From bcc9ce484cb10c58e5a2bd3f10adc22cf360a45d Mon Sep 17 00:00:00 2001
From: Michele Balistreri <michele@bitgamma.com>
Date: Thu, 4 Jul 2024 15:26:54 +0200
Subject: [PATCH] basic parsing

---
 app/core/core_btc.c | 116 ++++++++++++++++++++++++++++++++++++++++++--
 1 file changed, 112 insertions(+), 4 deletions(-)

diff --git a/app/core/core_btc.c b/app/core/core_btc.c
index afb74ec..e35503c 100644
--- a/app/core/core_btc.c
+++ b/app/core/core_btc.c
@@ -1,16 +1,124 @@
 #include "core.h"
+#include "mem.h"
 #include "bitcoin/psbt.h"
 
-void core_btc_tx_elem_handler(psbt_elem_t* rec) {
+#define BTC_MAX_INPUTS 10
+#define BTC_MAX_OUTPUTS 10
+
+enum btc_input_type {
+  BTC_INPUT_TYPE_LEGACY,
+  BTC_INPUT_TYPE_SEGWIT
+};
+
+enum btc_sighash_flag {
+  SIGHASH_DEFAULT = 0x00,
+  SIGHASH_ALL = 0x01,
+  SIGHASH_NONE = 0x02,
+  SIGHASH_SINGLE = 0x03,
+};
+
+typedef struct {
+  uint8_t* pubkey_hash;
+  uint8_t* amount;
+  uint8_t* bip32_path;
+  uint32_t bip32_path_len;
+  uint32_t master_fingerprint;
+  uint32_t sighash_flag;
+  enum btc_input_type input_type;
+} psbt_input_data_t;
+
+struct btc_tx_ctx {
+  psbt_tx_t tx;
+  psbt_txin_t inputs[BTC_MAX_INPUTS];
+  psbt_txout_t outputs[BTC_MAX_OUTPUTS];
+  psbt_input_data_t input_data[BTC_MAX_INPUTS];
+  size_t input_count;
+  size_t output_count;
+  app_err_t error;
+};
+
+static void core_btc_psbt_rec_handler(struct btc_tx_ctx* tx_data, size_t index, psbt_record_t* rec) {
+  if (rec->scope != PSBT_SCOPE_INPUTS) {
+    return;
+  } else if (index >= tx_data->input_count) {
+    tx_data->error = ERR_DATA;
+    return;
+  }
+
+  switch (rec->type) {
+  case PSBT_IN_NON_WITNESS_UTXO:
+  case PSBT_IN_REDEEM_SCRIPT:
+  case PSBT_IN_WITNESS_SCRIPT:
+    //TODO: implement
+    tx_data->error = ERR_DECODE;
+    break;
+  case PSBT_IN_WITNESS_UTXO:
+    if ((rec->val[8] != 22) || (rec->val[9] != 0x00) || (rec->val[10] != 20)) {
+      tx_data->error = ERR_DECODE;
+      return;
+    }
+
+    tx_data->input_data[index].input_type = BTC_INPUT_TYPE_SEGWIT;
+    tx_data->input_data[index].amount = rec->val;
+    tx_data->input_data[index].pubkey_hash = &rec->val[11];
+    break;
+  case PSBT_IN_BIP32_DERIVATION:
+    memcpy(&tx_data->input_data[index].master_fingerprint, rec->val, sizeof(uint32_t));
+    tx_data->input_data[index].bip32_path = &rec->val[4];
+    tx_data->input_data[index].bip32_path_len = rec->val_size - 4;
+    break;
+  case PSBT_IN_SIGHASH_TYPE:
+    memcpy(&tx_data->input_data[index].sighash_flag, rec->val, sizeof(uint32_t));
+    break;
+  }
+}
+
+static void core_btc_txelem_handler(struct btc_tx_ctx* tx_data, psbt_txelem_t* elem) {
+  switch (elem->elem_type) {
+  case PSBT_TXELEM_TX:
+    memcpy(&tx_data->tx, elem->elem.tx, sizeof(psbt_tx_t));
+    break;
+  case PSBT_TXELEM_TXIN:
+    if (tx_data->input_count < BTC_MAX_INPUTS) {
+      memcpy(&tx_data->inputs[tx_data->input_count++], elem->elem.txin, sizeof(psbt_txin_t));
+    } else {
+      tx_data->error = ERR_FULL;
+    }
+    break;
+  case PSBT_TXELEM_TXOUT:
+    if (tx_data->output_count < BTC_MAX_OUTPUTS) {
+      memcpy(&tx_data->outputs[tx_data->output_count++], elem->elem.txout, sizeof(psbt_txout_t));
+    } else {
+      tx_data->error = ERR_FULL;
+    }
+    break;
+  default:
+    break;
+  }
+}
+
+static void core_btc_parser_cb(psbt_elem_t* rec) {
+  struct btc_tx_ctx* tx_data = (struct btc_tx_ctx*) rec->user_data;
+
   if (rec->type == PSBT_ELEM_RECORD) {
-
+    core_btc_psbt_rec_handler(tx_data, rec->index, rec->elem.rec);
   } else if (rec->type == PSBT_ELEM_TXELEM) {
-
+    core_btc_txelem_handler(tx_data, rec->elem.txelem);
   }
 }
 
 void core_btc_psbt_run(struct zcbor_string* qr_request) {
+  struct btc_tx_ctx* tx_ctx = (struct btc_tx_ctx*) &qr_request->value[(qr_request->len + 3) & ~0x3];
+  memset(tx_ctx, 0, sizeof(struct btc_tx_ctx));
+
   psbt_t psbt;
   psbt_init(&psbt, (uint8_t*) qr_request->value, qr_request->len);
-  psbt_read(qr_request->value, qr_request->len, &psbt, core_btc_tx_elem_handler, NULL);
+  psbt_read(qr_request->value, qr_request->len, &psbt, core_btc_parser_cb, tx_ctx);
+
+  if (!tx_ctx->error != ERR_OK) {
+    //TODO: add error message
+    return;
+  }
+
+
 }