Userland: Add support for printing multiple columns to the cal command

Now cal is able to print the entire year when only that is passed
as an argument. For example: `cal 1992`.

However this meant breaking the highlighted day escape sequence
as it messed up the layout and the character count for each of the
rows :(

Now the current day is specified like 17* (for example for day 17).

Userland/cal.cpp

@@ -1,6 +1,21 @@
+#include <LibCore/CArgsParser.h>
 #include <stdio.h>
 #include <time.h>
 
+const int line_width = 70;
+const int line_count = 8;
+const int column_width = 22;
+
+char print_buffer[line_width * line_count];
+char temp_buffer[line_width * 8];
+
+int target_year;
+int target_month;
+int target_day;
+
+int current_year;
+int current_month;
+
 int day_of_week(int day, int month, int year)
 {
     static const int seek_table[] = { 0, 3, 2, 5, 0, 3, 5, 1, 4, 6, 2, 4 };
@@ -21,29 +36,139 @@ int get_number_of_days(int month, int year)
     return is_long_month ? 31 : 30;
 }
 
+void append_to_print(char* buffer, int row, int column, char* text)
+{
+    int starting_point = (line_width * row) + (column * column_width);
+    for (int i = 0; text[i] != '\0'; i++) {
+        buffer[starting_point + i] = text[i];
+    }
+}
+
+void insert_month_to_print(int column, int month, int year)
+{
+    int printing_column = column;
+    int printing_row = 0;
+
+    // FIXME: Both the month name and month header text should be provided by a locale
+    sprintf(temp_buffer, "     %02u - %04u    ", month, year);
+    append_to_print(print_buffer, printing_row, printing_column, temp_buffer);
+    printing_row++;
+
+    sprintf(temp_buffer, "Su Mo Tu We Th Fr Sa");
+    append_to_print(print_buffer, printing_row, printing_column, temp_buffer);
+    printing_row++;
+
+    int day_to_print = 1;
+    int first_day_of_week_for_month = day_of_week(1, month, year);
+    int days_in_the_month = get_number_of_days(month, year);
+    int last_written_chars = 0;
+    for (int i = 1; day_to_print <= days_in_the_month; ++i) {
+        if (i - 1 < first_day_of_week_for_month) {
+            last_written_chars += sprintf(temp_buffer + last_written_chars, "   ");
+        } else {
+            if (year == current_year && month == current_month && target_day == day_to_print) {
+                // FIXME: To replicate Unix cal it would be better to use "\x1b[30;47m%2d\x1b[0m " in here instead of *.
+                //        However, doing that messes up the layout.
+                last_written_chars += sprintf(temp_buffer + last_written_chars, "%2d*", day_to_print);
+            } else {
+                last_written_chars += sprintf(temp_buffer + last_written_chars, "%2d ", day_to_print);
+            }
+            day_to_print++;
+        }
+
+        append_to_print(print_buffer, printing_row, printing_column, temp_buffer);
+
+        if (i % 7 == 0) {
+            printing_row++;
+            memset(temp_buffer, ' ', line_width * 8);
+            temp_buffer[line_width * 8 - 1] = '\0';
+            last_written_chars = 0;
+        }
+    }
+}
+
+void clean_buffers()
+{
+    for (int i = 1; i < line_width * line_count; ++i) {
+        print_buffer[i - 1] = i % line_width == 0 ? '\n' : ' ';
+    }
+    print_buffer[line_width * line_count - 1] = '\0';
+
+    for (int i = 0; i < line_width; ++i) {
+        temp_buffer[i] = ' ';
+    }
+    temp_buffer[line_width - 1] = '\0';
+}
+
 int main(int argc, char** argv)
 {
-    (void)argc;
+    CArgsParser args_parser("cal");
-    (void)argv;
+    // FIXME: This i a bit of a cheat, as no nested optional args are available on CArgsParser
+    args_parser.add_single_value("[[day] month] year");
+
+    CArgsParserResult args = args_parser.parse(argc, argv);
+    Vector<String> values = args.get_single_values();
+
+    if (values.size() > 3) {
+        printf("Invalid number of values\n");
+        args_parser.print_usage();
+        return 0;
+    }
 
     time_t now = time(nullptr);
     auto* tm = localtime(&now);
-    int target_day = tm->tm_mday;
-    int target_month = tm->tm_mon + 1;
-    int target_year = tm->tm_year + 1900;
-    int target_day_of_week = day_of_week(1, target_month, target_year);
 
-    printf("     %02u - %04u    \n", target_month, target_year);
+    target_year = tm->tm_year + 1900;
-    printf("Su Mo Tu We Th Fr Sa\n");
+    target_month = tm->tm_mon + 1;
+    target_day = tm->tm_mday;
 
-    for (int i = 1; i <= get_number_of_days(target_month, target_year); ++i) {
+    current_year = target_year;
-        if (i < target_day_of_week) {
+    current_month = target_month;
+
+    bool year_mode = false;
+    switch (values.size()) {
+    case 3:
+        target_day = atoi(values[0].characters());
+        target_month = atoi(values[1].characters());
+        target_year = atoi(values[2].characters());
+
+        // When passing the 3 parameters (day, month and year) we assume we're there.
+        current_year = target_year;
+        current_month = target_month;
+        break;
+    case 2:
+        target_month = atoi(values[0].characters());
+        target_year = atoi(values[1].characters());
+        break;
+    case 1:
+        target_year = atoi(values[0].characters());
+        year_mode = true;
+        break;
+    default:
+        break;
+    }
+
+    clean_buffers();
+
+    if (year_mode) {
         printf("                             ");
+        printf("Year %4d", target_year);
+        printf("                             \n\n");
+
+        for (int i = 1; i < 12; ++i) {
+            insert_month_to_print(0, i++, target_year);
+            insert_month_to_print(1, i++, target_year);
+            insert_month_to_print(2, i, target_year);
+            printf(print_buffer);
+            printf("\n");
+            clean_buffers();
+        }
     } else {
-            printf(i != target_day ? "%2d" : "\x1b[30;47m%2d\x1b[0m", i);
+        insert_month_to_print(0, target_month, target_year);
+        printf(print_buffer);
+        printf("\n\n");
+        clean_buffers();
     }
 
-        printf(i % 7 == 0 ? "\n" : " ");
+    return 0;
-    }
-    printf("\n\n");
 }