eknkc/amber/README.md

# amber [![GoDoc](https://godoc.org/github.com/golang/gddo?status.svg)](http://godoc.org/github.com/eknkc/amber) [![Build Status](https://travis-ci.org/eknkc/amber.svg?branch=master)](https://travis-ci.org/eknkc/amber)

## Notice
> While Amber is perfectly fine and stable to use, I've been working on a direct Pug.js port for Go. It is somewhat hacky at the moment but take a look at [Pug.go](https://github.com/eknkc/pug) if you are looking for a [Pug.js](https://github.com/pugjs/pug) compatible Go template engine.

### Usage
```go
import "github.com/eknkc/amber"
```

Amber is an elegant templating engine for Go Programming Language
It is inspired from HAML and Jade

### Tags

A tag is simply a word:

    html

is converted to

```html
<html></html>
```

It is possible to add ID and CLASS attributes to tags:

    div#main
    span.time

are converted to

```html
<div id="main"></div>
<span class="time"></span>
```

Any arbitrary attribute name / value pair can be added this way:

    a[href="http://www.google.com"]

You can mix multiple attributes together

    a#someid[href="/"][title="Main Page"].main.link Click Link

gets converted to

```html
<a id="someid" class="main link" href="/" title="Main Page">Click Link</a>
```

It is also possible to define these attributes within the block of a tag

    a
        #someid
        [href="/"]
        [title="Main Page"]
        .main
        .link
        | Click Link

### Doctypes

To add a doctype, use `!!!` or `doctype` keywords:

    !!! transitional
    // <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">

or use `doctype`

    doctype 5
    // <!DOCTYPE html>

Available options: `5`, `default`, `xml`, `transitional`, `strict`, `frameset`, `1.1`, `basic`, `mobile`

### Tag Content

For single line tag text, you can just append the text after tag name:

    p Testing!

would yield

    <p>Testing!</p>

For multi line tag text, or nested tags, use indentation:

    html
        head
            title Page Title
        body
            div#content
                p
                    | This is a long page content
                    | These lines are all part of the parent p

                    a[href="/"] Go To Main Page

### Data

Input template data can be reached by key names directly. For example, assuming the template has been
executed with following JSON data:

```json
{
  "Name": "Ekin",
  "LastName": "Koc",
  "Repositories": [
    "amber",
    "dateformat"
  ],
  "Avatar": "/images/ekin.jpg",
  "Friends": 17
}
```

It is possible to interpolate fields using `#{}`

    p Welcome #{Name}!

would print

```html
<p>Welcome Ekin!</p>
```

Attributes can have field names as well

    a[title=Name][href="/ekin.koc"]

would print

```html
<a title="Ekin" href="/ekin.koc"></a>
```

### Expressions

Amber can expand basic expressions. For example, it is possible to concatenate strings with + operator:

    p Welcome #{Name + " " + LastName}

Arithmetic expressions are also supported:

    p You need #{50 - Friends} more friends to reach 50!

Expressions can be used within attributes

    img[alt=Name + " " + LastName][src=Avatar]

### Variables

It is possible to define dynamic variables within templates,
all variables must start with a $ character and can be assigned as in the following example:

    div
        $fullname = Name + " " + LastName
        p Welcome #{$fullname}

If you need to access the supplied data itself (i.e. the object containing Name, LastName etc fields.) you can use `$` variable

    p $.Name

### Conditions

For conditional blocks, it is possible to use `if <expression>`

    div
        if Friends > 10
            p You have more than 10 friends
        else if Friends > 5
            p You have more than 5 friends
        else
            p You need more friends

Again, it is possible to use arithmetic and boolean operators

    div
        if Name == "Ekin" && LastName == "Koc"
            p Hey! I know you..

There is a special syntax for conditional attributes. Only block attributes can have conditions;

    div
        .hasfriends ? Friends > 0

This would yield a div with `hasfriends` class only if the `Friends > 0` condition holds. It is
perfectly fine to use the same method for other types of attributes:

    div
        #foo ? Name == "Ekin"
        [bar=baz] ? len(Repositories) > 0

### Iterations

It is possible to iterate over arrays and maps using `each`:

    each $repo in Repositories
        p #{$repo}

would print

    p amber
    p dateformat

It is also possible to iterate over values and indexes at the same time

    each $i, $repo in Repositories
        p
            .even ? $i % 2 == 0
            .odd ? $i % 2 == 1

### Mixins

Mixins (reusable template blocks that accept arguments) can be defined:

    mixin surprise
        span Surprise!
    mixin link($href, $title, $text)
        a[href=$href][title=$title] #{$text}

and then called multiple times within a template (or even within another mixin definition):

    div
        +surprise
        +surprise
        +link("http://google.com", "Google", "Check out Google")

Template data, variables, expressions, etc., can all be passed as arguments:

    +link(GoogleUrl, $googleTitle, "Check out " + $googleTitle)

### Imports

A template can import other templates using `import`:

    a.amber
        p this is template a

    b.amber
        p this is template b

    c.amber
        div
            import a
            import b

gets compiled to

    div
        p this is template a
        p this is template b

### Inheritance

A template can inherit other templates. In order to inherit another template, an `extends` keyword should be used.
Parent template can define several named blocks and child template can modify the blocks.

    master.amber
        !!! 5
        html
            head
                block meta
                    meta[name="description"][content="This is a great website"]

                title
                    block title
                        | Default title
            body
                block content

    subpage.amber
        extends master

        block title
            | Some sub page!

        block append meta
            // This will be added after the description meta tag. It is also possible
            // to prepend someting to an existing block
            meta[name="keywords"][content="foo bar"]

        block content
            div#main
                p Some content here

### License
(The MIT License)

Copyright (c) 2012 Ekin Koc <ekin@eknkc.com>

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the 'Software'), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED 'AS IS', WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.

## Usage

```go
var DefaultOptions = Options{true, false}
var DefaultDirOptions = DirOptions{".amber", true}
```

#### func  Compile

```go
func Compile(input string, options Options) (*template.Template, error)
```
Parses and compiles the supplied amber template string. Returns corresponding Go
Template (html/templates) instance. Necessary runtime functions will be injected
and the template will be ready to be executed.

#### func  CompileFile

```go
func CompileFile(filename string, options Options) (*template.Template, error)
```
Parses and compiles the contents of supplied filename. Returns corresponding Go
Template (html/templates) instance. Necessary runtime functions will be injected
and the template will be ready to be executed.

#### func  CompileDir
```go
func CompileDir(dirname string, dopt DirOptions, opt Options) (map[string]*template.Template, error)
```
Parses and compiles the contents of a supplied directory name. Returns a mapping of template name (extension stripped) to corresponding Go Template (html/template) instance. Necessary runtime functions will be injected and the template will be ready to be executed.

If there are templates in subdirectories, its key in the map will be it's path relative to `dirname`. For example:
```
templates/
   |-- index.amber
   |-- layouts/
         |-- base.amber
```
```go
templates, err := amber.CompileDir("templates/", amber.DefaultDirOptions, amber.DefaultOptions)
templates["index"] // index.amber Go Template
templates["layouts/base"] // base.amber Go Template
```
By default, the search will be recursive and will match only files ending in ".amber". If recursive is turned off, it will only search the top level of the directory. Specified extension must start with a period.

#### type Compiler

```go
type Compiler struct {
        // Compiler options
        Options
}
```

Compiler is the main interface of Amber Template Engine. In order to use an
Amber template, it is required to create a Compiler and compile an Amber source
to native Go template.

    compiler := amber.New()
    // Parse the input file
    err := compiler.ParseFile("./input.amber")
    if err == nil {
        // Compile input file to Go template
        tpl, err := compiler.Compile()
        if err == nil {
                // Check built in html/template documentation for further details
                tpl.Execute(os.Stdout, somedata)
        }
    }

#### func  New

```go
func New() *Compiler
```
Create and initialize a new Compiler

#### func (*Compiler) Compile

```go
func (c *Compiler) Compile() (*template.Template, error)
```
Compile amber and create a Go Template (html/templates) instance. Necessary
runtime functions will be injected and the template will be ready to be
executed.

#### func (*Compiler) CompileString

```go
func (c *Compiler) CompileString() (string, error)
```
Compile template and return the Go Template source You would not be using this
unless debugging / checking the output. Please use Compile method to obtain a
template instance directly.

#### func (*Compiler) CompileWriter

```go
func (c *Compiler) CompileWriter(out io.Writer) (err error)
```
Compile amber and write the Go Template source into given io.Writer instance You
would not be using this unless debugging / checking the output. Please use
Compile method to obtain a template instance directly.

#### func (*Compiler) Parse

```go
func (c *Compiler) Parse(input string) (err error)
```
Parse given raw amber template string.

#### func (*Compiler) ParseFile

```go
func (c *Compiler) ParseFile(filename string) (err error)
```
Parse the amber template file in given path

#### type Options

```go
type Options struct {
        // Setting if pretty printing is enabled.
        // Pretty printing ensures that the output html is properly indented and in human readable form.
        // If disabled, produced HTML is compact. This might be more suitable in production environments.
        // Defaukt: true
        PrettyPrint bool
        // Setting if line number emitting is enabled
        // In this form, Amber emits line number comments in the output template. It is usable in debugging environments.
        // Default: false
        LineNumbers bool
}
```

#### type DirOptions

```go
// Used to provide options to directory compilation
type DirOptions struct {
        // File extension to match for compilation
        Ext string
        // Whether or not to walk subdirectories
        Recursive bool
}
```
1	# amber [![GoDoc](https://godoc.org/github.com/golang/gddo?status.svg)](http://godoc.org/github.com/eknkc/amber) [![Build Status](https://travis-ci.org/eknkc/amber.svg?branch=master)](https://travis-ci.org/eknkc/amber)
2
3	## Notice
4	> While Amber is perfectly fine and stable to use, I've been working on a direct Pug.js port for Go. It is somewhat hacky at the moment but take a look at [Pug.go](https://github.com/eknkc/pug) if you are looking for a [Pug.js](https://github.com/pugjs/pug) compatible Go template engine.
5
6	### Usage
7	```go
8	import "github.com/eknkc/amber"
9	```
10
11	Amber is an elegant templating engine for Go Programming Language
12	It is inspired from HAML and Jade
13
14	### Tags
15
16	A tag is simply a word:
17
18	html
19
20	is converted to
21
22	```html
23	<html></html>
24	```
25
26	It is possible to add ID and CLASS attributes to tags:
27
28	div#main
29	span.time
30
31	are converted to
32
33	```html
34	<div id="main"></div>
35	<span class="time"></span>
36	```
37
38	Any arbitrary attribute name / value pair can be added this way:
39
40	a[href="http://www.google.com"]
41
42	You can mix multiple attributes together
43
44	a#someid[href="/"][title="Main Page"].main.link Click Link
45
46	gets converted to
47
48	```html
49	<a id="someid" class="main link" href="/" title="Main Page">Click Link</a>
50	```
51
52	It is also possible to define these attributes within the block of a tag
53
54	a
55	#someid
56	[href="/"]
57	[title="Main Page"]
58	.main
59	.link
60	\| Click Link
61
62	### Doctypes
63
64	To add a doctype, use `!!!` or `doctype` keywords:
65
66	!!! transitional
67	// <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
68
69	or use `doctype`
70
71	doctype 5
72	// <!DOCTYPE html>
73
74	Available options: `5`, `default`, `xml`, `transitional`, `strict`, `frameset`, `1.1`, `basic`, `mobile`
75
76	### Tag Content
77
78	For single line tag text, you can just append the text after tag name:
79
80	p Testing!
81
82	would yield
83
84	<p>Testing!</p>
85
86	For multi line tag text, or nested tags, use indentation:
87
88	html
89	head
90	title Page Title
91	body
92	div#content
93	p
94	\| This is a long page content
95	\| These lines are all part of the parent p
96
97	a[href="/"] Go To Main Page
98
99	### Data
100
101	Input template data can be reached by key names directly. For example, assuming the template has been
102	executed with following JSON data:
103
104	```json
105	{
106	"Name": "Ekin",
107	"LastName": "Koc",
108	"Repositories": [
109	"amber",
110	"dateformat"
111	],
112	"Avatar": "/images/ekin.jpg",
113	"Friends": 17
114	}
115	```
116
117	It is possible to interpolate fields using `#{}`
118
119	p Welcome #{Name}!
120
121	would print
122
123	```html
124	<p>Welcome Ekin!</p>
125	```
126
127	Attributes can have field names as well
128
129	a[title=Name][href="/ekin.koc"]
130
131	would print
132
133	```html
134	<a title="Ekin" href="/ekin.koc"></a>
135	```
136
137	### Expressions
138
139	Amber can expand basic expressions. For example, it is possible to concatenate strings with + operator:
140
141	p Welcome #{Name + " " + LastName}
142
143	Arithmetic expressions are also supported:
144
145	p You need #{50 - Friends} more friends to reach 50!
146
147	Expressions can be used within attributes
148
149	img[alt=Name + " " + LastName][src=Avatar]
150
151	### Variables
152
153	It is possible to define dynamic variables within templates,
154	all variables must start with a $ character and can be assigned as in the following example:
155
156	div
157	$fullname = Name + " " + LastName
158	p Welcome #{$fullname}
159
160	If you need to access the supplied data itself (i.e. the object containing Name, LastName etc fields.) you can use `$` variable
161
162	p $.Name
163
164	### Conditions
165
166	For conditional blocks, it is possible to use `if <expression>`
167
168	div
169	if Friends > 10
170	p You have more than 10 friends
171	else if Friends > 5
172	p You have more than 5 friends
173	else
174	p You need more friends
175
176	Again, it is possible to use arithmetic and boolean operators
177
178	div
179	if Name == "Ekin" && LastName == "Koc"
180	p Hey! I know you..
181
182	There is a special syntax for conditional attributes. Only block attributes can have conditions;
183
184	div
185	.hasfriends ? Friends > 0
186
187	This would yield a div with `hasfriends` class only if the `Friends > 0` condition holds. It is
188	perfectly fine to use the same method for other types of attributes:
189
190	div
191	#foo ? Name == "Ekin"
192	[bar=baz] ? len(Repositories) > 0
193
194	### Iterations
195
196	It is possible to iterate over arrays and maps using `each`:
197
198	each $repo in Repositories
199	p #{$repo}
200
201	would print
202
203	p amber
204	p dateformat
205
206	It is also possible to iterate over values and indexes at the same time
207
208	each $i, $repo in Repositories
209	p
210	.even ? $i % 2 == 0
211	.odd ? $i % 2 == 1
212
213	### Mixins
214
215	Mixins (reusable template blocks that accept arguments) can be defined:
216
217	mixin surprise
218	span Surprise!
219	mixin link($href, $title, $text)
220	a[href=$href][title=$title] #{$text}
221
222	and then called multiple times within a template (or even within another mixin definition):
223
224	div
225	+surprise
226	+surprise
227	+link("http://google.com", "Google", "Check out Google")
228
229	Template data, variables, expressions, etc., can all be passed as arguments:
230
231	+link(GoogleUrl, $googleTitle, "Check out " + $googleTitle)
232
233	### Imports
234
235	A template can import other templates using `import`:
236
237	a.amber
238	p this is template a
239
240	b.amber
241	p this is template b
242
243	c.amber
244	div
245	import a
246	import b
247
248	gets compiled to
249
250	div
251	p this is template a
252	p this is template b
253
254	### Inheritance
255
256	A template can inherit other templates. In order to inherit another template, an `extends` keyword should be used.
257	Parent template can define several named blocks and child template can modify the blocks.
258
259	master.amber
260	!!! 5
261	html
262	head
263	block meta
264	meta[name="description"][content="This is a great website"]
265
266	title
267	block title
268	\| Default title
269	body
270	block content
271
272	subpage.amber
273	extends master
274
275	block title
276	\| Some sub page!
277
278	block append meta
279	// This will be added after the description meta tag. It is also possible
280	// to prepend someting to an existing block
281	meta[name="keywords"][content="foo bar"]
282
283	block content
284	div#main
285	p Some content here
286
287	### License
288	(The MIT License)
289
290	Copyright (c) 2012 Ekin Koc <ekin@eknkc.com>
291
292	Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the 'Software'), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:
293
294	The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.
295
296	THE SOFTWARE IS PROVIDED 'AS IS', WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
297
298	## Usage
299
300	```go
301	var DefaultOptions = Options{true, false}
302	var DefaultDirOptions = DirOptions{".amber", true}
303	```
304
305	#### func Compile
306
307	```go
308	func Compile(input string, options Options) (*template.Template, error)
309	```
310	Parses and compiles the supplied amber template string. Returns corresponding Go
311	Template (html/templates) instance. Necessary runtime functions will be injected
312	and the template will be ready to be executed.
313
314	#### func CompileFile
315
316	```go
317	func CompileFile(filename string, options Options) (*template.Template, error)
318	```
319	Parses and compiles the contents of supplied filename. Returns corresponding Go
320	Template (html/templates) instance. Necessary runtime functions will be injected
321	and the template will be ready to be executed.
322
323	#### func CompileDir
324	```go
325	func CompileDir(dirname string, dopt DirOptions, opt Options) (map[string]*template.Template, error)
326	```
327	Parses and compiles the contents of a supplied directory name. Returns a mapping of template name (extension stripped) to corresponding Go Template (html/template) instance. Necessary runtime functions will be injected and the template will be ready to be executed.
328
329	If there are templates in subdirectories, its key in the map will be it's path relative to `dirname`. For example:
330	```
331	templates/
332	\|-- index.amber
333	\|-- layouts/
334	\|-- base.amber
335	```
336	```go
337	templates, err := amber.CompileDir("templates/", amber.DefaultDirOptions, amber.DefaultOptions)
338	templates["index"] // index.amber Go Template
339	templates["layouts/base"] // base.amber Go Template
340	```
341	By default, the search will be recursive and will match only files ending in ".amber". If recursive is turned off, it will only search the top level of the directory. Specified extension must start with a period.
342
343	#### type Compiler
344
345	```go
346	type Compiler struct {
347	// Compiler options
348	Options
349	}
350	```
351
352	Compiler is the main interface of Amber Template Engine. In order to use an
353	Amber template, it is required to create a Compiler and compile an Amber source
354	to native Go template.
355
356	compiler := amber.New()
357	// Parse the input file
358	err := compiler.ParseFile("./input.amber")
359	if err == nil {
360	// Compile input file to Go template
361	tpl, err := compiler.Compile()
362	if err == nil {
363	// Check built in html/template documentation for further details
364	tpl.Execute(os.Stdout, somedata)
365	}
366	}
367
368	#### func New
369
370	```go
371	func New() *Compiler
372	```
373	Create and initialize a new Compiler
374
375	#### func (*Compiler) Compile
376
377	```go
378	func (c Compiler) Compile() (template.Template, error)
379	```
380	Compile amber and create a Go Template (html/templates) instance. Necessary
381	runtime functions will be injected and the template will be ready to be
382	executed.
383
384	#### func (*Compiler) CompileString
385
386	```go
387	func (c *Compiler) CompileString() (string, error)
388	```
389	Compile template and return the Go Template source You would not be using this
390	unless debugging / checking the output. Please use Compile method to obtain a
391	template instance directly.
392
393	#### func (*Compiler) CompileWriter
394
395	```go
396	func (c *Compiler) CompileWriter(out io.Writer) (err error)
397	```
398	Compile amber and write the Go Template source into given io.Writer instance You
399	would not be using this unless debugging / checking the output. Please use
400	Compile method to obtain a template instance directly.
401
402	#### func (*Compiler) Parse
403
404	```go
405	func (c *Compiler) Parse(input string) (err error)
406	```
407	Parse given raw amber template string.
408
409	#### func (*Compiler) ParseFile
410
411	```go
412	func (c *Compiler) ParseFile(filename string) (err error)
413	```
414	Parse the amber template file in given path
415
416	#### type Options
417
418	```go
419	type Options struct {
420	// Setting if pretty printing is enabled.
421	// Pretty printing ensures that the output html is properly indented and in human readable form.
422	// If disabled, produced HTML is compact. This might be more suitable in production environments.
423	// Defaukt: true
424	PrettyPrint bool
425	// Setting if line number emitting is enabled
426	// In this form, Amber emits line number comments in the output template. It is usable in debugging environments.
427	// Default: false
428	LineNumbers bool
429	}
430	```
431
432	#### type DirOptions
433
434	```go
435	// Used to provide options to directory compilation
436	type DirOptions struct {
437	// File extension to match for compilation
438	Ext string
439	// Whether or not to walk subdirectories
440	Recursive bool
441	}
442	```
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