
var particleColor = rl.Color{R: 0xD4, G: 0xB0, B: 0xB5, A: 0x80} // D4B0B5 with some transparency

func InitBackground(width, height int) {
	rand.Seed(time.Now().UnixNano())
	particles = make([]Particle, 100)
	for i := range particles {
		particles[i].Pos = rl.Vector2{X: float32(rand.Intn(width)), Y: float32(rand.Intn(height))}
		particles[i].Vel = rl.Vector2{X: (rand.Float32() - 0.5) * 0.2, Y: (rand.Float32() - 0.5) * 0.2}
		particles[i].Size = rand.Float32()*1.5 + 0.5 // Particles size ~0.5-2.0
	}
}

func UpdateBackground(screenWidth, screenHeight int) {
	for i := range particles {
		particles[i].Pos.X += particles[i].Vel.X
		particles[i].Pos.Y += particles[i].Vel.Y
		// Wrap around screen
		if particles[i].Pos.X < 0 {
			particles[i].Pos.X += float32(screenWidth)
		} else if particles[i].Pos.X > float32(screenWidth) {
			particles[i].Pos.X -= float32(screenWidth)
		}
		if particles[i].Pos.Y < 0 {
			particles[i].Pos.Y += float32(screenHeight)
		} else if particles[i].Pos.Y > float32(screenHeight) {
			particles[i].Pos.Y -= float32(screenHeight)
		}
	}
}

func DrawBackground(screenWidth, screenHeight int) {
	// Draw vertical gradient
	rl.DrawRectangleGradientV(0, 0, int32(screenWidth), int32(screenHeight), topColor, bottomColor)
	// Draw particles
	for _, p := range particles {
		rl.DrawCircleV(p.Pos, p.Size, particleColor)
	}
}