Add SRC-7 helper functions (#194)

## Type of change

<!--Delete points that do not apply-->

- New feature

## Changes

The following changes have been made:

- Splits the single file into multiple files and groups functions by
standard
- Adds helper functions for the `Metadata` type of the SRC-7 standard

## Notes

- This will require FuelLabs/sway-standards#20
to be merged first

---------

Co-authored-by: bitzoic <[email protected]>

README.md

@@ -37,7 +37,7 @@ These libraries contain helper functions and other tools valuable to blockchain
 - [Signed Integers](./libs/signed_integers/) is an interface to implement signed integers.
 - [Fixed Point Number](./libs/fixed_point/) is an interface to implement fixed-point numbers.
 - [Queue](./libs/queue/) is a linear data structure that provides First-In-First-Out (FIFO) operations. 
-- [Token](./libs/token/) is a basic implementation of the [SRC-20](https://github.com/FuelLabs/sway-standards/tree/master/standards/src_20) and [SRC-3](https://github.com/FuelLabs/sway-standards/tree/master/standards/src_3) standards.
+- [Token](./libs/token/) provides helper functions for the [SRC-20](https://github.com/FuelLabs/sway-standards/tree/master/standards/src_20), [SRC-3](https://github.com/FuelLabs/sway-standards/tree/master/standards/src_3), and [SRC-7](https://github.com/FuelLabs/sway-standards/tree/master/standards/src_7) standards.
 
 ## Using a library
 

libs/token/Forc.toml

@@ -3,3 +3,6 @@ authors = ["Fuel Labs <[email protected]>"]
 entry = "lib.sw"
 license = "Apache-2.0"
 name = "token"
+
+[dependencies]
+src_7 = { git = "https://github.com/FuelLabs/sway-standards", tag = "v0.1.2" }

libs/token/README.md

@@ -7,7 +7,7 @@
 
 # Overview
 
-The Token library provides basic function implementations of the [SRC-20; Token Standard](https://github.com/FuelLabs/sway-standards/tree/master/standards/src_20) and the [SRC-3; Mint and Burn Standard](https://github.com/FuelLabs/sway-standards/tree/master/standards/src_3). It is intended to make develpment of Native Assets using Sway quick and easy while following the standard's specifications.
+The Token library provides basic helper functions for the [SRC-20; Token Standard](https://github.com/FuelLabs/sway-standards/tree/master/standards/src_20), [SRC-3; Mint and Burn Standard](https://github.com/FuelLabs/sway-standards/tree/master/standards/src_3), and the [SRC-7; Arbitrary Asset Metadata Standard](https://github.com/FuelLabs/sway-standards/tree/master/standards/src_7). It is intended to make develpment of Native Assets using Sway quick and easy while following the standard's specifications.
 
 For more information please see the [specification](./SPECIFICATION.md).
 
@@ -40,7 +40,7 @@ storage {
 To use a function, simply pass the `StorageKey` from the prescribed storage block above. The example below shows the implementation of the [SRC-20](https://github.com/FuelLabs/sway-standards/tree/master/standards/src_20) standard in combination with the Token library with no user defined restrictions or custom functionality.
 
 ```rust
-use token::{
+use token::base::{
     _total_assets, 
     _total_supply,
     _name,
@@ -87,3 +87,5 @@ impl SRC20 for Contract {
 ```
 
 For more information please see the [specification](./SPECIFICATION.md).
+
+> **NOTE** Until [Issue #5025](https://github.com/FuelLabs/sway/issues/5025) is resolved, in order to use the SRC-7 portion of the library, you must also add the [SRC-7](https://github.com/FuelLabs/sway-standards/tree/master/standards/src_7) standard as a dependency.

libs/token/SPECIFICATION.md

@@ -10,42 +10,85 @@ The Token library can be used anytime a contract needs a basic implementation of
 
 ## Public Functions
 
-### `_total_assets()`
+### SRC-20
+
+#### `_total_assets()`
 
 This function will return the total number of individual assets for a contract.
 
-### `_total_supply()`
+#### `_total_supply()`
 
 This function will return the total supply of tokens for an asset.
 
-### `_name()`
+#### `_name()`
 
 This function will return the name of an asset, such as “Ether”.
 
-### `_symbol()`
+#### `_symbol()`
 
 This function will return the symbol of an asset, such as “ETH”.
 
-### `_decimals()`
+#### `_decimals()`
 
 This function will return the number of decimals an asset uses.
 
-### `_mint()`
+#### `_set_name()`
+
+This function will unconditionally set the name of an asset.
+
+#### `_set_symbol()`
+
+This function will unconditionally set the symbol of an asset.
+
+#### `_set_decimals`
+
+This function will unconditionally set the decimals of an asset.
+
+### SRC-3
+
+#### `_mint()`
 
 This function will unconditionally mint new tokens using a sub-identifier.
 
-### `_burn()`
+#### `_burn()`
 
 This function will burns tokens with the given sub-identifier.
 
-### `_set_name()`
+### SRC-7
 
-This function will unconditionally set the name of an asset.
+### `_set_metadata()`
 
-### `_set_symbol()`
+This function will set metdata for an asset.
 
-This function will unconditionally set the symbol of an asset.
+#### `as_string()`
 
-### `_set_decimals`
+This function will return the metadata as a string.
+
+#### `as_int()`
+
+This function will return the metadata as an int.
+
+#### `as_bytes()`
+
+This function will return the metadata as bytes.
+
+#### `as_b256()`
+
+This function will return the metadata as a b256.
+
+#### `is_string()`
+
+This function will return whether the metadata is a string.
+
+#### `is_int()`
+
+This function will return the whether metadata is an int.
+
+#### `is_bytes()`
+
+This function will return the whether metadata are bytes.
+
+#### `is_b256()`
+
+This function will return the whether metadata is a b256.
 
-This function will unconditionally set the decimals of an asset.