# `ket`

**ket** is the configuration language of **tek**.
it's based on [edn](https://en.wikipedia.org/wiki/Clojure#Extensible_Data_Notation)
but without all the features.

## usage

### with `tengri_output`

this is a `tengri_output` view layout defined using ket:

```edn
(bsp/s (fixed/y 2 :toolbar)
  (fill/x (align/c (bsp/w :pool
    (bsp/s :outputs (bsp/s :inputs (bsp/s :tracks :scenes)))))))
```

### with `tengri_input`

this is a `tengri_input` keymap defined using ket:

```edn
(@u       undo 1)
(@shift-u redo 1)
(@e       editor show :pool-clip)
(@ctrl-a  scene add)
(@ctrl-t  track add)
(@tab     pool toggle)
```

## tokens

ket has 4 "types", represented by variants of the `Value` enum:

* `Num` - numeric literal
* `Sym` - textual symbol
* `Key` - textual key
* `Exp` - parenthesized group of tokens

### numeric literal

numbers are passed through as is. only non-negative integers are supported.

```edn
0
123456
```

### keys

keys are the names of available operations. they look like this:

```edn
simple-key
multi-part/key
```

keys are implemented by the underlying subsystem:

* in `tengri_output`, keys are names of layout primitives
* in `tengri_input`, keys are names of commands

### symbols

symbols that start with `:` represent the names of variables
provided by the `Context` trait - such as command parameters,
or entire layout components:

```edn
:symbol-name
```

symbols that start with `@` represent keybindings.
they are parsed in `tengri_tui` and look like this:

```edn
@ctrl-alt-shift-space
```

### parenthesized groups

parenthesized groups represent things like expressions
or configuration statements, and look like this:

```edn
(some-key :symbol (some/other-key @another-symbol 123) 456)
```

## goals

* [ ] const parse
* [ ] live reload
* [ ] serialize modified code back to original indentation

## implementation notes

### `DslExpr` trait behavior

this is the trait which differentiates "a thing" from
"a thing that is many things".

|source         |key|exp    |head     |tail           |
|---------------|---|-------|---------|---------------|
|`a`            |`a`|e0     |`a`      |None           |
|`(a)`          |e1 |`a`    |`(a)`    |None           |
|`a b c`        |e2 |e0     |`a`      |`b c`          |
|`(a b c)`      |e1 |`a b c`|`(a b c)`|               |
|`(a b c) d e`  |e1 |e3     |`(a b c)`|`d e`          |
|`a (b c d) e f`|e1 |e0     |`a`      |`(b c d) e f`  |

* e0: Unexpected 'a'
* e1: Unexpected '('
* e2: Unexpected 'b'
* e3: Unexpected 'd'

## todo

### operators

* replace: `(:= :name :value1 :valueN)`
* append:  `(:+ :name :value2 :valueN)`
* filter:  `(:- :name :value2 :valueN)`
* map:     `(:* :name op)`
* reduce:  `(:/ :name op)`