Implement a dumb line reader for comint mode

src/lineedit.cpp

@@ -5,6 +5,7 @@
 #include <unistd.h>
 
 #include <cstdlib>
+#include <cstring>
 
 #include "common.hpp"
 #include "fio.hpp"
@@ -389,8 +390,42 @@ class LineEdit {
   RefreshState last_refresh;
 };
 
-Result<String> read_line(const char* prompt) {
-  auto rl = TRY(LineEdit::create(prompt));
+Result<String> read_dumb(const char* prompt) {
+  std::cout << prompt << std::flush;
 
-  return rl.read_one();
+  String res = TRY(String::create(""));
+
+  int input_fd = STDIN_FILENO;
+
+  const size_t bufsize = 256;
+  char buf[bufsize];
+  bool endstr = false;
+  while (!endstr) {
+    size_t i = 0;
+    while (i < sizeof(buf) - 1) {
+      if (read(input_fd, buf + i, 1) != 1) break;
+      if (buf[i] == '\n') {
+        endstr = true;
+        break;
+      }
+      i++;
+    }
+    buf[i] = '\0';
+
+    res = TRY(res.concat(buf));
+  }
+
+  return res;
+}
+
+Result<String> read_line(const char* prompt) {
+  const char* term = std::getenv("TERM");
+
+  if (strncmp(term, "dumb", 4) == 0) {
+    return read_dumb(prompt);
+  } else {
+    auto rl = TRY(LineEdit::create(prompt));
+
+    return rl.read_one();
+  }
 }