From e39ee041514bd4daa1fe9e9e059bb5765cdf894a Mon Sep 17 00:00:00 2001
From: Ajay Bura <32841439+ajbura@users.noreply.github.com>
Date: Sun, 5 May 2024 18:25:49 +0530
Subject: [PATCH] add ASCIILexicalTable algorithms

---
 src/app/utils/ASCIILexicalTable.ts | 293 +++++++++++++++++++++++++++++
 1 file changed, 293 insertions(+)
 create mode 100644 src/app/utils/ASCIILexicalTable.ts

diff --git a/src/app/utils/ASCIILexicalTable.ts b/src/app/utils/ASCIILexicalTable.ts
new file mode 100644
index 00000000..c9001876
--- /dev/null
+++ b/src/app/utils/ASCIILexicalTable.ts
@@ -0,0 +1,293 @@
+export class ASCIILexicalTable {
+  readonly startCode: number;
+
+  readonly endCode: number;
+
+  readonly maxStrWidth: number;
+
+  private readonly widthToSize: number[];
+
+  private readonly rangeCount: (i: number, j: number) => number;
+
+  constructor(startCode: number, endCode: number, maxStrWidth: number) {
+    if (startCode > endCode) {
+      throw new Error('Invalid ASCII code! startCode is greater than endCode.');
+    }
+    if (startCode < 0 || endCode > 128) {
+      throw new Error('Invalid ASCII code range!');
+    }
+
+    if (maxStrWidth <= 0) {
+      throw new Error('Invalid max string width!');
+    }
+
+    this.maxStrWidth = maxStrWidth;
+    this.startCode = startCode;
+    this.endCode = endCode;
+
+    /**
+     * @param i smaller - inclusive
+     * @param j larger - inclusive
+     * @returns number
+     */
+    this.rangeCount = (i: number, j: number): number => j - i + 1;
+
+    this.widthToSize = [];
+    this.populateWidthToSize();
+
+    if (this.size() > Number.MAX_SAFE_INTEGER) {
+      console.warn(
+        `[!] Warning: ASCIILexicalTable size is larger than the Number.MAX_SAFE_INTEGER: ${this.size()} > ${
+          Number.MAX_SAFE_INTEGER
+        }`
+      );
+    }
+  }
+
+  private populateWidthToSize() {
+    const chars = this.rangeCount(this.startCode, this.endCode);
+    for (let i = 0, count = 0; i < this.maxStrWidth; i += 1) {
+      count = count * chars + chars;
+      this.widthToSize[i] = count;
+    }
+  }
+
+  private getWidthToSize(width: number): number {
+    return this.widthToSize[width - 1];
+  }
+
+  first(): string {
+    return String.fromCharCode(this.startCode);
+  }
+
+  last(): string {
+    let str = '';
+    for (let i = 0; i < this.maxStrWidth; i += 1) {
+      str += String.fromCharCode(this.endCode);
+    }
+    return str;
+  }
+
+  hasIndex(index: number): boolean {
+    return index >= 0 && index < this.size();
+  }
+
+  has(str: string): boolean {
+    if (str.length === 0 || str.length > this.maxStrWidth) {
+      return false;
+    }
+
+    let charCode: number;
+    for (let i = 0; i < str.length; i += 1) {
+      charCode = str.charCodeAt(i);
+      if (charCode < this.startCode || charCode > this.endCode) {
+        return false;
+      }
+    }
+    return true;
+  }
+
+  size(): number {
+    return this.getWidthToSize(this.maxStrWidth);
+  }
+
+  index(str: string): number {
+    if (!this.has(str)) {
+      return -1;
+    }
+
+    let index = 0;
+    const chars = this.rangeCount(this.startCode, this.endCode);
+
+    for (let i = 0; i < this.maxStrWidth; i += 1) {
+      const code = str.charCodeAt(i);
+
+      if (Number.isNaN(code)) {
+        return index;
+      }
+
+      const opStrWidth = this.maxStrWidth - i;
+      const opStrTableSize = this.getWidthToSize(opStrWidth);
+
+      const segmentSize = opStrTableSize / chars;
+
+      const codeIndex = code - this.startCode;
+      const emptyCount = i === 0 ? 0 : 1;
+
+      index += segmentSize * codeIndex + emptyCount;
+    }
+
+    return index;
+  }
+
+  get(index: number): string | undefined {
+    if (!this.hasIndex(index)) {
+      return undefined;
+    }
+
+    let str = '';
+    const chars = this.rangeCount(this.startCode, this.endCode);
+
+    for (let toIndex = index, i = 0; i < this.maxStrWidth; i += 1) {
+      const opStrWidth = this.maxStrWidth - i;
+      const opStrTableSize = this.getWidthToSize(opStrWidth);
+
+      const segmentSize = opStrTableSize / chars;
+
+      const segmentIndex = Math.floor(toIndex / segmentSize);
+      str += String.fromCharCode(this.startCode + segmentIndex);
+
+      toIndex -= segmentIndex * segmentSize;
+      if (toIndex === 0) {
+        break;
+      }
+      toIndex -= 1;
+    }
+
+    return str;
+  }
+
+  previous(str: string): string | undefined {
+    if (!this.has(str)) return undefined;
+    let prev = str;
+    const lastCode = prev.charCodeAt(prev.length - 1);
+    prev = prev.slice(0, prev.length - 1);
+
+    if (lastCode === this.startCode) {
+      if (prev.length === 0) return undefined;
+      return prev;
+    }
+
+    prev += String.fromCharCode(lastCode - 1);
+    while (prev.length < this.maxStrWidth) {
+      prev += String.fromCharCode(this.endCode);
+    }
+    return prev;
+  }
+
+  next(str: string): string | undefined {
+    if (!this.has(str)) return undefined;
+    let next = str;
+
+    if (next.length < this.maxStrWidth) {
+      next += String.fromCharCode(this.startCode);
+      return next;
+    }
+
+    for (let i = next.length - 1; i >= 0; i -= 1) {
+      const lastCode = next.charCodeAt(i);
+      if (lastCode !== this.endCode) {
+        next = next.slice(0, i) + String.fromCharCode(lastCode + 1);
+        return next;
+      }
+      next = next.slice(0, i);
+    }
+    return undefined;
+  }
+
+  between(i: string, j: string): string | undefined {
+    if (!this.has(i) || !this.has(j)) {
+      return undefined;
+    }
+
+    const centerIndex = Math.floor((this.index(i) + this.index(j)) / 2);
+
+    const b = this.get(centerIndex);
+    if (b === i || b === j) return undefined;
+    return b;
+  }
+}
+
+// const printLex = (lex: ASCIILexicalTable) => {
+//   const padRight = (s: string, maxWidth: number, padding: string): string => {
+//     let ns = s;
+//     for (let i = s.length; i < maxWidth; i += 1) {
+//       ns += padding;
+//     }
+//     return ns;
+//   };
+
+//   const formattedLine = (n: number, item: string): string =>
+//     `|${padRight(n.toString(), lex.size().toString().length, ' ')}|${item}|`;
+
+//   const hr = `|${padRight('-', lex.size().toString().length, '-')}|${padRight(
+//     '-',
+//     lex.maxStrWidth,
+//     '-'
+//   )}|`;
+
+//   console.log(`All lexicographic string combination in order.`);
+//   console.log(`Start ASCII code: "${lex.startCode}"`);
+//   console.log(`End ASCII code: "${lex.endCode}"`);
+//   console.log(`Max string width: ${lex.maxStrWidth}`);
+//   console.log(`Total String Combination Count: ${lex.size()}\n`);
+//   console.log('Table:');
+//   console.log(hr);
+//   for (let i = 0; i < lex.size(); i += 1) {
+//     const str = lex.get(i);
+//     if (str) {
+//       console.log(formattedLine(i, padRight(str, lex.maxStrWidth, '_')));
+//     }
+//   }
+//   console.log(hr);
+// };
+
+// console.log('\n');
+
+// const lex = new ASCIILexicalTable('a'.charCodeAt(0), 'c'.charCodeAt(0), 5);
+// printLex(lex);
+// console.log(lex.between('a', 'aacb'));
+// console.log(lex.get(123) === 'baa');
+// console.log(lex.get(11) === 'aaac');
+
+// const lex4 = new ASCIILexicalTable(' '.charCodeAt(0), '~'.charCodeAt(0), 5);
+// console.log('Size: ', lex4.size());
+// console.log('Between: ', lex4.between('7g7g5', 'caccc'));
+// printLex(lex4);
+
+// console.log('\n');
+
+// const perf = () => {
+//   const loopLength = 99999;
+//   const lexT = new ASCIILexicalTable('a'.charCodeAt(0), 'z'.charCodeAt(0), 9);
+//   console.log(lexT.size());
+//   const str = 'bcbba';
+//   const strI = lexT.index(str);
+//   console.log('================');
+//   console.time('index');
+//   console.log(lexT.index(str));
+//   for (let i = 0; i < loopLength; i += 1) {
+//     lexT.index(str);
+//   }
+//   console.timeEnd('index');
+//   console.log('================');
+//   console.time('get');
+//   console.log(lexT.get(strI));
+//   for (let i = 0; i < loopLength; i += 1) {
+//     lexT.get(strI);
+//   }
+//   console.timeEnd('get');
+//   console.log('================');
+//   console.time('previous');
+//   console.log(lexT.previous(str));
+//   for (let i = 0; i < loopLength; i += 1) {
+//     lexT.previous(str);
+//   }
+//   console.timeEnd('previous');
+//   console.log('================');
+//   console.time('next');
+//   console.log(lexT.next(str));
+//   for (let i = 0; i < loopLength; i += 1) {
+//     lexT.next(str);
+//   }
+//   console.timeEnd('next');
+//   console.log('================');
+//   console.time('between');
+//   console.log(lexT.between(str, 'cbbca'));
+//   for (let i = 0; i < loopLength; i += 1) {
+//     lexT.between(str, 'cbbca');
+//   }
+//   console.timeEnd('between');
+// };
+
+// perf();