Parse 'select' and 'insert'.

cstack · cstack · commit bd29bdbf6012 · 2017-08-31T17:47:20.000-07:00
diff --git a/db.c b/db.c
@@ -10,6 +10,23 @@ struct InputBuffer_t {
 };
 typedef struct InputBuffer_t InputBuffer;
 
+enum MetaCommandResult_t {
+  META_COMMAND_SUCCESS,
+  META_COMMAND_UNRECOGNIZED_COMMAND
+};
+typedef enum MetaCommandResult_t MetaCommandResult;
+
+enum PrepareResult_t { PREPARE_SUCCESS, PREPARE_UNRECOGNIZED_STATEMENT };
+typedef enum PrepareResult_t PrepareResult;
+
+enum StatementType_t { STATEMENT_INSERT, STATEMENT_SELECT };
+typedef enum StatementType_t StatementType;
+
+struct Statement_t {
+  StatementType type;
+};
+typedef struct Statement_t Statement;
+
 InputBuffer* new_input_buffer() {
   InputBuffer* input_buffer = malloc(sizeof(InputBuffer));
   input_buffer->buffer = NULL;
@@ -35,16 +52,66 @@ void read_input(InputBuffer* input_buffer) {
   input_buffer->buffer[bytes_read - 1] = 0;
 }
 
+MetaCommandResult do_meta_command(InputBuffer* input_buffer) {
+  if (strcmp(input_buffer->buffer, ".exit") == 0) {
+    exit(EXIT_SUCCESS);
+  } else {
+    return META_COMMAND_UNRECOGNIZED_COMMAND;
+  }
+}
+
+PrepareResult prepare_statement(InputBuffer* input_buffer,
+                                Statement* statement) {
+  if (strncmp(input_buffer->buffer, "insert", 6) == 0) {
+    statement->type = STATEMENT_INSERT;
+    return PREPARE_SUCCESS;
+  }
+  if (strcmp(input_buffer->buffer, "select") == 0) {
+    statement->type = STATEMENT_SELECT;
+    return PREPARE_SUCCESS;
+  }
+
+  return PREPARE_UNRECOGNIZED_STATEMENT;
+}
+
+void execute_statement(Statement* statement) {
+  switch (statement->type) {
+    case (STATEMENT_INSERT):
+      printf("This is where we would do an insert.\n");
+      break;
+    case (STATEMENT_SELECT):
+      printf("This is where we would do a select.\n");
+      break;
+  }
+}
+
 int main(int argc, char* argv[]) {
   InputBuffer* input_buffer = new_input_buffer();
   while (true) {
     print_prompt();
     read_input(input_buffer);
 
-    if (strcmp(input_buffer->buffer, ".exit") == 0) {
-      exit(EXIT_SUCCESS);
-    } else {
-      printf("Unrecognized command '%s'.\n", input_buffer->buffer);
+    if (input_buffer->buffer[0] == '.') {
+      switch (do_meta_command(input_buffer)) {
+        case (META_COMMAND_SUCCESS):
+          continue;
+        case (META_COMMAND_UNRECOGNIZED_COMMAND):
+          printf("Unrecognized command '%s'\n", input_buffer->buffer);
+          continue;
+      }
     }
+
+    Statement statement;
+    switch (prepare_statement(input_buffer, &statement)) {
+      case (PREPARE_SUCCESS):
+        break;
+      case (PREPARE_UNRECOGNIZED_STATEMENT):
+        printf("Unrecognized keyword at start of '%s'.\n",
+               input_buffer->buffer);
+        continue;
+    }
+
+    execute_statement(&statement);
+    printf("Executed.\n");
   }
 }
