liquid/engine.go

package liquid

import (
	"fmt"
	"io"

	"github.com/osteele/liquid/chunks"
	"github.com/osteele/liquid/expressions"
	"github.com/osteele/liquid/filters"
	"github.com/osteele/liquid/tags"
)

// TODO move the filters and tags from globals to the engine
func init() {
	tags.DefineStandardTags()
	filters.DefineStandardFilters()
}

type engine struct{}

type template struct {
	ast chunks.ASTNode
}

// NewEngine returns a new template engine.
func NewEngine() Engine {
	return engine{}
}

// DefineStartTag is in the Engine interface.
func (e engine) DefineStartTag(name string, td TagDefinition) {
	chunks.DefineStartTag(name).Parser(func(c chunks.ASTControlTag) (func(io.Writer, chunks.RenderContext) error, error) {
		return func(io.Writer, chunks.RenderContext) error {
			fmt.Println("unimplemented tag:", name)
			return nil
		}, nil
	})
}

// DefineFilter is in the Engine interface.
func (e engine) DefineFilter(name string, fn interface{}) {
	// TODO define this on the engine, not globally
	expressions.DefineFilter(name, fn)
}

// ParseAndRenderString is in the Engine interface.
func (e engine) DefineTag(name string, td TagDefinition) {
	// TODO define this on the engine, not globally
	chunks.DefineTag(name, chunks.TagDefinition(td))
}

// ParseTemplate is in the Engine interface.
func (e engine) ParseTemplate(text []byte) (Template, error) {
	tokens := chunks.Scan(string(text), "")
	ast, err := chunks.Parse(tokens)
	if err != nil {
		return nil, err
	}
	return &template{ast}, nil
}

// ParseAndRender is in the Engine interface.
func (e engine) ParseAndRender(text []byte, bindings map[string]interface{}) ([]byte, error) {
	t, err := e.ParseTemplate(text)
	if err != nil {
		return nil, err
	}
	return t.Render(bindings)
}

// ParseAndRenderString is in the Engine interface.
func (e engine) ParseAndRenderString(text string, bindings map[string]interface{}) (string, error) {
	b, err := e.ParseAndRender([]byte(text), bindings)
	if err != nil {
		return "", err
	}
	return string(b), nil
}