liquid/liquid.go

/*
Package liquid is a very early-stage pure Go library that implements Shopify Liquid <https://shopify.github.io/liquid> templates.

It's intended for use in for use in https://github.com/osteele/gojekyll.
*/
package liquid

import (
	"bytes"

	"github.com/osteele/liquid/chunks"
)

// Engine parses template source into renderable text.
//
// In the future, it will be configured with additional tags, filters, and the {%include%} search path.
type Engine interface {
	Parse(text []byte) (Template, error)
	ParseAndRender(text []byte, scope map[string]interface{}) ([]byte, error)
	ParseAndRenderString(text string, scope map[string]interface{}) (string, error)
}

// Template renders a template according to scope.
//
// Scope is a map of liquid variable names to objects.
type Template interface {
	Render(scope map[string]interface{}) ([]byte, error)
	RenderString(scope map[string]interface{}) (string, error)
}

type engine struct{}

type template struct {
	ast chunks.ASTNode
}

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

func (e engine) Parse(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 parses and then renders the template.
func (e engine) ParseAndRender(text []byte, scope map[string]interface{}) ([]byte, error) {
	t, err := e.Parse(text)
	if err != nil {
		return nil, err
	}
	return t.Render(scope)
}

// ParseAndRenderString is a convenience wrapper for ParseAndRender, that has string input and output.
func (e engine) ParseAndRenderString(text string, scope map[string]interface{}) (string, error) {
	b, err := e.ParseAndRender([]byte(text), scope)
	if err != nil {
		return "", err
	}
	return string(b), nil
}

// Render applies the template to the scope.
func (t *template) Render(scope map[string]interface{}) ([]byte, error) {
	buf := new(bytes.Buffer)
	err := t.ast.Render(buf, chunks.Context{scope})
	if err != nil {
		return nil, err
	}
	return buf.Bytes(), nil
}

// RenderString is a convenience wrapper for Render, that has string input and output.
func (t *template) RenderString(scope map[string]interface{}) (string, error) {
	b, err := t.Render(scope)
	if err != nil {
		return "", err
	}
	return string(b), nil
}