gilt 0.5.0

//! Box-drawing character sets for tables.
//!
//! Port of Python `rich/box.py`. Defines 19 built-in box styles for rendering
//! table borders and separators.

use std::sync::LazyLock;

/// Which level of row separator to render.
#[derive(Debug, Clone, Copy, PartialEq, Eq)]
pub enum RowLevel {
    /// Separator below the header row.
    Head,
    /// Separator between body rows.
    Row,
    /// Separator above the footer row.
    Foot,
    /// Mid-level separator (between header and body when there's a distinct mid section).
    Mid,
}

/// A set of box-drawing characters for rendering table borders.
///
/// Parsed from an 8-line definition string where each line has exactly 4 characters:
///
/// ```text
/// Line 1 (top):      top_left, top, top_divider, top_right
/// Line 2 (head):     head_left, _, head_vertical, head_right
/// Line 3 (head_row): head_row_left, head_row_horizontal, head_row_cross, head_row_right
/// Line 4 (mid):      mid_left, _, mid_vertical, mid_right
/// Line 5 (row):      row_left, row_horizontal, row_cross, row_right
/// Line 6 (foot_row): foot_row_left, foot_row_horizontal, foot_row_cross, foot_row_right
/// Line 7 (foot):     foot_left, _, foot_vertical, foot_right
/// Line 8 (bottom):   bottom_left, bottom_char, bottom_divider, bottom_right
/// ```
#[derive(Debug, Clone)]
pub struct BoxChars {
    /// Top-left corner character (e.g. `┌`).
    pub top_left: char,
    /// Top border horizontal fill character (e.g. `─`).
    pub top: char,
    /// Top border column divider character (e.g. `┬`).
    pub top_divider: char,
    /// Top-right corner character (e.g. `┐`).
    pub top_right: char,

    /// Left border character for the header row (e.g. `│`).
    pub head_left: char,
    /// Vertical column divider in the header row (e.g. `│`).
    pub head_vertical: char,
    /// Right border character for the header row (e.g. `│`).
    pub head_right: char,

    /// Left border character for the header separator (e.g. `├`).
    pub head_row_left: char,
    /// Horizontal fill character for the header separator (e.g. `─`).
    pub head_row_horizontal: char,
    /// Cross/intersection character for the header separator (e.g. `┼`).
    pub head_row_cross: char,
    /// Right border character for the header separator (e.g. `┤`).
    pub head_row_right: char,

    /// Left border character for the mid separator (e.g. `│`).
    pub mid_left: char,
    /// Vertical column divider for the mid separator (e.g. `│`).
    pub mid_vertical: char,
    /// Right border character for the mid separator (e.g. `│`).
    pub mid_right: char,

    /// Left border character for body row separators (e.g. `├`).
    pub row_left: char,
    /// Horizontal fill character for body row separators (e.g. `─`).
    pub row_horizontal: char,
    /// Cross/intersection character for body row separators (e.g. `┼`).
    pub row_cross: char,
    /// Right border character for body row separators (e.g. `┤`).
    pub row_right: char,

    /// Left border character for the footer separator (e.g. `├`).
    pub foot_row_left: char,
    /// Horizontal fill character for the footer separator (e.g. `─`).
    pub foot_row_horizontal: char,
    /// Cross/intersection character for the footer separator (e.g. `┼`).
    pub foot_row_cross: char,
    /// Right border character for the footer separator (e.g. `┤`).
    pub foot_row_right: char,

    /// Left border character for the footer row (e.g. `│`).
    pub foot_left: char,
    /// Vertical column divider in the footer row (e.g. `│`).
    pub foot_vertical: char,
    /// Right border character for the footer row (e.g. `│`).
    pub foot_right: char,

    /// Bottom-left corner character (e.g. `└`).
    pub bottom_left: char,
    /// Bottom border horizontal fill character (e.g. `─`).
    pub bottom_char: char,
    /// Bottom border column divider character (e.g. `┴`).
    pub bottom_divider: char,
    /// Bottom-right corner character (e.g. `┘`).
    pub bottom_right: char,

    /// Whether this box uses only ASCII characters.
    pub ascii: bool,
}

impl BoxChars {
    /// Parse a box definition string into a `BoxChars`.
    ///
    /// The string must contain 8 lines separated by `\n`, each with exactly 4 characters.
    ///
    /// # Panics
    ///
    /// Panics if the string does not have exactly 8 lines or any line does not have
    /// exactly 4 characters.
    pub fn new(box_str: &str, ascii: bool) -> Self {
        let lines: Vec<&str> = box_str.split('\n').collect();
        assert_eq!(lines.len(), 8, "Box string must have exactly 8 lines");

        let parse_line = |line: &str| -> Vec<char> {
            let chars: Vec<char> = line.chars().collect();
            assert_eq!(
                chars.len(),
                4,
                "Each box line must have exactly 4 characters, got {} in {:?}",
                chars.len(),
                line,
            );
            chars
        };

        let top = parse_line(lines[0]);
        let head = parse_line(lines[1]);
        let head_row = parse_line(lines[2]);
        let mid = parse_line(lines[3]);
        let row = parse_line(lines[4]);
        let foot_row = parse_line(lines[5]);
        let foot = parse_line(lines[6]);
        let bottom = parse_line(lines[7]);

        Self {
            top_left: top[0],
            top: top[1],
            top_divider: top[2],
            top_right: top[3],

            head_left: head[0],
            head_vertical: head[2],
            head_right: head[3],

            head_row_left: head_row[0],
            head_row_horizontal: head_row[1],
            head_row_cross: head_row[2],
            head_row_right: head_row[3],

            mid_left: mid[0],
            mid_vertical: mid[2],
            mid_right: mid[3],

            row_left: row[0],
            row_horizontal: row[1],
            row_cross: row[2],
            row_right: row[3],

            foot_row_left: foot_row[0],
            foot_row_horizontal: foot_row[1],
            foot_row_cross: foot_row[2],
            foot_row_right: foot_row[3],

            foot_left: foot[0],
            foot_vertical: foot[2],
            foot_right: foot[3],

            bottom_left: bottom[0],
            bottom_char: bottom[1],
            bottom_divider: bottom[2],
            bottom_right: bottom[3],

            ascii,
        }
    }

    /// Build the top border string for columns of given widths.
    ///
    /// Example for widths `[5, 3]` with SQUARE box:
    /// `"┌─────┬───┐"`
    pub fn get_top(&self, widths: &[usize]) -> String {
        let mut s = String::new();
        s.push(self.top_left);
        for (i, &width) in widths.iter().enumerate() {
            for _ in 0..width {
                s.push(self.top);
            }
            if i < widths.len() - 1 {
                s.push(self.top_divider);
            }
        }
        s.push(self.top_right);
        s
    }

    /// Build a row separator string for columns of given widths.
    ///
    /// `level` determines which set of characters to use.
    /// If `edge` is false, the left and right border characters are omitted.
    pub fn get_row(&self, widths: &[usize], level: RowLevel, edge: bool) -> String {
        let (left, horizontal, cross, right) = match level {
            RowLevel::Head => (
                self.head_row_left,
                self.head_row_horizontal,
                self.head_row_cross,
                self.head_row_right,
            ),
            RowLevel::Row => (
                self.row_left,
                self.row_horizontal,
                self.row_cross,
                self.row_right,
            ),
            RowLevel::Foot => (
                self.foot_row_left,
                self.foot_row_horizontal,
                self.foot_row_cross,
                self.foot_row_right,
            ),
            RowLevel::Mid => (
                self.mid_left,
                self.row_horizontal,
                self.mid_vertical,
                self.mid_right,
            ),
        };

        let mut s = String::new();
        if edge {
            s.push(left);
        }
        for (i, &width) in widths.iter().enumerate() {
            for _ in 0..width {
                s.push(horizontal);
            }
            if i < widths.len() - 1 {
                s.push(cross);
            }
        }
        if edge {
            s.push(right);
        }
        s
    }

    /// Build the bottom border string for columns of given widths.
    ///
    /// Example for widths `[5, 3]` with SQUARE box:
    /// `"└─────┴───┘"`
    pub fn get_bottom(&self, widths: &[usize]) -> String {
        let mut s = String::new();
        s.push(self.bottom_left);
        for (i, &width) in widths.iter().enumerate() {
            for _ in 0..width {
                s.push(self.bottom_char);
            }
            if i < widths.len() - 1 {
                s.push(self.bottom_divider);
            }
        }
        s.push(self.bottom_right);
        s
    }

    /// Return a reference to an ASCII-compatible box if `ascii_only` is true and this
    /// box is not already ASCII.
    ///
    /// Specific substitutions:
    /// - ROUNDED -> SQUARE (not truly ASCII, but a simpler fallback)
    /// - MINIMAL_HEAVY_HEAD -> MINIMAL
    /// - SIMPLE_HEAVY -> SIMPLE
    /// - HEAVY -> SQUARE
    /// - HEAVY_EDGE -> SQUARE
    /// - HEAVY_HEAD -> SQUARE
    ///
    /// If no specific substitution is found, returns `self`.
    pub fn substitute(&self, ascii_only: bool) -> &BoxChars {
        if !ascii_only {
            return self;
        }
        // We can identify boxes by comparing top_left char
        // For a more robust approach, we compare the full character set
        // by using the top-left + head_row_horizontal as a fingerprint.
        //
        // This uses pointer equality with the statics or character matching.
        // Since we can't easily do pointer comparison with Lazy, we match on characters.
        match (self.top_left, self.head_row_horizontal) {
            // ROUNDED: top_left='╭', head_row_horizontal='─'
            ('\u{256D}', '\u{2500}') => &SQUARE,
            // MINIMAL_HEAVY_HEAD: top_left=' ', head_row_horizontal='━'
            // Distinguish from SIMPLE_HEAVY by checking head_row_cross
            (' ', '\u{2501}') => {
                if self.head_row_cross == '\u{253F}' {
                    // MINIMAL_HEAVY_HEAD: cross='┿'
                    &MINIMAL
                } else {
                    // SIMPLE_HEAVY: cross='━'
                    &SIMPLE
                }
            }
            // HEAVY: top_left='┏', head_row_horizontal='━'
            ('\u{250F}', '\u{2501}') => {
                // Matches HEAVY (cross='╋') and HEAVY_HEAD (cross='╇')
                &SQUARE
            }
            // HEAVY_EDGE: top_left='┏', head_row_horizontal='─'
            ('\u{250F}', '\u{2500}') => &SQUARE,
            _ => self,
        }
    }

    /// Return a plain-headed variant of this box style.
    ///
    /// Replaces double/heavy header separators with single-line equivalents:
    /// - HEAVY_HEAD -> SQUARE
    /// - SQUARE_DOUBLE_HEAD -> SQUARE
    /// - MINIMAL_DOUBLE_HEAD -> MINIMAL
    /// - MINIMAL_HEAVY_HEAD -> MINIMAL
    /// - ASCII_DOUBLE_HEAD -> ASCII2
    pub fn get_plain_headed_box(&self) -> &BoxChars {
        match (self.top_left, self.head_row_horizontal) {
            // HEAVY_HEAD: top_left='┏', head_row_horizontal='━', cross='╇'
            ('\u{250F}', '\u{2501}') if self.head_row_cross == '\u{2547}' => &SQUARE,
            // SQUARE_DOUBLE_HEAD: top_left='┌', head_row_horizontal='═'
            ('\u{250C}', '\u{2550}') => &SQUARE,
            // MINIMAL_DOUBLE_HEAD: top_left=' ', head_row_horizontal='═'
            (' ', '\u{2550}') => &MINIMAL,
            // MINIMAL_HEAVY_HEAD: top_left=' ', head_row_horizontal='━', cross='┿'
            (' ', '\u{2501}') if self.head_row_cross == '\u{253F}' => &MINIMAL,
            // ASCII_DOUBLE_HEAD: top_left='+', head_row_horizontal='='
            ('+', '=') => &ASCII2,
            _ => self,
        }
    }
}

// ──────────────────────────────────────────────────────────
// Box constant definitions
// ──────────────────────────────────────────────────────────

/// ASCII box style using `+`, `-`, and `|` characters.
pub static ASCII: LazyLock<BoxChars> =
    LazyLock::new(|| BoxChars::new("+--+\n| ||\n|-+|\n| ||\n|-+|\n|-+|\n| ||\n+--+", true));

/// Alternate ASCII box style with `+` at every intersection.
pub static ASCII2: LazyLock<BoxChars> =
    LazyLock::new(|| BoxChars::new("+-++\n| ||\n+-++\n| ||\n+-++\n+-++\n| ||\n+-++", true));

/// ASCII box style with `=` for the header separator row.
pub static ASCII_DOUBLE_HEAD: LazyLock<BoxChars> =
    LazyLock::new(|| BoxChars::new("+-++\n| ||\n+=++\n| ||\n+-++\n+-++\n| ||\n+-++", true));

/// Standard single-line Unicode box style (`┌─┬┐`, `│`, `└─┴┘`).
pub static SQUARE: LazyLock<BoxChars> =
    LazyLock::new(|| BoxChars::new("┌─┬┐\n│ ││\n├─┼┤\n│ ││\n├─┼┤\n├─┼┤\n│ ││\n└─┴┘", false));

/// Single-line Unicode box with a double-line header separator (`╞═╪╡`).
pub static SQUARE_DOUBLE_HEAD: LazyLock<BoxChars> =
    LazyLock::new(|| BoxChars::new("┌─┬┐\n│ ││\n╞═╪╡\n│ ││\n├─┼┤\n├─┼┤\n│ ││\n└─┴┘", false));

/// Minimal box style with no outer borders, only column dividers and row separators.
pub static MINIMAL: LazyLock<BoxChars> =
    LazyLock::new(|| BoxChars::new("  ╷ \n  │ \n╶─┼╴\n  │ \n╶─┼╴\n╶─┼╴\n  │ \n  ╵ ", false));

/// Minimal box style with a heavy (thick) header separator (`╺━┿╸`).
pub static MINIMAL_HEAVY_HEAD: LazyLock<BoxChars> =
    LazyLock::new(|| BoxChars::new("  ╷ \n  │ \n╺━┿╸\n  │ \n╶─┼╴\n╶─┼╴\n  │ \n  ╵ ", false));

/// Minimal box style with a double-line header separator (`═╪`).
pub static MINIMAL_DOUBLE_HEAD: LazyLock<BoxChars> =
    LazyLock::new(|| BoxChars::new("  ╷ \n  │ \n ═╪ \n  │ \n ─┼ \n ─┼ \n  │ \n  ╵ ", false));

/// Simple box style with only horizontal rules for header and footer separators.
pub static SIMPLE: LazyLock<BoxChars> =
    LazyLock::new(|| BoxChars::new("    \n    \n ── \n    \n    \n ── \n    \n    ", false));

/// Simple box style with only a header separator rule (no footer rule).
pub static SIMPLE_HEAD: LazyLock<BoxChars> =
    LazyLock::new(|| BoxChars::new("    \n    \n ── \n    \n    \n    \n    \n    ", false));

/// Simple box style with heavy (thick) horizontal rules (`━`).
pub static SIMPLE_HEAVY: LazyLock<BoxChars> =
    LazyLock::new(|| BoxChars::new("    \n    \n ━━ \n    \n    \n ━━ \n    \n    ", false));

/// Box style using only horizontal rules for all borders and separators.
pub static HORIZONTALS: LazyLock<BoxChars> =
    LazyLock::new(|| BoxChars::new(" ── \n    \n ── \n    \n ── \n ── \n    \n ── ", false));

/// Single-line Unicode box with rounded corners (`╭╮╰╯`).
pub static ROUNDED: LazyLock<BoxChars> =
    LazyLock::new(|| BoxChars::new("╭─┬╮\n│ ││\n├─┼┤\n│ ││\n├─┼┤\n├─┼┤\n│ ││\n╰─┴╯", false));

/// Heavy (thick) Unicode box style (`┏━┳┓`, `┃`, `┗━┻┛`).
pub static HEAVY: LazyLock<BoxChars> =
    LazyLock::new(|| BoxChars::new("┏━┳┓\n┃ ┃┃\n┣━╋┫\n┃ ┃┃\n┣━╋┫\n┣━╋┫\n┃ ┃┃\n┗━┻┛", false));

/// Heavy outer edges with light inner dividers (`┏━┯┓`, `┃│┃`).
pub static HEAVY_EDGE: LazyLock<BoxChars> =
    LazyLock::new(|| BoxChars::new("┏━┯┓\n┃ │┃\n┠─┼┨\n┃ │┃\n┠─┼┨\n┠─┼┨\n┃ │┃\n┗━┷┛", false));

/// Heavy header section with light body (`┏━┳┓` header, `├─┼┤` body).
pub static HEAVY_HEAD: LazyLock<BoxChars> =
    LazyLock::new(|| BoxChars::new("┏━┳┓\n┃ ┃┃\n┡━╇┩\n│ ││\n├─┼┤\n├─┼┤\n│ ││\n└─┴┘", false));

/// Double-line Unicode box style (`╔═╦╗`, `║`, `╚═╩╝`).
pub static DOUBLE: LazyLock<BoxChars> =
    LazyLock::new(|| BoxChars::new("╔═╦╗\n║ ║║\n╠═╬╣\n║ ║║\n╠═╬╣\n╠═╬╣\n║ ║║\n╚═╩╝", false));

/// Double-line outer edges with single-line inner dividers (`╔═╤╗`, `║│║`).
pub static DOUBLE_EDGE: LazyLock<BoxChars> =
    LazyLock::new(|| BoxChars::new("╔═╤╗\n║ │║\n╟─┼╢\n║ │║\n╟─┼╢\n╟─┼╢\n║ │║\n╚═╧╝", false));

/// Markdown-compatible table box style using `|` and `-` characters.
pub static MARKDOWN: LazyLock<BoxChars> =
    LazyLock::new(|| BoxChars::new("    \n| ||\n|-||\n| ||\n|-||\n|-||\n| ||\n    ", true));

#[cfg(test)]
mod tests {
    use super::*;

    // ---- Parsing tests ----

    #[test]
    fn test_parse_ascii() {
        let b = &*ASCII;
        assert_eq!(b.top_left, '+');
        assert_eq!(b.top, '-');
        assert_eq!(b.top_divider, '-');
        assert_eq!(b.top_right, '+');
        assert_eq!(b.head_left, '|');
        assert_eq!(b.head_vertical, '|');
        assert_eq!(b.head_right, '|');
        assert_eq!(b.head_row_left, '|');
        assert_eq!(b.head_row_horizontal, '-');
        assert_eq!(b.head_row_cross, '+');
        assert_eq!(b.head_row_right, '|');
        assert_eq!(b.bottom_left, '+');
        assert_eq!(b.bottom_char, '-');
        assert_eq!(b.bottom_divider, '-');
        assert_eq!(b.bottom_right, '+');
        assert!(b.ascii);
    }

    #[test]
    fn test_parse_square() {
        let b = &*SQUARE;
        assert_eq!(b.top_left, '┌');
        assert_eq!(b.top, '─');
        assert_eq!(b.top_divider, '┬');
        assert_eq!(b.top_right, '┐');
        assert_eq!(b.head_left, '│');
        assert_eq!(b.head_vertical, '│');
        assert_eq!(b.head_right, '│');
        assert_eq!(b.head_row_left, '├');
        assert_eq!(b.head_row_horizontal, '─');
        assert_eq!(b.head_row_cross, '┼');
        assert_eq!(b.head_row_right, '┤');
        assert_eq!(b.bottom_left, '└');
        assert_eq!(b.bottom_char, '─');
        assert_eq!(b.bottom_divider, '┴');
        assert_eq!(b.bottom_right, '┘');
        assert!(!b.ascii);
    }

    #[test]
    fn test_parse_heavy() {
        let b = &*HEAVY;
        assert_eq!(b.top_left, '┏');
        assert_eq!(b.top, '━');
        assert_eq!(b.top_divider, '┳');
        assert_eq!(b.top_right, '┓');
        assert_eq!(b.head_row_cross, '╋');
        assert!(!b.ascii);
    }

    #[test]
    fn test_parse_double() {
        let b = &*DOUBLE;
        assert_eq!(b.top_left, '╔');
        assert_eq!(b.top, '═');
        assert_eq!(b.top_divider, '╦');
        assert_eq!(b.top_right, '╗');
        assert_eq!(b.bottom_left, '╚');
        assert_eq!(b.bottom_char, '═');
        assert_eq!(b.bottom_divider, '╩');
        assert_eq!(b.bottom_right, '╝');
    }

    #[test]
    fn test_parse_rounded() {
        let b = &*ROUNDED;
        assert_eq!(b.top_left, '╭');
        assert_eq!(b.top_right, '╮');
        assert_eq!(b.bottom_left, '╰');
        assert_eq!(b.bottom_right, '╯');
    }

    #[test]
    fn test_parse_all_19_boxes() {
        // Just force initialization of all 19 constants to ensure none panic
        let _ = &*ASCII;
        let _ = &*ASCII2;
        let _ = &*ASCII_DOUBLE_HEAD;
        let _ = &*SQUARE;
        let _ = &*SQUARE_DOUBLE_HEAD;
        let _ = &*MINIMAL;
        let _ = &*MINIMAL_HEAVY_HEAD;
        let _ = &*MINIMAL_DOUBLE_HEAD;
        let _ = &*SIMPLE;
        let _ = &*SIMPLE_HEAD;
        let _ = &*SIMPLE_HEAVY;
        let _ = &*HORIZONTALS;
        let _ = &*ROUNDED;
        let _ = &*HEAVY;
        let _ = &*HEAVY_EDGE;
        let _ = &*HEAVY_HEAD;
        let _ = &*DOUBLE;
        let _ = &*DOUBLE_EDGE;
        let _ = &*MARKDOWN;
    }

    #[test]
    fn test_ascii_flag() {
        assert!(ASCII.ascii);
        assert!(ASCII2.ascii);
        assert!(ASCII_DOUBLE_HEAD.ascii);
        assert!(MARKDOWN.ascii);
        assert!(!SQUARE.ascii);
        assert!(!ROUNDED.ascii);
        assert!(!HEAVY.ascii);
        assert!(!DOUBLE.ascii);
    }

    // ---- get_top tests ----

    #[test]
    fn test_get_top_square() {
        let top = SQUARE.get_top(&[5, 3]);
        assert_eq!(top, "┌─────┬───┐");
    }

    #[test]
    fn test_get_top_ascii() {
        // ASCII top_divider is '-', same as top fill char
        let top = ASCII.get_top(&[3, 4]);
        assert_eq!(top, "+--------+");
    }

    #[test]
    fn test_get_top_ascii2() {
        // ASCII2 top_divider is '+'
        let top = ASCII2.get_top(&[3, 4]);
        assert_eq!(top, "+---+----+");
    }

    #[test]
    fn test_get_top_single_column() {
        let top = SQUARE.get_top(&[10]);
        assert_eq!(top, "┌──────────┐");
    }

    #[test]
    fn test_get_top_three_columns() {
        let top = HEAVY.get_top(&[2, 3, 4]);
        assert_eq!(top, "┏━━┳━━━┳━━━━┓");
    }

    // ---- get_bottom tests ----

    #[test]
    fn test_get_bottom_square() {
        let bottom = SQUARE.get_bottom(&[5, 3]);
        assert_eq!(bottom, "└─────┴───┘");
    }

    #[test]
    fn test_get_bottom_heavy() {
        let bottom = HEAVY.get_bottom(&[4, 4]);
        assert_eq!(bottom, "┗━━━━┻━━━━┛");
    }

    #[test]
    fn test_get_bottom_single_column() {
        let bottom = DOUBLE.get_bottom(&[6]);
        assert_eq!(bottom, "╚══════╝");
    }

    // ---- get_row tests ----

    #[test]
    fn test_get_row_head_square() {
        let row = SQUARE.get_row(&[5, 3], RowLevel::Head, true);
        assert_eq!(row, "├─────┼───┤");
    }

    #[test]
    fn test_get_row_head_no_edge() {
        let row = SQUARE.get_row(&[5, 3], RowLevel::Head, false);
        assert_eq!(row, "─────┼───");
    }

    #[test]
    fn test_get_row_body_square() {
        let row = SQUARE.get_row(&[5, 3], RowLevel::Row, true);
        assert_eq!(row, "├─────┼───┤");
    }

    #[test]
    fn test_get_row_foot_square() {
        let row = SQUARE.get_row(&[5, 3], RowLevel::Foot, true);
        assert_eq!(row, "├─────┼───┤");
    }

    #[test]
    fn test_get_row_head_heavy() {
        let row = HEAVY.get_row(&[3, 3], RowLevel::Head, true);
        assert_eq!(row, "┣━━━╋━━━┫");
    }

    #[test]
    fn test_get_row_ascii() {
        let row = ASCII2.get_row(&[4, 4], RowLevel::Head, true);
        assert_eq!(row, "+----+----+");
    }

    // ---- substitute tests ----

    #[test]
    fn test_substitute_not_ascii() {
        let b = SQUARE.substitute(false);
        assert_eq!(b.top_left, '┌');
    }

    #[test]
    fn test_substitute_rounded_to_square() {
        let b = ROUNDED.substitute(true);
        assert_eq!(b.top_left, '┌');
        assert_eq!(b.bottom_left, '└');
    }

    #[test]
    fn test_substitute_heavy_to_square() {
        let b = HEAVY.substitute(true);
        assert_eq!(b.top_left, '┌');
    }

    #[test]
    fn test_substitute_heavy_edge_to_square() {
        let b = HEAVY_EDGE.substitute(true);
        assert_eq!(b.top_left, '┌');
    }

    #[test]
    fn test_substitute_simple_heavy_to_simple() {
        let b = SIMPLE_HEAVY.substitute(true);
        assert_eq!(b.head_row_horizontal, '─');
    }

    #[test]
    fn test_substitute_minimal_heavy_head_to_minimal() {
        let b = MINIMAL_HEAVY_HEAD.substitute(true);
        assert_eq!(b.head_row_horizontal, '─');
        assert_eq!(b.head_row_cross, '┼');
    }

    // ---- get_plain_headed_box tests ----

    #[test]
    fn test_plain_headed_heavy_head() {
        let b = HEAVY_HEAD.get_plain_headed_box();
        assert_eq!(b.top_left, '┌');
        assert_eq!(b.head_row_horizontal, '─');
    }

    #[test]
    fn test_plain_headed_square_double_head() {
        let b = SQUARE_DOUBLE_HEAD.get_plain_headed_box();
        assert_eq!(b.top_left, '┌');
        assert_eq!(b.head_row_horizontal, '─');
    }

    #[test]
    fn test_plain_headed_minimal_double_head() {
        let b = MINIMAL_DOUBLE_HEAD.get_plain_headed_box();
        assert_eq!(b.head_row_horizontal, '─');
        assert_eq!(b.head_row_cross, '┼');
    }

    #[test]
    fn test_plain_headed_ascii_double_head() {
        let b = ASCII_DOUBLE_HEAD.get_plain_headed_box();
        assert_eq!(b.head_row_horizontal, '-');
        assert_eq!(b.head_row_cross, '+');
    }

    #[test]
    fn test_plain_headed_identity() {
        // SQUARE has no special headed variant, returns itself
        let b = SQUARE.get_plain_headed_box();
        assert_eq!(b.top_left, '┌');
        assert_eq!(b.head_row_horizontal, '─');
    }

    // ---- Edge case tests ----

    #[test]
    fn test_get_top_empty_widths() {
        let top = SQUARE.get_top(&[]);
        assert_eq!(top, "┌┐");
    }

    #[test]
    fn test_get_bottom_empty_widths() {
        let bottom = SQUARE.get_bottom(&[]);
        assert_eq!(bottom, "└┘");
    }

    #[test]
    fn test_get_row_empty_widths() {
        let row = SQUARE.get_row(&[], RowLevel::Head, true);
        assert_eq!(row, "├┤");
    }

    #[test]
    fn test_get_top_zero_width_column() {
        let top = SQUARE.get_top(&[0, 3]);
        assert_eq!(top, "┌┬───┐");
    }

    #[test]
    fn test_markdown_box() {
        let b = &*MARKDOWN;
        assert_eq!(b.head_left, '|');
        assert_eq!(b.head_vertical, '|');
        assert_eq!(b.head_right, '|');
        assert_eq!(b.head_row_horizontal, '-');
        assert_eq!(b.head_row_cross, '|');
        assert!(b.ascii);
    }

    #[test]
    #[should_panic(expected = "8 lines")]
    fn test_bad_line_count() {
        BoxChars::new("abc\ndef", false);
    }

    #[test]
    #[should_panic(expected = "4 characters")]
    fn test_bad_char_count() {
        BoxChars::new("ab\nabcd\nabcd\nabcd\nabcd\nabcd\nabcd\nabcd", false);
    }
}