use std::{env, fmt::Write, fs, path::Path};

#[path = "src/int.rs"]
mod int;
use self::int::BinInteger as _;

fn main() {
    let mut glyphsets_rs = String::new();

    for &glyph_set_in in GLYPH_SETS {
        process_one_glyph_set(&mut glyphsets_rs, glyph_set_in);
    }

    let out_dir = env::var_os("OUT_DIR").unwrap();
    let dest_path = Path::new(&out_dir).join("glyphsets.rs");
    fs::write(&dest_path, glyphsets_rs).unwrap();
    println!("cargo:rerun-if-changed=build.rs");
}

fn process_one_glyph_set(glyphsets_rs: &mut String, gs: &GlyphSetIn) {
    macro_rules! wl {
        ($($tt:tt)*) => { writeln!(glyphsets_rs, $($tt)*).unwrap() };
    }

    let mask_dims = gs.mask_dims;

    #[derive(Clone, Copy)]
    struct IndexEnt {
        glyph_i: usize,
        distance: usize,
    }
    let mut index = vec![None; 1 << (mask_dims[0] * mask_dims[1])];

    // Put the exact matches
    for (glyph_i, &(_, mask)) in gs.glyphs.iter().enumerate() {
        let mask = decode_mask(mask, mask_dims);
        if index[mask as usize].is_some() {
            // If there are two glyphs with identical masks, the first one
            // takes precedence
            continue;
        }
        index[mask as usize] = Some(IndexEnt {
            glyph_i,
            distance: 0,
        });
    }

    // Mutate known patterns to create lesser matches
    let mut last_distance = 0;
    for base_distance in 0.. {
        let mut should_continue = false;

        for mask in 0..index.len() {
            if let Some(IndexEnt { distance, glyph_i }) = index[mask] {
                if distance != base_distance {
                    // Already processed by a previous iteration
                    continue;
                }

                mutate_fragment_by_dilation_and_erosion(mask_dims, mask as Fragment, |new_mask| {
                    if index[new_mask as usize].is_some() {
                        return;
                    }

                    index[new_mask as usize] = Some(IndexEnt {
                        glyph_i,
                        distance: base_distance + 1,
                    });
                    eprintln!("{:09b} -> {:09b}, {}", mask, new_mask, base_distance + 1);
                    should_continue = true;
                });
            }
        }

        if !should_continue {
            break;
        }

        last_distance = base_distance;
    }

    // The above mutation technique doesn't cover the entire space. Now bring a
    // bigger gun
    for base_distance in 0.. {
        let mut should_continue = false;

        for mask in 0..index.len() {
            if let Some(IndexEnt { distance, glyph_i }) = index[mask] {
                if distance != base_distance {
                    // Already processed by a previous iteration
                    continue;
                }

                mutate_fragment_unconditional(mask_dims, mask as Fragment, |new_mask| {
                    if index[new_mask as usize].is_some() {
                        return;
                    }

                    index[new_mask as usize] = Some(IndexEnt {
                        glyph_i,
                        distance: base_distance + 1,
                    });
                    eprintln!("{:09b} -> {:09b}, {}", mask, new_mask, base_distance + 1);
                    should_continue = true;
                });
            }
        }

        if !should_continue && base_distance > last_distance {
            break;
        }
    }

    let max_glyph_len = gs.glyphs.iter().map(|x| x.0.len()).max().unwrap();

    wl!("pub const {}: &dyn GlyphSet =", gs.const_name);
    wl!("    &IndexedGlyphSet {{");
    wl!(
        "        mask_dims: [{}, {}],",
        gs.mask_dims[0],
        gs.mask_dims[1]
    );
    wl!(
        "        mask_overlap: [{}, {}],",
        gs.mask_overlap[0],
        gs.mask_overlap[1]
    );
    wl!("        max_glyph_len: {},", max_glyph_len);
    wl!("        index: &[");
    for ent in index.iter() {
        wl!(
            "            r##\"{}\"##,",
            gs.glyphs[ent.unwrap().glyph_i].0
        );
    }
    wl!("        ],");
    wl!("    }};");
}

/// Mutate a fragment.
fn mutate_fragment_by_dilation_and_erosion(
    [w, h]: [usize; 2],
    frag: Fragment,
    mut cb: impl FnMut(Fragment),
) {
    let mut i = 0;
    for y in 0..h {
        for x in 0..w {
            let cur = frag.get_bit(i);

            // Deny dilation (the outcome is opposite - the result image will
            // be dilated)
            if cur {
                continue;
            }

            // try copying this pixel to a neighboring one
            for &(sx, sy) in &[(-1isize, 0), (1, 0), (0, -1isize), (0, 1)] {
                let nx = x.wrapping_add(sx as usize);
                let ny = y.wrapping_add(sy as usize);
                if nx >= w || ny >= h {
                    continue; // OOB
                }

                let ni = (nx + ny * w) as u32;
                let nei = frag.get_bit(ni);

                if cur == nei {
                    continue; // no change
                }

                // mutate
                let new_frag = frag ^ (1 << ni);

                cb(new_frag);
            }

            i += 1;
        }
    }
}

/// Mutate a fragment differently.
fn mutate_fragment_unconditional([w, h]: [usize; 2], frag: Fragment, mut cb: impl FnMut(Fragment)) {
    for i in 0..w * h {
        cb(frag & !(1 << i));
    }
}

const GLYPH_SETS: &[&GlyphSetIn] = &[
    &GLYPH_SET_SLC,
    &GLYPH_SET_MS_2X3,
    &GLYPH_SET_1X1,
    &GLYPH_SET_1X2,
    &GLYPH_SET_2X2,
    &GLYPH_SET_2X3,
];

/// A small bitmap image, whose dimensions are specified implciitly (e.g., by
/// `GlyphSetIn::mask_dims`).
type Fragment = u32;

struct GlyphSetIn {
    const_name: &'static str,
    mask_dims: [usize; 2],
    mask_overlap: [usize; 2],
    glyphs: &'static [(&'static str, Fragment)],
}

/// The masks in `GlyphSetIn` are in reverse order so that their writing
/// direction matches the visual order. This function converts a mask to
/// the standard order (LSB = upper left corner, MSB = lower right corner).
fn decode_mask(mask: Fragment, mask_dims: [usize; 2]) -> Fragment {
    mask.reverse_bits() >> (32 - (mask_dims[0] * mask_dims[1]))
}

const GLYPH_SET_SLC: GlyphSetIn = GlyphSetIn {
    const_name: "GLYPH_SET_SLC",
    mask_dims: [3, 3],
    mask_overlap: [0, 0],
    glyphs: &[
        (" ", 0b000_000_000),
        ("╋", 0b010_111_010),
        ("🬃", 0b000_110_000),
        ("🬃", 0b000_100_000),
        ("╹", 0b010_010_000),
        ("🬇", 0b000_011_000),
        ("🬇", 0b000_001_000),
        ("╻", 0b000_010_010),
        ("█", 0b111_111_111),
        ("▋", 0b110_110_110),
        ("▍", 0b100_100_100),
        ("🬀", 0b110_000_000),
        ("🬁", 0b011_000_000),
        ("🬂", 0b111_000_000),
        ("🬋", 0b000_111_000),
        ("🬎", 0b111_111_000),
        ("🬏", 0b000_000_110),
        ("🬞", 0b000_000_011),
        ("🬭", 0b000_000_111),
        ("🬰", 0b111_000_111),
        ("🬹", 0b000_111_111),
        ("🬼", 0b000_000_100),
        ("🬾", 0b000_100_100),
        ("🬿", 0b000_100_111),
        ("🬿", 0b000_110_111),
        ("🭀", 0b100_100_110),
        ("🭀", 0b100_110_110),
        ("🭁", 0b011_111_111),
        ("🭂", 0b001_111_111),
        ("🭄", 0b001_011_111),
        ("🭅", 0b011_011_111),
        ("🭆", 0b000_001_111),
        ("🭆", 0b000_011_111),
        ("🭇", 0b000_000_001),
        ("🭉", 0b000_001_001),
        ("🭌", 0b110_111_111),
        ("🭍", 0b100_111_111),
        ("🭐", 0b110_110_111),
        ("🭒", 0b111_111_011),
        ("🭕", 0b111_011_001),
        ("🭖", 0b111_011_011),
        ("🭗", 0b100_000_000),
        ("🭙", 0b100_100_000),
        ("🭜", 0b111_100_000),
        ("🭜", 0b111_110_000),
        ("🭝", 0b111_111_110),
        ("🭞", 0b111_111_100),
        ("🭠", 0b111_110_100),
        ("🭡", 0b111_110_110),
        ("🭢", 0b001_000_000),
        ("🭤", 0b001_001_000),
        ("🭧", 0b111_001_000),
        ("🭧", 0b111_011_000),
        ("🭨", 0b111_011_111),
        ("🭩", 0b101_111_111),
        ("🭪", 0b111_110_111),
        ("🭫", 0b111_111_101),
        ("🭬", 0b100_110_100),
        ("🭭", 0b111_010_000),
        ("🭮", 0b001_011_001),
        ("🭯", 0b000_010_111),
        ("🮚", 0b111_010_111),
        ("🮛", 0b101_111_101),
        ("🭲", 0b010_010_010),
        ("🮇", 0b001_001_001),
        ("🮉", 0b011_011_011),
    ],
};

/// Marching square approximation using Symbols for Legacy Computing.
///
/// The following exterior verticies are permitted:
///
/// ┌───X───┐
/// │       │
/// X       X
/// │       │
/// ├───────┤
/// │       │
/// X       X
/// │       │
/// └───X───┘
///
/// The glyph outline is unambigous, so glyphs will connect to others seemlessly.
const GLYPH_SET_MS_2X3: GlyphSetIn = GlyphSetIn {
    const_name: "GLYPH_SET_MS_2X3",
    mask_dims: [2, 3],
    mask_overlap: [1, 1],
    glyphs: &[
        (" ", 0b00_00_00),
        ("█", 0b11_11_11),
        ("🬂", 0b11_00_00),
        ("🬋", 0b00_11_00),
        ("🬎", 0b11_11_00),
        ("🬭", 0b00_00_11),
        ("🬰", 0b11_00_11),
        ("🬹", 0b00_11_11),
        // -----
        ("🭁", 0b01_11_11),
        ("🭃", 0b01_01_11),
        ("🭆", 0b00_01_11),
        ("🭇", 0b00_00_01),
        ("🭉", 0b00_01_01),
        // -----
        ("🬼", 0b00_00_10),
        ("🭌", 0b10_11_11),
        ("🭎", 0b10_10_11),
        ("🭑", 0b00_10_11),
        ("🬾", 0b00_10_10),
        // -----
        ("🭗", 0b10_00_00),
        ("🭙", 0b10_10_00),
        ("🭜", 0b11_10_00),
        ("🭟", 0b11_10_10),
        ("🭝", 0b11_11_10),
        // -----
        ("🭢", 0b01_00_00),
        ("🭤", 0b01_01_00),
        ("🭧", 0b11_01_00),
        ("🭔", 0b11_01_01),
        ("🭒", 0b11_11_01),
        // -----
        ("▌", 0b10_10_10),
        ("▐", 0b01_01_01),
        // -----
        // last resort; introduces extra interior verices
        ("🬀", 0b10_00_00),
        ("🬁", 0b01_00_00),
        ("🬂", 0b11_00_00),
        ("🬃", 0b00_10_00),
        ("🬄", 0b10_10_00),
        ("🬅", 0b01_10_00),
        ("🬆", 0b11_10_00),
        ("🬇", 0b00_01_00),
        ("🬈", 0b10_01_00),
        ("🬉", 0b01_01_00),
        ("🬊", 0b11_01_00),
        ("🬋", 0b00_11_00),
        ("🬌", 0b10_11_00),
        ("🬍", 0b01_11_00),
        ("🬎", 0b11_11_00),
        ("🬏", 0b00_00_10),
        ("🬐", 0b10_00_10),
        ("🬑", 0b01_00_10),
        ("🬒", 0b11_00_10),
        ("🬓", 0b00_10_10),
        ("▌", 0b10_10_10),
        ("🬔", 0b01_10_10),
        ("🬕", 0b11_10_10),
        ("🬖", 0b00_01_10),
        ("🬗", 0b10_01_10),
        ("🬘", 0b01_01_10),
        ("🬙", 0b11_01_10),
        ("🬚", 0b00_11_10),
        ("🬛", 0b10_11_10),
        ("🬜", 0b01_11_10),
        ("🬝", 0b11_11_10),
        ("🬞", 0b00_00_01),
        ("🬟", 0b10_00_01),
        ("🬠", 0b01_00_01),
        ("🬡", 0b11_00_01),
        ("🬢", 0b00_10_01),
        ("🬣", 0b10_10_01),
        ("🬤", 0b01_10_01),
        ("🬥", 0b11_10_01),
        ("🬦", 0b00_01_01),
        ("▐", 0b01_01_01),
        ("🬧", 0b10_01_01),
        ("🬨", 0b11_01_01),
        ("🬩", 0b00_11_01),
        ("🬪", 0b10_11_01),
        ("🬫", 0b01_11_01),
        ("🬬", 0b11_11_01),
        ("🬭", 0b00_00_11),
        ("🬮", 0b10_00_11),
        ("🬯", 0b01_00_11),
        ("🬰", 0b11_00_11),
        ("🬱", 0b00_10_11),
        ("🬲", 0b10_10_11),
        ("🬳", 0b01_10_11),
        ("🬴", 0b11_10_11),
        ("🬵", 0b00_01_11),
        ("🬶", 0b10_01_11),
        ("🬷", 0b01_01_11),
        ("🬸", 0b11_01_11),
        ("🬹", 0b00_11_11),
        ("🬺", 0b10_11_11),
        ("🬻", 0b01_11_11),
    ],
};

const GLYPH_SET_1X1: GlyphSetIn = GlyphSetIn {
    const_name: "GLYPH_SET_1X1",
    mask_dims: [1, 1],
    mask_overlap: [0, 0],
    glyphs: &[("█", 0b1), (" ", 0b0)],
};

const GLYPH_SET_1X2: GlyphSetIn = GlyphSetIn {
    const_name: "GLYPH_SET_1X2",
    mask_dims: [1, 2],
    mask_overlap: [0, 0],
    glyphs: &[("█", 0b1_1), (" ", 0b0_0), ("▀", 0b1_0), ("▄", 0b0_1)],
};

const GLYPH_SET_2X2: GlyphSetIn = GlyphSetIn {
    const_name: "GLYPH_SET_2X2",
    mask_dims: [2, 2],
    mask_overlap: [0, 0],
    glyphs: &[
        ("█", 0b11_11),
        ("▖", 0b00_10),
        ("▗", 0b00_01),
        ("▘", 0b10_00),
        ("▙", 0b10_11),
        ("▚", 0b10_01),
        ("▛", 0b11_10),
        ("▜", 0b11_01),
        ("▝", 0b01_00),
        ("▞", 0b01_10),
        ("▟", 0b01_11),
        (" ", 0b00_00),
        ("🬎", 0b11_00),
        ("🬹", 0b00_11),
        ("▌", 0b10_10),
        ("▐", 0b01_01),
    ],
};

const GLYPH_SET_2X3: GlyphSetIn = GlyphSetIn {
    const_name: "GLYPH_SET_2X3",
    mask_dims: [2, 3],
    mask_overlap: [0, 0],
    glyphs: &[
        ("█", 0b11_11_11),
        (" ", 0b00_00_00),
        ("🬀", 0b10_00_00),
        ("🬁", 0b01_00_00),
        ("🬂", 0b11_00_00),
        ("🬃", 0b00_10_00),
        ("🬄", 0b10_10_00),
        ("🬅", 0b01_10_00),
        ("🬆", 0b11_10_00),
        ("🬇", 0b00_01_00),
        ("🬈", 0b10_01_00),
        ("🬉", 0b01_01_00),
        ("🬊", 0b11_01_00),
        ("🬋", 0b00_11_00),
        ("🬌", 0b10_11_00),
        ("🬍", 0b01_11_00),
        ("🬎", 0b11_11_00),
        ("🬏", 0b00_00_10),
        ("🬐", 0b10_00_10),
        ("🬑", 0b01_00_10),
        ("🬒", 0b11_00_10),
        ("🬓", 0b00_10_10),
        ("▌", 0b10_10_10),
        ("🬔", 0b01_10_10),
        ("🬕", 0b11_10_10),
        ("🬖", 0b00_01_10),
        ("🬗", 0b10_01_10),
        ("🬘", 0b01_01_10),
        ("🬙", 0b11_01_10),
        ("🬚", 0b00_11_10),
        ("🬛", 0b10_11_10),
        ("🬜", 0b01_11_10),
        ("🬝", 0b11_11_10),
        ("🬞", 0b00_00_01),
        ("🬟", 0b10_00_01),
        ("🬠", 0b01_00_01),
        ("🬡", 0b11_00_01),
        ("🬢", 0b00_10_01),
        ("🬣", 0b10_10_01),
        ("🬤", 0b01_10_01),
        ("🬥", 0b11_10_01),
        ("🬦", 0b00_01_01),
        ("▐", 0b01_01_01),
        ("🬧", 0b10_01_01),
        ("🬨", 0b11_01_01),
        ("🬩", 0b00_11_01),
        ("🬪", 0b10_11_01),
        ("🬫", 0b01_11_01),
        ("🬬", 0b11_11_01),
        ("🬭", 0b00_00_11),
        ("🬮", 0b10_00_11),
        ("🬯", 0b01_00_11),
        ("🬰", 0b11_00_11),
        ("🬱", 0b00_10_11),
        ("🬲", 0b10_10_11),
        ("🬳", 0b01_10_11),
        ("🬴", 0b11_10_11),
        ("🬵", 0b00_01_11),
        ("🬶", 0b10_01_11),
        ("🬷", 0b01_01_11),
        ("🬸", 0b11_01_11),
        ("🬹", 0b00_11_11),
        ("🬺", 0b10_11_11),
        ("🬻", 0b01_11_11),
    ],
};