Rewrite algorithm

* Improve performance
* Fix a couple of bugs (such as trailing whitespace)
* Remove minimum of three character in alignment row cells
  — this isn’t needed in Markdown anymore
* Don’t double pad empty cells
* Fix tests

Related to remarkjs/remark-lint#217.

index.js

@@ -1,206 +1,249 @@
 'use strict'
 
+var repeat = require('repeat-string')
+
 module.exports = markdownTable
 
+var trailingWhitespace = / +$/
+
 // Characters.
 var space = ' '
 var lineFeed = '\n'
 var dash = '-'
 var colon = ':'
-var lowercaseC = 'c'
-var lowercaseL = 'l'
-var lowercaseR = 'r'
 var verticalBar = '|'
 
-var minCellSize = 3
+var x = 0
+var C = 67
+var L = 76
+var R = 82
+var c = 99
+var l = 108
+var r = 114
 
 // Create a table from a matrix of strings.
 function markdownTable(table, options) {
   var settings = options || {}
-  var padding = settings.padding === false ? '' : space
-  var between = padding + verticalBar + padding
-  var start = settings.delimiterStart === false ? '' : verticalBar + padding
-  var end = settings.delimiterEnd === false ? '' : padding + verticalBar
-  var alignment = settings.align
-  var calculateStringLength = settings.stringLength || lengthNoop
-  var cellCount = 0
+  var padding = settings.padding !== false
+  var start = settings.delimiterStart !== false
+  var end = settings.delimiterEnd !== false
+  var align = (settings.align || []).concat()
+  var alignDelimiters = settings.alignDelimiters !== false
+  var alignments = []
+  var stringLength = settings.stringLength || defaultStringLength
   var rowIndex = -1
   var rowLength = table.length
+  var cellMatrix = []
+  var sizeMatrix = []
+  var row = []
   var sizes = []
-  var align
-  var rule
-  var rows
-  var row
+  var longestCellByColumn = []
+  var mostCellsPerRow = 0
   var cells
-  var index
-  var position
+  var columnIndex
+  var columnLength
+  var largest
   var size
-  var value
-  var spacing
+  var cell
+  var lines
+  var line
   var before
   var after
+  var code
 
-  alignment = alignment ? alignment.concat() : []
-
+  // This is a superfluous loop if we don’t align delimiters, but otherwise we’d
+  // do superfluous work when aligning, so optimize for aligning.
   while (++rowIndex < rowLength) {
-    row = table[rowIndex]
+    cells = table[rowIndex]
+    columnIndex = -1
+    columnLength = cells.length
+    row = []
+    sizes = []
+
+    if (columnLength > mostCellsPerRow) {
+      mostCellsPerRow = columnLength
+    }
 
-    index = -1
+    while (++columnIndex < columnLength) {
+      cell = serialize(cells[columnIndex])
 
-    if (row.length > cellCount) {
-      cellCount = row.length
-    }
+      if (alignDelimiters === true) {
+        size = stringLength(cell)
+        sizes[columnIndex] = size
 
-    while (++index < cellCount) {
-      position = row[index] ? row[index].length : null
+        largest = longestCellByColumn[columnIndex]
 
-      if (!sizes[index]) {
-        sizes[index] = minCellSize
+        if (largest === undefined || size > largest) {
+          longestCellByColumn[columnIndex] = size
+        }
       }
 
-      if (position > sizes[index]) {
-        sizes[index] = position
-      }
+      row.push(cell)
     }
-  }
 
-  if (typeof alignment === 'string') {
-    alignment = pad(cellCount, alignment).split('')
+    cellMatrix[rowIndex] = row
+    sizeMatrix[rowIndex] = sizes
   }
 
-  // Make sure only valid alignments are used.
-  index = -1
-
-  while (++index < cellCount) {
-    align = alignment[index]
+  // Figure out which alignments to use.
+  columnIndex = -1
+  columnLength = mostCellsPerRow
 
-    if (typeof align === 'string') {
-      align = align.charAt(0).toLowerCase()
+  if (typeof align === 'object' && 'length' in align) {
+    while (++columnIndex < columnLength) {
+      alignments[columnIndex] = toAlignment(align[columnIndex])
     }
+  } else {
+    code = toAlignment(align)
 
-    if (align !== lowercaseL && align !== lowercaseR && align !== lowercaseC) {
-      align = ''
+    while (++columnIndex < columnLength) {
+      alignments[columnIndex] = code
     }
-
-    alignment[index] = align
   }
 
-  rowIndex = -1
-  rows = []
-
-  while (++rowIndex < rowLength) {
-    row = table[rowIndex]
-
-    index = -1
-    cells = []
+  // Inject the alignment row.
+  columnIndex = -1
+  columnLength = mostCellsPerRow
+  row = []
+  sizes = []
 
-    while (++index < cellCount) {
-      cells[index] = stringify(row[index])
+  while (++columnIndex < columnLength) {
+    code = alignments[columnIndex]
+    before = ''
+    after = ''
+
+    if (code === l) {
+      before = colon
+    } else if (code === r) {
+      after = colon
+    } else if (code === c) {
+      before = colon
+      after = colon
     }
 
-    rows[rowIndex] = cells
-  }
+    // There *must* be at least one hyphen-minus in each alignment cell.
+    size = alignDelimiters
+      ? Math.max(
+          1,
+          longestCellByColumn[columnIndex] - before.length - after.length
+        )
+      : 1
 
-  sizes = []
-  rowIndex = -1
-
-  while (++rowIndex < rowLength) {
-    cells = rows[rowIndex]
+    cell = before + repeat(dash, size) + after
 
-    index = -1
+    if (alignDelimiters === true) {
+      size = before.length + size + after.length
 
-    while (++index < cellCount) {
-      value = cells[index]
-
-      if (!sizes[index]) {
-        sizes[index] = minCellSize
+      if (size > longestCellByColumn[columnIndex]) {
+        longestCellByColumn[columnIndex] = size
       }
 
-      size = calculateStringLength(value)
-
-      if (size > sizes[index]) {
-        sizes[index] = size
-      }
+      sizes[columnIndex] = size
     }
+
+    row[columnIndex] = cell
   }
 
+  // Inject the alignment row.
+  cellMatrix.splice(1, 0, row)
+  sizeMatrix.splice(1, 0, sizes)
+
   rowIndex = -1
+  rowLength = cellMatrix.length
+  lines = []
 
   while (++rowIndex < rowLength) {
-    cells = rows[rowIndex]
+    row = cellMatrix[rowIndex]
+    sizes = sizeMatrix[rowIndex]
+    columnIndex = -1
+    columnLength = mostCellsPerRow
+    line = []
+
+    while (++columnIndex < columnLength) {
+      cell = row[columnIndex] || ''
+      before = ''
+      after = ''
+
+      if (alignDelimiters === true) {
+        size = longestCellByColumn[columnIndex] - (sizes[columnIndex] || 0)
+        code = alignments[columnIndex]
+
+        if (code === r) {
+          before = repeat(space, size)
+        } else if (code === c) {
+          if (size % 2 === 0) {
+            before = repeat(space, size / 2)
+            after = before
+          } else {
+            before = repeat(space, size / 2 + 0.5)
+            after = repeat(space, size / 2 - 0.5)
+          }
+        } else {
+          after = repeat(space, size)
+        }
+      }
 
-    index = -1
+      if (start === true && columnIndex === 0) {
+        line.push(verticalBar)
+      }
 
-    if (settings.alignDelimiters !== false) {
-      while (++index < cellCount) {
-        value = cells[index]
+      if (
+        padding === true &&
+        // Don’t add the opening space if we’re not aligning and the cell is
+        // empty: there will be a closing space.
+        !(alignDelimiters === false && cell === '') &&
+        (start === true || columnIndex !== 0)
+      ) {
+        line.push(space)
+      }
 
-        position = sizes[index] - (calculateStringLength(value) || 0)
-        spacing = pad(position)
+      if (alignDelimiters === true) {
+        line.push(before)
+      }
 
-        if (alignment[index] === lowercaseR) {
-          value = spacing + value
-        } else if (alignment[index] === lowercaseC) {
-          position /= 2
+      line.push(cell)
 
-          if (position % 1 === 0) {
-            before = position
-            after = position
-          } else {
-            before = position + 0.5
-            after = position - 0.5
-          }
+      if (alignDelimiters === true) {
+        line.push(after)
+      }
 
-          value = pad(before) + value + pad(after)
-        } else {
-          value += spacing
-        }
+      if (padding === true) {
+        line.push(space)
+      }
 
-        cells[index] = value
+      if (end === true || columnIndex !== columnLength - 1) {
+        line.push(verticalBar)
       }
     }
 
-    rows[rowIndex] = cells.join(between)
-  }
+    line = line.join('')
 
-  index = -1
-  rule = []
-
-  while (++index < cellCount) {
-    // When `pad` is false, make the rule the same size as the first row.
-    if (settings.alignDelimiters === false) {
-      value = table[0][index]
-      spacing = calculateStringLength(stringify(value))
-      spacing = spacing > minCellSize ? spacing : minCellSize
-    } else {
-      spacing = sizes[index]
+    if (end === false) {
+      line = line.replace(trailingWhitespace, '')
     }
 
-    align = alignment[index]
-
-    // When `align` is left, don't add colons.
-    value = align === lowercaseR || align === '' ? dash : colon
-    value += pad(spacing - 2, dash)
-    value += align !== lowercaseL && align !== '' ? colon : dash
-
-    rule[index] = value
+    lines.push(line)
   }
 
-  rows.splice(1, 0, rule.join(between))
-
-  return start + rows.join(end + lineFeed + start) + end
+  return lines.join(lineFeed)
 }
 
-function stringify(value) {
+function serialize(value) {
   return value === null || value === undefined ? '' : String(value)
 }
 
-// Get the length of `value`.
-function lengthNoop(value) {
-  return String(value).length
+function defaultStringLength(value) {
+  return value.length
 }
 
-// Get a string consisting of `length` `character`s.
-function pad(length, character) {
-  return new Array(length + 1).join(character || space)
+function toAlignment(value) {
+  var code = typeof value === 'string' ? value.charCodeAt(0) : x
+
+  return code === L || code === l
+    ? l
+    : code === R || code === r
+    ? r
+    : code === C || code === c
+    ? c
+    : x
 }