wallet: Add tooling to extract SQL queries and generate driver info

This is the counterpart of the annotations we did in the last few commits. It
extracts queries, passes them through a driver-specific query rewriter and
dumps them into a driver-specific query-list, along with some metadata to
facilitate processing later on. The generated query list is then registered as
a `db_config` and will be loaded by the driver upon instantiation.

Signed-off-by: Christian Decker <decker.christian@gmail.com>

devtools/sql-rewrite.py

@@ -0,0 +1,102 @@
+#!/usr/bin/env python3
+
+from mako.template import Template
+
+import sys
+
+
+class Sqlite3Rewriter(object):
+    def rewrite(self, query):
+        return query
+
+
+rewriters = {
+    "sqlite3": Sqlite3Rewriter(),
+}
+
+template = Template("""#ifndef LIGHTNINGD_WALLET_GEN_DB_${f.upper()}
+#define LIGHTNINGD_WALLET_GEN_DB_${f.upper()}
+
+#include <config.h>
+#include <wallet/db_common.h>
+
+#if HAVE_${f.upper()}
+
+struct db_query db_${f}_queries[] = {
+
+% for elem in queries:
+    {
+         .name = "${elem['name']}",
+         .query = "${elem['query']}",
+         .placeholders = ${elem['placeholders']}
+    },
+% endfor
+};
+
+#define DB_${f.upper()}_QUERY_COUNT ${len(queries)}
+
+#endif /* HAVE_${f.upper()} */
+
+#endif /* LIGHTNINGD_WALLET_GEN_DB_${f.upper()} */
+""")
+
+
+def extract_queries(pofile):
+    # Given a po-file, extract all queries and their associated names, and
+    # return them as a list.
+
+    def chunk(pofile):
+        # Chunk a given file into chunks separated by an empty line
+        with open(pofile, 'r') as f:
+            chunk = []
+            for line in f:
+                line = line.strip()
+                if line.strip() == "":
+                    yield chunk
+                    chunk = []
+                else:
+                    chunk.append(line.strip())
+            if chunk != []:
+                yield chunk
+
+    queries = []
+    for c in chunk(pofile):
+        name = c[0][3:]
+
+        # Skip other comments
+        i = 1
+        while c[i][0] == '#':
+            i += 1
+
+        # Strip header and surrounding quotes
+        query = c[i][7:][:-1]
+
+        queries.append({
+            'name': name,
+            'query': query,
+            'placeholders': query.count('?'),
+            'readonly': "true" if query.upper().startswith("SELECT") else "false",
+        })
+    return queries
+
+
+if __name__ == "__main__":
+    if len(sys.argv) != 3:
+        print("Usage:\n\t{} <statements.po-file> <output-dialect>".format(sys.argv[0]))
+        sys.exit(1)
+
+    dialect = sys.argv[2]
+
+    if dialect not in rewriters:
+        print("Unknown dialect {}. The following are available: {}".format(
+            dialect,
+            ", ".join(rewriters.keys())
+        ))
+        sys.exit(1)
+
+    rewriter = rewriters[dialect]
+
+    queries = extract_queries(sys.argv[1])
+    queries = rewriter.rewrite(queries)
+
+    print(template.render(f=dialect, queries=queries))