/**
 * Diff Match and Patch
 * Copyright 2018 The diff-match-patch Authors.
 * https://github.com/google/diff-match-patch
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *   http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

/**
 * @fileoverview Computes the difference between two texts to create a patch.
 * Applies the patch onto another text, allowing for errors.
 * @author fraser@google.com (Neil Fraser)
 */

/**
 * CHANGES by pedrottimark to diff_match_patch_uncompressed.ts file:
 *
 * 1. Delete anything not needed to use diff_cleanupSemantic method
 * 2. Convert from prototype properties to var declarations
 * 3. Convert Diff to class from constructor and prototype
 * 4. Add type annotations for arguments and return values
 * 5. Add exports
 */

/**
 * The data structure representing a diff is an array of tuples:
 * [[DIFF_DELETE, 'Hello'], [DIFF_INSERT, 'Goodbye'], [DIFF_EQUAL, ' world.']]
 * which means: delete 'Hello', add 'Goodbye' and keep ' world.'
 */
const DIFF_DELETE = -1
const DIFF_INSERT = 1
const DIFF_EQUAL = 0

/**
 * Class representing one diff tuple.
 * Attempts to look like a two-element array (which is what this used to be).
 * @param {number} op Operation, one of: DIFF_DELETE, DIFF_INSERT, DIFF_EQUAL.
 * @param {string} text Text to be deleted, inserted, or retained.
 * @constructor
 */
class Diff {
  0: number
  1: string

  constructor(op: number, text: string) {
    this[0] = op
    this[1] = text
  }
}

/**
 * Determine the common prefix of two strings.
 * @param {string} text1 First string.
 * @param {string} text2 Second string.
 * @return {number} The number of characters common to the start of each
 *     string.
 */
const diff_commonPrefix = function (text1: string, text2: string): number {
  // Quick check for common null cases.
  if (!text1 || !text2 || text1.charAt(0) !== text2.charAt(0))
    return 0

  // Binary search.
  // Performance analysis: https://neil.fraser.name/news/2007/10/09/
  let pointermin = 0
  let pointermax = Math.min(text1.length, text2.length)
  let pointermid = pointermax
  let pointerstart = 0
  while (pointermin < pointermid) {
    if (text1.substring(pointerstart, pointermid) === text2.substring(pointerstart, pointermid)) {
      pointermin = pointermid
      pointerstart = pointermin
    }
    else {
      pointermax = pointermid
    }
    pointermid = Math.floor((pointermax - pointermin) / 2 + pointermin)
  }
  return pointermid
}

/**
 * Determine the common suffix of two strings.
 * @param {string} text1 First string.
 * @param {string} text2 Second string.
 * @return {number} The number of characters common to the end of each string.
 */
const diff_commonSuffix = function (text1: string, text2: string): number {
  // Quick check for common null cases.
  if (!text1 || !text2
    || text1.charAt(text1.length - 1) !== text2.charAt(text2.length - 1))
    return 0

  // Binary search.
  // Performance analysis: https://neil.fraser.name/news/2007/10/09/
  let pointermin = 0
  let pointermax = Math.min(text1.length, text2.length)
  let pointermid = pointermax
  let pointerend = 0
  while (pointermin < pointermid) {
    if (text1.substring(text1.length - pointermid, text1.length - pointerend)
      === text2.substring(text2.length - pointermid, text2.length - pointerend)) {
      pointermin = pointermid
      pointerend = pointermin
    }
    else {
      pointermax = pointermid
    }
    pointermid = Math.floor((pointermax - pointermin) / 2 + pointermin)
  }
  return pointermid
}

/**
 * Determine if the suffix of one string is the prefix of another.
 * @param {string} text1 First string.
 * @param {string} text2 Second string.
 * @return {number} The number of characters common to the end of the first
 *     string and the start of the second string.
 * @private
 */
const diff_commonOverlap_ = function (text1: string, text2: string): number {
  // Cache the text lengths to prevent multiple calls.
  const text1_length = text1.length
  const text2_length = text2.length
  // Eliminate the null case.
  if (text1_length === 0 || text2_length === 0)
    return 0

  // Truncate the longer string.
  if (text1_length > text2_length)
    text1 = text1.substring(text1_length - text2_length)

  else if (text1_length < text2_length)
    text2 = text2.substring(0, text1_length)

  const text_length = Math.min(text1_length, text2_length)
  // Quick check for the worst case.
  if (text1 === text2)
    return text_length

  // Start by looking for a single character match
  // and increase length until no match is found.
  // Performance analysis: https://neil.fraser.name/news/2010/11/04/
  let best = 0
  let length = 1
  while (true) {
    const pattern = text1.substring(text_length - length)
    const found = text2.indexOf(pattern)
    if (found === -1)
      return best

    length += found
    if (found === 0 || text1.substring(text_length - length)
      === text2.substring(0, length)) {
      best = length
      length++
    }
  }
}

/**
 * Reduce the number of edits by eliminating semantically trivial equalities.
 * @param {!Array.<!diff_match_patch.Diff>} diffs Array of diff tuples.
 */
const diff_cleanupSemantic = function (diffs: Array<Diff>) {
  let changes = false
  const equalities = [] // Stack of indices where equalities are found.
  let equalitiesLength = 0 // Keeping our own length var is faster in JS.
  /** @type {?string} */
  let lastEquality = null
  // Always equal to diffs[equalities[equalitiesLength - 1]][1]
  let pointer = 0 // Index of current position.
  // Number of characters that changed prior to the equality.
  let length_insertions1 = 0
  let length_deletions1 = 0
  // Number of characters that changed after the equality.
  let length_insertions2 = 0
  let length_deletions2 = 0
  while (pointer < diffs.length) {
    if (diffs[pointer][0] === DIFF_EQUAL) { // Equality found.
      equalities[equalitiesLength++] = pointer
      length_insertions1 = length_insertions2
      length_deletions1 = length_deletions2
      length_insertions2 = 0
      length_deletions2 = 0
      lastEquality = diffs[pointer][1]
    }
    else { // An insertion or deletion.
      if (diffs[pointer][0] === DIFF_INSERT)
        length_insertions2 += diffs[pointer][1].length

      else
        length_deletions2 += diffs[pointer][1].length

      // Eliminate an equality that is smaller or equal to the edits on both
      // sides of it.
      if (lastEquality && (lastEquality.length
        <= Math.max(length_insertions1, length_deletions1))
        && (lastEquality.length <= Math.max(length_insertions2, length_deletions2))) {
        // Duplicate record.
        diffs.splice(equalities[equalitiesLength - 1], 0, new Diff(DIFF_DELETE, lastEquality))
        // Change second copy to insert.
        diffs[equalities[equalitiesLength - 1] + 1][0] = DIFF_INSERT
        // Throw away the equality we just deleted.
        equalitiesLength--
        // Throw away the previous equality (it needs to be reevaluated).
        equalitiesLength--
        pointer = equalitiesLength > 0 ? equalities[equalitiesLength - 1] : -1
        length_insertions1 = 0 // Reset the counters.
        length_deletions1 = 0
        length_insertions2 = 0
        length_deletions2 = 0
        lastEquality = null
        changes = true
      }
    }
    pointer++
  }

  // Normalize the diff.
  if (changes)
    diff_cleanupMerge(diffs)

  diff_cleanupSemanticLossless(diffs)

  // Find any overlaps between deletions and insertions.
  // e.g: <del>abcxxx</del><ins>xxxdef</ins>
  //   -> <del>abc</del>xxx<ins>def</ins>
  // e.g: <del>xxxabc</del><ins>defxxx</ins>
  //   -> <ins>def</ins>xxx<del>abc</del>
  // Only extract an overlap if it is as big as the edit ahead or behind it.
  pointer = 1
  while (pointer < diffs.length) {
    if (diffs[pointer - 1][0] === DIFF_DELETE
      && diffs[pointer][0] === DIFF_INSERT) {
      const deletion = diffs[pointer - 1][1]
      const insertion = diffs[pointer][1]
      const overlap_length1 = diff_commonOverlap_(deletion, insertion)
      const overlap_length2 = diff_commonOverlap_(insertion, deletion)
      if (overlap_length1 >= overlap_length2) {
        if (overlap_length1 >= deletion.length / 2
          || overlap_length1 >= insertion.length / 2) {
          // Overlap found.  Insert an equality and trim the surrounding edits.
          diffs.splice(pointer, 0, new Diff(DIFF_EQUAL, insertion.substring(0, overlap_length1)))
          diffs[pointer - 1][1]
              = deletion.substring(0, deletion.length - overlap_length1)
          diffs[pointer + 1][1] = insertion.substring(overlap_length1)
          pointer++
        }
      }
      else {
        if (overlap_length2 >= deletion.length / 2
          || overlap_length2 >= insertion.length / 2) {
          // Reverse overlap found.
          // Insert an equality and swap and trim the surrounding edits.
          diffs.splice(pointer, 0, new Diff(DIFF_EQUAL, deletion.substring(0, overlap_length2)))
          diffs[pointer - 1][0] = DIFF_INSERT
          diffs[pointer - 1][1]
              = insertion.substring(0, insertion.length - overlap_length2)
          diffs[pointer + 1][0] = DIFF_DELETE
          diffs[pointer + 1][1]
              = deletion.substring(overlap_length2)
          pointer++
        }
      }
      pointer++
    }
    pointer++
  }
}

// Define some regex patterns for matching boundaries.
const nonAlphaNumericRegex_ = /[^a-zA-Z0-9]/
const whitespaceRegex_ = /\s/
const linebreakRegex_ = /[\r\n]/
const blanklineEndRegex_ = /\n\r?\n$/
const blanklineStartRegex_ = /^\r?\n\r?\n/

/**
 * Look for single edits surrounded on both sides by equalities
 * which can be shifted sideways to align the edit to a word boundary.
 * e.g: The c<ins>at c</ins>ame. -> The <ins>cat </ins>came.
 * @param {!Array.<!diff_match_patch.Diff>} diffs Array of diff tuples.
 */
function diff_cleanupSemanticLossless(diffs: Array<Diff>) {
  /**
   * Given two strings, compute a score representing whether the internal
   * boundary falls on logical boundaries.
   * Scores range from 6 (best) to 0 (worst).
   * Closure, but does not reference any external variables.
   * @param {string} one First string.
   * @param {string} two Second string.
   * @return {number} The score.
   * @private
   */
  function diff_cleanupSemanticScore_(one: string, two: string): number {
    if (!one || !two) {
      // Edges are the best.
      return 6
    }

    // Each port of this function behaves slightly differently due to
    // subtle differences in each language's definition of things like
    // 'whitespace'.  Since this function's purpose is largely cosmetic,
    // the choice has been made to use each language's native features
    // rather than force total conformity.
    const char1 = one.charAt(one.length - 1)
    const char2 = two.charAt(0)
    const nonAlphaNumeric1 = char1.match(nonAlphaNumericRegex_)
    const nonAlphaNumeric2 = char2.match(nonAlphaNumericRegex_)
    const whitespace1 = nonAlphaNumeric1
      && char1.match(whitespaceRegex_)
    const whitespace2 = nonAlphaNumeric2
      && char2.match(whitespaceRegex_)
    const lineBreak1 = whitespace1
      && char1.match(linebreakRegex_)
    const lineBreak2 = whitespace2
      && char2.match(linebreakRegex_)
    const blankLine1 = lineBreak1
      && one.match(blanklineEndRegex_)
    const blankLine2 = lineBreak2
      && two.match(blanklineStartRegex_)

    if (blankLine1 || blankLine2) {
      // Five points for blank lines.
      return 5
    }
    else if (lineBreak1 || lineBreak2) {
      // Four points for line breaks.
      return 4
    }
    else if (nonAlphaNumeric1 && !whitespace1 && whitespace2) {
      // Three points for end of sentences.
      return 3
    }
    else if (whitespace1 || whitespace2) {
      // Two points for whitespace.
      return 2
    }
    else if (nonAlphaNumeric1 || nonAlphaNumeric2) {
      // One point for non-alphanumeric.
      return 1
    }
    return 0
  }

  let pointer = 1
  // Intentionally ignore the first and last element (don't need checking).
  while (pointer < diffs.length - 1) {
    if (diffs[pointer - 1][0] === DIFF_EQUAL
      && diffs[pointer + 1][0] === DIFF_EQUAL) {
      // This is a single edit surrounded by equalities.
      let equality1 = diffs[pointer - 1][1]
      let edit = diffs[pointer][1]
      let equality2 = diffs[pointer + 1][1]

      // First, shift the edit as far left as possible.
      const commonOffset = diff_commonSuffix(equality1, edit)
      if (commonOffset) {
        const commonString = edit.substring(edit.length - commonOffset)
        equality1 = equality1.substring(0, equality1.length - commonOffset)
        edit = commonString + edit.substring(0, edit.length - commonOffset)
        equality2 = commonString + equality2
      }

      // Second, step character by character right, looking for the best fit.
      let bestEquality1 = equality1
      let bestEdit = edit
      let bestEquality2 = equality2
      let bestScore = diff_cleanupSemanticScore_(equality1, edit)
        + diff_cleanupSemanticScore_(edit, equality2)
      while (edit.charAt(0) === equality2.charAt(0)) {
        equality1 += edit.charAt(0)
        edit = edit.substring(1) + equality2.charAt(0)
        equality2 = equality2.substring(1)
        const score = diff_cleanupSemanticScore_(equality1, edit)
          + diff_cleanupSemanticScore_(edit, equality2)
        // The >= encourages trailing rather than leading whitespace on edits.
        if (score >= bestScore) {
          bestScore = score
          bestEquality1 = equality1
          bestEdit = edit
          bestEquality2 = equality2
        }
      }

      if (diffs[pointer - 1][1] !== bestEquality1) {
        // We have an improvement, save it back to the diff.
        if (bestEquality1) {
          diffs[pointer - 1][1] = bestEquality1
        }
        else {
          diffs.splice(pointer - 1, 1)
          pointer--
        }
        diffs[pointer][1] = bestEdit
        if (bestEquality2) {
          diffs[pointer + 1][1] = bestEquality2
        }
        else {
          diffs.splice(pointer + 1, 1)
          pointer--
        }
      }
    }
    pointer++
  }
}

/**
 * Reorder and merge like edit sections.  Merge equalities.
 * Any edit section can move as long as it doesn't cross an equality.
 * @param {!Array.<!diff_match_patch.Diff>} diffs Array of diff tuples.
 */
function diff_cleanupMerge(diffs: Array<Diff>) {
  // Add a dummy entry at the end.
  diffs.push(new Diff(DIFF_EQUAL, ''))
  let pointer = 0
  let count_delete = 0
  let count_insert = 0
  let text_delete = ''
  let text_insert = ''
  let commonlength
  while (pointer < diffs.length) {
    switch (diffs[pointer][0]) {
      case DIFF_INSERT:
        count_insert++
        text_insert += diffs[pointer][1]
        pointer++
        break
      case DIFF_DELETE:
        count_delete++
        text_delete += diffs[pointer][1]
        pointer++
        break
      case DIFF_EQUAL:
        // Upon reaching an equality, check for prior redundancies.
        if (count_delete + count_insert > 1) {
          if (count_delete !== 0 && count_insert !== 0) {
            // Factor out any common prefixies.
            commonlength = diff_commonPrefix(text_insert, text_delete)
            if (commonlength !== 0) {
              if ((pointer - count_delete - count_insert) > 0
                && diffs[pointer - count_delete - count_insert - 1][0]
                === DIFF_EQUAL) {
                diffs[pointer - count_delete - count_insert - 1][1]
                    += text_insert.substring(0, commonlength)
              }
              else {
                diffs.splice(0, 0, new Diff(DIFF_EQUAL, text_insert.substring(0, commonlength)))
                pointer++
              }
              text_insert = text_insert.substring(commonlength)
              text_delete = text_delete.substring(commonlength)
            }
            // Factor out any common suffixies.
            commonlength = diff_commonSuffix(text_insert, text_delete)
            if (commonlength !== 0) {
              diffs[pointer][1] = text_insert.substring(text_insert.length
              - commonlength) + diffs[pointer][1]
              text_insert = text_insert.substring(0, text_insert.length
              - commonlength)
              text_delete = text_delete.substring(0, text_delete.length
              - commonlength)
            }
          }
          // Delete the offending records and add the merged ones.
          pointer -= count_delete + count_insert
          diffs.splice(pointer, count_delete + count_insert)
          if (text_delete.length) {
            diffs.splice(pointer, 0, new Diff(DIFF_DELETE, text_delete))
            pointer++
          }
          if (text_insert.length) {
            diffs.splice(pointer, 0, new Diff(DIFF_INSERT, text_insert))
            pointer++
          }
          pointer++
        }
        else if (pointer !== 0 && diffs[pointer - 1][0] === DIFF_EQUAL) {
          // Merge this equality with the previous one.
          diffs[pointer - 1][1] += diffs[pointer][1]
          diffs.splice(pointer, 1)
        }
        else {
          pointer++
        }
        count_insert = 0
        count_delete = 0
        text_delete = ''
        text_insert = ''
        break
    }
  }
  if (diffs[diffs.length - 1][1] === '')
    diffs.pop() // Remove the dummy entry at the end.

  // Second pass: look for single edits surrounded on both sides by equalities
  // which can be shifted sideways to eliminate an equality.
  // e.g: A<ins>BA</ins>C -> <ins>AB</ins>AC
  let changes = false
  pointer = 1
  // Intentionally ignore the first and last element (don't need checking).
  while (pointer < diffs.length - 1) {
    if (diffs[pointer - 1][0] === DIFF_EQUAL
      && diffs[pointer + 1][0] === DIFF_EQUAL) {
      // This is a single edit surrounded by equalities.
      if (diffs[pointer][1].substring(diffs[pointer][1].length
        - diffs[pointer - 1][1].length) === diffs[pointer - 1][1]) {
        // Shift the edit over the previous equality.
        diffs[pointer][1] = diffs[pointer - 1][1]
        + diffs[pointer][1].substring(0, diffs[pointer][1].length
        - diffs[pointer - 1][1].length)
        diffs[pointer + 1][1] = diffs[pointer - 1][1] + diffs[pointer + 1][1]
        diffs.splice(pointer - 1, 1)
        changes = true
      }
      else if (diffs[pointer][1].substring(0, diffs[pointer + 1][1].length)
        === diffs[pointer + 1][1]) {
        // Shift the edit over the next equality.
        diffs[pointer - 1][1] += diffs[pointer + 1][1]
        diffs[pointer][1]
            = diffs[pointer][1].substring(diffs[pointer + 1][1].length)
            + diffs[pointer + 1][1]
        diffs.splice(pointer + 1, 1)
        changes = true
      }
    }
    pointer++
  }
  // If shifts were made, the diff needs reordering and another shift sweep.
  if (changes)
    diff_cleanupMerge(diffs)
}

export {
  Diff,
  DIFF_EQUAL,
  DIFF_DELETE,
  DIFF_INSERT,
  diff_cleanupSemantic as cleanupSemantic,
}
