# gwg_pathfinding

[![Package Version](https://img.shields.io/hexpm/v/gwg_pathfinding)](https://hex.pm/packages/gwg_pathfinding)
[![Hex Docs](https://img.shields.io/badge/hex-docs-ffaff3)](https://hexdocs.pm/gwg_pathfinding/)

This is a generic searching/pathfinding algorithm library for the [Gleam programming language](https://gleam.run).

## Installation

```sh
gleam add gwg_pathfinding
```

```gleam
import gleam/bool
import gleam/dict
import gleam/float
import gleam/list
import gwg/pathfinding.{Action}
import vec/dict/vec2i_dict
import vec/vec2.{Vec2}
import vec/vec2i.{type Vec2i}

pub fn main() {
  let actions = [
    Vec2(-1, 0),
    Vec2(1, 0),
    Vec2(0, -1),
    Vec2(0, 1),
    Vec2(-1, -1),
    Vec2(-1, 1),
    Vec2(1, -1),
    Vec2(1, 1),
  ]

  let world =
    vec2i_dict.from_string(
      ""
      <> "###########\n"
      <> "#   #     #\n"
      <> "#   #     #\n"
      <> "#   #     #\n"
      <> "#   ## ####\n"
      <> "#   #     #\n"
      <> "#   #     #\n"
      <> "## ##### ##\n"
      <> "#   # #   #\n"
      <> "#         #\n"
      <> "###########\n",
    )

  let init = Vec2(2, 2)
  let target = Vec2(7, 2)

  pathfinding.astar(
    init:,
    successor: fn(state, g_score) {
      actions
      |> list.filter_map(fn(action) {
        let weight = action |> vec2i.length

        use <- bool.guard(g_score +. weight >. 32.0, Error(Nil))

        let state = state |> vec2i.add(action)

        case world |> dict.has_key(state) {
          True -> Error(Nil)
          False -> Ok(Action(action:, state:, weight:))
        }
      })
    },
    heuristic: fn(state: Vec2i) -> Float { vec2i.distance(state, target) },
  )
  // ###########
  // #   #     #
  // # @ #  *  #
  // # ↓ # ↗   #
  // # ↓ ##↑####
  // # ↓ #  ↖  #
  // # ↓ #   ↖ #
  // ##↘#####↑##
  // #  ↘# #↗  #
  // #   →→↗   #
  // ###########
}
```

Further documentation can be found at <https://hexdocs.pm/gwg_pathfinding>.