parse.go

package gowd

import (
	"errors"
	"fmt"
	"io"
	"io/ioutil"
	"strings"

	"golang.org/x/net/html"
	"golang.org/x/net/html/atom"
)

//ElementsMap maps Elements by their `id` attributes
type ElementsMap map[string]*Element

//NewElementMap creates a new ElementMap
func NewElementMap() ElementsMap {
	return make(ElementsMap)
}

//ParseElements parse an html fragment and return a list of elements
func ParseElements(r io.Reader, em ElementsMap) ([]*Element, error) {
	nodes, err := html.ParseFragment(r, &html.Node{
		Type:     html.ElementNode,
		Data:     "body",
		DataAtom: atom.Body,
	})
	if err != nil {
		return nil, err
	}
	elems := make([]*Element, 0)
	for _, node := range nodes {
		elems = append(elems, NewElementFromNode(node, em))
	}
	return elems, nil
}

//NewElementFromNode creates an element from existing node
func NewElementFromNode(node *html.Node, em ElementsMap) *Element {
	elem := &Element{
		data:          elementText(node.Data),
		Attributes:    node.Attr,
		nodeType:      node.Type,
		Kids:          make([]*Element, 0),
		eventHandlers: make(map[string]EventHandler),
	}
	if em != nil && elem.GetID() != "" {
		em[elem.GetID()] = elem
	}
	for c := node.FirstChild; c != nil; c = c.NextSibling {
		elem.AddElement(NewElementFromNode(c, em))
	}
	return elem
}

//ParseElement parses an html with only one root tag, returns the root element.
func ParseElement(innerHTML string, em ElementsMap) (*Element, error) {
	elems, err := ParseElements(strings.NewReader(innerHTML), em)
	if err != nil {
		return nil, err
	}
	if len(elems) != 1 {
		tags := "["
		for _, e := range elems {
			tags += fmt.Sprintf("%v:'%s', ", e.nodeType, strings.Trim(e.data, "\t\n\r "))

		}
		tags += "]"
		return nil, errors.New("The provided html must yield only one html element, I have: " + tags)
	}
	return elems[0], nil
}

//ParseElementFromFile like ParseElement, but reads input from a file
func ParseElementFromFile(fileName string, em ElementsMap) (*Element, error) {
	data, err := ioutil.ReadFile(fileName)
	if err != nil {
		return nil, err
	}
	return ParseElement(string(data), em)
}