start writing psql module, start writing exercise 1 with that module, small header file changes as needed for module programming

1 files changed, 85 insertions, 0 deletions

diff --git a/modules/psql_lisp.c b/modules/psql_lisp.c
new file mode 100644
index 0000000..87ea748
--- /dev/null
+++ b/modules/psql_lisp.c
@@ -0,0 +1,85 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <libpq-fe.h>
+#include "../lisp_api.h"
+
+value *hello_fun(env *e, value *args) {
+	printf("Hello from dynamically loaded module!\n");
+	return make_nil();
+}
+
+value *pg_execute(env *e, value *args) {
+	value *fst_arg = eval(e, car(args));
+	value *snd_arg = eval(e, car(cdr(args)));
+
+	if (fst_arg->type != VT_STRING) {
+		printf("not a string:");
+		println_value(fst_arg);
+		return make_nil(); //TODO: make error
+	}
+	if (snd_arg->type != VT_STRING) {
+		printf("not a string:");
+		println_value(snd_arg);
+		return make_nil(); //TODO: make error
+	}
+
+	const char *conn_str = fst_arg->as.str;
+	const char *query_str = snd_arg->as.str;
+
+	PGconn *conn = PQconnectdb(conn_str);
+	if (PQstatus(conn) != CONNECTION_OK) {
+		fprintf(stderr, "Connection failed: %s", PQerrorMessage(conn));
+		PQfinish(conn);
+		return make_nil(); //TODO: make error
+	}
+
+	PGresult *res = PQexec(conn, query_str);
+	if (PQresultStatus(res) != PGRES_TUPLES_OK) {
+		fprintf(stderr, "Query failed: %s", PQerrorMessage(conn));
+		PQclear(res);
+		PQfinish(conn);
+		return make_nil(); //TODO: make error
+	}
+
+	int rows = PQntuples(res);
+	int cols = PQnfields(res);
+
+	value *table = make_nil();
+
+	for (int row = 0; row < rows; row++) {
+		value *row_val = make_nil();
+		for (int col = 0; col < cols; col++) {
+			switch (PQftype(res, col)) {
+				case 23:
+					row_val=cons(make_int(atoi(PQgetvalue(res, row, col))), row_val);
+				break;
+				case 1700:
+				case 20:
+					row_val=cons(make_int(atof(PQgetvalue(res, row, col))), row_val);
+				break;
+				default:
+					const char *str;
+					row_val=cons(make_string(PQgetvalue(res, row, col)), row_val);
+				break;
+			}
+		}
+		table = cons(reverse(row_val), table);
+	}
+	PQclear(res);
+	PQfinish(conn);
+
+	table = reverse(table);
+	return table;
+}
+
+module_export *module_init() {
+	static module_export exports[2];
+
+	exports[0].name = "pg_execute";
+	exports[0].v    = make_procedure(&pg_execute);
+
+	exports[1].name = NULL;
+	exports[1].v    = NULL;
+
+	return exports;
+}