mkpage

README

This is experimental..., things are sure to change

mkpage

An experimental template engine with an embedded markdown processor. mkpage (pronounced "make page") is a simple command line tool which accepts key value pairs and applies them to a Golang text/template. The key side of a pair corresponds to the template element names that will be replaced in the render version of the document. If a key was cllaed "pageContent" the template element would look like {{ .pageContent }}. The value of "pageContent" would replace {{ .pageContent }}. Go text/templates elements can do more than that but the is the core idea. On the value side of the key/value pair you have strings of one of three formats - plain text, markdown and JSON. These three formatted strings can be explicit strings, data from a file or content received from a URL. Here's a basic demonstration starting with the template.

    Date: {{.now}}

    Hello {{.name -}},
    
    Forecast:

    {{range .weather.data.text}}
       + {{ . }}
    {{end}}

    Thank you

    {{.signature}}

To render the template above (i.e. myformletter.tmpl) is expecting values from various data sources. This break down is as follows.

• "now" and "name" are explicit strings
• "weather" comes from a URL of JSON content
• "signature" comes from a file in our local disc

Here is how we would express the key/value pairs on the command line.

    mkpage "now=text:$(date)" \
        "name=text:Little Frieda" \
        "weather=http://forecast.weather.gov/MapClick.php?lat=13.47190933300044&lon=144.74977715100056&FcstType=json" \
        signature=testdata/signature.txt \
        testdata/myformletter.tmpl

Notice the two explicit strings are prefixed with "text:" (other possible formats are "markdown:", "json:"). Values without a prefix are assumed to be file paths. We see that in testdata/signature.txt. Likewise the weather data is coming from a URL. mkpage distinguishes that by the prefixes "http://" and "https://". Since a HTTP response contains headers describing the content type (e.g. "Content-Type: text/markdown") we do not require any other prefix. Likewise a filename's extension can give us an inference of the data format it contains. ".json" is a JSON document, ".md" is a Markdown document and everything else is just plain text.

Since we are leveraging Go's text/template the template itself can be more than a simple substitution. It can contain conditional expressions, ranges for data and even include blocks from other templates.

Templates

mkpage template engine is the Go text/template package. Other template systems could be implemented but I'm keeping the experiment simple at this point.

Conditional elements

One nice feature of Go's text/template DSL is that template elements can be condition. This can be done using the "if" and "with" template functions. Here's how to show a title conditionally using the "if" function.

    {{if .title}}And the title is: {{.title}}{{end}}

or using "with"

    {{with .title}}{{ . }}{{end}}

Template blocks

Go text/templates support defining blocks and rendering them in conjuction with a main template. This is also supported by mkpage. For each template encountered on the command line it is added to an array of templates parsed by the text/template package. Collectively they are then executed which causes final results render to stdout by mkpage.

    mkpage "content=text:Hello World" testdata/page.tmpl testdata/header.tmpl testdata/footer.tmpl

Here is what page.tmpl would look like

    {{template "header" . }}

        {{.content}}

    {{template "footer" . }}

The header and footer are then defined in their own template files (though they also could be combined into one or even be defined in the main template file itself).

header.tmpl

    {{define "header"}}This is the document header{{end}}

footer.tmpl

    {{define "footer"}}This is the footer{{end}}

In this example the output would look like

    This is the document header

        Hello World

    This is the footer

Content formats and data sources

mkpage support three content formats

• text/plain (e.g. "text:" when specifying strings and any file expect those having the extension ".md" or ".json")
• text/markdown (e.g. "markdown:" when specifying strings, file extension ".md")
• application/json (e.g. "json:" when specifying strings, file extension ".json")

It also supports three data sources

• an explicit string (prefixed with a hint, e.g. "text:", "markdown:", "json:")
• a filepath and filename
• a URL

Content type is evaluate and if necessary transformed before going into the Go text/template.

A note about Markdown dialect

In additional to populating a template with values from data sources mkpage also includes the blackfriday markdown processor. The blackfriday.MarkdownCommon() function is envoked whenever markdown content is suggested. That means for strings that have the "markdown:" hint prefix, files ending in ".md" file extension or URL content with the content type returned as "text/markdown".

Options

• -h, -help - get command line help
• -v, -version - show mkpage version number
• -l, -license - show mkpage license information
• -t, -template - show mkpage's default template

Documentation

Overview

mkpage is an experiment in a light weight template and markdown processor.

@author R. S. Doiel, <rsdoiel@caltech.edu>

Copyright (c) 2016, Caltech All rights not granted herein are expressly reserved by Caltech.

Redistribution and use in source and binary forms, with or without modification, are permitted provided that the following conditions are met:

1. Redistributions of source code must retain the above copyright notice, this list of conditions and the following disclaimer.

2. Redistributions in binary form must reproduce the above copyright notice, this list of conditions and the following disclaimer in the documentation and/or other materials provided with the distribution.

3. Neither the name of the copyright holder nor the names of its contributors may be used to endorse or promote products derived from this software without specific prior written permission.

THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

Index

• Constants
• func MakePage(wr io.Writer, tmpl *template.Template, keyValues map[string]string) error
• func MakePageString(tmpl *template.Template, keyValues map[string]string) (string, error)
• func ResolveData(data map[string]string) (map[string]interface{}, error)

Constants

const (
	// Version of the mkpage package.
	Version = "v0.0.7"

	// JSONPrefix designates a string as JSON formatted content
	JSONPrefix = "json:"
	// MarkdownPrefix designates a string as Markdown content
	MarkdownPrefix = "markdown:"
	// TextPrefix designates a string as text/plain not needed processing
	TextPrefix = "text:"

	// The default HTML provided by md2slides package, you probably want to override this...
	DefaultTemplateSource = `` /* 4707-byte string literal not displayed */

)

Functions

func MakePage

func MakePage(wr io.Writer, tmpl *template.Template, keyValues map[string]string) error

MakePage applies the key/value map to the template and renders to writer and returns an error if something goes wrong

func MakePageString

func MakePageString(tmpl *template.Template, keyValues map[string]string) (string, error)

MakePageString applies the key/value map to the template and renders the results to a string and error if someting goes wrong

func ResolveData

func ResolveData(data map[string]string) (map[string]interface{}, error)

ResolveData takes a data map and reads in the files and URL sources as needed turning the data into strings to be applied to the template.