//! Module: table
//!
//! Responsibility: render fixed-width plain-text tables for human CLI reports.
//!
//! Does not own: report-specific row construction, JSON output, or terminal styling.
//!
//! Boundary: provides deterministic alignment and width calculation for report text
//! modules that need compact tabular output.

const COLUMN_GAP: &str = "   ";

///
/// ColumnAlign
///
/// Text alignment to apply when rendering a table column.
///

#[derive(Clone, Copy, Debug, Eq, PartialEq)]
pub enum ColumnAlign {
    Left,
    Right,
}

/// Renders a table with headers, separator row, and aligned body rows.
#[must_use]
pub fn render_table<const N: usize>(
    headers: &[&str; N],
    rows: &[[String; N]],
    alignments: &[ColumnAlign; N],
) -> String {
    let widths = table_widths(headers, rows);
    let mut lines = Vec::with_capacity(rows.len() + 2);
    lines.push(render_table_row(headers, &widths, alignments));
    lines.push(render_separator(&widths));
    lines.extend(
        rows.iter()
            .map(|row| render_table_row(row, &widths, alignments)),
    );
    lines.join("\n")
}

/// Computes display widths from header and row cell character counts.
#[must_use]
pub fn table_widths<const N: usize>(headers: &[&str; N], rows: &[[String; N]]) -> [usize; N] {
    let mut widths = headers.map(str::chars).map(Iterator::count);

    for row in rows {
        for (index, cell) in row.iter().enumerate() {
            widths[index] = widths[index].max(cell.chars().count());
        }
    }

    widths
}

/// Renders one fixed-width table row using the provided widths and alignments.
#[must_use]
pub fn render_table_row<const N: usize>(
    row: &[impl AsRef<str>],
    widths: &[usize; N],
    alignments: &[ColumnAlign; N],
) -> String {
    widths
        .iter()
        .zip(alignments)
        .enumerate()
        .map(|(index, (width, alignment))| {
            let value = row.get(index).map_or("", AsRef::as_ref);
            pad_cell(value, *width, *alignment)
        })
        .collect::<Vec<_>>()
        .join(COLUMN_GAP)
        .trim_end()
        .to_string()
}

/// Renders the dashed separator row for the provided column widths.
#[must_use]
pub fn render_separator<const N: usize>(widths: &[usize; N]) -> String {
    widths
        .iter()
        .map(|width| "-".repeat(*width))
        .collect::<Vec<_>>()
        .join(COLUMN_GAP)
}

fn pad_cell(value: &str, width: usize, alignment: ColumnAlign) -> String {
    let padding = " ".repeat(width.saturating_sub(value.chars().count()));
    match alignment {
        ColumnAlign::Left => format!("{value}{padding}"),
        ColumnAlign::Right => format!("{padding}{value}"),
    }
}
