use std::fmt::Display;

use pancurses::Window;

use crate::rooms;

/// A dungeon root.
pub struct Dungeon {
    main_branch: DungeonBranch,
}

/// A single branch of a dungeon, which has a number of levels and
/// which can potentially contain passages to other branches.
pub struct DungeonBranch {
    config: BranchConfig,
    levels: Vec<DungeonLevel>,
}

/// The parameters that characterize a particular dungeon branch.
/// Currently a unit struct because there's only one type of branch,
/// but will later include e.g. architectural styles, good vs. evil &
/// lawful vs. chaotic weights, etc.
pub struct BranchConfig;

/// The size of a dungeon level, in tiles.
pub const LEVEL_SIZE: (usize, usize) = (80, 24);

/// A single level of the dungeon.
pub struct DungeonLevel {
    /// The tiles at every position in the level.
    tiles: [[DungeonTile; LEVEL_SIZE.0]; LEVEL_SIZE.1],
}

/// The smallest measurable independent location in the dungeon,
/// corresponding to a single character on the screen.
#[derive(Debug, Clone, Copy, PartialEq)]
pub enum DungeonTile {
    Floor,
    Wall,
    Hallway,
}

impl DungeonLevel {
    /// Creates a new level in a branch that has the given
    /// configuration.
    pub fn new(_cfg: &BranchConfig) -> Self {
        Self {
            tiles: rooms::generate_level(100, &mut rand::thread_rng()),
        }
    }

    /// Draws a level on the display window.
    pub fn draw(&self, win: &Window) {
        for y in 0..LEVEL_SIZE.1 {
            win.mv(y as _, 0);
            for x in 0..LEVEL_SIZE.0 {
                win.addch(self.render_tile(x, y));
            }
        }
    }

    /// Renders the tile at the given coordinates.
    pub fn render_tile(&self, x: usize, y: usize) -> char {
        match self.tiles[y][x] {
            DungeonTile::Floor => '.',
            DungeonTile::Wall => {
                // Walls are rendered like so:
                // - If the wall has any floor tiles to its north or
                //   south, then it is rendered as '-', because it is
                //   the north or south wall of a room.
                // - Otherwise, if the wall has any floor tiles to its
                //   east or west, then it is rendered as '|'.
                // - Otherwise, if any floor tiles are diagonally
                //   adjacent to the wall, then the wall is rendered as
                //   '+', because it is in the corner of a room.
                // - Otherwise, no floor tiles are adjacent to the
                //   wall, therefore it is surrounded by stone and will
                //   never be discovered by the player, so we don't
                //   render it at all.

                let has_floor = |deltas: &[(i32, i32)]| -> bool {
                    deltas
                        .iter()
                        .map(|(dx, dy)| (x as i32 + dx, y as i32 + dy))
                        .filter(|(x, y)| {
                            (0..LEVEL_SIZE.0 as i32).contains(x)
                                && (0..LEVEL_SIZE.1 as i32).contains(y)
                        })
                        .any(|(x, y)| self.tile(x, y) == &DungeonTile::Floor)
                };

                if has_floor(&[(0, -1), (0, 1)]) {
                    '-'
                } else if has_floor(&[(-1, 0), (1, 0)]) {
                    '|'
                } else if has_floor(&[(-1, -1), (-1, 1), (1, -1), (1, 1)]) {
                    '+'
                } else {
                    ' '
                }
            }
            DungeonTile::Hallway => '#',
        }
    }

    /// Gets a reference to the tile at the given coordinates. Panics
    /// of the coordinates are out of bounds.
    pub fn tile(&self, x: i32, y: i32) -> &DungeonTile {
        &self.tiles[y as usize][x as usize]
    }
}

impl Display for DungeonLevel {
    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
        for y in 0..LEVEL_SIZE.1 {
            for x in 0..LEVEL_SIZE.0 {
                write!(f, "{}", self.render_tile(x, y))?;
            }

            writeln!(f)?;
        }

        Ok(())
    }
}