path: root/internal/ui/table.go

package ui

import (
	"strings"

	"thehouseoficarus/internal/color"
)

type tableGlyphs struct {
	topLeft, topSep, topRight   rune
	side, colSep                rune
	sepLeft, sepCross, sepRight rune
	botLeft, botSep, botRight   rune
	fillH, fillHSep             rune
	titleSep                    rune
}

func tableGlyphSet(unicode bool) tableGlyphs {
	if unicode {
		return tableGlyphs{
			topLeft: '╔', topSep: '╤', topRight: '╗', side: '║', colSep: '│',
			sepLeft: '╟', sepCross: '┼', sepRight: '╢',
			botLeft: '╚', botSep: '╧', botRight: '╝', fillH: '═', fillHSep: '─',
			titleSep: '┬',
		}
	}
	return tableGlyphs{
		topLeft: '+', topSep: '+', topRight: '+', side: '|', colSep: '|',
		sepLeft: '+', sepCross: '+', sepRight: '+',
		botLeft: '+', botSep: '+', botRight: '+', fillH: '-', fillHSep: '-',
		titleSep: '+',
	}
}

type Table struct {
	Title   string
	Columns []string
	Rows    [][]string
}

// rebalanceWidths shrinks column widths in place so their sum fits budget.
// Rather than crushing only the last column, every column wider than the
// fair share (budget/nCols) is capped first, then columns are trimmed one
// rune at a time from the widest until the table fits. Leftover slack is
// handed back round-robin to columns that lost width so wide layouts still
// use the full line.
func rebalanceWidths(colWidths []int, budget int) {
	original := make([]int, len(colWidths))
	copy(original, colWidths)

	fair := budget / len(colWidths)
	if fair < 1 {
		fair = 1
	}
	for i, w := range colWidths {
		if w > fair {
			colWidths[i] = fair
		}
	}

	sum := func() int {
		t := 0
		for _, w := range colWidths {
			t += w
		}
		return t
	}

	// Tight tables: trim the widest column until we fit (or hit 1).
	for sum() > budget {
		widest := 0
		for i, w := range colWidths {
			if w > colWidths[widest] {
				widest = i
			}
		}
		if colWidths[widest] <= 1 {
			break
		}
		colWidths[widest]--
	}

	// Give unused width back to the columns that were reduced.
	for {
		extra := budget - sum()
		if extra <= 0 {
			break
		}
		progress := false
		for i := 0; i < len(colWidths) && extra > 0; i++ {
			if colWidths[i] < original[i] {
				colWidths[i]++
				extra--
				progress = true
			}
		}
		if !progress {
			break
		}
	}
}

func (t *Table) Render(unicode bool, maxWidth int) []string {
	g := tableGlyphSet(unicode)

	nCols := len(t.Columns)
	if nCols == 0 && len(t.Rows) > 0 {
		nCols = len(t.Rows[0])
	}
	if nCols == 0 {
		return nil
	}

	colWidths := make([]int, nCols)
	for i, h := range t.Columns {
		colWidths[i] = color.VisibleLen(h)
	}
	for _, row := range t.Rows {
		for i, cell := range row {
			if i >= nCols {
				break
			}
			vl := color.VisibleLen(cell)
			if vl > colWidths[i] {
				colWidths[i] = vl
			}
		}
	}

	headerCells := t.Columns
	bodyRows := t.Rows

	if maxWidth > 0 {
		// Cell padding: one space on each side of every cell, plus one
		// separator between columns.
		overhead := 3*nCols + 1
		budget := maxWidth - overhead
		if budget < nCols {
			budget = nCols
		}

		total := 0
		for _, w := range colWidths {
			total += w
		}
		if total > budget {
			rebalanceWidths(colWidths, budget)

			// Truncate every cell to its (possibly reduced) column width.
			// Work on copies so rendering never mutates the table.
			headerCells = make([]string, len(t.Columns))
			copy(headerCells, t.Columns)
			for i := range headerCells {
				headerCells[i] = color.TruncateVisible(headerCells[i], colWidths[i], unicode)
			}
			bodyRows = make([][]string, len(t.Rows))
			for i := range t.Rows {
				bodyRows[i] = make([]string, len(t.Rows[i]))
				copy(bodyRows[i], t.Rows[i])
				for j := 0; j < len(bodyRows[i]) && j < nCols; j++ {
					bodyRows[i][j] = color.TruncateVisible(bodyRows[i][j], colWidths[j], unicode)
				}
			}
		}
	}

	makeSep := func(left, cross, right rune, fill rune) string {
		var b strings.Builder
		b.WriteRune(left)
		for i := 0; i < nCols; i++ {
			if i > 0 {
				b.WriteRune(cross)
			}
			b.WriteString(strings.Repeat(string(fill), colWidths[i]+2))
		}
		b.WriteRune(right)
		return b.String()
	}

	makeRow := func(cells []string) string {
		var b strings.Builder
		b.WriteRune(g.side)
		for i := 0; i < nCols; i++ {
			if i > 0 {
				b.WriteRune(g.colSep)
			}
			cell := ""
			if i < len(cells) {
				cell = cells[i]
			}
			pad := colWidths[i] - color.VisibleLen(cell)
			if pad < 0 {
				pad = 0
			}
			b.WriteString(" " + cell + strings.Repeat(" ", pad) + " ")
		}
		b.WriteRune(g.side)
		return b.String()
	}

	hasTitle := t.Title != ""
	hasCols := len(t.Columns) > 0

	var out []string

	if hasTitle {
		innerWidth := 0
		for _, w := range colWidths {
			innerWidth += w + 2
		}
		innerWidth += nCols - 1

		var tb strings.Builder
		tb.WriteRune(g.topLeft)
		tb.WriteString(strings.Repeat(string(g.fillH), innerWidth))
		tb.WriteRune(g.topRight)
		out = append(out, tb.String())

		var tr strings.Builder
		tr.WriteRune(g.side)
		tr.WriteString(" ")
		title := t.Title
		if max := innerWidth - 2; max > 0 && color.VisibleLen(title) > max {
			title = color.TruncateVisible(title, max, unicode)
		}
		tr.WriteString(title)
		padding := innerWidth - 2 - color.VisibleLen(title)
		if padding < 0 {
			padding = 0
		}
		tr.WriteString(strings.Repeat(" ", padding))
		tr.WriteString(" ")
		tr.WriteRune(g.side)
		out = append(out, tr.String())

		out = append(out, makeSep(g.sepLeft, g.titleSep, g.sepRight, g.fillHSep))
	} else {
		out = append(out, makeSep(g.topLeft, g.topSep, g.topRight, g.fillH))
	}

	if hasCols {
		out = append(out, makeRow(headerCells))
		out = append(out, makeSep(g.sepLeft, g.sepCross, g.sepRight, g.fillHSep))
	}

	for _, row := range bodyRows {
		out = append(out, makeRow(row))
	}

	out = append(out, makeSep(g.botLeft, g.botSep, g.botRight, g.fillH))

	return out
}