// SVG text cannot ellipsize itself, so labels are measured by estimate (full-width glyphs 1em, others ~0.6em) and shortened here.

export function textWidth(text: string, fontSize: number) {
  let width = 0
  for (const char of text) width += (char.codePointAt(0) ?? 0) > 0x2e7f ? fontSize : fontSize * 0.6
  return width
}

/** The longest start of `text` plus an ellipsis that fits `maxWidth`; "" when not even one character fits. */
export function fitText(text: string, maxWidth: number, fontSize: number) {
  if (textWidth(text, fontSize) <= maxWidth) return text
  const chars = [...text]
  for (let count = chars.length - 1; count > 0; count -= 1) {
    const candidate = `${chars.slice(0, count).join("").trimEnd()}…`
    if (textWidth(candidate, fontSize) <= maxWidth) return candidate
  }
  return ""
}