xrfragment/doc/RFC.md

# `://foo.com/my3d.asset#pos=1,0,0&prio=-5`

# URI parser

> icanhazcode? yes, see [URI.hx](https://github.com/coderofsalvation/xrfragment/blob/main/src/xrfragment/URI.hx)

1. fragment URI starts with `#`
1. fragments are split by `&`
1. `=` is used to split fragment key/values 
1. fragment-values are urlencoded (space becomes `+` using `encodeUriComponent` e.g.)
1. every recognized fragment key/value-pair is added to a central map/associative array/object

# XR Fragments (key/value params)
 
> ⛁ = supported in 3D asset-file (custom property or projection)<br>
> ⚂ = supported in navigator URI (`document.location.href` e.g.)<br>

| param   | type          | scope(s) | category          | notes                            |
|---------|---------------|-------|--------------------|---------------------------------|
| prio    | int (-10..1)  | ⛁     | Asset loading / linking | \#static allow client to ignore lower-prio objects in the renderloop, to compensate frame-drop/cpu/gpu-overload scenario’soc/notes/prio.md |
| pos     | 3D vector     | ⛁ ⚂   |HREF navigation/portals |  |


# XR Fragments parser
note: community parsers will prolly outperform this initial parser :)
> icanhazcode? yes, see [Parser.hx](https://github.com/coderofsalvation/xrfragment/blob/main/src/xrfragment/Parser.hx)

the gist of it:
1. each key has a regex to validate its value-type (see regexes) 
1. `|` is used to split multiple/fallback values
1. `,` assumes 1D/2D/3D vector-values like x[,y[,z]]
1. parseFloat(..) and parseInt(..) is applied to vector/float and int values 
1. anything else will be treated as string-value 
1. incompatible value-types will be dropped / not used

> the xrfragment specification should stay simple enough
> for anyone to write a parser using either regexes or grammar/lexers
> therefore expressions/comprehensions are not supported (max wildcard/comparison operators for queries e.g.)

# Parser Value types

| type | info | format | example                          |
|------|------|--------|----------------------------------|
|vector| x,y,z| comma-separated    | #pos=1,2,3           |
|string| color| FFFFFF (hex)      | #fog=5m,FFAACC        |
|string|      |                   | #q=-sun               |
|int   |      | [-]x[xxxxx]       | #price:>=100          |
|float |      | [-]x[.xxxx] (ieee)| #prio=-20
|array | mixed| \|-separated      | #pos=0,0,0|90,0,0     |

> rule for thumb: type-limitations will piggyback JSON limitations (IEEE floatsize e.g.)

1. hex colors are detected using regex `/^#([A-Fa-f0-9]{6}|[A-Fa-f0-9]{3})$/`
1. integers are detected using regex `/^[0-9]+$/`
1. floats are detected using regex `/^[0-9]+\.[0-9]+$/`
1. vectors are detected using regex `/[,]/` (but can also be an string referring to an entity-ID in the asset)

# Tests
 
the spec is tested with [JSON unittests](./../src/spec) consumed by [Test.hx](./../src/Test.hx) to cross-test all languages.