/**
 * Copyright (c) Microsoft Corporation.
 *
 * 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.
 */

export function compressCallLog(log: string[]): string[] {
  const lines: string[] = [];

  for (const block of findRepeatedSubsequences(log)) {
    for (let i = 0; i < block.sequence.length; i++) {
      const line = block.sequence[i];
      const leadingWhitespace = line.match(/^\s*/);
      const whitespacePrefix = '  ' + leadingWhitespace?.[0] || '';
      const countPrefix = `${block.count} × `;
      if (block.count > 1 && i === 0)
        lines.push(whitespacePrefix + countPrefix + line.trim());
      else if (block.count > 1)
        lines.push(whitespacePrefix + ' '.repeat(countPrefix.length - 2) + '- ' + line.trim());
      else
        lines.push(whitespacePrefix + '- ' + line.trim());
    }
  }
  return lines;
}

function findRepeatedSubsequences(s: string[]): { sequence: string[]; count: number }[] {
  const n = s.length;
  const result = [];
  let i = 0;

  const arraysEqual = (a1: string[], a2: string[]) => {
    if (a1.length !== a2.length)
      return false;
    for (let j = 0; j < a1.length; j++) {
      if (a1[j] !== a2[j])
        return false;
    }

    return true;
  };

  while (i < n) {
    let maxRepeatCount = 1;
    let maxRepeatSubstr = [s[i]]; // Initialize with the element at index i
    let maxRepeatLength = 1;

    // Try substrings of length from 1 to the remaining length of the array
    for (let p = 1; p <= n - i; p++) {
      const substr = s.slice(i, i + p); // Extract substring as array
      let k = 1;

      // Count how many times the substring repeats consecutively
      while (
        i + p * k <= n &&
        arraysEqual(s.slice(i + p * (k - 1), i + p * k), substr)
      )
        k += 1;

      k -= 1; // Adjust k since it increments one extra time in the loop

      // Update the maximal repeating substring if necessary
      if (k > 1 && (k * p) > (maxRepeatCount * maxRepeatLength)) {
        maxRepeatCount = k;
        maxRepeatSubstr = substr;
        maxRepeatLength = p;
      }
    }

    // Record the substring and its count
    result.push({ sequence: maxRepeatSubstr, count: maxRepeatCount });
    i += maxRepeatLength * maxRepeatCount; // Move index forward
  }

  return result;
}

export const findRepeatedSubsequencesForTest = findRepeatedSubsequences;