## Nim wrappers for the functions defined in librln
import
  ../protocol_types


when (NimMajor, NimMinor) < (1, 4):
  {.push raises: [Defect].}
else:
  {.push raises: [].}


## Buffer struct is taken from
# https://github.com/celo-org/celo-threshold-bls-rs/blob/master/crates/threshold-bls-ffi/src/ffi.rs
type Buffer* = object
  `ptr`*: ptr uint8
  len*: uint

proc toBuffer*(x: openArray[byte]): Buffer =
  ## converts the input to a Buffer object
  ## the Buffer object is used to communicate data with the rln lib
  var temp = @x
  let baseAddr = cast[pointer](x)
  let output = Buffer(`ptr`: cast[ptr uint8](baseAddr), len: uint(temp.len))
  return output


######################################################################
## RLN Zerokit module APIs
######################################################################

#------------------------------ Merkle Tree operations -----------------------------------------
proc update_next_member*(ctx: ptr RLN, input_buffer: ptr Buffer): bool {.importc: "set_next_leaf".}
## adds an element in the merkle tree to the next available position
## input_buffer points to the id commitment byte seq
## the return bool value indicates the success or failure of the operation

proc delete_member*(ctx: ptr RLN, index: uint): bool {.importc: "delete_leaf".}
## index is the position of the id commitment key to be deleted from the tree
## the deleted id commitment key is replaced with a zero leaf
## the return bool value indicates the success or failure of the operation

proc get_root*(ctx: ptr RLN, output_buffer: ptr Buffer): bool {.importc: "get_root".}
## get_root populates the passed pointer output_buffer with the current tree root
## the output_buffer holds the Merkle tree root of size 32 bytes
## the return bool value indicates the success or failure of the operation

proc get_merkle_proof*(ctx: ptr RLN, index: uint, output_buffer: ptr Buffer): bool {.importc: "get_proof".}
## populates the passed pointer output_buffer with the merkle proof for the leaf at position index in the tree stored by ctx
## the output_buffer holds a serialized Merkle proof (vector of 32 bytes nodes)
## the return bool value indicates the success or failure of the operation

proc set_leaf*(ctx: ptr RLN, index: uint, input_buffer: ptr Buffer): bool {.importc: "set_leaf".}
## sets the leaf at position index in the tree stored by ctx to the value passed by input_buffer
## the input_buffer holds a serialized leaf of 32 bytes
## the return bool value indicates the success or failure of the operation

proc init_tree_with_leaves*(ctx: ptr RLN, input_buffer: ptr Buffer): bool {.importc: "init_tree_with_leaves".}
## sets multiple leaves in the tree stored by ctx to the value passed by input_buffer
## the input_buffer holds a serialized vector of leaves (32 bytes each)
## the input_buffer size is prefixed by a 8 bytes integer indicating the number of leaves
## leaves are set one after each other starting from index 0
## the return bool value indicates the success or failure of the operation

proc atomic_write*(ctx: ptr RLN, index: uint, leaves_buffer: ptr Buffer, indices_buffer: ptr Buffer): bool {.importc: "atomic_operation".}
## sets multiple leaves, and zeroes out indices in the tree stored by ctx to the value passed by input_buffer
## the leaves_buffer holds a serialized vector of leaves (32 bytes each)
## the leaves_buffer size is prefixed by a 8 bytes integer indicating the number of leaves
## the indices_bufffer holds a serialized vector of indices (8 bytes each)
## the indices_buffer size is prefixed by a 8 bytes integer indicating the number of indices
## leaves are set one after each other starting from index `index`
## the return bool value indicates the success or failure of the operation

proc reset_tree*(ctx: ptr RLN, tree_height: uint): bool {.importc: "set_tree".}
## resets the tree stored by ctx to the the empty tree (all leaves set to 0) of height tree_height
## the return bool value indicates the success or failure of the operation

#----------------------------------------------------------------------------------------------

#-------------------------------- zkSNARKs operations -----------------------------------------
proc key_gen*(ctx: ptr RLN, output_buffer: ptr Buffer): bool {.importc: "extended_key_gen".}
## generates identity trapdoor, identity nullifier, identity secret hash and id commitment tuple serialized inside output_buffer as | identity_trapdoor<32> | identity_nullifier<32> | identity_secret_hash<32> | id_commitment<32> |
## identity secret hash is the poseidon hash of [identity_trapdoor, identity_nullifier]
## id commitment is the poseidon hash of the identity secret hash
## the return bool value indicates the success or failure of the operation

proc seeded_key_gen*(ctx: ptr RLN, input_buffer: ptr Buffer, output_buffer: ptr Buffer): bool {.importc: "seeded_extended_key_gen".}
## generates identity trapdoor, identity nullifier, identity secret hash and id commitment tuple serialized inside output_buffer as | identity_trapdoor<32> | identity_nullifier<32> | identity_secret_hash<32> | id_commitment<32> | using ChaCha20
## seeded with an arbitrary long seed serialized in input_buffer
## The input seed provided by the user is hashed using Keccak256 before being passed to ChaCha20 as seed.
## identity secret hash is the poseidon hash of [identity_trapdoor, identity_nullifier]
## id commitment is the poseidon hash of the identity secret hash
## the return bool value indicates the success or failure of the operation

proc generate_proof*(ctx: ptr RLN,
                         input_buffer: ptr Buffer,
                         output_buffer: ptr Buffer): bool {.importc: "generate_rln_proof".}
## input_buffer has to be serialized as [ id_key<32> | id_index<8> | epoch<32> | signal_len<8> | signal<var> ]
## output_buffer holds the proof data and should be parsed as [ proof<128> | root<32> | epoch<32> | share_x<32> | share_y<32> | nullifier<32> | rln_identifier<32> ]
## integers wrapped in <> indicate value sizes in bytes
## the return bool value indicates the success or failure of the operation

proc verify*(ctx: ptr RLN,
                       proof_buffer: ptr Buffer,
                       proof_is_valid_ptr: ptr bool): bool {.importc: "verify_rln_proof".}
## proof_buffer has to be serialized as [ proof<128> | root<32> | epoch<32> | share_x<32> | share_y<32> | nullifier<32> | rln_identifier<32> | signal_len<8> | signal<var> ]
## the return bool value indicates the success or failure of the call to the verify function
## the verification of the zk proof is available in proof_is_valid_ptr, where a value of true indicates success and false a failure

proc verify_with_roots*(ctx: ptr RLN,
                      proof_buffer: ptr Buffer,
                      roots_buffer: ptr Buffer,
                      proof_is_valid_ptr: ptr bool): bool {.importc: "verify_with_roots".}
## proof_buffer has to be serialized as [ proof<128> | root<32> | epoch<32> | share_x<32> | share_y<32> | nullifier<32> | rln_identifier<32> | signal_len<8> | signal<var> ]
## roots_buffer contains the concatenation of 32 bytes long serializations in little endian of root values
## the return bool value indicates the success or failure of the call to the verify function
## the verification of the zk proof is available in proof_is_valid_ptr, where a value of true indicates success and false a failure

proc zk_prove*(ctx: ptr RLN,
            input_buffer: ptr Buffer,
            output_buffer: ptr Buffer): bool {.importc: "prove".}
## Computes the zkSNARK proof and stores it in output_buffer for input values stored in input_buffer
## input_buffer is serialized as input_data as [ id_key<32> | path_elements<Vec<32>> | identity_path_index<Vec<1>> | x<32> | epoch<32> | rln_identifier<32> ]
## output_buffer holds the proof data and should be parsed as [ proof<128> ]
## path_elements and indentity_path elements serialize a merkle proof for id_key and are vectors of elements of 32 and 1 bytes, respectively (not. Vec<>).
## x is the x coordinate of the Shamir's secret share for which the proof is computed
## epoch is the input epoch (equivalently, the nullifier)
## the return bool value indicates the success or failure of the operation

proc zk_verify*(ctx: ptr RLN,
             proof_buffer: ptr Buffer,
             proof_is_valid_ptr: ptr bool): bool {.importc: "verify".}
## Verifies the zkSNARK proof passed in proof_buffer
## input_buffer is serialized as input_data as [ proof<128> ]
## the verification of the zk proof is available in proof_is_valid_ptr, where a value of true indicates success and false a failure
## the return bool value indicates the success or failure of the operation

#----------------------------------------------------------------------------------------------

#-------------------------------- Common procedures -------------------------------------------
proc new_circuit*(tree_height: uint, input_buffer: ptr Buffer, ctx: ptr (ptr RLN)): bool {.importc: "new".}
## creates an instance of rln object as defined by the zerokit RLN lib
## tree_height represent the depth of the Merkle tree
## input_buffer contains a serialization of the path where the circuit resources can be found (.r1cs, .wasm, .zkey and optionally the verification_key.json)
## ctx holds the final created rln object
## the return bool value indicates the success or failure of the operation

proc new_circuit_from_data*(tree_height: uint, circom_buffer: ptr Buffer, zkey_buffer: ptr Buffer, vk_buffer: ptr Buffer, ctx: ptr (ptr RLN)): bool {.importc: "new_with_params".}
## creates an instance of rln object as defined by the zerokit RLN lib by passing the required inputs as byte arrays
## tree_height represent the depth of the Merkle tree
## circom_buffer contains the bytes read from the Circom .wasm circuit
## zkey_buffer contains the bytes read from the .zkey proving key
## vk_buffer contains the bytes read from the verification_key.json
## ctx holds the final created rln object
## the return bool value indicates the success or failure of the operation

#-------------------------------- Hashing utils -------------------------------------------

proc sha256*(input_buffer: ptr Buffer,
             output_buffer: ptr Buffer): bool {.importc: "hash".}
## it hashes (sha256) the plain text supplied in inputs_buffer and then maps it to a field element
## this proc is used to map arbitrary signals to field element for the sake of proof generation
## inputs_buffer holds the hash input as a byte seq
## the hash output is generated and populated inside output_buffer
## the output_buffer contains 32 bytes hash output

proc poseidon*(input_buffer: ptr Buffer,
               output_buffer: ptr Buffer): bool {.importc: "poseidon_hash".}
## it hashes (poseidon) the plain text supplied in inputs_buffer
## this proc is used to compute the identity secret hash, and external nullifier
## inputs_buffer holds the hash input as a byte seq
## the hash output is generated and populated inside output_buffer
## the output_buffer contains 32 bytes hash output