From 51c543b8fefabc0a6f25bb4ef8e9901df9e16c45 Mon Sep 17 00:00:00 2001
From: Lassi Kortela <lassi@lassi.io>
Date: Mon, 30 Sep 2019 17:08:51 +0300
Subject: [PATCH] Implement command line help and version flags

---
 c/flmain.c | 169 ++++++++++++++++++++++++++++++++++++++++++++++++++++-
 1 file changed, 168 insertions(+), 1 deletion(-)

diff --git a/c/flmain.c b/c/flmain.c
index c1cd8b0..6b5cef3 100644
--- a/c/flmain.c
+++ b/c/flmain.c
@@ -11,6 +11,10 @@
 
 #include "scheme.h"
 
+#define BOOT_ENV_NULL 0
+#define BOOT_ENV_R7RS 1
+#define BOOT_ENV_UNSTABLE 2
+
 extern void write_defaults_indent(struct ios *f, value_t v);
 
 static value_t argv_list(int argc, char *argv[])
@@ -27,8 +31,171 @@ static value_t argv_list(int argc, char *argv[])
     return lst;
 }
 
-int main(int argc, char *argv[])
+static const char usage_message[] =
+"usage: upscheme -h|--help"
+"\n"
+"usage: upscheme -V|--version"
+"\n"
+"usage: upscheme [options]"
+"\n"
+"usage: upscheme [options] -e expression..."
+"\n"
+"usage: upscheme [options] script-file [script-arg...]"
+"\n";
+
+static int evalflag;
+static int helpflag;
+static int versionflag;
+static int boot_env;
+
+static void generic_usage(FILE *out, int status)
 {
+    fprintf(out, "%s", usage_message);
+    exit(status);
+}
+
+static void usage(void) { generic_usage(stderr, 2); }
+
+#define VERSION_STRING "0.1.0"
+
+static void version(void)
+{
+    printf("(version \"%s\")\n", VERSION_STRING);
+    printf("(canonical-command \"upscheme\")\n");
+    printf("(scheme-id upscheme)\n");
+    printf("(languages scheme r7rs)\n");
+    exit(0);
+}
+
+static char **long_option(char **argv, const char *option)
+{
+    if (!strcmp(option, "--help")) {
+        helpflag = 1;
+    } else if (!strcmp(option, "--version")) {
+        versionflag = 1;
+    } else {
+        usage();
+    }
+    return argv;
+}
+
+static void runtime_option(const char *name, const char *value)
+{
+    if (!strcmp("null", name)) {
+        if (value)
+            usage();
+        boot_env = BOOT_ENV_NULL;
+    } else if (!strcmp("r7rs", name)) {
+        if (value)
+            usage();
+        boot_env = BOOT_ENV_R7RS;
+    } else if (!strcmp("unstable", name)) {
+        if (value)
+            usage();
+        boot_env = BOOT_ENV_UNSTABLE;
+    } else if (!strcmp("debug", name)) {
+        if (!value)
+            usage();
+    } else if (!strcmp("search", name)) {
+        if (!value)
+            usage();
+    } else {
+        usage();
+    }
+}
+
+static void runtime_options(const char *arg)
+{
+    char *whole;
+    char *name;
+    char *value;
+    char *limit;
+
+    if (!(name = whole = strdup(arg))) {
+        usage();  // TODO: out of memory
+    }
+    while (name[0]) {
+        if (!(limit = strchr(name, ','))) {
+            limit = strchr(name, 0);
+        }
+        if ((value = strchr(name, '='))) {
+            if (value < limit) {
+                *value++ = 0;
+            } else {
+                value = 0;
+            }
+        }
+        runtime_option(name, value);
+        name = limit;
+    }
+    free(whole);
+}
+
+static char **short_option(char **argv, int option)
+{
+    switch (option) {
+    case 'e':
+        evalflag = 1;
+        break;
+    case 'h':
+        helpflag = 1;
+        break;
+    case 'V':
+        versionflag = 1;
+        break;
+    case ':':
+        if (!argv[0])
+            usage();
+        runtime_options(*argv++);
+        break;
+    default:
+        usage();
+        break;
+    }
+    return argv;
+}
+
+static char **parse_command_line_flags(char **argv)
+{
+    char *arg;
+    int option;
+
+    while ((arg = *argv)) {
+        if (arg[0] == '-') {
+            if (arg[1] == '-') {
+                if (arg[2] == '-') {
+                    usage();
+                } else if (!arg[2]) {
+                    break;
+                } else {
+                    argv++;
+                    argv = long_option(argv, arg);
+                }
+            } else if (!arg[1]) {
+                break;
+            } else {
+                argv++;
+                for (arg++; (option = *arg); arg++) {
+                    argv = short_option(argv, option);
+                }
+            }
+        } else {
+            break;
+        }
+    }
+    return argv;
+}
+
+int main(int argc, char **argv)
+{
+    char **newargv;
+
+    newargv = parse_command_line_flags(argv + 1);
+    if (helpflag) {
+        generic_usage(stdout, 0);
+    } else if (versionflag) {
+        version();
+    }
     fl_init(512 * 1024);
     {
         FL_TRY_EXTERN