Add markdown table rendering with box-drawing characters and alignment support

src/markdown.ts

@@ -1,3 +1,74 @@
+function stripAnsi(s: string): string {
+  return s.replace(/\x1b\]8;;[^\x07]*\x07/g, "").replace(/\x1b\[[0-9;]*m/g, "")
+}
+
+function renderTable(block: string): string {
+  const lines = block.trim().split("\n")
+  if (lines.length < 2) return block
+
+  const parseRow = (line: string): string[] =>
+    line.replace(/^\|/, "").replace(/\|$/, "").split("|").map(c => c.trim())
+
+  const header = parseRow(lines[0])
+  const sepCells = parseRow(lines[1])
+
+  // Validate separator row
+  if (!sepCells.every(s => /^:?-+:?$/.test(s.trim()))) return block
+
+  const cols = header.length
+  const align: ("left" | "center" | "right")[] = sepCells.map(s => {
+    const t = s.trim()
+    if (t.startsWith(":") && t.endsWith(":")) return "center"
+    if (t.endsWith(":")) return "right"
+    return "left"
+  })
+
+  const rows = lines.slice(2).map(parseRow)
+
+  // Column widths based on visible text (no ANSI codes)
+  const widths = new Array(cols).fill(0)
+  for (let c = 0; c < cols; c++) {
+    widths[c] = Math.max(widths[c], stripAnsi(header[c] ?? "").length)
+    for (const row of rows) {
+      widths[c] = Math.max(widths[c], stripAnsi(row[c] ?? "").length)
+    }
+  }
+
+  const pad = (text: string, width: number, a: "left" | "center" | "right"): string => {
+    const needed = width - stripAnsi(text).length
+    if (needed <= 0) return text
+    if (a === "right") return " ".repeat(needed) + text
+    if (a === "center") {
+      const l = Math.floor(needed / 2)
+      return " ".repeat(l) + text + " ".repeat(needed - l)
+    }
+    return text + " ".repeat(needed)
+  }
+
+  const D = "\x1b[2m" // dim
+  const R = "\x1b[22m" // reset intensity
+
+  const renderRow = (cells: string[], bold: boolean): string => {
+    const parts = cells.map((c, i) => pad(c ?? "", widths[i] ?? 0, align[i] ?? "left"))
+    if (bold) {
+      return `${D}│${R} ${parts.map(p => `\x1b[1m${p}\x1b[22m`).join(` ${D}│${R} `)} ${D}│${R}`
+    }
+    return `${D}│${R} ${parts.join(` ${D}│${R} `)} ${D}│${R}`
+  }
+
+  const hline = (l: string, m: string, r: string): string => {
+    return `${D}${l}${widths.map(w => "─".repeat(w + 2)).join(m)}${r}${R}`
+  }
+
+  const out: string[] = []
+  out.push(hline("┌", "┬", "┐"))
+  out.push(renderRow(header, true))
+  out.push(hline("├", "┼", "┤"))
+  for (const row of rows) out.push(renderRow(row, false))
+  out.push(hline("└", "┴", "┘"))
+  return out.join("\n")
+}
+
 export function renderMarkdown(text: string): string {
   // Extract fenced code blocks before anything else
   const codeBlocks: string[] = []
@@ -57,6 +128,14 @@ export function renderMarkdown(text: string): string {
   // Restore backslash escapes as literal characters
   result = result.replace(/\x00ESC(\d+)\x00/g, (_, i) => escapes[parseInt(i)])
 
+  // Tables: render pipe tables with box-drawing characters
+  // Processed after inline formatting so cell contents are styled,
+  // but before code block restoration so tables inside code blocks are ignored.
+  result = result.replace(
+    /^(\|[^\n]+\|\n)(\|[\s:|-]+\|\n)((?:\|[^\n]+\|\n?)*)/gm,
+    (match) => renderTable(match),
+  )
+
   // Restore fenced code blocks as plain text
   result = result.replace(/\x00CODEBLOCK(\d+)\x00/g, (_, i) => codeBlocks[parseInt(i)])