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import gleam/int
import gleam/bool
import gleam/list
import gleam/set.{type Set}
pub type Pos2 =
#(Int, Int)
pub const zero = #(0, 0)
pub fn directions8() -> Set(Pos2) {
set.from_list({
use x <- list.flat_map(over: [-1, 0, 1])
use y <- list.flat_map(over: [-1, 0, 1])
let pos = #(x, y)
use <- bool.guard(when: pos == zero, return: [])
[pos]
})
}
pub fn add(p1: Pos2, p2: Pos2) -> Pos2 {
#(p1.0 + p2.0, p1.1 + p2.1)
}
pub fn sub(p1: Pos2, p2: Pos2) -> Pos2 {
#(p1.0 - p2.0, p1.1 - p2.1)
}
pub fn mul(p: Pos2, by scalar: Int) -> Pos2 {
#(p.0 * scalar, p.1 * scalar)
}
pub fn neighbours8(p: Pos2) -> Set(Pos2) {
directions8()
|> set.to_list
|> list.map(with: add(p, _))
|> set.from_list
}
pub fn manhattan_dist(from p1: Pos2, to p2: Pos2) -> Int {
int.absolute_value(p1.0 - p2.0) + int.absolute_value(p1.1 - p2.1)
}
pub fn rotate_around_origin(this p: Pos2, by times: Int) -> Pos2 {
let assert Ok(sin) = list.at([0, -1, 0, 1], times)
let assert Ok(cos) = list.at([1, 0, -1, 0], times)
#(p.0 * cos - p.1 * sin, p.0 * sin + p.1 * cos)
}
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