// Copyright 2019 the V8 project authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

namespace string {
  macro TryFastStringCompareSequence(
      string: String, searchStr: String, start: Number,
      searchLength: Smi): Boolean labels Slow {
    const directString = Cast<DirectString>(string) otherwise Slow;
    const directSearchStr = Cast<DirectString>(searchStr) otherwise Slow;
    const stringIndexSmi: Smi = Cast<Smi>(start) otherwise Slow;

    let searchIndex: intptr = 0;
    let stringIndex = Convert<intptr>(stringIndexSmi);
    const searchLengthInteger = Convert<intptr>(searchLength);

    while (searchIndex < searchLengthInteger) {
      if (StringCharCodeAt(directSearchStr, searchIndex) !=
          StringCharCodeAt(directString, stringIndex)) {
        return False;
      }

      searchIndex++;
      stringIndex++;
    }
    return True;
  }

  // https://tc39.github.io/ecma262/#sec-string.prototype.endswith
  transitioning javascript builtin StringPrototypeEndsWith(
      js-implicit context: Context, receiver: Object)(...arguments): Boolean {
    const searchString: Object = arguments[0];
    const endPosition: Object = arguments[1];
    const kBuiltinName: constexpr string = 'String.prototype.endsWith';

    // 1. Let O be ? RequireObjectCoercible(this value).
    const object: Object = RequireObjectCoercible(receiver, kBuiltinName);

    // 2. Let S be ? ToString(O).
    const string: String = ToString_Inline(context, object);

    // 3. Let isRegExp be ? IsRegExp(searchString).
    // 4. If isRegExp is true, throw a TypeError exception.
    if (IsRegExp(searchString)) {
      ThrowTypeError(kFirstArgumentNotRegExp, kBuiltinName);
    }

    // 5. Let searchStr be ? ToString(searchString).
    const searchStr: String = ToString_Inline(context, searchString);

    // 6. Let len be the length of S.
    const len: Number = string.length_smi;

    // 7. If endPosition is undefined, let pos be len,
    // else let pos be ? ToInteger(endPosition).
    const pos: Number = (endPosition == Undefined) ?
        len :
        ToInteger_Inline(context, endPosition);

    // 8. Let end be min(max(pos, 0), len).
    const end: Number = NumberMin(NumberMax(pos, 0), len);

    // 9. Let searchLength be the length of searchStr.
    const searchLength: Smi = searchStr.length_smi;

    // 10. Let start be end - searchLength.
    const start = end - searchLength;

    // 11. If start is less than 0, return false.
    if (start < 0) return False;

    // 12. If the sequence of code units of S starting at start of length
    // searchLength is the same as the full code unit sequence of searchStr,
    // return true.
    // 13. Otherwise, return false.
    try {
      // Fast Path: If both strings are direct and relevant indices are Smis.
      return TryFastStringCompareSequence(
          string, searchStr, start, searchLength) otherwise Slow;
    }
    label Slow {
      // Slow Path: If either of the string is indirect, bail into runtime.
      return StringCompareSequence(context, string, searchStr, start);
    }
  }
}