Postgres requires parameters to be correctly typed

Signed-off-by: itowlson <ivan.towlson@fermyon.com>

crates/outbound-pg/src/lib.rs

@@ -37,14 +37,14 @@ impl outbound_pg::OutboundPg for OutboundPg {
         &mut self,
         address: &str,
         statement: &str,
-        params: Vec<&str>,
+        params: Vec<ParameterValue<'_>>,
     ) -> Result<u64, PgError> {
         let mut client = Client::connect(address, NoTls)
             .map_err(|e| PgError::ConnectionFailed(format!("{:?}", e)))?;
 
         let params: Vec<&(dyn ToSql + Sync)> = params
             .iter()
-            .map(|item| item as &(dyn ToSql + Sync))
+            .map(to_sql_parameter)
             .collect();
 
         let nrow = client
@@ -58,14 +58,14 @@ impl outbound_pg::OutboundPg for OutboundPg {
         &mut self,
         address: &str,
         statement: &str,
-        params: Vec<&str>,
+        params: Vec<ParameterValue<'_>>,
     ) -> Result<RowSet, PgError> {
         let mut client = Client::connect(address, NoTls)
             .map_err(|e| PgError::ConnectionFailed(format!("{:?}", e)))?;
 
         let params: Vec<&(dyn ToSql + Sync)> = params
             .iter()
-            .map(|item| item as &(dyn ToSql + Sync))
+            .map(to_sql_parameter)
             .collect();
 
         let results = client
@@ -86,6 +86,18 @@ impl outbound_pg::OutboundPg for OutboundPg {
     }
 }
 
+const DB_NULL: Option<i32> = None;
+
+fn to_sql_parameter<'a>(value: &'a ParameterValue) -> &'a (dyn ToSql + Sync) {
+    match value {
+        ParameterValue::Boolean(v) => v,
+        ParameterValue::Int32(v) => v,
+        ParameterValue::Int64(v) => v,
+        ParameterValue::DbString(v) => v,
+        ParameterValue::DbNull => &DB_NULL,
+    }
+}
+
 fn infer_columns(row: &Row) -> Vec<Column> {
     let mut result = Vec::with_capacity(row.len());
     for index in 0..row.len() {

wit/ephemeral/outbound-pg.wit

@@ -2,7 +2,7 @@ use * from pg-types
 use * from rdbms-types
 
 // query the database: select
-query: func(address: string, statement: string, params: list<string>) -> expected<row-set, pg-error>
+query: func(address: string, statement: string, params: list<parameter-value>) -> expected<row-set, pg-error>
 
 // execute command to the database: insert, update, delete
-execute: func(address: string, statement: string, params: list<string>) -> expected<u64, pg-error>
+execute: func(address: string, statement: string, params: list<parameter-value>) -> expected<u64, pg-error>

wit/ephemeral/rdbms-types.wit

@@ -15,6 +15,14 @@ variant db-value {
     unsupported,
 }
 
+variant parameter-value {
+    boolean(bool),
+    int32(s32),
+    int64(s64),
+    db-string(string),
+    db-null,
+}
+
 record column {
     name: string,
     data-type: db-data-type,