/* This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this
 * file, You can obtain one at http://mozilla.org/MPL/2.0/. */

(function() {
"use strict";

var DEBUG_ENABLED = false;
var MATCH_HIGHLIGHT_ACTIVE = "#f19750";
var MATCH_HIGHLIGHT_INACTIVE = "#ffde49";
var SCROLL_INTERVAL_INCREMENT = 5;
var SCROLL_INTERVAL_DURATION = 400;
var SCROLL_OFFSET = 60;

var activeHighlightSpan = null;
var lastSearch;
var scrollInterval;
var activeIndex = 0;
var highlightSpans = [];

function debug(str) {
  if (DEBUG_ENABLED) {
    console.log("FindInPage: " + str);
  }
}

function isElementVisible(elem) {
  return getComputedStyle(elem).visibility !== "hidden";
}

function isRectInViewport(rect) {
  var left = rect.left + document.body.scrollLeft;
  var right = rect.right + document.body.scrollLeft;
  var top = rect.top + document.body.scrollTop;
  var bottom = rect.bottom + document.body.scrollTop;

  return rect.width > 0 &&
         rect.height > 0 &&
         right >= 0 &&
         bottom >= 0 &&
         left <= document.body.scrollWidth &&
         top <= document.body.scrollHeight;
}

function findMatches(text) {
  // For case-insensitive matching.
  var lowerText = text.toLocaleLowerCase();
  var upperText = text.toLocaleUpperCase();

  var matches = [];
  var range = document.createRange();
  var walker = document.createTreeWalker(document.body, NodeFilter.SHOW_TEXT, null, false);
  var textLength = text.length;
  var node;
  while (node = walker.nextNode()) {
    var textContent = node.textContent;
    findString: for (var i = 0; i < textContent.length - textLength + 1; ++i) {
      for (var j = 0; j < textLength; ++j) {
        var nextChar = textContent[i + j];
        if (lowerText[j] !== nextChar && upperText[j] !== nextChar) {
          continue findString;
        }
      }

      // This node is a TextNode, not an Element. Its parent is the nearest Element.
      var element = node.parentNode;

      // Find the rect of just the text for this match.
      range.setStart(node, i);
      range.setEnd(node, i + textLength);
      var textRect = range.getBoundingClientRect();

      // We have a match, but we need to make sure it's visible. The condition
      // below checks the following cases:
      // * If this element or any of its parents has style visibility hidden.
      //   The visibility style is inherited, so we need to check only this
      //   element and not all of its ancestors.
      // * If the highlight will be outside of the page's bounds. We determine
      //   this by comparing the bounds of the text rect.
      // * If the element style display is set to none. display:none collapses
      //   the element's space, so this will again be detected by looking at
      //   the text's rect: if the element is collapsed, the width and height
      //   will be zero.
      if (isElementVisible(element) && isRectInViewport(textRect)) {
        matches.push({ node: node, index: i });

        // Resume searching after this match to prevent overlapping results.
        i += textLength- 1;
      }
    }
  }

  return matches;
}

function flattenNode(node) {
  var parent = node.parentNode;
  if (!parent) {
    return;
  }

  while (node.firstChild) {
    parent.insertBefore(node.firstChild, node);
  }

  node.remove();
  parent.normalize();
}

function clearHighlights() {
  if (highlightSpans.length > 0) {
    for (var span of highlightSpans) {
      flattenNode(span);
    }
    highlightSpans = [];
  }

  activeHighlightSpan = null;
}

function highlightAllMatches(text) {
  debug("Searching: " + text);

  clearHighlights();

  if (!text.trim()) {
    webkit.messageHandlers.findInPageHandler.postMessage({ totalResults: 0 });
    return;
  }

  var range = document.createRange();
  var matches = findMatches(text);
  var highlightTemplate = document.createElement("span");
  highlightTemplate.style.backgroundColor = MATCH_HIGHLIGHT_INACTIVE;

  // If there are multiple matches in the same node, inserting a highlight span before other matches
  // in that node will invalidate other matches since the node itself changes. By iterating through
  // results in reverse, we highlight matches last in the node first so earlier matches are unaffected.
  for (var i = matches.length - 1; i >= 0; --i) {
    var match = matches[i];
    var highlight = highlightTemplate.cloneNode();

    range.setStart(match.node, match.index);
    range.setEnd(match.node, match.index + text.length);
    range.surroundContents(highlight);
    highlightSpans.unshift(highlight);
  }

  debug(matches.length + " highlighted rects created!");
  webkit.messageHandlers.findInPageHandler.postMessage({ totalResults: matches.length });
}

function getIDForRect(rect) {
  return rect.top + "," + rect.bottom + "," + rect.left + "," + rect.right;
}

function updateActiveHighlight() {
  // Reset the color of the previous highlight.
  if (activeHighlightSpan) {
    activeHighlightSpan.style.backgroundColor = MATCH_HIGHLIGHT_INACTIVE;
  }

  if (!highlightSpans.length) {
    return;
  }

  activeHighlightSpan = highlightSpans[activeIndex];
  activeHighlightSpan.style.backgroundColor = MATCH_HIGHLIGHT_ACTIVE;

  // Find the position of the element centered on the screen, then scroll to it.
  var rect = activeHighlightSpan.getBoundingClientRect();
  var top = SCROLL_OFFSET + rect.top + scrollY - window.innerHeight / 2;
  var left = rect.left + scrollX - window.innerWidth / 2;
  left = clamp(left, 0, document.body.scrollWidth);
  top = clamp(top, 0, document.body.scrollHeight);
  scrollToSelection(left, top, SCROLL_INTERVAL_DURATION);
  debug("Scrolled to: " + left + ", " + top);
}

function scrollToSelection(left, top, duration) {
  var time = 0;
  var startX = scrollX;
  var startY = scrollY;
  clearInterval(scrollInterval);
  scrollInterval = setInterval(function() {
    var xStep = easeOutCubic(time, startX, left - startX, duration);
    var yStep = easeOutCubic(time, startY, top - startY, duration);
    window.scrollTo(xStep, yStep);
    time += SCROLL_INTERVAL_INCREMENT;
    if (time >= duration) {
      clearInterval(scrollInterval);
    }                 
  }, SCROLL_INTERVAL_INCREMENT);
}

function easeOutCubic(currentTime, startValue, changeInValue, duration) {
  return changeInValue * (Math.pow(currentTime / duration - 1, 3) + 1) + startValue;
}

function clamp(number, min, max) {
  return Math.max(min, Math.min(number, max));
}

function updateSearch(text) {
  if (lastSearch == text) {
    // The text is the same, so we're either finding either the next or previous result.
    var totalResults = highlightSpans.length;
    activeIndex = (activeIndex + totalResults) % totalResults;
  } else {
    // Store the current active rect to decide which new match should be active.
    var activeHighlightRect = null;
    if (activeHighlightSpan) {
      activeHighlightRect = activeHighlightSpan.getBoundingClientRect();
    }

    // The search text changed, so scan the page for new results.
    highlightAllMatches(text);

    // If we found a match at or after the last match, use that position
    // instead of starting again from the top.
    activeIndex = 0;
    if (activeHighlightRect) {
      for (var i = 0; i < highlightSpans.length; i++) {
        var highlight = highlightSpans[i];
        var highlightRect = highlight.getBoundingClientRect();
        if ((highlightRect.top == activeHighlightRect.top && highlightRect.left >= activeHighlightRect.left) ||
            (highlightRect.top > activeHighlightRect.top)) {
          activeIndex = i;
          break;
        }
      }
    }

    lastSearch = text;
  }

  // Update the UI with the current match index.
  var currentResult = highlightSpans.length ? activeIndex + 1 : 0;
  webkit.messageHandlers.findInPageHandler.postMessage({ currentResult: currentResult });

  updateActiveHighlight();
}

if (!window.__firefox__) {
  Object.defineProperty(window, '__firefox__', {
    enumerable: false,
    configurable: false,
    writable: false,
    value: {}
  });
}

Object.defineProperty(window.__firefox__, 'find', {
  enumerable: false,
  configurable: false,
  writable: false,
  value: function(text) {
    updateSearch(text);
  }
});

Object.defineProperty(window.__firefox__, 'findNext', {
  enumerable: false,
  configurable: false,
  writable: false,
  value: function(text) {
    activeIndex++;
    updateSearch(text);
  }
});

Object.defineProperty(window.__firefox__, 'findPrevious', {
  enumerable: false,
  configurable: false,
  writable: false,
  value: function(text) {
    activeIndex--;
    updateSearch(text);
  }
});

Object.defineProperty(window.__firefox__, 'findDone', {
  enumerable: false,
  configurable: false,
  writable: false,
  value: function() {
    clearHighlights();
    lastSearch = null;
  }
});

})();