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# odin-mustache
Native implementation of {{mustache}} templates in [Odin](https://odin-lang.org).
https://github.com/benjamindblock/odin-mustache/assets/1155805/7d794861-e308-4132-aaa0-f800392208a4
All features are implemented, except for the ability to change delimiters.
All in tests in the [official mustache spec](https://github.com/mustache/spec) pass successfully (except for the delimiters spec suite).
## Documentation
For more information about mustache, see the [mustache project page](https://mustache.github.io) or the mustache [man](https://mustache.github.io/mustache.5.html) [pages](https://mustache.github.io/mustache.1.html).
View some [example mustache files](https://github.com/mustache/mustache/tree/master/examples) to get an overview.
## Spec
The [mustache-spec](https://github.com/mustache/spec) repo is added as a git submodule for testing purposes. To run tests, ensure that you run `git clone --recursive` and/or `git submodule update` as needed.
## Usage
### CLI Usage
```
Usage:
odin-mustache [path to template] [path to JSON] [OPTIONAL - layout]
Examples:
$ odin-mustache template.txt data.json
```
### Odin Usage
#### 1. `render(template: string, data: any, partials: any, allocator := context.allocator)`
Renders a template, provided as a `string`. `data` and `partials` should be *either* a `map[string]...` or a `struct`.
All `map` arguments passed **must** be keyed with `string` type data. When parsing a Mustache template, the text inside a tag (eg. `name` inside `{{name}}`) will be parsed as a `string`.
#### 2. `render_from_filename(filename: string, data: any, partials: any, allocator := context.allocator)`
Renders a template stored in a text file using `data` and `partials` provided.
#### 3. `render_with_json(template: string, json_filename: string, allocator := context.allocator)`
Renders a template `string` using data and partials stored inside a JSON file. `odin-mustache` will handle loading the JSON into a usable format for Mustache to work with.
**NOTE**: The JSON file leverages the following top-level keys:
```
"data": [required]
"partials": [optional]
```
#### 4. `render_from_filename_with_json(filename: string, json_filename: string, allocator := context.allocator)`
Renders a template stored in a text file using data and partials stored inside a JSON file. `odin-mustache` will handle loading the JSON into a usable format for Mustache to work with.
#### Example
```odin
input := "Hello, {{name}}!"
data: map[string]string = {
"name" = "St. Charles",
}
output, err := render(input, data, context.temp_allocator)
// => "Hello, St. Charles!"
```
## Escaping
`odin-mustache` follows the official mustache HTML escaping rules. That is, if you enclose a variable with two curly brackets, `{{var}}`, the contents are HTML-escaped. For instance, strings like `5 > 2` are converted to `5 > 2`. To use raw characters, use three curly brackets `{{{var}}}`.
## Layouts
`odin-mustache` supports rendering templates with layouts.
A layout is a regular template with a special function. It accepts **a `{{content}}` tag**. This is where the output of a child template will be inserted. Layouts have access to the same data provided to the regular template.
Layouts can render content in both `{{normal}}` and `{{{literal}}}` tags.
This is helpful for rendering scenarios like websites where the same elements (`<head>`, `<footer>`, etc.) are shared across all pages, each of which has their own page-specific template.
```
<html>
{{{head}}
<body>
{{{content}}}
</body>
{{{footer}}
</html>
```
### CLI Usage
```
Usage:
odin-mustache [path to template] [path to JSON] [OPTIONAL - layout]
Examples:
$ odin-mustache template.html data.json layout.html
```
### Odin Usage
To render a layout in Odin, all four of the above render procedures have `in_layout` and `in_layout_file` variations. These methods will insert the rendered content of a template within the given layout. This is convenient for rendering HTML views inside a larger layout, amongst other use-cases.
The full list of corresponding methods is:
- `render_in_layout(template: string, data: any, layout: string, partials: any, allocator := context.allocator)`
- `render_in_layout_file(template: string, data: any, layout_filename: string, partials: any, allocator := context.allocator)`
- `render_from_filename_in_layout(filename: string, data: any, layout: string, partials: any, allocator := context.allocator)`
- `render_from_filename_in_layout_file(filename: string, data: any, layout_filename: string, partials: any, allocator := context.allocator)`
- `render_with_json_in_layout(template: string, json_filename: string, layout: string, allocator := context.allocator)`
- `render_with_json_in_layout_file(template: string, json_filename: string, layout_filename: string, allocator := context.allocator)`
- `render_from_filename_with_json_in_layout(filename: string, json_filename: string, layout: string, allocator := context.allocator)`
- `render_from_filename_with_json_in_layout_file(filename: string, json_filename: string, layout_filename: string, allocator := context.allocator)`
#### Example
```odin
template := "Hello, {{name}}."
data := map[string]string{"name" = "Kilgarvan"}
layout := `Above >>
{{content}}
<< Below`
output, _ := render_in_layout(template, data, layout, allocator := context.temp_allocator)
fmt.println(output)
// Above >>
// Hello, Kilgarvan.
// << Below
```
## Precompiled Templates
`odin-mustache` works in two steps:
1. Lexing and parsing
2. Rendering with data
If you are rendering the same template multiple times (ex: sending out personalized emails to subscribers), the lexing+parsing step can be performed once to create a compiled template. This compiled template can then be used multiple times with different data.
### Example
```odin
src := "Hello, {{name}}!"
template: Template
output: string
data: map[string]string
partials: map[string]string
lexer := Lexer{src=src, delim=CORE_DEF}
lexer_parse(&lexer)
data = {"name" = "St. Charles"}
template = Template{lexer=lexer, data=data, partials=partials}
output, _ = template_render(&template)
// => Hello, St. Charles!
data = {"name" = "Edouard"}
template = Template{lexer=lexer, data=data, partials=partials}
output, _ = template_render(&template)
// => Hello, Edouard!
```
## Future Work
- Validate JSON keys
- Better CLI argument parsing
- Improve error handling and reporting
- Add optional logging for debugging and performance work
- Configurable precision for floating point types
- Add support for changing delimiters
- Special loop conditionals (eg., checking for the first iteration or last iteration)