working on /refresh/melt operation

5 files changed, 304 insertions, 337 deletions

diff --git a/src/mint/mint_db.c b/src/mint/mint_db.c
index 9a35ddbd4..57a1014b7 100644
--- a/src/mint/mint_db.c
+++ b/src/mint/mint_db.c
@@ -494,51 +494,6 @@ TALER_MINT_DB_prepare (PGconn *db_conn)
 }
 
 
-/**
- * Insert a refresh order into the database.
- */
-int
-TALER_MINT_DB_insert_refresh_order (PGconn *db_conn,
-                                    uint16_t newcoin_index,
-                                    const struct GNUNET_CRYPTO_EddsaPublicKey *session_pub,
-                                    const struct GNUNET_CRYPTO_rsa_PublicKey *denom_pub)
-{
-  uint16_t newcoin_index_nbo = htons (newcoin_index);
-  char *buf;
-  size_t buf_size;
-  PGresult *result;
-
-  buf_size = GNUNET_CRYPTO_rsa_public_key_encode (denom_pub,
-                                                  &buf);
-
-  {
-    struct TALER_DB_QueryParam params[] = {
-      TALER_DB_QUERY_PARAM_PTR (&newcoin_index_nbo),
-      TALER_DB_QUERY_PARAM_PTR (session_pub),
-      TALER_DB_QUERY_PARAM_PTR_SIZED (buf, buf_size),
-      TALER_DB_QUERY_PARAM_END
-    };
-    result = TALER_DB_exec_prepared (db_conn,
-                                     "insert_refresh_order",
-                                     params);
-  }
-  GNUNET_free (buf);
-  if (PGRES_COMMAND_OK != PQresultStatus (result))
-  {
-    break_db_err (result);
-    PQclear (result);
-    return GNUNET_SYSERR;
-  }
-  if (0 != strcmp ("1", PQcmdTuples (result)))
-  {
-    GNUNET_break (0);
-    return GNUNET_SYSERR;
-  }
-  PQclear (result);
-  return GNUNET_OK;
-}
-
-
 int
 TALER_MINT_DB_set_commit_signature (PGconn *db_conn,
                                     const struct GNUNET_CRYPTO_EddsaPublicKey *session_pub,
@@ -578,55 +533,6 @@ TALER_MINT_DB_set_reveal_ok (PGconn *db_conn,
 }
 
 
-struct GNUNET_CRYPTO_rsa_PublicKey *
-TALER_MINT_DB_get_refresh_order (PGconn *db_conn,
-                                 uint16_t newcoin_index,
-                                 const struct GNUNET_CRYPTO_EddsaPublicKey *session_pub)
-
-{
-  char *buf;
-  size_t buf_size;
-  struct GNUNET_CRYPTO_rsa_PublicKey *denom_pub;
-  uint16_t newcoin_index_nbo = htons (newcoin_index);
-
-  struct TALER_DB_QueryParam params[] = {
-    TALER_DB_QUERY_PARAM_PTR(session_pub),
-    TALER_DB_QUERY_PARAM_PTR(&newcoin_index_nbo),
-    TALER_DB_QUERY_PARAM_END
-  };
-
-  PGresult *result = TALER_DB_exec_prepared (db_conn, "get_refresh_order", params);
-
-  if (PGRES_TUPLES_OK != PQresultStatus (result))
-  {
-    break_db_err (result);
-    PQclear (result);
-    return NULL;
-  }
-
-  if (0 == PQntuples (result))
-  {
-    PQclear (result);
-    /* FIXME: may want to distinguish between different error cases! */
-    return NULL;
-  }
-  GNUNET_assert (1 == PQntuples (result));
-  struct TALER_DB_ResultSpec rs[] = {
-    TALER_DB_RESULT_SPEC_VAR ("denom_pub", &buf, &buf_size),
-    TALER_DB_RESULT_SPEC_END
-  };
-  if (GNUNET_OK != TALER_DB_extract_result (result, rs, 0))
-  {
-    PQclear (result);
-    GNUNET_break (0);
-    return NULL;
-  }
-  PQclear (result);
-  denom_pub = GNUNET_CRYPTO_rsa_public_key_decode (buf, buf_size);
-  GNUNET_free (buf);
-  return denom_pub;
-}
-
 
 int
 TALER_MINT_DB_insert_refresh_collectable (PGconn *db_conn,
@@ -1480,61 +1386,23 @@ TALER_MINT_DB_update_refresh_session (PGconn *db_conn,
 
 
 /**
- * Test if the given /refresh/melt request is known to us.
- *
- * @param db_conn database connection
- * @param melt melt operation
- * @return #GNUNET_YES if known,
- *         #GNUENT_NO if not,
- *         #GNUNET_SYSERR on internal error
- */
-int
-TALER_MINT_DB_have_refresh_melt (PGconn *db_conn,
-                                 const struct RefreshMelt *melt)
-{
-  // FIXME: check logic!
-  uint16_t oldcoin_index_nbo = htons (melt->oldcoin_index);
-  struct TALER_DB_QueryParam params[] = {
-    TALER_DB_QUERY_PARAM_PTR(&melt->session_pub),
-    TALER_DB_QUERY_PARAM_PTR(&oldcoin_index_nbo),
-    TALER_DB_QUERY_PARAM_END
-  };
-
-  PGresult *result = TALER_DB_exec_prepared (db_conn,
-                                             "get_refresh_melt",
-                                             params);
-  if (PGRES_TUPLES_OK != PQresultStatus (result))
-  {
-    break_db_err (result);
-    PQclear (result);
-    return GNUNET_SYSERR;
-  }
-
-  if (0 == PQntuples (result))
-  {
-    PQclear (result);
-    return GNUNET_NO;
-  }
-  GNUNET_break (1 == PQntuples (result));
-  PQclear (result);
-  return GNUNET_YES;
-}
-
-
-/**
  * Store the given /refresh/melt request in the database.
  *
  * @param db_conn database connection
+ * @param session session key of the melt operation
+ * @param oldcoin_index index of the coin to store
  * @param melt melt operation
  * @return #GNUNET_OK on success
  *         #GNUNET_SYSERR on internal error
  */
 int
 TALER_MINT_DB_insert_refresh_melt (PGconn *db_conn,
+                                   const struct GNUNET_CRYPTO_EddsaPublicKey *session,
+                                   uint16_t oldcoin_index,
                                    const struct RefreshMelt *melt)
 {
   // FIXME: check logic!
-  uint16_t oldcoin_index_nbo = htons (melt->oldcoin_index);
+  uint16_t oldcoin_index_nbo = htons (oldcoin_index);
   char *buf;
   size_t buf_size;
   PGresult *result;
@@ -1543,7 +1411,7 @@ TALER_MINT_DB_insert_refresh_melt (PGconn *db_conn,
                                                   &buf);
   {
     struct TALER_DB_QueryParam params[] = {
-      TALER_DB_QUERY_PARAM_PTR(&melt->session_pub),
+      TALER_DB_QUERY_PARAM_PTR(session),
       TALER_DB_QUERY_PARAM_PTR(&oldcoin_index_nbo),
       TALER_DB_QUERY_PARAM_PTR(&melt->coin.coin_pub),
       TALER_DB_QUERY_PARAM_PTR_SIZED(buf, buf_size),
@@ -1586,6 +1454,121 @@ TALER_MINT_DB_get_refresh_melt (PGconn *db_conn,
 
 
 /**
+ * Store in the database which coin(s) we want to create
+ * in a given refresh operation.
+ *
+ * @param db_conn database connection
+ * @param session_pub refresh session key
+ * @param newcoin_index index of the coin to generate
+ * @param denom_pub denomination of the coin to create
+ * @return #GNUNET_OK on success
+ *         #GNUNET_SYSERR on internal error
+ */
+int
+TALER_MINT_DB_insert_refresh_order (PGconn *db_conn,
+                                    const struct GNUNET_CRYPTO_EddsaPublicKey *session_pub,
+                                    uint16_t newcoin_index,
+                                    const struct GNUNET_CRYPTO_rsa_PublicKey *denom_pub)
+{
+  // FIXME: check logic
+  uint16_t newcoin_index_nbo = htons (newcoin_index);
+  char *buf;
+  size_t buf_size;
+  PGresult *result;
+
+  buf_size = GNUNET_CRYPTO_rsa_public_key_encode (denom_pub,
+                                                  &buf);
+
+  {
+    struct TALER_DB_QueryParam params[] = {
+      TALER_DB_QUERY_PARAM_PTR (&newcoin_index_nbo),
+      TALER_DB_QUERY_PARAM_PTR (session_pub),
+      TALER_DB_QUERY_PARAM_PTR_SIZED (buf, buf_size),
+      TALER_DB_QUERY_PARAM_END
+    };
+    result = TALER_DB_exec_prepared (db_conn,
+                                     "insert_refresh_order",
+                                     params);
+  }
+  GNUNET_free (buf);
+  if (PGRES_COMMAND_OK != PQresultStatus (result))
+  {
+    break_db_err (result);
+    PQclear (result);
+    return GNUNET_SYSERR;
+  }
+  if (0 != strcmp ("1", PQcmdTuples (result)))
+  {
+    GNUNET_break (0);
+    return GNUNET_SYSERR;
+  }
+  PQclear (result);
+  return GNUNET_OK;
+}
+
+
+/**
+ * Lookup in the database the @a newcoin_index coin that we want to
+ * create in the given refresh operation.
+ *
+ * @param db_conn database connection
+ * @param session_pub refresh session key
+ * @param newcoin_index index of the coin to generate
+ * @param denom_pub denomination of the coin to create
+ * @return NULL on error (not found or internal error)
+ */
+struct GNUNET_CRYPTO_rsa_PublicKey *
+TALER_MINT_DB_get_refresh_order (PGconn *db_conn,
+                                 const struct GNUNET_CRYPTO_EddsaPublicKey *session_pub,
+                                 uint16_t newcoin_index)
+{
+  // FIXME: check logic
+  char *buf;
+  size_t buf_size;
+  struct GNUNET_CRYPTO_rsa_PublicKey *denom_pub;
+  uint16_t newcoin_index_nbo = htons (newcoin_index);
+
+  struct TALER_DB_QueryParam params[] = {
+    TALER_DB_QUERY_PARAM_PTR(session_pub),
+    TALER_DB_QUERY_PARAM_PTR(&newcoin_index_nbo),
+    TALER_DB_QUERY_PARAM_END
+  };
+
+  PGresult *result = TALER_DB_exec_prepared (db_conn, "get_refresh_order", params);
+
+  if (PGRES_TUPLES_OK != PQresultStatus (result))
+  {
+    break_db_err (result);
+    PQclear (result);
+    return NULL;
+  }
+
+  if (0 == PQntuples (result))
+  {
+    PQclear (result);
+    /* FIXME: may want to distinguish between different error cases! */
+    return NULL;
+  }
+  GNUNET_assert (1 == PQntuples (result));
+  struct TALER_DB_ResultSpec rs[] = {
+    TALER_DB_RESULT_SPEC_VAR ("denom_pub", &buf, &buf_size),
+    TALER_DB_RESULT_SPEC_END
+  };
+  if (GNUNET_OK != TALER_DB_extract_result (result, rs, 0))
+  {
+    PQclear (result);
+    GNUNET_break (0);
+    return NULL;
+  }
+  PQclear (result);
+  denom_pub = GNUNET_CRYPTO_rsa_public_key_decode (buf, buf_size);
+  GNUNET_free (buf);
+  return denom_pub;
+}
+
+
+
+/**
  * Store information about the commitment of the
  * given coin for the given refresh session in the database.
  *
diff --git a/src/mint/mint_db.h b/src/mint/mint_db.h
index 0c0288ab2..ec9947bc2 100644
--- a/src/mint/mint_db.h
+++ b/src/mint/mint_db.h
@@ -35,19 +35,6 @@ int
 TALER_MINT_DB_prepare (PGconn *db_conn);
 
 
-int
-TALER_MINT_DB_insert_refresh_order (PGconn *db_conn,
-                                    uint16_t newcoin_index,
-                                    const struct GNUNET_CRYPTO_EddsaPublicKey *session_pub,
-                                    const struct GNUNET_CRYPTO_rsa_PublicKey *denom_pub);
-
-
-
-struct GNUNET_CRYPTO_rsa_PublicKey *
-TALER_MINT_DB_get_refresh_order (PGconn *db_conn,
-                                 uint16_t newcoin_index,
-                                 const struct GNUNET_CRYPTO_EddsaPublicKey *session_pub);
-
 
 int
 TALER_MINT_DB_insert_refresh_collectable (PGconn *db_conn,
@@ -520,6 +507,8 @@ TALER_MINT_DB_update_refresh_session (PGconn *db_conn,
 
 /**
  * Specification for coin in a /refresh/melt operation.
+ * FIXME: same as `struct MeltDetails`, and not by accident!
+ * We should merge the structs!
  */
 struct RefreshMelt /* FIXME: name to make it clearer this is about ONE coin! */
 {
@@ -529,11 +518,6 @@ struct RefreshMelt /* FIXME: name to make it clearer this is about ONE coin! */
   struct TALER_CoinPublicInfo coin;
 
   /**
-   * Public key of the melting session.
-   */
-  struct GNUNET_CRYPTO_EddsaPublicKey session_pub;
-
-  /**
    * Signature over the melting operation.
    */
   struct GNUNET_CRYPTO_EcdsaSignature coin_sig;
@@ -543,41 +527,27 @@ struct RefreshMelt /* FIXME: name to make it clearer this is about ONE coin! */
    */
   struct TALER_Amount amount;
 
-  /**
-   * What is the index of this coin in the melting session?
-   */
-  uint16_t oldcoin_index;
-
 };
 
 
 /**
- * Test if the given /refresh/melt request is known to us.
- *
- * @param db_conn database connection
- * @param melt melt operation
- * @return #GNUNET_YES if known,
- *         #GNUENT_NO if not,
- *         #GNUNET_SYSERR on internal error
- */
-int
-TALER_MINT_DB_have_refresh_melt (PGconn *db_conn,
-                                 const struct RefreshMelt *melt);
-
-
-/**
  * Store the given /refresh/melt request in the database.
  *
  * @param db_conn database connection
- * @param melt melt operation
+ * @param session session key of the melt operation
+ * @param oldcoin_index index of the coin to store
+ * @param melt coin melt operation details to store
  * @return #GNUNET_OK on success
  *         #GNUNET_SYSERR on internal error
  */
 int
 TALER_MINT_DB_insert_refresh_melt (PGconn *db_conn,
+                                   const struct GNUNET_CRYPTO_EddsaPublicKey *session,
+                                   uint16_t oldcoin_index,
                                    const struct RefreshMelt *melt);
 
 
+
 /**
  * Get information about melted coin details from the database.
  *
@@ -596,6 +566,40 @@ TALER_MINT_DB_get_refresh_melt (PGconn *db_conn,
 
 
 /**
+ * Store in the database which coin(s) we want to create
+ * in a given refresh operation.
+ *
+ * @param db_conn database connection
+ * @param session_pub refresh session key
+ * @param newcoin_index index of the coin to generate
+ * @param denom_pub denomination of the coin to create
+ * @return #GNUNET_OK on success
+ *         #GNUNET_SYSERR on internal error
+ */
+int
+TALER_MINT_DB_insert_refresh_order (PGconn *db_conn,
+                                    const struct GNUNET_CRYPTO_EddsaPublicKey *session_pub,
+                                    uint16_t newcoin_index,
+                                    const struct GNUNET_CRYPTO_rsa_PublicKey *denom_pub);
+
+
+/**
+ * Lookup in the database the @a newcoin_index coin that we want to
+ * create in the given refresh operation.
+ *
+ * @param db_conn database connection
+ * @param session_pub refresh session key
+ * @param newcoin_index index of the coin to generate
+ * @param denom_pub denomination of the coin to create
+ * @return NULL on error (not found or internal error)
+ */
+struct GNUNET_CRYPTO_rsa_PublicKey *
+TALER_MINT_DB_get_refresh_order (PGconn *db_conn,
+                                 const struct GNUNET_CRYPTO_EddsaPublicKey *session_pub,
+                                 uint16_t newcoin_index);
+
+
+/**
  * We have as many `struct RefreshCommitCoin` as there are new
  * coins being created by the refresh (for each of the kappa
  * sets).  These are the coins we ask the mint to sign if the
diff --git a/src/mint/taler-mint-httpd_db.c b/src/mint/taler-mint-httpd_db.c
index 0da207747..39a0bffdd 100644
--- a/src/mint/taler-mint-httpd_db.c
+++ b/src/mint/taler-mint-httpd_db.c
@@ -420,50 +420,6 @@ TALER_MINT_db_execute_withdraw_sign (struct MHD_Connection *connection,
 }
 
 
-
-
-
-/**
- * Insert  all requested denominations  into the DB, and  compute the
- * required cost of the denominations, including fees.
- *
- * @param connection the connection to send an error response to
- * @param db_conn the database connection
- * @param key_state the mint's key state to use
- * @param session_pub the refresh session public key
- * @param denom_pubs_count number of entries in @a denom_pubs
- * @param denom_pubs array of public keys for the refresh
- * @return FIXME!
- */
-static int
-refresh_accept_denoms (struct MHD_Connection *connection,
-                       PGconn *db_conn,
-                       const struct MintKeyState *key_state,
-                       const struct GNUNET_CRYPTO_EddsaPublicKey *session_pub,
-                       unsigned int denom_pubs_count,
-                       struct GNUNET_CRYPTO_rsa_PublicKey *const*denom_pubs)
-{
-  unsigned int i;
-  int res;
-
-  for (i = 0; i < denom_pubs_count; i++)
-  {
-    /* Insert the requested coin into the DB, so we'll know later
-     * what denomination the request had */
-
-    if (GNUNET_OK !=
-        (res = TALER_MINT_DB_insert_refresh_order (db_conn,
-                                                   i,
-                                                   session_pub,
-                                                   denom_pubs[i])))
-      return res; // ???
-  }
-  return GNUNET_OK;
-}
-
-
-
-
 /**
  * Parse coin melt requests from a JSON object and write them to
  * the database.
@@ -472,9 +428,9 @@ refresh_accept_denoms (struct MHD_Connection *connection,
  * @param db_conn the database connection
  * @param key_state the mint's key state
  * @param session_pub the refresh session's public key
- * @param coin_count number of coins in @a coin_public_infos to melt
- * @param coin_public_infos the coins to melt
- * @param r_melt_balance[OUT] FIXME (#3636: check earlier, pass expected value IN, not OUT!)
+ * @param coin_public_info the coin to melt
+ * @param coin_details details about the coin being melted
+ * @param oldcoin_index what is the number assigned to this coin
  * @return #GNUNET_OK on success,
  *         #GNUNET_NO if an error message was generated,
  *         #GNUNET_SYSERR on internal errors (no response generated)
@@ -484,69 +440,58 @@ refresh_accept_melts (struct MHD_Connection *connection,
                       PGconn *db_conn,
                       const struct MintKeyState *key_state,
                       const struct GNUNET_CRYPTO_EddsaPublicKey *session_pub,
-                      unsigned int coin_count,
-                      const struct TALER_CoinPublicInfo *coin_public_infos,
-                      struct TALER_Amount *r_melt_balance)
+                      const struct TALER_CoinPublicInfo *coin_public_info,
+                      const struct MeltDetails *coin_details,
+                      uint16_t oldcoin_index)
 {
-  size_t i;
+  struct TALER_MINT_DenomKeyIssue *dki;
+  struct TALER_MINT_DB_TransactionList *tl;
+  struct TALER_Amount coin_gain;
+  struct RefreshMelt melt;
 
-  memset (r_melt_balance, 0, sizeof (struct TALER_Amount));
+  dki = &TALER_MINT_get_denom_key (key_state,
+                                   coin_public_info->denom_pub)->issue;
 
-  for (i = 0; i < coin_count; i++)
-  {
-    struct TALER_MINT_DenomKeyIssue *dki;
-    struct TALER_MINT_DB_TransactionList *tl;
-    // money the customer gets by melting the current coin
-    struct TALER_Amount coin_gain;
-    struct RefreshMelt melt;
+  if (NULL == dki)
+    return (MHD_YES ==
+            TALER_MINT_reply_json_pack (connection,
+                                        MHD_HTTP_NOT_FOUND,
+                                        "{s:s}",
+                                        "error",
+                                        "denom not found"))
+      ? GNUNET_NO : GNUNET_SYSERR;
+
+  coin_gain = TALER_amount_ntoh (dki->value);
+  tl = TALER_MINT_DB_get_coin_transactions (db_conn,
+                                            &coin_public_info->coin_pub);
+  /* FIXME: #3636: compute how much value is left with this coin and
+     compare to `expected_value`! (subtract from "coin_gain") */
+  TALER_MINT_DB_free_coin_transaction_list (tl);
 
-    dki = &TALER_MINT_get_denom_key (key_state,
-                                     coin_public_infos[i].denom_pub)->issue;
+  /* Refuse to refresh when the coin does not have enough money left to
+   * pay the refreshing fees of the coin. */
 
-    if (NULL == dki)
-      return (MHD_YES ==
-              TALER_MINT_reply_json_pack (connection,
-                                          MHD_HTTP_NOT_FOUND,
-                                          "{s:s}",
-                                          "error",
-                                          "denom not found"))
-        ? GNUNET_NO : GNUNET_SYSERR;
-
-    coin_gain = TALER_amount_ntoh (dki->value);
-    tl = TALER_MINT_DB_get_coin_transactions (db_conn,
-                                              &coin_public_infos[i].coin_pub);
-    /* FIXME: compute how much value is left with this coin! */
-    TALER_MINT_DB_free_coin_transaction_list (tl);
+  if (TALER_amount_cmp (coin_gain,
+                        coin_details->melt_amount) < 0)
+    return (MHD_YES ==
+            TALER_MINT_reply_json_pack (connection,
+                                        MHD_HTTP_NOT_FOUND,
+                                        "{s:s}",
+                                        "error", "depleted")) ? GNUNET_NO : GNUNET_SYSERR;
 
-    melt.coin = coin_public_infos[i];
-    melt.session_pub = *session_pub;
-    // melt.coin_sig = FIXME;
-    // melt.amount = FIXME;
-    melt.oldcoin_index = i;
-    if (GNUNET_OK !=
-        TALER_MINT_DB_insert_refresh_melt (db_conn,
-                                           &melt))
-    {
-      GNUNET_break (0);
-      return GNUNET_SYSERR;
-    }
-
-
-    /* Refuse to refresh when the coin does not have enough money left to
-     * pay the refreshing fees of the coin. */
 
-    if (TALER_amount_cmp (coin_gain,
-                          TALER_amount_ntoh (dki->fee_refresh)) < 0)
-      return (MHD_YES ==
-              TALER_MINT_reply_json_pack (connection,
-                                          MHD_HTTP_NOT_FOUND,
-                                          "{s:s}",
-                                          "error", "depleted")) ? GNUNET_NO : GNUNET_SYSERR;
 
-    coin_gain = TALER_amount_subtract (coin_gain,
-                                       TALER_amount_ntoh (dki->fee_refresh));
-    *r_melt_balance = TALER_amount_add (*r_melt_balance,
-                                        coin_gain);
+  melt.coin = *coin_public_info;
+  melt.coin_sig = coin_details->melt_sig;
+  melt.amount = coin_details->melt_amount;
+  if (GNUNET_OK !=
+      TALER_MINT_DB_insert_refresh_melt (db_conn,
+                                         session_pub,
+                                         oldcoin_index,
+                                         &melt))
+  {
+    GNUNET_break (0);
+    return GNUNET_SYSERR;
   }
   return GNUNET_OK;
 }
@@ -565,8 +510,9 @@ refresh_accept_melts (struct MHD_Connection *connection,
  *         over the melting request
  * @param num_new_denoms number of entries in @a denom_pubs
  * @param denum_pubs public keys of the coins we want to withdraw in the end
- * @param coin_count number of entries in @a coin_public_infos
+ * @param coin_count number of entries in @a coin_public_infos and @a coin_melt_details
  * @param coin_public_infos information about the coins to melt
+ * @param coin_melt_details signatures and (residual) value of the respective coin should be melted
  * @return MHD result code
  */
 int
@@ -576,13 +522,14 @@ TALER_MINT_db_execute_refresh_melt (struct MHD_Connection *connection,
                                     unsigned int num_new_denoms,
                                     struct GNUNET_CRYPTO_rsa_PublicKey *const*denom_pubs,
                                     unsigned int coin_count,
-                                    const struct TALER_CoinPublicInfo *coin_public_infos)
+                                    const struct TALER_CoinPublicInfo *coin_public_infos,
+                                    const struct MeltDetails *coin_melt_details)
 {
-  struct TALER_Amount melt_balance;
   struct MintKeyState *key_state;
   struct RefreshSession session;
   PGconn *db_conn;
   int res;
+  unsigned int i;
 
   if (NULL == (db_conn = TALER_MINT_DB_get_connection ()))
   {
@@ -612,6 +559,41 @@ TALER_MINT_db_execute_refresh_melt (struct MHD_Connection *connection,
     return TALER_MINT_reply_internal_db_error (connection);
   }
 
+  /* Melt old coins and check that they had enough residual value */
+  key_state = TALER_MINT_key_state_acquire ();
+  for (i=0;i<coin_count;i++)
+  {
+    if (GNUNET_OK !=
+        (res = refresh_accept_melts (connection,
+                                     db_conn,
+                                     key_state,
+                                     refresh_session_pub,
+                                     &coin_public_infos[i],
+                                     &coin_melt_details[i],
+                                     i)))
+    {
+      TALER_MINT_key_state_release (key_state);
+      TALER_MINT_DB_rollback (db_conn);
+      return (GNUNET_SYSERR == res) ? MHD_NO : MHD_YES;
+    }
+  }
+  TALER_MINT_key_state_release (key_state);
+
+  /* store requested new denominations */
+  for (i=0;i<num_new_denoms;i++)
+  {
+    if (GNUNET_OK !=
+        TALER_MINT_DB_insert_refresh_order (db_conn,
+                                            refresh_session_pub,
+                                            i,
+                                            denom_pubs[i]))
+    {
+      TALER_MINT_DB_rollback (db_conn);
+      return TALER_MINT_reply_internal_db_error (connection);
+    }
+  }
+
+  /* store 'global' session data */
   session.melt_sig = *client_signature;
   session.num_oldcoins = coin_count;
   session.num_newcoins = num_new_denoms;
@@ -627,61 +609,16 @@ TALER_MINT_db_execute_refresh_melt (struct MHD_Connection *connection,
     return TALER_MINT_reply_internal_db_error (connection);
   }
 
-  /* The next two operations must see the same key state,
-   * thus we acquire it here. */
-
-  key_state = TALER_MINT_key_state_acquire ();
-  if (GNUNET_OK !=
-      (res = refresh_accept_denoms (connection, db_conn, key_state,
-                                    refresh_session_pub,
-                                    num_new_denoms,
-                                    denom_pubs)))
-  {
-    TALER_MINT_key_state_release (key_state);
-    TALER_MINT_DB_rollback (db_conn);
-    return (GNUNET_SYSERR == res) ? MHD_NO : MHD_YES;
-  }
-
-  /* Write old coins to db and sum their value */
-  if (GNUNET_OK !=
-      (res = refresh_accept_melts (connection, db_conn, key_state,
-                                   refresh_session_pub,
-                                   coin_count,
-                                   coin_public_infos,
-                                   &melt_balance)))
-  {
-    TALER_MINT_key_state_release (key_state);
-    TALER_MINT_DB_rollback (db_conn);
-    return (GNUNET_SYSERR == res) ? MHD_NO : MHD_YES;
-  }
-
-  TALER_MINT_key_state_release (key_state);
-
-
-  /* Request is only ok if cost of requested coins
-   * does not exceed value of melted coins. */
-
   if (GNUNET_OK !=
       TALER_MINT_DB_commit (db_conn))
   {
     LOG_WARNING ("/refresh/melt transaction commit failed\n");
     return TALER_MINT_reply_commit_error (connection);
   }
-  if (GNUNET_OK !=
-      (res = TALER_MINT_DB_get_refresh_session (db_conn,
-                                                refresh_session_pub,
-                                                &session)))
-  {
-    // FIXME: send internal error
-    GNUNET_break (0);
-    return MHD_NO;
-  }
   return TALER_MINT_reply_refresh_melt_success (connection,
                                                 client_signature,
                                                 refresh_session_pub,
                                                 session.kappa);
-
-
 }
 
 
@@ -1042,8 +979,8 @@ TALER_MINT_db_execute_refresh_reveal (struct MHD_Connection *connection,
       GNUNET_CRYPTO_ecdsa_key_get_public (&link_data->coin_priv,
                                           &coin_pub);
       denom_pub = TALER_MINT_DB_get_refresh_order (db_conn,
-                                                   j,
-                                                   refresh_session_pub);
+                                                   refresh_session_pub,
+                                                   j);
       if (NULL == denom_pub)
       {
         GNUNET_break (0);
@@ -1110,7 +1047,9 @@ TALER_MINT_db_execute_refresh_reveal (struct MHD_Connection *connection,
               // FIXME: return error code!
       return MHD_NO;
     }
-    denom_pub = TALER_MINT_DB_get_refresh_order (db_conn, j, refresh_session_pub);
+    denom_pub = TALER_MINT_DB_get_refresh_order (db_conn,
+                                                 refresh_session_pub,
+                                                 j);
     if (NULL == denom_pub)
     {
       GNUNET_break (0);
diff --git a/src/mint/taler-mint-httpd_db.h b/src/mint/taler-mint-httpd_db.h
index d2566cf7c..e34139868 100644
--- a/src/mint/taler-mint-httpd_db.h
+++ b/src/mint/taler-mint-httpd_db.h
@@ -80,6 +80,24 @@ TALER_MINT_db_execute_withdraw_sign (struct MHD_Connection *connection,
                                      const struct GNUNET_CRYPTO_EddsaSignature *signature);
 
 
+/**
+ * Details about a melt operation of an individual coin.
+ */
+struct MeltDetails
+{
+  /**
+   * Signature allowing the melt (using
+   * a `struct RefreshMeltConfirmSignRequestBody`) to sign over.
+   */
+  struct GNUNET_CRYPTO_EcdsaSignature melt_sig;
+
+  /**
+   * How much of the coin's value did the client allow to be melted?
+   * (FIXME: are the fees included here!?)
+   */
+  struct TALER_Amount melt_amount;
+};
+
 
 /**
  * Execute a "/refresh/melt". We have been given a list of valid
@@ -94,8 +112,9 @@ TALER_MINT_db_execute_withdraw_sign (struct MHD_Connection *connection,
  *         over the melting request
  * @param num_new_denoms number of entries in @a denom_pubs
  * @param denum_pubs array of public denomination keys for the refresh (?)
- * @param coin_count number of entries in @a coin_public_infos
+ * @param coin_count number of entries in @a coin_public_infos and @ a coin_melt_details
  * @param coin_public_infos information about the coins to melt
+ * @param coin_melt_details signatures and (residual) value of the respective coin should be melted
  * @return MHD result code
  */
 int
@@ -105,7 +124,8 @@ TALER_MINT_db_execute_refresh_melt (struct MHD_Connection *connection,
                                     unsigned int num_new_denoms,
                                     struct GNUNET_CRYPTO_rsa_PublicKey *const*denom_pubs,
                                     unsigned int coin_count,
-                                    const struct TALER_CoinPublicInfo *coin_public_infos);
+                                    const struct TALER_CoinPublicInfo *coin_public_infos,
+                                    const struct MeltDetails *coin_melt_details);
 
 
 /**
diff --git a/src/mint/taler-mint-httpd_refresh.c b/src/mint/taler-mint-httpd_refresh.c
index e9222be27..f4cff6537 100644
--- a/src/mint/taler-mint-httpd_refresh.c
+++ b/src/mint/taler-mint-httpd_refresh.c
@@ -145,9 +145,12 @@ request_json_check_signature (struct MHD_Connection *connection,
  *
  * @param connection the MHD connection to handle
  * @param refresh_session_pub public key of the melt operation
- * @param new_denoms array of denomination keys
- * @param melt_coins array of coins to melt
- * @param melt_sig_json signature affirming the melt operation
+ * @param num_new_denoms number of coins to be created
+ * @param denom_pubs array of @a num_new_denoms keys
+ * @param coin_count number of coins to be melted
+ * @param coin_public_infos array with @a coin_count entries about the coins
+ * @param coin_melt_details array with @a coin_count entries with melting details
+ * @param melt_sig_json signature affirming the overall melt operation
  * @return MHD result code
  */
 static int
@@ -157,6 +160,7 @@ handle_refresh_melt_binary (struct MHD_Connection *connection,
                             struct GNUNET_CRYPTO_rsa_PublicKey *const*denom_pubs,
                             unsigned int coin_count,
                             struct TALER_CoinPublicInfo *coin_public_infos,
+                            const struct MeltDetails *coin_melt_details,
                             const json_t *melt_sig_json)
 {
   int res;
@@ -248,7 +252,8 @@ handle_refresh_melt_binary (struct MHD_Connection *connection,
                                              num_new_denoms,
                                              denom_pubs,
                                              coin_count,
-                                             coin_public_infos);
+                                             coin_public_infos,
+                                             coin_melt_details);
 }
 
 
@@ -264,6 +269,7 @@ handle_refresh_melt_binary (struct MHD_Connection *connection,
  * @param session_pub public key of the session the coin is melted into
  * @param coin_info the JSON object to extract the coin info from
  * @param r_public_info[OUT] set to the coin's public information
+ * @param r_melt_detail[OUT] set to details about the coin's melting permission (if valid)
  * @return #GNUNET_YES if coin public info in JSON was valid
  *         #GNUNET_NO JSON was invalid, response was generated
  *         #GNUNET_SYSERR on internal error
@@ -272,7 +278,8 @@ static int
 get_and_verify_coin_public_info (struct MHD_Connection *connection,
                                  const struct GNUNET_CRYPTO_EddsaPublicKey *session_pub,
                                  json_t *coin_info,
-                                 struct TALER_CoinPublicInfo *r_public_info)
+                                 struct TALER_CoinPublicInfo *r_public_info,
+                                 struct MeltDetails *r_melt_detail)
 {
   int ret;
   struct GNUNET_CRYPTO_EcdsaSignature melt_sig;
@@ -281,11 +288,13 @@ get_and_verify_coin_public_info (struct MHD_Connection *connection,
   struct RefreshMeltConfirmSignRequestBody body;
   struct MintKeyState *key_state;
   struct TALER_MINT_DenomKeyIssuePriv *dki;
+  struct TALER_Amount amount;
   struct GNUNET_MINT_ParseFieldSpec spec[] = {
     TALER_MINT_PARSE_FIXED ("coin_pub", &r_public_info->coin_pub),
     TALER_MINT_PARSE_RSA_SIGNATURE ("denom_sig", &sig),
     TALER_MINT_PARSE_RSA_PUBLIC_KEY ("denom_pub", &pk),
     TALER_MINT_PARSE_FIXED ("confirm_sig", &melt_sig),
+    /* FIXME: #3636! */
     TALER_MINT_PARSE_END
   };
 
@@ -296,6 +305,7 @@ get_and_verify_coin_public_info (struct MHD_Connection *connection,
     return ret;
   /* FIXME: include amount of coin value to be melted here (#3636!) and
     in what we return!? */
+  memset (&amount, 0, sizeof (amount)); // FIXME: #3636!
   body.purpose.size = htonl (sizeof (struct RefreshMeltConfirmSignRequestBody));
   body.purpose.purpose = htonl (TALER_SIGNATURE_REFRESH_MELT_CONFIRM);
   body.session_pub = *session_pub;
@@ -344,6 +354,8 @@ get_and_verify_coin_public_info (struct MHD_Connection *connection,
                                         "error", "coin invalid"))
       ? GNUNET_NO : GNUNET_SYSERR;
   }
+  r_melt_detail->melt_sig = melt_sig;
+  r_melt_detail->melt_amount = amount;
   return GNUNET_OK;
 }
 
@@ -375,6 +387,7 @@ handle_refresh_melt_json (struct MHD_Connection *connection,
   struct GNUNET_CRYPTO_rsa_PublicKey **denom_pubs;
   unsigned int num_new_denoms;
   struct TALER_CoinPublicInfo *coin_public_infos;
+  struct MeltDetails *coin_melt_details;
   unsigned int coin_count;
 
   num_new_denoms = json_array_size (new_denoms);
@@ -395,15 +408,20 @@ handle_refresh_melt_json (struct MHD_Connection *connection,
   }
 
   coin_count = json_array_size (melt_coins);
+  /* FIXME: make 'struct TALER_CoinPublicInfo' part of `struct MeltDetails`
+     and combine these two arrays/arguments! */
   coin_public_infos = GNUNET_malloc (coin_count *
                                      sizeof (struct TALER_CoinPublicInfo));
+  coin_melt_details = GNUNET_malloc (coin_count *
+                                     sizeof (struct MeltDetails));
   for (i=0;i<coin_count;i++)
   {
     /* decode JSON data on coin to melt */
     res = get_and_verify_coin_public_info (connection,
                                            refresh_session_pub,
                                            json_array_get (melt_coins, i),
-                                           &coin_public_infos[i]);
+                                           &coin_public_infos[i],
+                                           &coin_melt_details[i]);
     if (GNUNET_OK != res)
     {
       for (j=0;j<i;j++)
@@ -414,6 +432,7 @@ handle_refresh_melt_json (struct MHD_Connection *connection,
       GNUNET_free (coin_public_infos);
       for (j=0;j<num_new_denoms;j++)
         GNUNET_CRYPTO_rsa_public_key_free (denom_pubs[j]);
+      GNUNET_free (coin_melt_details);
       GNUNET_free (denom_pubs);
       return (GNUNET_NO == res) ? MHD_YES : MHD_NO;
     }
@@ -425,6 +444,7 @@ handle_refresh_melt_json (struct MHD_Connection *connection,
                                     denom_pubs,
                                     coin_count,
                                     coin_public_infos,
+                                    coin_melt_details,
                                     melt_sig_json);
   for (j=0;j<coin_count;j++)
   {
@@ -436,6 +456,7 @@ handle_refresh_melt_json (struct MHD_Connection *connection,
   {
     GNUNET_CRYPTO_rsa_public_key_free (denom_pubs[j]);
   }
+  GNUNET_free (coin_melt_details);
   GNUNET_free (denom_pubs);
   return res;
 }