From 31f030bb17c5147850e764267227ecfd0431df66 Mon Sep 17 00:00:00 2001
From: Jakob Kaivo <jkk@ung.org>
Date: Wed, 13 Apr 2022 13:57:31 -0400
Subject: begin implementing strfmon()

---
 src/monetary/strfmon.c | 89 ++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 89 insertions(+)

diff --git a/src/monetary/strfmon.c b/src/monetary/strfmon.c
index 0b8d73f5..cf88a9ba 100644
--- a/src/monetary/strfmon.c
+++ b/src/monetary/strfmon.c
@@ -1,7 +1,96 @@
 #include <monetary.h>
+#include <ctype.h>
+#include <stdarg.h>
+#include <stdio.h>
+#include <stdlib.h>
 
 ssize_t strfmon(char * restrict s, size_t maxsize, const char * restrict format, ...)
 {
+	size_t i = 0;
+	va_list ap;
+	va_start(ap, format);
+
+	while (*format && i < maxsize) {
+		if (*format != '%') {
+			s[i++] = *format++;
+			continue;
+		}
+
+		format++;
+
+		if (*format == '%') {
+			s[i++] = '%';
+			format++;
+			continue;
+		}
+
+		char fill = ' ';
+		char style = '+';
+		int grouping = 1;
+		int symbol = 1;
+		enum { left, right } align = right;
+
+		switch (*format) {
+		case '=':
+			fill = format[1];
+			format += 2;
+			break;
+		case '^':
+			grouping = 0;
+			format++;
+			break;
+		case '+':
+		case '(':
+			style = *format;
+			format++;
+			break;
+		case '!':
+			symbol = 0;
+			format++;
+			break;
+		case '-':
+			align = left;
+			format++;
+			break;
+		}
+
+		unsigned long width = 0;
+		if (isdigit(*format)) {
+			char *end = NULL;
+			width = strtoul(format, &end, 10);
+			format = end + 1;
+		}
+
+		if (*format == '#') {
+			/* TODO: left precision */
+		}
+
+		if (*format == '.') {
+			/* TODO: right precision */
+		}
+
+		if (*format == 'i') {
+			/* international format */
+			double value = va_arg(ap, double);
+			i += snprintf(s + i, maxsize - i, "USD %.2g", value);
+			format++;
+			continue;
+		}
+
+		if (*format == 'n') {
+			/* national format */
+			double value = va_arg(ap, double);
+			i += snprintf(s + i, maxsize - i, "$%.2g", value);
+			format++;
+			continue;
+		}
+
+		va_end(ap);
+		return -1;
+	}
+
+	va_end(ap);
+	return i;
 }
 
 /*
-- 
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