mark2web/helper/template_filters.go

package helper

import (
	"errors"
	"fmt"
	"io/ioutil"
	"path"
	"strconv"
	"strings"

	"github.com/ddliu/motto"
	"github.com/disintegration/imaging"
	"github.com/flosch/pongo2"
	_ "github.com/flosch/pongo2-addons"
	_ "github.com/robertkrimen/otto/underscore"
)

func init() {
	err := pongo2.ReplaceFilter("markdown", MarkdownFilter)
	if err != nil {
		panic(err)
	}

	newFilters := map[string]pongo2.FilterFunction{
		"image_resize":  ImageResizeFilter,
		"relative_path": RelativePathFilter,
	}
	for name, fn := range newFilters {
		err := pongo2.RegisterFilter(name, fn)
		if err != nil {
			panic(err)
		}
	}
}

// MarkdownFilter is a pongo2 filter, which converts markdown to html
func MarkdownFilter(in *pongo2.Value, param *pongo2.Value) (*pongo2.Value, *pongo2.Error) {
	return pongo2.AsSafeValue(
			string(
				renderMarkdown(
					[]byte(in.String()),
					currentPathConfig.Markdown,
				))),
		nil
}

type imageParams struct {
	width    int
	height   int
	filename string
}

func parseImageParams(str string) (*imageParams, error) {
	if str == "" {
		return nil, errors.New("missing image parameters")
	}
	p := imageParams{}
	for _, s := range strings.Split(str, ",") {
		e := strings.Split(s, "=")
		if len(e) < 2 {
			return nil, fmt.Errorf("invalid image parameter: %s", s)
		}
		var err error
		switch e[0] {
		case "w":
			p.width, err = strconv.Atoi(e[1])
		case "h":
			p.height, err = strconv.Atoi(e[1])
		case "f":
			p.filename = e[1]
		default:
			return nil, fmt.Errorf("invalid image parameter: %s", s)
		}
		if err != nil {
			return nil, fmt.Errorf("could not convert image parameter to correct value type for '%s': %s", s, err)
		}
	}
	return &p, nil
}

// ImageResizeFilter read the image url and resize parameters and saves the resized image
// param: w=WITDH,h=HEIGHT
func ImageResizeFilter(in *pongo2.Value, param *pongo2.Value) (*pongo2.Value, *pongo2.Error) {
	imgSource := in.String()
	p, err := parseImageParams(param.String())
	if err != nil {
		return nil, &pongo2.Error{
			Sender:    "filter:image_resize",
			OrigError: err,
		}
	}

	imgSource = ResolveInputPath(imgSource)
	if p.filename == "" {
		p.filename = fmt.Sprintf("%dx%d_%s", p.width, p.height, path.Base(imgSource))
	}
	imgTarget := ResolveOutputPath(p.filename)
	Log.Noticef("resizing image from %s to %s", imgSource, imgTarget)

	img, err := imaging.Open(imgSource, imaging.AutoOrientation(true))
	if err != nil {
		return nil, &pongo2.Error{
			Sender:    "filter:image_resize",
			OrigError: fmt.Errorf("could not open image '%s': %s", imgSource, err),
		}
	}
	img = imaging.Resize(img, p.width, p.height, imaging.Lanczos)

	err = imaging.Save(img, imgTarget)
	if err != nil {
		return nil, &pongo2.Error{
			Sender:    "filter:image_resize",
			OrigError: fmt.Errorf("could save image '%s': %s", imgTarget, err),
		}
	}

	return pongo2.AsValue(ResolveNavPath(p.filename)), nil
}

// RelativePathFilter returns the relative path to navpoint based on current nav
func RelativePathFilter(in, param *pongo2.Value) (*pongo2.Value, *pongo2.Error) {
	return pongo2.AsValue(
		ResolveNavPath(
			in.String(),
		),
	), nil
}

// RegisterFilters reads a directory and register filters from files within it
func RegisterFilters(dir string) {
	files, err := ioutil.ReadDir(dir)
	if err != nil {
		Log.Panicf("could not read from template filters dir '%s': %s", dir, err)
	}
	for _, f := range files {
		if !f.IsDir() {
			switch path.Ext(f.Name()) {
			case ".js":
				fileBase := strings.TrimSuffix(f.Name(), ".js")
				jsFile := dir + "/" + f.Name()
				Log.Debugf("trying to register filter from: %s", jsFile)
				/*
					jsStr, err := ioutil.ReadFile(jsFile)
					if err != nil {
						Log.Panicf("could not read '%s': %s", jsFile, err)
					}
				*/
				vm := motto.New()
				fn, err := vm.Run(jsFile)
				if err != nil {
					Log.Panicf("error in javascript vm for '%s': %s", jsFile, err)
				}
				if !fn.IsFunction() {
					Log.Panicf("%s does not contain a function code", jsFile)
				}

				err = pongo2.RegisterFilter(
					fileBase,
					func(in, param *pongo2.Value) (out *pongo2.Value, erro *pongo2.Error) {
						thisObj, _ := vm.Object("({})")
						if currentContext != nil {
							thisObj.Set("context", *currentContext)
						}

						if err != nil {
							Log.Panicf("could not set context as in '%s': %s", jsFile, err)
						}
						ret, err := fn.Call(thisObj.Value(), in.Interface(), param.Interface())
						if err != nil {
							Log.Panicf("error in javascript file '%s' while calling returned function: %s", jsFile, err)
						}
						retGo, err := ret.Export()
						if err != nil {
							Log.Panicf("export error for '%s': %s", jsFile, err)
						}
						return pongo2.AsValue(retGo), nil
					},
				)
				if err != nil {
					Log.Panicf("could not register filter from '%s': %s", jsFile, err)
				}

			}
		}
	}

}