Method parseFilter

path.go:318–385

parseFilter parses a path filter contained within [brackets].

(path string)

// parseFilter parses a path filter contained within [brackets].
func (c *compiler) parseFilter(path string) filter {
	if len(path) == 0 {
		c.err = ErrPath("path contains an empty filter expression.")
		return nil
	}

	// Filter contains [@attr='val'], [@attr="val"], [fn()='val'],
	// [fn()="val"], [tag='val'] or [tag="val"]?
	eqindex := strings.IndexByte(path, '=')
	if eqindex == 0 {
		c.err = ErrPath("path contains a filter expression with no key.")
		return nil
	}
	if eqindex > 0 && eqindex+1 < len(path) {
		quote := path[eqindex+1]
		if quote == '\'' || quote == '"' {
			rindex := nextIndex(path, quote, eqindex+2)
			if rindex != len(path)-1 {
				c.err = ErrPath("path has mismatched filter quotes.")
				return nil
			}

			key := path[:eqindex]
			value := path[eqindex+2 : rindex]

			switch {
			case key[0] == '@':
				if len(key) == 1 {
					c.err = ErrPath("path contains a filter expression with no key.")
					return nil
				}
				return newFilterAttrVal(key[1:], value)
			case strings.HasSuffix(key, "()"):
				name := key[:len(key)-2]
				if fn, ok := fnTable[name]; ok {
					return newFilterFuncVal(fn, value)
				}
				c.err = ErrPath("path has unknown function " + name)
				return nil
			default:
				return newFilterChildText(key, value)
			}
		}
	}

	// Filter contains [@attr], [N], [tag] or [fn()]
	switch {
	case path[0] == '@':
		return newFilterAttr(path[1:])
	case strings.HasSuffix(path, "()"):
		name := path[:len(path)-2]
		if fn, ok := fnTable[name]; ok {
			return newFilterFunc(fn)
		}
		c.err = ErrPath("path has unknown function " + name)
		return nil
	case isInteger(path):
		pos, _ := strconv.Atoi(path)