// CodeMirror, copyright (c) by Marijn Haverbeke and others
// Distributed under an MIT license: http://codemirror.net/LICENSE
/**
 * CodeMirror 代码折叠核心功能
 * 实现折叠/展开的基础逻辑、命令（如 toggleFold/foldAll）、扩展接口，支持自定义配置
 */
(function(mod) {
  if (typeof exports == "object" && typeof module == "object") // CommonJS
    mod(require("../../lib/codemirror"));
  else if (typeof define == "function" && define.amd) // AMD
    define(["../../lib/codemirror"], mod);
  else // Plain browser env
    mod(CodeMirror);
})(function(CodeMirror) {
  "use strict";
  /**
   * 执行代码折叠/展开操作（核心内部函数）
   * @param {CodeMirror} cm - 编辑器实例
   * @param {CodeMirror.Pos/number} pos - 折叠起始位置（行号或 Pos 对象）
   * @param {Object/Function} options - 配置项或折叠范围查找函数
   * @param {string} [force] - 强制操作类型（"fold"=强制折叠，"unfold"=强制展开，默认自动切换）
   */
  function doFold(cm, pos, options, force) {
    if (options && options.call) {
      var finder = options;
      options = null;
    } else {
      var finder = getOption(cm, options, "rangeFinder");
    }
    if (typeof pos == "number") pos = CodeMirror.Pos(pos, 0);
    var minSize = getOption(cm, options, "minFoldSize");
    /**
     * 查找可折叠的范围（内部子函数）
     * @param {boolean} allowFolded - 是否允许处理已折叠的块（true=已折叠则先展开）
     * @return {Object|null} 可折叠范围（含 from/to，无则返回 null）
     */
    function getRange(allowFolded) {
      var range = finder(cm, pos);
      if (!range || range.to.line - range.from.line < minSize) return null;
      var marks = cm.findMarksAt(range.from);
      for (var i = 0; i < marks.length; ++i) {
        if (marks[i].__isFold && force !== "fold") {
          if (!allowFolded) return null;
          range.cleared = true;
          marks[i].clear();
        }
      }
      return range;
    }

    var range = getRange(true);
    if (getOption(cm, options, "scanUp")) while (!range && pos.line > cm.firstLine()) {
      pos = CodeMirror.Pos(pos.line - 1, 0);
      range = getRange(false);
    }
    if (!range || range.cleared || force === "unfold") return;

    var myWidget = makeWidget(cm, options);
    CodeMirror.on(myWidget, "mousedown", function(e) {
      myRange.clear();
      CodeMirror.e_preventDefault(e);
    });
    var myRange = cm.markText(range.from, range.to, {
      replacedWith: myWidget,
      clearOnEnter: true,
      __isFold: true
    });
    myRange.on("clear", function(from, to) {
      CodeMirror.signal(cm, "unfold", cm, from, to);
    });
    CodeMirror.signal(cm, "fold", cm, range.from, range.to);
  }
  /**
   * 创建折叠标识（Widget）（内部工具函数）
   * @param {CodeMirror} cm - 编辑器实例
   * @param {Object} options - 配置项（含 widget 配置）
   * @return {HTMLElement} 折叠标识 DOM 元素
   */
  function makeWidget(cm, options) {
    var widget = getOption(cm, options, "widget");
    if (typeof widget == "string") {
      var text = document.createTextNode(widget);
      widget = document.createElement("span");
      widget.appendChild(text);
      widget.className = "CodeMirror-foldmarker";
    }
    return widget;
  }

  // Clumsy backwards-compatible interface
  CodeMirror.newFoldFunction = function(rangeFinder, widget) {
    return function(cm, pos) { doFold(cm, pos, {rangeFinder: rangeFinder, widget: widget}); };
  };

  // New-style interface
  CodeMirror.defineExtension("foldCode", function(pos, options, force) {
    doFold(this, pos, options, force);
  });

  CodeMirror.defineExtension("isFolded", function(pos) {
    var marks = this.findMarksAt(pos);
    for (var i = 0; i < marks.length; ++i)
      if (marks[i].__isFold) return true;
  });

  CodeMirror.commands.toggleFold = function(cm) {
    cm.foldCode(cm.getCursor());
  };
  CodeMirror.commands.fold = function(cm) {
    cm.foldCode(cm.getCursor(), null, "fold");
  };
  CodeMirror.commands.unfold = function(cm) {
    cm.foldCode(cm.getCursor(), null, "unfold");
  };
  CodeMirror.commands.foldAll = function(cm) {
    cm.operation(function() {
      for (var i = cm.firstLine(), e = cm.lastLine(); i <= e; i++)
        cm.foldCode(CodeMirror.Pos(i, 0), null, "fold");
    });
  };
  CodeMirror.commands.unfoldAll = function(cm) {
    cm.operation(function() {
      for (var i = cm.firstLine(), e = cm.lastLine(); i <= e; i++)
        cm.foldCode(CodeMirror.Pos(i, 0), null, "unfold");
    });
  };

  CodeMirror.registerHelper("fold", "combine", function() {
    var funcs = Array.prototype.slice.call(arguments, 0);
    return function(cm, start) {
      for (var i = 0; i < funcs.length; ++i) {
        var found = funcs[i](cm, start);
        if (found) return found;
      }
    };
  });

  CodeMirror.registerHelper("fold", "auto", function(cm, start) {
    var helpers = cm.getHelpers(start, "fold");
    for (var i = 0; i < helpers.length; i++) {
      var cur = helpers[i](cm, start);
      if (cur) return cur;
    }
  });

  var defaultOptions = {
    rangeFinder: CodeMirror.fold.auto,
    widget: "\u2194",
    minFoldSize: 0,
    scanUp: false
  };

  CodeMirror.defineOption("foldOptions", null);
  /**
   * 获取折叠配置项（优先级：函数参数 > 编辑器全局配置 > 默认配置）
   * @param {CodeMirror} cm - 编辑器实例
   * @param {Object} options - 函数参数配置
   * @param {string} name - 配置项名称
   * @return {*} 配置项值
   */
  function getOption(cm, options, name) {
    if (options && options[name] !== undefined)
      return options[name];
    var editorOptions = cm.options.foldOptions;
    if (editorOptions && editorOptions[name] !== undefined)
      return editorOptions[name];
    return defaultOptions[name];
  }

  CodeMirror.defineExtension("foldOption", function(options, name) {
    return getOption(this, options, name);
  });
});
