/*
 * blogmirror - mirror blog.sillylaird.ca into flat mothra-friendly HTML.
 *
 * Reads the blog's RSS 2.0 feed (which carries the full post body in
 * <content:encoded>) and writes a static tree:
 *
 *	index.html			list of posts
 *	YYYY/MM/DD/slug.html		one page per post
 *
 * Plain ANSI C: builds with pcc on 9front (APE) and with cc elsewhere.
 *
 *	blogmirror [-u url] [-f file] [-o outdir] [-n maxposts]
 *
 * With -f it parses a feed already on disk; otherwise it shells out to
 * hget(1) (curl elsewhere) to fetch -u into a temporary file first.
 */

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/types.h>
#include <sys/stat.h>

#define FEEDURL	"https://blog.sillylaird.ca/feed.xml.php"
#define SITE	"https://blog.sillylaird.ca/"
#define TMPFEED	"/tmp/blogmirror.rss"

static char *outdir = "html";
static int maxposts = 0;		/* 0 = all */
static int nposts = 0;

static void *
emalloc(size_t n)
{
	void *p = malloc(n);
	if(p == NULL){
		fprintf(stderr, "blogmirror: out of memory\n");
		exit(1);
	}
	return p;
}

static char *
estrdup(const char *s)
{
	char *p = emalloc(strlen(s) + 1);
	strcpy(p, s);
	return p;
}

/* bounded concatenation; returns 0 if it would not fit */
static int
cats(char *d, size_t n, const char *s)
{
	size_t have = strlen(d), want = strlen(s);

	if(have + want + 1 > n)
		return 0;
	memcpy(d + have, s, want + 1);
	return 1;
}

/* does this file exist? */
static int
exists(const char *path)
{
	FILE *f = fopen(path, "rb");

	if(f == NULL)
		return 0;
	fclose(f);
	return 1;
}

/* read a whole file, NUL terminated */
static char *
slurp(const char *path)
{
	FILE *f;
	char *b;
	long n;

	if((f = fopen(path, "rb")) == NULL)
		return NULL;
	fseek(f, 0L, SEEK_END);
	n = ftell(f);
	rewind(f);
	if(n < 0){
		fclose(f);
		return NULL;
	}
	b = emalloc((size_t)n + 1);
	if(fread(b, 1, (size_t)n, f) != (size_t)n){
		fclose(f);
		free(b);
		return NULL;
	}
	b[n] = '\0';
	fclose(f);
	return b;
}

/* text between open and close, starting at p, not past end.  malloc'd. */
static char *
between(char *p, char *end, const char *open, const char *close)
{
	char *a, *b, *s;
	size_t n;

	if((a = strstr(p, open)) == NULL || a >= end)
		return NULL;
	a += strlen(open);
	if((b = strstr(a, close)) == NULL || b > end)
		return NULL;
	n = (size_t)(b - a);
	s = emalloc(n + 1);
	memcpy(s, a, n);
	s[n] = '\0';
	return s;
}

/* one UTF-8 rune out of a code point */
static int
putrune(char *d, long r)
{
	if(r < 0x80){
		d[0] = (char)r;
		return 1;
	}
	if(r < 0x800){
		d[0] = (char)(0xC0 | (r >> 6));
		d[1] = (char)(0x80 | (r & 0x3F));
		return 2;
	}
	if(r < 0x10000){
		d[0] = (char)(0xE0 | (r >> 12));
		d[1] = (char)(0x80 | ((r >> 6) & 0x3F));
		d[2] = (char)(0x80 | (r & 0x3F));
		return 3;
	}
	d[0] = (char)(0xF0 | (r >> 18));
	d[1] = (char)(0x80 | ((r >> 12) & 0x3F));
	d[2] = (char)(0x80 | ((r >> 6) & 0x3F));
	d[3] = (char)(0x80 | (r & 0x3F));
	return 4;
}

/* &amp; &lt; &gt; &quot; &apos; &#39; &#x2019; -> text, in place */
static char *
unxml(char *s)
{
	char *r, *w;
	long v;

	if(s == NULL)
		return NULL;
	for(r = w = s; *r != '\0'; ){
		if(*r != '&'){
			*w++ = *r++;
			continue;
		}
		if(strncmp(r, "&amp;", 5) == 0){ *w++ = '&'; r += 5; continue; }
		if(strncmp(r, "&lt;", 4) == 0){ *w++ = '<'; r += 4; continue; }
		if(strncmp(r, "&gt;", 4) == 0){ *w++ = '>'; r += 4; continue; }
		if(strncmp(r, "&quot;", 6) == 0){ *w++ = '"'; r += 6; continue; }
		if(strncmp(r, "&apos;", 6) == 0){ *w++ = '\''; r += 6; continue; }
		if(r[1] == '#'){
			char *e;
			if(r[2] == 'x' || r[2] == 'X')
				v = strtol(r + 3, &e, 16);
			else
				v = strtol(r + 2, &e, 10);
			if(*e == ';' && v > 0){
				w += putrune(w, v);
				r = e + 1;
				continue;
			}
		}
		*w++ = *r++;
	}
	*w = '\0';
	return s;
}

/* escape text for HTML output */
static void
puthtml(FILE *f, const char *s)
{
	if(s == NULL)
		return;
	for(; *s != '\0'; s++)
		switch(*s){
		case '&': fputs("&amp;", f); break;
		case '<': fputs("&lt;", f); break;
		case '>': fputs("&gt;", f); break;
		case '"': fputs("&quot;", f); break;
		default: fputc(*s, f); break;
		}
}

/* mkdir -p over the directory part of path */
static void
mkpath(const char *path)
{
	char buf[1024];
	char *p;

	if(strlen(path) >= sizeof buf)
		return;
	strcpy(buf, path);
	for(p = strchr(buf, '/'); p != NULL; p = strchr(p + 1, '/')){
		*p = '\0';
		if(buf[0] != '\0')
			mkdir(buf, 0777);
		*p = '/';
	}
}

/* blog URL -> repo-relative path, e.g. 2026/05/29/hello-world.html */
static const char *
urlpath(const char *link)
{
	const char *p = link;

	if(strncmp(p, SITE, strlen(SITE)) == 0)
		p += strlen(SITE);
	else if((p = strstr(link, "://")) != NULL){
		p += 3;
		p = strchr(p, '/');
		if(p == NULL)
			return "";
		p++;
	} else
		p = link;
	while(*p == '/')
		p++;
	return p;
}

static void
header(FILE *f, const char *title)
{
	fputs("<!DOCTYPE html>\n<html>\n\n<head>\n"
		"  <meta charset=\"utf-8\">\n  <title>", f);
	puthtml(f, title);
	fputs(" \xe2\x80\x93 SillyLaird</title>\n</head>\n\n<body>\n", f);
}

static void
footer(FILE *f, const char *up)
{
	fputs("\n  <hr>\n\n  <p>\n    <a href=\"", f);
	fputs(up, f);
	fputs("index.html\">Blog index</a>\n  </p>\n\n</body>\n\n</html>\n", f);
}

static void
writepost(const char *path, const char *title, const char *date,
	const char *body, const char *link)
{
	char file[1024];
	char up[64];
	const char *p;
	FILE *f;
	int depth;

	if(path[0] == '\0')
		return;
	file[0] = '\0';
	if(!cats(file, sizeof file, outdir) || !cats(file, sizeof file, "/")
	|| !cats(file, sizeof file, path)){
		fprintf(stderr, "blogmirror: path too long: %s\n", path);
		return;
	}
	mkpath(file);
	if((f = fopen(file, "wb")) == NULL){
		fprintf(stderr, "blogmirror: %s: cannot create\n", file);
		return;
	}

	up[0] = '\0';
	for(depth = 0, p = path; *p != '\0'; p++)
		if(*p == '/')
			depth++;
	for(; depth > 0 && strlen(up) + 3 < sizeof up; depth--)
		strcat(up, "../");

	header(f, title);
	fputs("  <h2>", f);
	puthtml(f, title);
	fputs("</h2>\n\n  <p><font size=\"-1\">", f);
	puthtml(f, date);
	fputs("</font></p>\n\n", f);
	fputs(body, f);			/* already HTML from the blog */
	fputs("\n\n  <p><font size=\"-1\">Mirror of <a href=\"", f);
	puthtml(f, link);
	fputs("\">", f);
	puthtml(f, link);
	fputs("</a></font></p>\n", f);
	footer(f, up);
	fclose(f);
	fprintf(stderr, "%s\n", file);
}

int
main(int argc, char *argv[])
{
	char *url = FEEDURL;
	char *feedfile = NULL;
	char *feed, *p, *end, *item;
	char cmd[1024];
	char file[1024];
	FILE *ix;
	int i;

	for(i = 1; i < argc; i++){
		if(strcmp(argv[i], "-u") == 0 && i + 1 < argc)
			url = argv[++i];
		else if(strcmp(argv[i], "-f") == 0 && i + 1 < argc)
			feedfile = argv[++i];
		else if(strcmp(argv[i], "-o") == 0 && i + 1 < argc)
			outdir = argv[++i];
		else if(strcmp(argv[i], "-n") == 0 && i + 1 < argc)
			maxposts = atoi(argv[++i]);
		else {
			fprintf(stderr,
				"usage: blogmirror [-u url] [-f file] [-o outdir] [-n maxposts]\n");
			exit(1);
		}
	}

	if(feedfile == NULL){
		cmd[0] = '\0';
		if(exists("/bin/hget")){		/* 9front */
			cats(cmd, sizeof cmd, "hget '");
			cats(cmd, sizeof cmd, url);
			cats(cmd, sizeof cmd, "' >");
			cats(cmd, sizeof cmd, TMPFEED);
		} else {
			cats(cmd, sizeof cmd, "curl -fsS '");
			cats(cmd, sizeof cmd, url);
			cats(cmd, sizeof cmd, "' -o ");
			cats(cmd, sizeof cmd, TMPFEED);
		}
		if(system(cmd) != 0){
			fprintf(stderr, "blogmirror: fetch failed: %s\n", url);
			exit(1);
		}
		feedfile = TMPFEED;
	}

	if((feed = slurp(feedfile)) == NULL){
		fprintf(stderr, "blogmirror: %s: cannot read\n", feedfile);
		exit(1);
	}

	mkdir(outdir, 0777);
	file[0] = '\0';
	cats(file, sizeof file, outdir);
	cats(file, sizeof file, "/index.html");
	if((ix = fopen(file, "wb")) == NULL){
		fprintf(stderr, "blogmirror: %s: cannot create\n", file);
		exit(1);
	}
	header(ix, "Blog");
	fputs("  <h2>Blog</h2>\n\n"
		"  <p>Mirror of <a href=\"" SITE "\">blog.sillylaird.ca</a>.</p>\n\n"
		"  <table cellspacing=\"0\" cellpadding=\"0\" border=\"0\">\n", ix);

	for(p = feed; (p = strstr(p, "<item>")) != NULL; p = end){
		char *title, *link, *date, *desc, *body;
		const char *path;

		if((end = strstr(p, "</item>")) == NULL)
			break;
		item = p;
		title = unxml(between(item, end, "<title>", "</title>"));
		link  = unxml(between(item, end, "<link>", "</link>"));
		date  = unxml(between(item, end, "<pubDate>", "</pubDate>"));
		desc  = unxml(between(item, end, "<description>", "</description>"));
		body  = between(item, end, "<content:encoded><![CDATA[", "]]></content:encoded>");

		if(title == NULL || link == NULL){
			free(title); free(link); free(date); free(desc); free(body);
			continue;
		}
		if(date == NULL)
			date = estrdup("");
		if(body == NULL)
			body = estrdup(desc != NULL ? desc : "");

		path = urlpath(link);
		writepost(path, title, date, body, link);

		fputs("    <tr>\n      <td width=\"10\"></td>\n      <td valign=\"top\">\n"
			"        <a href=\"", ix);
		puthtml(ix, path);
		fputs("\">", ix);
		puthtml(ix, title);
		fputs("</a><br>\n"
			"        <table cellspacing=\"0\" cellpadding=\"0\" border=\"0\">\n"
			"          <tr>\n            <td width=\"10\"></td>\n            <td>\n"
			"              <font size=\"-1\">\n                ", ix);
		puthtml(ix, date);
		fputs("<br>\n                ", ix);
		puthtml(ix, desc != NULL ? desc : "");
		fputs("\n              </font>\n            </td>\n          </tr>\n"
			"        </table>\n      </td>\n    </tr>\n", ix);

		free(title); free(link); free(date); free(desc); free(body);
		nposts++;
		if(maxposts > 0 && nposts >= maxposts)
			break;
		end += 7;		/* past </item> */
	}

	fputs("  </table>\n", ix);
	footer(ix, "");
	fclose(ix);
	free(feed);

	fprintf(stderr, "%s: %d posts\n", file, nposts);
	return 0;
}