Cut long values in SQL result tables to fit the terminal

One long value made every line of the table wider than the terminal,
so the whole table wrapped. Narrow the widest columns until the table
fits and end cut values with an ellipsis. Adding --full to the query,
which is an SQL comment, shows the values in full as before.

js/index.js

@@ -203,7 +203,10 @@
     }
 
     // Tabular rendering of SELECT results, psql-style.
-    function renderTable(term, rows) {
+    // Unless full is set, the widest columns are narrowed until the table
+    // fits the terminal, so one long value doesn't wrap the whole table.
+    // Returns true when a value was cut.
+    function renderTable(term, rows, full) {
       if (!rows || !rows.length) {
         return;
       }
@@ -234,9 +237,34 @@
         }, col.length);
       });
 
+      var MIN_WIDTH = 10;
+      var cut = false;
+      if (!full) {
+        var available = term.cols() - 1;
+        var total = function () {
+          return widths.reduce(function (sum, w) { return sum + w + 3; }, -1);
+        };
+        while (total() > available) {
+          var widest = widths.indexOf(Math.max.apply(null, widths));
+          if (widths[widest] <= MIN_WIDTH) {
+            break;
+          }
+          widths[widest] = Math.max(MIN_WIDTH, widths[widest] - (total() - available));
+        }
+      }
+
+      function fit(str, width) {
+        str = String(str);
+        if (str.length <= width) {
+          return str;
+        }
+        cut = true;
+        return str.slice(0, width - 1) + '\u2026';
+      }
+
       function formatRow(cells) {
         return cells.map(function (cell, i) {
-          return ' ' + pad(cell, widths[i]) + ' ';
+          return ' ' + pad(fit(cell, widths[i]), widths[i]) + ' ';
         }).join('|');
       }
 
@@ -248,9 +276,10 @@
       });
 
       term.echo($.terminal.escape_formatting(lines.join('\n')));
+      return cut;
     }
 
-    function renderSqlResponse(term, response) {
+    function renderSqlResponse(term, response, full) {
       if (!response) {
         term.echo('[[;#ff5555;]Empty response from server]');
         return;
@@ -270,8 +299,8 @@
           term.echo('[[;#ff5555;]  Error: ]' + $.terminal.escape_formatting(r.error || 'unknown error'));
         } else if (r.type === 'select') {
           term.echo('[[;gray;]  ' + r.count + ' row(s)]');
-          if (r.count > 0) {
-            renderTable(term, r.data);
+          if (r.count > 0 && renderTable(term, r.data, full)) {
+            term.echo('[[;gray;]  Long values are cut to fit the terminal. Add --full to the query to see them in full.]');
           }
           if (r.truncated) {
             term.echo('[[;yellow;]  Result truncated — showing only the first ' + r.count + ' rows, add LIMIT to see more precisely.]');
@@ -327,7 +356,8 @@
           askDeleteConfirmation(term, sql, response.error);
           return;
         }
-        renderSqlResponse(term, response);
+        // "--full" is a plain SQL comment, so the database ignores it
+        renderSqlResponse(term, response, /(^|\s)-- ?full\b/.test(sql));
         term.resume();
       }).fail(function (xhr, status) {
         if (status === 'timeout') {