package uuid

import "core:crypto/legacy/md5"
import "core:crypto/legacy/sha1"
import "core:math/rand"
import "core:mem"

/*
Generate a version 3 UUID.

This UUID is generated from a name within a namespace.
MD5 is used to hash the name with the namespace to produce the UUID.

Inputs:
- namespace: Another `Identifier` that is used to represent the underlying namespace.
  This can be any one of the `Namespace_*` values provided in this package.
- name: The byte slice used to generate the name on top of the namespace.

Returns:
- result: The generated UUID.
*/
generate_v3_bytes :: proc(
	namespace: Identifier,
	name: []byte,
) -> (
	result: Identifier,
) {
	namespace := namespace

	ctx: md5.Context
	md5.init(&ctx)
	md5.update(&ctx, namespace[:])
	md5.update(&ctx, name)
	md5.final(&ctx, result[:])

	result[VERSION_BYTE_INDEX] &= 0x0F
	result[VERSION_BYTE_INDEX] |= 0x30

	result[VARIANT_BYTE_INDEX] &= 0x3F
	result[VARIANT_BYTE_INDEX] |= 0x80

	return
}

/*
Generate a version 3 UUID.

This UUID is generated from a name within a namespace.
MD5 is used to hash the name with the namespace to produce the UUID.

Inputs:
- namespace: Another `Identifier` that is used to represent the underlying namespace.
  This can be any one of the `Namespace_*` values provided in this package.
- name: The string used to generate the name on top of the namespace.

Returns:
- result: The generated UUID.
*/
generate_v3_string :: proc(
	namespace: Identifier,
	name: string,
) -> (
	result: Identifier,
) {
	return generate_v3_bytes(namespace, transmute([]byte)name)
}

generate_v3 :: proc {
	generate_v3_bytes,
	generate_v3_string,
}

/*
Generate a version 4 UUID.

This UUID will be pseudorandom, save for 6 pre-determined version and variant bits.

Returns:
- result: The generated UUID.
*/
generate_v4 :: proc() -> (result: Identifier) {
	bytes_generated := rand.read(result[:])
	assert(bytes_generated == 16, "RNG failed to generate 16 bytes for UUID v4.")

	result[VERSION_BYTE_INDEX] &= 0x0F
	result[VERSION_BYTE_INDEX] |= 0x40

	result[VARIANT_BYTE_INDEX] &= 0x3F
	result[VARIANT_BYTE_INDEX] |= 0x80

	return
}

/*
Generate a version 5 UUID.

This UUID is generated from a name within a namespace.
SHA1 is used to hash the name with the namespace to produce the UUID.

Inputs:
- namespace: Another `Identifier` that is used to represent the underlying namespace.
  This can be any one of the `Namespace_*` values provided in this package.
- name: The byte slice used to generate the name on top of the namespace.

Returns:
- result: The generated UUID.
*/
generate_v5_bytes :: proc(
	namespace: Identifier,
	name: []byte,
) -> (
	result: Identifier,
) {
	namespace := namespace
	digest: [sha1.DIGEST_SIZE]byte

	ctx: sha1.Context
	sha1.init(&ctx)
	sha1.update(&ctx, namespace[:])
	sha1.update(&ctx, name)
	sha1.final(&ctx, digest[:])

	mem.copy_non_overlapping(&result, &digest, 16)

	result[VERSION_BYTE_INDEX] &= 0x0F
	result[VERSION_BYTE_INDEX] |= 0x50

	result[VARIANT_BYTE_INDEX] &= 0x3F
	result[VARIANT_BYTE_INDEX] |= 0x80

	return
}

/*
Generate a version 5 UUID.

This UUID is generated from a name within a namespace.
SHA1 is used to hash the name with the namespace to produce the UUID.

Inputs:
- namespace: Another `Identifier` that is used to represent the underlying namespace.
  This can be any one of the `Namespace_*` values provided in this package.
- name: The string used to generate the name on top of the namespace.

Returns:
- result: The generated UUID.
*/
generate_v5_string :: proc(
	namespace: Identifier,
	name: string,
) -> (
	result: Identifier,
) {
	return generate_v5_bytes(namespace, transmute([]byte)name)
}

generate_v5 :: proc {
	generate_v5_bytes,
	generate_v5_string,
}