Updates ABI spec with hash based ids, versions and program type.

Adds specification for how hashes based ids are generated from a string
representation of types.

Updates `json-abi-format.md` with versions, program type, and hash based ids.

src/SUMMARY.md

@@ -28,6 +28,7 @@
  - [Receipts](./abi/receipts.md)
  - [Function Selector Encoding](./abi/fn-selector-encoding.md)
  - [Argument Encoding](./abi/argument-encoding.md)
+ - [Hash Based Ids](./abi/hash-based-ids.md)
 - [FuelVM](./fuel-vm/index.md)
  - [Instruction Set](./fuel-vm/instruction-set.md)
 - [Networks](./networks/index.md)

src/abi/hash-based-ids.md

@@ -0,0 +1,72 @@
+# Hash based IDs
+
+Hash based ids are deterministically generated from associated types and are used in the JSON ABI for `type` IDs and for `logId`.
+This document specifies how the hash based IDS are generated for `type` IDs and for `logId`.
+
+## Generation
+
+Hash based ids for `type` IDs are generated from the `sha256` of a string that represents the type.
+
+For `logIds` we use the first 8 bytes of the `sha256` of a string that represents the type, this is because the `LOG` and `LOGD` opcodes use a 64bit value as log id.
+
+## String representation of types
+
+For describing the string representation of type we will use the notation `{abi_str(T)}` that should be replaced by the respective ABI string representation of the respective type `T`.
+
+### Intrinsics
+
+ `u8` => `"u8"`
+ `u16` => `"u16"`
+ `u32` => `"u32"`
+ `u64` => `"u64"`
+ `u256` => `"u256"`
+ `b256` => `"b256"`
+ `bool` => `"bool"`
+
+### String arrays
+
+ String array of size `1` => `"str[1]"`
+ String array of size `2` => `"str[2]"`
+ etc.
+
+### String slices
+
+ String slice => `"str"`
+
+### Arrays
+
+ `[T; 1]` => `"[{abi_str(T)}; 1]"`
+ `[T; 2]` => `"[{abi_str(T)}; 2]"`
+etc.
+
+### Tuples
+
+ `()` => `"()"`
+ `(T1)` => `"({abi_str(T1)})"`
+ `(T1,T2)` => `"({abi_str(T1)}, {abi_str(T2)})"`
+etc.
+
+### Enums
+
+ `Option` enum with type parameter `T` => `"enum std::option::Option<{abi_str(T)}>"`
+ Enum without type parameters named `MyEnum` => `"enum MyEnum"`
+ Enum with type parameter `T1` named `MyEnum` => `"enum MyEnum<{abi_str(T1)}>"`
+ Enum with type parameters `T1`, `T2` named `MyEnum` in `my_module` => `"enum my_module::MyEnum<{abi_str(T1)},{abi_str(T2)}>"`
+
+### Structs
+
+ `Vec` struct with type parameter `T` => `"struct std::vec::Vec<{abi_str(T)}>"`
+ Struct without type parameters named `MyStruct` => `"struct MyStruct"`
+ Struct with type parameter `T1` named `MyStruct` => `"struct MyStruct<{abi_str(T1)}>"`
+ Struct with type parameters `T1`, `T2` named `MyStruct` in `my_module` => `"struct my_module::MyStruct<{abi_str(T1)},{abi_str(T2)}>"`
+
+### Generic Type Parameter
+
+ Generic type parameter `T` if root type => `"generic T"`
+ Generic type parameter `T` if not root type => `"T"` as in `"struct MyStruct<T>"`
+
+### Complex examples composition
+
+ Tuple of array and `u64` => `"([u64,1]; u64)"`
+ Array of `Option<u64>`=> `"[enum std::option::Option<u64>; 3]"`
+ Struct with tuple type parameter => `"struct my_module::MyStruct<(u64, u64)>"`

src/abi/index.md

@@ -6,3 +6,4 @@ This document describes and specifies the ABI (Application Binary Interface) of
 - [Receipts](./receipts.md)
 - [Function Selector Encoding](./fn-selector-encoding.md)
 - [Argument Encoding](./argument-encoding.md)
+- [Hash Based Ids](./hash-based-ids.md)