Function entriesInPossibleKeyOrder

go/bundle/encoder.go:231–272

entriesInPossibleKeyOrder reorders es by VariantKey, in the order they should appear in the index section; the row-major order of possible keys for Variants. All entries in es must have the same Variants value. For example, if the Variants value is "Accept-Language;en;fr, Accept-Encoding:gzip;br",

(es []*indexEntry)

// If entries in es do not cover all combination of possible keys or two entries
// have overwrapping possible keys, this returns an error.
func entriesInPossibleKeyOrder(es []*indexEntry) ([]*indexEntry, error) {
	if es[0].Variants == "" {
		return nil, errors.New("no Variants header")
	}
	variants, err := parseVariants(es[0].Variants)
	if err != nil {
		return nil, fmt.Errorf("cannot parse Variants header value %q: %v", es[0].Variants, err)
	}
	numPossibleKeys, err := variants.numberOfPossibleKeys()
	if err != nil {
		return nil, fmt.Errorf("invalid Variants header value %q: %v", es[0].Variants, err)
	}

	result := make([]*indexEntry, numPossibleKeys)
	for _, e := range es {
		// TODO: Compare Variants values as lists
		// (e.g. "Accept;foo;bar" == "Accept; foo; bar").
		if e.Variants != es[0].Variants {
			return nil, fmt.Errorf("inconsistent Variants value. %q != %q", e.Variants, es[0].Variants)
		}
		vks, err := parseListOfStringLists(e.VariantKey)
		if err != nil {
			return nil, fmt.Errorf("cannot parse Variant-Key header %q: %v", e.VariantKey, err)
		}
		for _, vk := range vks {
			i := variants.indexInPossibleKeys(vk)
			if i == -1 {
				return nil, fmt.Errorf("Variant-Key %q is not covered by variants %q", e.VariantKey, e.Variants)
			}
			if result[i] != nil {
				return nil, fmt.Errorf("duplicated entries with Variant-Key %q", vk)
			}
			result[i] = e
		}
	}
	for i, e := range result {
		if e == nil {
			return nil, fmt.Errorf("no entry for Variant-Key %v", variants.possibleKeyAt(i))
		}
	}
	return result, nil
}

func parseListOfStringLists(s string) ([][]string, error) {
	ll, err := structuredheader.ParseListOfLists(s)