#pragma version 5
// ================================================================================================
// Price-Reference Program 
// ================================================================================================
//
// This contract has the following invariants at
// deployment stage:
//
// TMPL_VALIDATOR Unique data validator address that signs and sends the incoming message
//
// App-globals:
// symbol   : pair supported by this app.
// nonce    : last sequence ID
// price    : current price 
// stdev    : current confidence (standard deviation)
// ts       : timestamp
//
// Slots:
// 0        Input message block 
// 1        SHA256-Hashed message 
// 
// The Message format must have the packed fields:
// 
//  Field size
//  10          header      Literal "PRICE_DATA"
//  1           version     int8 (Must be 1)
//  8           dest        This appId 
//  8           nonce       uint64 Sequence identifier 
//  16          symbol      String filled with spaces e.g ("ALGO/USD        ")
//  8           price       uint64 encoded price
//  8           conf        uint64 encoded confidence (kind of SD) 
//  8           ts          timestamp of this price
//  32          r           Signature r-component
//  32          s           Signature s-component 
//  1           v           Signature v-component 
//
//  Size: 131 bytes. 
//
// ------------------------------------------------------------------------------------------------


// Application creation.
int 0
txn ApplicationID
==
bnz success

// Handle app call: send price message
txn OnCompletion
int NoOp
==
bnz handle_call

// Fail otherwise
err

// -----------------------------------------------------
// Receive price message 
// -----------------------------------------------------

handle_call:

// Verify if sender is the data validator
txn Sender 
addr PIQHXRVFDP4KSEZUPW6TB4UCDVJ5GJ3YYJIQWKWMEW2AUHJJCHPB4GPNCU
==
assert

// Retrieve message, store in slot 0
txn ApplicationArgs 0
store 0

// ------------------------------------------------------
// Validate message 
// ------------------------------------------------------

// Check length

load 0
len
int 131
==
assert

// Check header

load 0
byte "PRICEDATA"
extract 0 9
==
assert

// Check version - must be 1.

load 0
extract 9 1
byte 0x01
==
assert

// Check destination - must be this appId.

load 0
extract 10 8
btoi
txn ApplicationID
==
assert 

// Check nonce 

load 0
extract 18 8
btoi
byte "nonce"
app_global_get
>
assert

// Check timestamp  order

load 0 
extract 58 8
btoi 
global LatestTimestamp
<=
assert 

// Hash message block  

load 0
extract 0 65
sha512_256
store 1

// push data, followed by signature S, signature R, pubkey X, pubkey Y
load 0
dup
extract 66 32
load 0
extract 98 32

// Unpack pubkey X,Y components
ecdsa_pk_decompress Secp256k1

// Verify signature 
ecdsa_verify Secp256k1
int 1
==
assert

// ----------------------------------------------------------------------------
// Verified. Store data to app globals.
// ----------------------------------------------------------------------------

byte "nonce"
load 0
extract 18 8
app_global_put

byte "ts"
load 0 
extract 58 8
btoi 
app_global_put

byte "price"
load 0
extract 42 8 
btoi 
app_global_put

byte "stdev"
load 0
extract 50 8
btoi
app_global_put

b success

// ----------------------------------------------------------------------------

fail: 
int 0
return 

success:
int 1 
return