source: code/trunk/vendor/github.com/yosssi/gcss/declaration.go@ 75

package gcss

import (
        "bytes"
        "fmt"
        "io"
        "strings"
)

// declaration represents a declaration of CSS.
type declaration struct {
        elementBase
        property string
        value    string
}

// WriteTo writes the declaration to the writer.
func (dec *declaration) WriteTo(w io.Writer) (int64, error) {
        return dec.writeTo(w, nil)
}

// writeTo writes the declaration to the writer.
func (dec *declaration) writeTo(w io.Writer, params map[string]string) (int64, error) {
        bf := new(bytes.Buffer)

        bf.WriteString(dec.property)
        bf.WriteString(colon)

        for i, v := range strings.Split(dec.value, space) {
                if i > 0 {
                        bf.WriteString(space)
                }

                for j, w := range strings.Split(v, comma) {
                        if j > 0 {
                                bf.WriteString(comma)
                        }

                        if strings.HasPrefix(w, dollarMark) {
                                // Writing to the bytes.Buffer never returns an error.
                                dec.writeParamTo(bf, strings.TrimPrefix(w, dollarMark), params)
                        } else {
                                bf.WriteString(w)
                        }
                }
        }

        bf.WriteString(semicolon)

        n, err := w.Write(bf.Bytes())

        return int64(n), err
}

// writeParam writes the param to the writer.
func (dec *declaration) writeParamTo(w io.Writer, name string, params map[string]string) (int64, error) {
        if s, ok := params[name]; ok {
                if strings.HasPrefix(s, dollarMark) {
                        if v, ok := dec.Context().vars[strings.TrimPrefix(s, dollarMark)]; ok {
                                return v.WriteTo(w)
                        }
                        return 0, nil
                }

                n, err := w.Write([]byte(s))
                return int64(n), err
        }

        if v, ok := dec.Context().vars[name]; ok {
                return v.WriteTo(w)
        }

        return 0, nil
}

// declarationPV extracts a declaration property and value
// from the line.
func declarationPV(ln *line) (string, string, error) {
        pv := strings.SplitN(strings.TrimSpace(ln.s), space, 2)

        if len(pv) < 2 {
                return "", "", fmt.Errorf("declaration's property and value should be divided by a space [line: %d]", ln.no)
        }

        if !strings.HasSuffix(pv[0], colon) {
                return "", "", fmt.Errorf("property should end with a colon [line: %d]", ln.no)
        }

        return strings.TrimSuffix(pv[0], colon), pv[1], nil
}

// newDeclaration creates and returns a declaration.
func newDeclaration(ln *line, parent element) (*declaration, error) {
        property, value, err := declarationPV(ln)

        if err != nil {
                return nil, err
        }

        if strings.HasSuffix(value, semicolon) {
                return nil, fmt.Errorf("declaration must not end with %q [line: %d]", semicolon, ln.no)
        }

        return &declaration{
                elementBase: newElementBase(ln, parent),
                property:    property,
                value:       value,
        }, nil
}