text: var utils = require('keystone-utils');
  
  /**
   * Expands a comma-separated string or array of columns into valid column objects.
   *
   * Columns can be:
   *    - A Field, in the format "field|width"
   *    - A Field in a single related List, in the format "list:field|width"
   *    - Any valid path in the Schema, in the format "path|width"
   *
   * The width part is optional, and can be in the format "n%" or "npx".
   *
   * The path __name__ is automatically mapped to the namePath of the List.
   *
   * The field or path for the name of the item (defaults to ID if not set or detected)
   * is automatically prepended if not explicitly included.
   */
  function expandColumns(cols) {
  	if (typeof cols === 'string') {
  		cols = cols.split(',');
  	}
  	if (!Array.isArray(cols)) {
  		throw new Error('List.expandColumns: cols must be an array.');
  	}
  	var list = this;
  	var expanded = [];
  	var nameCol = false;
  	var getCol = function(def) {
  		if (def.path === '__name__') {
  			def.path = list.namePath;
  		}
  		var field = list.fields[def.path];
  		var col = null;
  		if (field) {
  			col = {
  				field: field,
  				path: field.path,
  				type: field.type,
  				label: def.label || field.label
  			};
  			if (col.type === 'relationship') {
  				col.refList = col.field.refList;
  				if (col.refList) {
  					col.refPath = def.subpath || col.refList.namePath;
  					col.subField = col.refList.fields[col.refPath];
  					col.populate = { path: col.field.path, subpath: col.refPath };
  				}
  				if (!def.label && def.subpath) {
  					col.label = field.label + ': ' + (col.subField ? col.subField.label : utils.keyToLabel(def.subpath));
  				}
  			}
  		} else if (list.model.schema.paths[def.path] || list.model.schema.virtuals[def.path]) {
  			// column refers to a path in the schema
  			// TODO: this needs to handle sophisticated types, including arrays, nested Schemas, and mixed types
  			col = {
  				path: def.path,
  				label: def.label || utils.keyToLabel(def.path)
  			};
  		}
  		if (col) {
  			col.width = def.width;
  			if (col.path === list.namePath) {
  				col.isName = true;
  				nameCol = col;
  			}
  			if (field && field.col) {
  				_.extend(col, field.col);
  			}
  		}
  		return col;
  	};
  	for (var i = 0; i < cols.length; i++) {
  		var def = {};
  		if (typeof cols[i] === 'string') {
  			var parts = cols[i].trim().split('|');
  			def.width = parts[1] || false;
  			parts = parts[0].split(':');
  			def.path = parts[0];
  			def.subpath = parts[1];
  		}
  		if (!utils.isObject(def) || !def.path) {
  			throw new Error('List.expandColumns: column definition must contain a path.');
  		}
  		var col = getCol(def);
  		if (col) {
  			expanded.push(col);
  		}
  	}
  	if (!nameCol) {
  		nameCol = getCol({ path: list.namePath });
  		if (nameCol) {
  			expanded.unshift(nameCol);
  		}
  	}
  	return expanded;
  }
  
  module.exports = expandColumns;
  