/**
 * Copyright (c) 2017 The xterm.js authors. All rights reserved.
 * @license MIT
 */

import { Terminal, IDisposable, ITerminalAddon, ISelectionPosition } from 'xterm';

export interface ISearchOptions {
  regex?: boolean;
  wholeWord?: boolean;
  caseSensitive?: boolean;
  incremental?: boolean;
}

export interface ISearchPosition {
  startCol: number;
  startRow: number;
}

export interface ISearchResult {
  term: string;
  col: number;
  row: number;
}

const NON_WORD_CHARACTERS = ' ~!@#$%^&*()+`-=[]{}|\;:"\',./<>?';
const LINES_CACHE_TIME_TO_LIVE = 15 * 1000; // 15 secs

export class SearchAddon implements ITerminalAddon {
  private _terminal: Terminal | undefined;

  /**
   * translateBufferLineToStringWithWrap is a fairly expensive call.
   * We memoize the calls into an array that has a time based ttl.
   * _linesCache is also invalidated when the terminal cursor moves.
   */
  private _linesCache: string[] | undefined;
  private _linesCacheTimeoutId = 0;
  private _cursorMoveListener: IDisposable | undefined;
  private _resizeListener: IDisposable | undefined;

  public activate(terminal: Terminal): void {
    this._terminal = terminal;
  }

  public dispose(): void { }

  /**
   * Find the next instance of the term, then scroll to and select it. If it
   * doesn't exist, do nothing.
   * @param term The search term.
   * @param searchOptions Search options.
   * @return Whether a result was found.
   */
  public findNext(term: string, searchOptions?: ISearchOptions): boolean {
    if (!this._terminal) {
      throw new Error('Cannot use addon until it has been loaded');
    }

    if (!term || term.length === 0) {
      this._terminal.clearSelection();
      return false;
    }

    let startCol = 0;
    let startRow = 0;
    let currentSelection: ISelectionPosition | undefined;
    if (this._terminal.hasSelection()) {
      const incremental = searchOptions ? searchOptions.incremental : false;
      // Start from the selection end if there is a selection
      // For incremental search, use existing row
      currentSelection = this._terminal.getSelectionPosition()!;
      startRow = incremental ? currentSelection.startRow : currentSelection.endRow;
      startCol = incremental ? currentSelection.startColumn : currentSelection.endColumn;
    }

    this._initLinesCache();

    const searchPosition: ISearchPosition = {
      startRow,
      startCol
    };

    // Search startRow
    let result = this._findInLine(term, searchPosition, searchOptions);

    // Search from startRow + 1 to end
    if (!result) {

      for (let y = startRow + 1; y < this._terminal.buffer.active.baseY + this._terminal.rows; y++) {
        searchPosition.startRow = y;
        searchPosition.startCol = 0;
        // If the current line is wrapped line, increase index of column to ignore the previous scan
        // Otherwise, reset beginning column index to zero with set new unwrapped line index
        result = this._findInLine(term, searchPosition, searchOptions);
        if (result) {
          break;
        }
      }
    }
    // If we hit the bottom and didn't search from the very top wrap back up
    if (!result && startRow !== 0) {
      for (let y = 0; y < startRow; y++) {
        searchPosition.startRow = y;
        searchPosition.startCol = 0;
        result = this._findInLine(term, searchPosition, searchOptions);
        if (result) {
          break;
        }
      }
    }

    // If there is only one result, wrap back and return selection if it exists.
    if (!result && currentSelection) {
      searchPosition.startRow = currentSelection.startRow;
      searchPosition.startCol = 0;
      result = this._findInLine(term, searchPosition, searchOptions);
    }

    // Set selection and scroll if a result was found
    return this._selectResult(result);
  }

  /**
   * Find the previous instance of the term, then scroll to and select it. If it
   * doesn't exist, do nothing.
   * @param term The search term.
   * @param searchOptions Search options.
   * @return Whether a result was found.
   */
  public findPrevious(term: string, searchOptions?: ISearchOptions): boolean {
    if (!this._terminal) {
      throw new Error('Cannot use addon until it has been loaded');
    }

    if (!term || term.length === 0) {
      this._terminal.clearSelection();
      return false;
    }

    const isReverseSearch = true;
    let startRow = this._terminal.buffer.active.baseY + this._terminal.rows;
    let startCol = this._terminal.cols;
    let result: ISearchResult | undefined;
    const incremental = searchOptions ? searchOptions.incremental : false;
    let currentSelection: ISelectionPosition | undefined;
    if (this._terminal.hasSelection()) {
      currentSelection = this._terminal.getSelectionPosition()!;
      // Start from selection start if there is a selection
      startRow = currentSelection.startRow;
      startCol = currentSelection.startColumn;
    }

    this._initLinesCache();
    const searchPosition: ISearchPosition = {
      startRow,
      startCol
    };

    if (incremental) {
      result = this._findInLine(term, searchPosition, searchOptions, false);
      if (!(result && result.row === startRow && result.col === startCol)) {
        result = this._findInLine(term, searchPosition, searchOptions, true);
      }
    } else {
      result = this._findInLine(term, searchPosition, searchOptions, isReverseSearch);
    }

    // Search from startRow - 1 to top
    if (!result) {
      searchPosition.startCol = Math.max(searchPosition.startCol, this._terminal.cols);
      for (let y = startRow - 1; y >= 0; y--) {
        searchPosition.startRow = y;
        result = this._findInLine(term, searchPosition, searchOptions, isReverseSearch);
        if (result) {
          break;
        }
      }
    }
    // If we hit the top and didn't search from the very bottom wrap back down
    if (!result && startRow !== (this._terminal.buffer.active.baseY + this._terminal.rows)) {
      for (let y = (this._terminal.buffer.active.baseY + this._terminal.rows); y >= startRow; y--) {
        searchPosition.startRow = y;
        result = this._findInLine(term, searchPosition, searchOptions, isReverseSearch);
        if (result) {
          break;
        }
      }
    }

    // If there is only one result, return true.
    if (!result && currentSelection) return true;

    // Set selection and scroll if a result was found
    return this._selectResult(result);
  }

  /**
   * Sets up a line cache with a ttl
   */
  private _initLinesCache(): void {
    const terminal = this._terminal!;
    if (!this._linesCache) {
      this._linesCache = new Array(terminal.buffer.active.length);
      this._cursorMoveListener = terminal.onCursorMove(() => this._destroyLinesCache());
      this._resizeListener = terminal.onResize(() => this._destroyLinesCache());
    }

    window.clearTimeout(this._linesCacheTimeoutId);
    this._linesCacheTimeoutId = window.setTimeout(() => this._destroyLinesCache(), LINES_CACHE_TIME_TO_LIVE);
  }

  private _destroyLinesCache(): void {
    this._linesCache = undefined;
    if (this._cursorMoveListener) {
      this._cursorMoveListener.dispose();
      this._cursorMoveListener = undefined;
    }
    if (this._resizeListener) {
      this._resizeListener.dispose();
      this._resizeListener = undefined;
    }
    if (this._linesCacheTimeoutId) {
      window.clearTimeout(this._linesCacheTimeoutId);
      this._linesCacheTimeoutId = 0;
    }
  }

  /**
   * A found substring is a whole word if it doesn't have an alphanumeric character directly adjacent to it.
   * @param searchIndex starting indext of the potential whole word substring
   * @param line entire string in which the potential whole word was found
   * @param term the substring that starts at searchIndex
   */
  private _isWholeWord(searchIndex: number, line: string, term: string): boolean {
    return (((searchIndex === 0) || (NON_WORD_CHARACTERS.indexOf(line[searchIndex - 1]) !== -1)) &&
      (((searchIndex + term.length) === line.length) || (NON_WORD_CHARACTERS.indexOf(line[searchIndex + term.length]) !== -1)));
  }

  /**
   * Searches a line for a search term. Takes the provided terminal line and searches the text line, which may contain
   * subsequent terminal lines if the text is wrapped. If the provided line number is part of a wrapped text line that
   * started on an earlier line then it is skipped since it will be properly searched when the terminal line that the
   * text starts on is searched.
   * @param term The search term.
   * @param position The position to start the search.
   * @param searchOptions Search options.
   * @return The search result if it was found.
   */
  protected _findInLine(term: string, searchPosition: ISearchPosition, searchOptions: ISearchOptions = {}, isReverseSearch: boolean = false): ISearchResult | undefined {
    const terminal = this._terminal!;
    let row = searchPosition.startRow;
    const col = searchPosition.startCol;

    // Ignore wrapped lines, only consider on unwrapped line (first row of command string).
    const firstLine = terminal.buffer.active.getLine(row);
    if (firstLine && firstLine.isWrapped) {
      if (isReverseSearch) {
        searchPosition.startCol += terminal.cols;
        return;
      }

      // This will iterate until we find the line start.
      // When we find it, we will search using the calculated start column.
      searchPosition.startRow--;
      searchPosition.startCol += terminal.cols;
      return this._findInLine(term, searchPosition, searchOptions);
    }
    let stringLine = this._linesCache ? this._linesCache[row] : void 0;
    if (stringLine === void 0) {
      stringLine = this._translateBufferLineToStringWithWrap(row, true);
      if (this._linesCache) {
        this._linesCache[row] = stringLine;
      }
    }

    const searchTerm = searchOptions.caseSensitive ? term : term.toLowerCase();
    const searchStringLine = searchOptions.caseSensitive ? stringLine : stringLine.toLowerCase();

    let resultIndex = -1;
    if (searchOptions.regex) {
      const searchRegex = RegExp(searchTerm, 'g');
      let foundTerm: RegExpExecArray | null;
      if (isReverseSearch) {
        // This loop will get the resultIndex of the _last_ regex match in the range 0..col
        while (foundTerm = searchRegex.exec(searchStringLine.slice(0, col))) {
          resultIndex = searchRegex.lastIndex - foundTerm[0].length;
          term = foundTerm[0];
          searchRegex.lastIndex -= (term.length - 1);
        }
      } else {
        foundTerm = searchRegex.exec(searchStringLine.slice(col));
        if (foundTerm && foundTerm[0].length > 0) {
          resultIndex = col + (searchRegex.lastIndex - foundTerm[0].length);
          term = foundTerm[0];
        }
      }
    } else {
      if (isReverseSearch) {
        if (col - searchTerm.length >= 0) {
          resultIndex = searchStringLine.lastIndexOf(searchTerm, col - searchTerm.length);
        }
      } else {
        resultIndex = searchStringLine.indexOf(searchTerm, col);
      }
    }

    if (resultIndex >= 0) {
      // Adjust the row number and search index if needed since a "line" of text can span multiple rows
      if (resultIndex >= terminal.cols) {
        row += Math.floor(resultIndex / terminal.cols);
        resultIndex = resultIndex % terminal.cols;
      }
      if (searchOptions.wholeWord && !this._isWholeWord(resultIndex, searchStringLine, term)) {
        return;
      }

      const line = terminal.buffer.active.getLine(row);

      if (line) {
        for (let i = 0; i < resultIndex; i++) {
          const cell = line.getCell(i);
          if (!cell) {
            break;
          }
          // Adjust the searchIndex to normalize emoji into single chars
          const char = cell.getChars();
          if (char.length > 1) {
            resultIndex -= char.length - 1;
          }
          // Adjust the searchIndex for empty characters following wide unicode
          // chars (eg. CJK)
          const charWidth = cell.getWidth();
          if (charWidth === 0) {
            resultIndex++;
          }
        }
      }
      return {
        term,
        col: resultIndex,
        row
      };
    }
  }

  /**
   * Translates a buffer line to a string, including subsequent lines if they are wraps.
   * Wide characters will count as two columns in the resulting string. This
   * function is useful for getting the actual text underneath the raw selection
   * position.
   * @param line The line being translated.
   * @param trimRight Whether to trim whitespace to the right.
   */
  private _translateBufferLineToStringWithWrap(lineIndex: number, trimRight: boolean): string {
    const terminal = this._terminal!;
    let lineString = '';
    let lineWrapsToNext: boolean;

    do {
      const nextLine = terminal.buffer.active.getLine(lineIndex + 1);
      lineWrapsToNext = nextLine ? nextLine.isWrapped : false;
      const line = terminal.buffer.active.getLine(lineIndex);
      if (!line) {
        break;
      }
      lineString += line.translateToString(!lineWrapsToNext && trimRight).substring(0, terminal.cols);
      lineIndex++;
    } while (lineWrapsToNext);

    return lineString;
  }

  /**
   * Selects and scrolls to a result.
   * @param result The result to select.
   * @return Whethera result was selected.
   */
  private _selectResult(result: ISearchResult | undefined): boolean {
    const terminal = this._terminal!;
    if (!result) {
      terminal.clearSelection();
      return false;
    }
    terminal.select(result.col, result.row, result.term.length);
    // If it is not in the viewport then we scroll else it just gets selected
    if (result.row >= (terminal.buffer.active.viewportY + terminal.rows) || result.row < terminal.buffer.active.viewportY) {
      let scroll = result.row - terminal.buffer.active.viewportY;
      scroll = scroll - Math.floor(terminal.rows / 2);
      terminal.scrollLines(scroll);
    }
    return true;
  }
}