1 use integral_geometry::Size;

     2 use land2d::Land2D;

     3 use std::collections::HashMap;

     4 

     5 #[derive(PartialEq, Eq, Hash, Clone, Copy, Debug)]

     6 enum Tile {

     7     Empty,

     8     Outside,

     9     Numbered(u32),

    10 }

    11 

    12 impl Tile {

    13     fn is(&self, i: u32) -> bool {

    14         *self == Tile::Numbered(i)

    15     }

    16 

    17     fn is_empty(&self) -> bool {

    18         match self {

    19             Tile::Empty => true,

    20             Tile::Outside => true,

    21             _ => false,

    22         }

    23     }

    24 

    25     fn is_empty_or(&self, i: u32) -> bool {

    26         match self {

    27             Tile::Numbered(n) => *n == i,

    28             Tile::Empty => true,

    29             _ => false,

    30         }

    31     }

    32 

    33     fn is_void_or(&self, i: u32) -> bool {

    34         match self {

    35             Tile::Numbered(n) => *n == i,

    36             _ => true,

    37         }

    38     }

    39 }

    40 

    41 impl Default for Tile {

    42     fn default() -> Self {

    43         Tile::Outside

    44     }

    45 }

    46 

    47 struct CollapseRule {

    48     to_tile: Tile,

    49     condition: fn([Tile; 4]) -> bool,

    50 }

    51 

    52 #[derive(Default)]

    53 struct WavefrontCollapse {

    54     rules: HashMap<Tile, Vec<CollapseRule>>,

    55 }

    56 

    57 impl WavefrontCollapse {

    58     pub fn generate_map<I: Iterator<Item = u32>, F: FnOnce(&mut Land2D<Tile>)>(

    59         &mut self,

    60         map_size: &Size,

    61         seed_fn: F,

    62         random_numbers: &mut I,

    63     ) -> Land2D<Tile> {

    64         let mut land = Land2D::new(map_size, Tile::Empty);

    65 

    66         seed_fn(&mut land);

    67 

    68         while self.collapse_step(&mut land, random_numbers) {}

    69 

    70         land

    71     }

    72 

    73     fn add_rule(&mut self, from_tile: Tile, to_tile: Tile, condition: fn([Tile; 4]) -> bool) {

    74         let rule = CollapseRule { to_tile, condition };

    75         self.rules

    76             .entry(from_tile)

    77             .or_insert_with(Vec::new)

    78             .push(rule);

    79     }

    80 

    81     fn collapse_step<I: Iterator<Item = u32>>(

    82         &self,

    83         land: &mut Land2D<Tile>,

    84         random_numbers: &mut I,

    85     ) -> bool {

    86         let mut collapse_occurred = false;

    87         for x in 0..land.width() {

    88             for y in 0..land.height() {

    89                 let current_tile = land.map(y as i32, x as i32, |p| *p);

    90 

    91                 if let Some(rules) = self.rules.get(&current_tile) {

    92                     for rule in rules

    93                         .iter()

    94                         .cycle()

    95                         .skip(

    96                             random_numbers.next().unwrap_or_default() as usize % (rules.len() + 1),

    97                         )

    98                         .take(rules.len())

    99                     {

   100                         let neighbors = self.get_neighbors(&land, x, y);

   101                         let have_neighbors = neighbors.iter().any(|t| !t.is_empty());

   102                         if have_neighbors && (rule.condition)(neighbors) {

   103                             land.map(y as i32, x as i32, |p| *p = rule.to_tile);

   104                             collapse_occurred = true;

   105                             break;

   106                         }

   107                     }

   108                 }

   109             }

   110         }

   111 

   112         collapse_occurred

   113     }

   114 

   115     fn get_neighbors(&self, land: &Land2D<Tile>, x: usize, y: usize) -> [Tile; 4] {

   116         [

   117             land.get(y as i32, x as i32 + 1),

   118             land.get(y as i32 + 1, x as i32),

   119             land.get(y as i32, x as i32 - 1),

   120             land.get(y as i32 - 1, x as i32),

   121         ]

   122     }

   123 }

   124 

   125 #[cfg(test)]

   126 mod tests {

   127     use super::{CollapseRule, Tile, WavefrontCollapse};

   128     use integral_geometry::Size;

   129     use land2d::Land2D;

   130     use std::collections::HashMap;

   131 

   132     #[test]

   133     fn test_wavefront_collapse() {

   134         let size = Size::new(4, 4);

   135         let mut rnd = [0u32; 64].into_iter();

   136         let mut wfc = WavefrontCollapse::default();

   137 

   138         let empty_land = Land2D::new(&size, Tile::Empty);

   139         let no_rules_land = wfc.generate_map(&size, |l| {}, &mut rnd);

   140 

   141         assert_eq!(empty_land.raw_pixels(), no_rules_land.raw_pixels());

   142 

   143         wfc.add_rule(Tile::Empty, Tile::Numbered(0), |neighbors| {

   144             neighbors.iter().filter(|&n| *n == Tile::Empty).count() >= 2

   145         });

   146         let ruled_map = wfc.generate_map(&size, |l| {}, &mut rnd);

   147 

   148         assert_eq!(ruled_map.raw_pixels(), empty_land.raw_pixels());

   149     }

   150 }