patience-diff/index.js

Linear Diff algorithm for Arrays.

var assert = require('assert')

var INSTRUCTION_BUFFER_SIZE = 512
var MAX_COMMAND_LENGTH = 3

module.exports = Diff

function Diff (from, to, result) {
  this.instructions = new Uint16Array(INSTRUCTION_BUFFER_SIZE * MAX_COMMAND_LENGTH)
}

Diff.prototype.diff = function (current, desired) {
  assert.ok(Array.isArray(current), 'patience-diff: current should be an Array')
  assert.ok(Array.isArray(desired), 'patience-diff: desired should be an Array')

  var m = current.length
  var n = desired.length
  var max = n + m

  var v = new Array(2 * max + 1)
  v[1] = 0  // pretend we're starting at (x, y) = (0,−1)

  var d, k, x, y
  for (d = 0; d < max; d++) {
    for (k = -d; k <= d; k += 2) {
      if (k === -d || (k !== d && v[k - 1] < v[k + 1])) {
        x = v[k + 1]
      } else {
        x = v[k - 1] + 1
      }

      y = x - k

      while (x < n && y < m && current[x] === desired[y]) {
        x = x + 1
        y = y + 1
      }

      v[k] = x
      if (x >= n && y >= m) {
        console.log(d)
        return d
      }
    }
  }
}