Use colored/styled text output for diagnostics and usage info (#1775)

src/usage.cpp

@@ -2,17 +2,111 @@
 
 #include "usage.hpp"
 
+#include <algorithm>
 #include <stdio.h>
 #include <stdlib.h>
 
+#include "helpers.hpp"
+#include "style.hpp"
+
+static constexpr size_t maxLineLen = 79;
+
+// LCOV_EXCL_START
+
 void Usage::printAndExit(int code) const {
-	fputs(usage, stderr);
+	FILE *file = code ? stderr : stdout;
+
+	// Print "Usage: <program name>"
+	style_Set(file, STYLE_GREEN, true);
+	fputs("Usage: ", file);
+	style_Set(file, STYLE_CYAN, true);
+	fputs(name.c_str(), file);
+	size_t padFlags = literal_strlen("Usage: ") + name.length();
+
+	// Print the flags after the program name, indented to the same level
+	style_Set(file, STYLE_CYAN, false);
+	size_t flagsWidth = padFlags;
+	for (std::string const &flag : flags) {
+		if (flagsWidth + 1 + flag.length() > maxLineLen) {
+			fprintf(file, "\n%*c", static_cast<int>(padFlags), ' ');
+			flagsWidth = padFlags;
+		}
+		fprintf(file, " %s", flag.c_str());
+		flagsWidth += 1 + flag.length();
+	}
+	fputs("\n\n", file);
+
+	// Measure the options' flags
+	size_t padOpts = 0;
+	for (auto const &item : options) {
+		size_t pad = 0;
+		for (size_t i = 0; i < item.first.size(); ++i) {
+			if (i > 0) {
+				pad += literal_strlen(", ");
+			}
+			pad += item.first[i].length();
+		}
+		if (pad > padOpts) {
+			padOpts = pad;
+		}
+	}
+	int optIndent = static_cast<int>(literal_strlen("    ") + padOpts);
+
+	// Print the options
+	if (!options.empty()) {
+		style_Set(file, STYLE_GREEN, true);
+		fputs("Useful options:\n", file);
+	}
+	for (auto const &[opts, description] : options) {
+		fputs("    ", file);
+
+		// Print the comma-separated options
+		size_t optWidth = 0;
+		for (size_t i = 0; i < opts.size(); ++i) {
+			if (i > 0) {
+				style_Reset(file);
+				fputs(", ", file);
+				optWidth += literal_strlen(", ");
+			}
+			style_Set(file, STYLE_CYAN, false);
+			fputs(opts[i].c_str(), file);
+			optWidth += opts[i].length();
+		}
+		if (optWidth < padOpts) {
+			fprintf(file, "%*c", static_cast<int>(padOpts - optWidth), ' ');
+		}
+
+		// Print the description lines, indented to the same level
+		for (size_t i = 0; i < description.size(); ++i) {
+			style_Reset(file);
+			if (i > 0) {
+				fprintf(file, "\n%*c", optIndent, ' ');
+			}
+			fprintf(file, "  %s", description[i].c_str());
+		}
+		putc('\n', file);
+	}
+
+	// Print the link for further help information
+	style_Reset(file);
+	fputs("\nFor more help, use `", file);
+	style_Set(file, STYLE_CYAN, true);
+	fprintf(file, "man %s", name.c_str());
+	style_Reset(file);
+	fputs("' or go to ", file);
+	style_Set(file, STYLE_BLUE, true);
+	fputs("https://rgbds.gbdev.io/docs/", file);
+	style_Reset(file);
+	putc('\n', file);
+
 	exit(code);
 }
 
 void Usage::printAndExit(char const *fmt, ...) const {
 	va_list args;
+	style_Set(stderr, STYLE_RED, true);
 	fputs("FATAL: ", stderr);
+	style_Reset(stderr);
 	va_start(args, fmt);
 	vfprintf(stderr, fmt, args);
 	va_end(args);
@@ -20,3 +114,5 @@ void Usage::printAndExit(char const *fmt, ...) const {
 
 	printAndExit(1);
 }
+
+// LCOV_EXCL_STOP