#define _GNU_SOURCE

#include <arpa/inet.h>
#include <err.h>
#include <errno.h>
#include <ctype.h>
#include <dirent.h>
#include <fcntl.h>
#include <limits.h>
#include <stdarg.h>
#include <stdbool.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/socket.h>
#include <sys/stat.h>
#include <sys/types.h>
#include <time.h>
#include <unistd.h>

#include "dpi.h"
#include "io.h"
#include "sundown/markdown.h"
#include "sundown/html.h"
#include "sundown/buffer.h"
#include "sundown/houdini.h"

static const size_t sigil_size = sizeof("§")-1;
static const int id_length = 16;

static const char ssb_ref_base[] = "http://localhost:8027/";
static const char ssb_channel_base[] = "http://localhost:8027/channel/";

static const int max_cols = 54;

static char server_hostname[256];
static char server_url[256];
static char zet_dir[_POSIX_PATH_MAX-64];
static bool seeded = false;

enum http_method {
	HTTP_METHOD_GET,
	HTTP_METHOD_HEAD,
	HTTP_METHOD_POST,
	HTTP_METHOD_OTHER
};

struct http_request {
	enum http_method method;
	char *path;
	char *query;
	char *hash;
	char *http_version;
	char *host;
	char *referer;
	ssize_t content_length;
	char *content_type;
	char *multipart_boundary;
	int fd;
	char *data, *full_data;
	size_t len;
	bool add_new_id;
};

struct zet_search {
	DIR *dir;
	const char *id;
	char *query;
};

struct zet_mtime {
	char *id;
	int mtime;
};

struct zet_renderopt {
	struct html_renderopt html;
	const char *query;
};

enum page {
	PAGE_NEW,
	PAGE_ALL,
	PAGE_RECENT,
	PAGE_ZET,
	PAGE_SEARCH,
};

static int count_lines_in(const char *str) {
	int count = 1;
	char c;
	int col = 0;
	while ((c = *str++)) {
		if (c == '\n' || col++ > max_cols) {
			count++;
			col = 0;
		}
	}
	return count;
}

static int count_lines(int fd) {
	int count = 1;
	if (fd >= 0) do {
		unsigned char buf[4096];
		size_t len = sizeof(buf)-1;
		int rc = read_some(fd, buf, &len);
		if (rc < 0) {
			if (errno == EPIPE) break;
			return -1;
		}
		buf[len] = '\0';
		count += count_lines_in((char *)buf);
	} while (1);
	return count;
}

static int write_html_char(int fd, char c) {
	switch (c) {
		case '&': return write_buf(fd, "&amp;");
		case '<': return write_buf(fd, "&lt;");
		case '>': return write_buf(fd, "&gt;");
		case '"': return write_buf(fd, "&quot;");
	}
	return write_char(fd, c);
}

static void write_err(int fd, const char *subject) {
	int rc = dprintf(fd,
		"\n<strong>Error</strong>: %s: %s\n",
		subject,
		strerror(errno));
	if (rc < 0) warnx("dprintf");
}

static int write_html(int fd, const char *buf, size_t len) {
	while (len > 0) {
		// note: buf must null-terminated
		char *next = strpbrk(buf, "&<>\"");
		if (next == NULL) return write_all(fd, (unsigned char *)buf, len);
		char c = *next;
		size_t sublen = next - buf;
		int rc = write_all(fd, (unsigned char *)buf, sublen);
		if (rc < 0) return -1;
		buf += sublen + 1;
		len -= sublen + 1;
		rc = write_html_char(fd, c);
		if (rc < 0) return -1;
	}
	return 0;
}

static int write_zet_link(int fd, const char *id, const char *title) {
	if (title == NULL) {
		return dprintf(fd, " <a href=\"%s\"><strong><code>§%s</code></strong></a>", id, id);
	}
	int rc = dprintf(fd, " <a href=\"%s\">[<strong>", id);
	rc |= write_html(fd, title, strlen(title));
	rc |= dprintf(fd, "</strong>](<code>§%s</code>)</a>", id);
	return rc;
}

static int write_topbar(int fd, enum page page, const char *id, const char *title) {
	int rc = write_buf(fd, "<form action=\"search\">");

	rc |= write_buf(fd, " ");
	if (page == PAGE_ALL) rc |= write_buf(fd, "<strong>");
	rc |= write_buf(fd, "<a href=\"all\">All</a>");
	if (page == PAGE_ALL) rc |= write_buf(fd, "</strong>");

	rc |= write_buf(fd, " ");
	if (page == PAGE_RECENT) rc |= write_buf(fd, "<strong>");
	rc |= write_buf(fd, "<a href=\"recent\">Recent</a>");
	if (page == PAGE_RECENT) rc |= write_buf(fd, "</strong>");

	rc |= write_buf(fd, " ");
	if (page == PAGE_NEW) rc |= write_buf(fd, "<strong>");
	rc |= write_buf(fd, "<a href=\"new\">New</a>");
	if (page == PAGE_NEW) rc |= write_buf(fd, "</strong>");

	rc |= write_buf(fd, " <input name=q placeholder=Search");
	if (page == PAGE_SEARCH) {
		rc |= write_buf(fd, " value=\"");
		rc |= write_html(fd, id, strlen(id));
		rc |= write_buf(fd, "\"");
	}
	rc |= write_buf(fd, ">");

	if (page == PAGE_ZET) {
		rc |= write_zet_link(fd, id, title);
	}

	rc |= write_buf(fd, "</form>");
	return rc;
}

static int passthrough_note_html(int fd, int note_fd) {
	int rc;
	if (note_fd >= 0) do {
		unsigned char buf[4096];
		size_t len = sizeof(buf)-1;
		rc = read_some(note_fd, buf, &len);
		if (rc < 0) {
			if (errno != EPIPE) dprintf(fd,
				"\n<strong>Error</strong>: %s", strerror(errno));
			break;
		}
		buf[len] = '\0';
		rc = write_html(fd, (char *)buf, len);
		if (rc < 0) warn("write_html");
	} while (rc == 0);
	return 0;
}

static int dpi_respond_err(int fd, const char *fmt, ...) {
	int rc;
	va_list ap;
	int err = errno;
	va_start(ap, fmt);
	rc = dpi_send_header(fd, "text/plain");
	rc |= vdprintf(fd, fmt, ap);
	rc |= dprintf(fd, ": %s", strerror(err));
	va_end(ap);
	rc |= close(fd);
	return rc;
}

static char *zet_get_title_fd(int fd, char *buf, size_t len) {
	if (fd < 0) return NULL;
	int rc = read_some(fd, (unsigned char *)buf, &len);
	if (rc < 0) return NULL;
	buf[len] = '\0';
	char *end = strchr(buf, '\n');
	if (end != NULL) *end = '\0';
	while (*buf == '#') buf++;
	while (*buf == ' ') buf++;
	return buf;
}

static char *zet_get_title(const char *id, char *buf, size_t len) {
	char path_buf[_POSIX_PATH_MAX];
	ssize_t sz = snprintf(path_buf, sizeof(path_buf), "%s/%s", zet_dir, id);
	if (sz < 0 || (size_t)sz >= sizeof(path_buf)) return NULL;
	int fd = open(path_buf, O_RDONLY);
	if (fd < 0) return NULL;
	char *title_buf = zet_get_title_fd(fd, buf, len);
	if (title_buf == NULL || *title_buf == '\0') {
		strncpy(buf, "§", sigil_size);
		strncpy(buf + sigil_size, id, len);
		title_buf = buf;
	}
	close(fd);
	return title_buf;
}

static int zet_stat(const char *id, struct stat *st) {
	char path_buf[_POSIX_PATH_MAX];
	ssize_t sz = snprintf(path_buf, sizeof(path_buf), "%s/%s", zet_dir, id);
	if (sz < 0 || (size_t)sz >= sizeof(path_buf)) return -1;
	return stat(path_buf, st);
}

static char *zet_get_buf_title(const struct buf *link, char *buf, size_t len) {
	char id_buf[128];
	strncpy(id_buf, (char *)link->data, link->size);
	id_buf[sizeof(id_buf)-1] = '\0';
	return zet_get_title(id_buf + sigil_size, buf, len);
}

static int zet_links_in(const char *str, const char *id_to) {
	while (1) {
		str = strstr(str, "§");
		if (str == NULL) return 0;
		str += sigil_size;
		if (!strncmp(str, id_to, id_length)) return 1;
	}
	return 0;
}

static int zet_links_to(const char *id_from, const char *id_to) {
	// TODO: index links, so that every source file doesn't have to be read all
	// the time
	int rc;
	char path_buf[_POSIX_PATH_MAX];
	ssize_t sz = snprintf(path_buf, sizeof(path_buf), "%s/%s", zet_dir, id_from);
	if (sz < 0 || (size_t)sz >= sizeof(path_buf)) return -1;
	int fd = open(path_buf, O_RDONLY);
	if (fd < 0) return -1;
	size_t fringe = 0;
	size_t link_len = strlen(id_to) + id_length;
	unsigned char buf[4096];
	do {
		size_t len = sizeof(buf)-fringe-1;
		rc = read_some(fd, buf + fringe, &len);
		if (rc < 0) {
			if (errno != EPIPE) { close(fd); return -1; }
			close(fd);
			return 0;
		}
		buf[len - fringe] = '\0';
		rc = zet_links_in((char *)buf, id_to);
		if (rc < 0) { close(fd); return -1; }
		// in case a link is across the boundary between this buf and the next,
		// keep some "fringe" of the end of this buf in the beginning of the
		// next one
		if (len > link_len) {
			fringe = link_len;
			memcpy(buf, buf + len - fringe, fringe);
		}
	} while (rc == 0);
	close(fd);
	return rc;
}

static int zet_matches_query(const char *id, const char *query) {
	char path_buf[_POSIX_PATH_MAX];
	ssize_t sz = snprintf(path_buf, sizeof(path_buf), "%s/%s", zet_dir, id);
	if (sz < 0 || (size_t)sz >= sizeof(path_buf)) return -1;

	int note_fd = open(path_buf, O_RDONLY);
	if (note_fd < 0) return -1;

	char *text = read_full(note_fd);
	bool found = strcasestr(text, query) != NULL;
	free(text);
	return found ? 1 : 0;
}

static int zet_search_start(struct zet_search *zs, const char *id, char *query) {
	zs->dir = opendir(zet_dir);
	if (zs->dir == NULL) return -1;
	zs->id = id;
	zs->query = query;
	return 0;
}

static int zet_search_next(struct zet_search *zs, const char **idp) {
	int rc;
	struct dirent *ent;
	const char *id;
	const char *dest_id = zs->id;
	const char *query = zs->query;
	while (1) {
		errno = 0;
		ent = readdir(zs->dir);
		if (ent == NULL) {
			if (errno != 0) return -1;
			id = NULL;
			break;
		}
		id = ent->d_name;
		if (id[0] == '.') continue;
		if (strpbrk(id, "<>&\"~") != NULL) continue;
		if (dest_id != NULL) {
			rc = zet_links_to(id, dest_id);
			if (rc < 0) return -1;
			if (rc != 1) continue;
		}
		if (query != NULL) {
			rc = zet_matches_query(id, query);
			if (rc < 0) return -1;
			if (rc != 1) continue;
		}
		break;
	};
	*idp = id;
	return 0;
}

static int zet_search_close(struct zet_search *sz) {
	return closedir(sz->dir);
}

static int dpi_serve_zet_all(int fd) {
	int rc;
	struct zet_search zs;
	rc = zet_search_start(&zs, NULL, NULL);
	if (rc < 0) return dpi_respond_err(fd, "Unable to list");
	rc = dpi_send_header(fd, "text/html");
	if (rc < 0) { warn("dpi_send_header"); close(fd); return 0; }
	rc = dprintf(fd,
			"<!doctype html><html><head>"
			"<title>Notes - All</title>"
			"<meta charset=utf-8>"
			"</head>"
			"<body style=\"margin:0\">");
	rc |= write_topbar(fd, PAGE_ALL, NULL, NULL);
	rc |= write_buf(fd, "<ul>");
	if (rc < 0) { warn("write"); close(fd); return 0; }
	const char *id;
	while (1) {
		rc = zet_search_next(&zs, &id);
		if (rc < 0) {
			rc = dprintf(fd,
				"\n<strong>Error</strong>: %s\n",
				strerror(errno));
			if (rc < 0) warnx("dprintf");
			close(fd);
			return 0;
		}
		if (id == NULL) break;
		char title_buf[128];
		char *title = zet_get_title(id, title_buf, sizeof(title_buf));
		if (title == NULL) {
			warn("zet_get_title");
			title = title_buf;
			strncpy(title, id, sizeof(title)-1);
			title[sizeof(title)-1] = '\0';
			return 0;
		}
		rc = dprintf(fd, "<li><a href=\"%s\">", id);
		rc |= write_html(fd, title, strlen(title));
		rc |= write_buf(fd, "</a></li>");
		if (rc < 0) { warnx("write"); close(fd); return 0; }
	}
	rc = dprintf(fd, "</ul></body></html>");
	if (rc < 0) { warn("dprintf"); close(fd); return 0; }
	rc = zet_search_close(&zs);
	if (rc < 0) warn("closedir");
	close(fd);
	return 0;
}

static int cmp_zet_mtimes(const void *ptr1, const void *ptr2) {
	const struct zet_mtime *zet_mtime1 = ptr1;
	const struct zet_mtime *zet_mtime2 = ptr2;
	return zet_mtime2->mtime - zet_mtime1->mtime;
}

static int dpi_serve_zet_recent(int fd) {
	int rc, i;
	struct zet_search zs;
	int capacity = 0;
	int count = 0;
	struct zet_mtime *zets = NULL;
	rc = zet_search_start(&zs, NULL, NULL);
	if (rc < 0) return dpi_respond_err(fd, "Unable to list");
	rc = dpi_send_header(fd, "text/html");
	if (rc < 0) { warn("dpi_send_header"); goto cleanup; }
	rc = dprintf(fd,
			"<!doctype html><html><head>"
			"<title>Notes - Recent</title>"
			"<meta charset=utf-8>"
			"</head>"
			"<body style=\"margin:0\">");
	rc |= write_topbar(fd, PAGE_RECENT, NULL, NULL);
	rc |= write_buf(fd, "<ul>");
	if (rc < 0) { warn("write"); goto cleanup; }
	const char *id;
	for (i = 0;; i++) {
		struct stat st;
		rc = zet_search_next(&zs, &id);
		if (rc == 0 && id == NULL) break;
		if (rc == 0) rc = zet_stat(id, &st);
		if (rc == 0 && i >= capacity) {
			if (capacity == 0) capacity = 256;
			else capacity *= 2;
			void *new_zets = reallocarray(zets, capacity, sizeof *zets);
			if (new_zets == NULL) rc = -1;
			else zets = new_zets;
		}

		if (rc < 0) {
			write_err(fd, "list");
			goto cleanup;
		}
		zets[i].mtime = st.st_mtime;
		zets[i].id = strdup(id);
		count++;
	}

	qsort(zets, count, sizeof(*zets), cmp_zet_mtimes);
	static int limit = 50;
	if (limit > count) limit = count;

	for (i = 0; i < limit; i++) {
		id = zets[i].id;
		char title_buf[128];
		char *title = zet_get_title(id, title_buf, sizeof(title_buf));
		if (title == NULL) {
			write_err(fd, "get_title");
			goto cleanup;
		}
		rc = dprintf(fd, "<li><a href=\"%s\">", id);
		rc |= write_html(fd, title, strlen(title));
		rc |= write_buf(fd, "</a></li>");
		if (rc < 0) { warnx("write"); goto cleanup; }
	}

	rc = dprintf(fd, "</ul></body></html>");
	if (rc < 0) warn("dprintf");

cleanup:
	for (i = 0; i < count; i++) {
		free(zets[i].id);
	}
	free(zets);

	rc = zet_search_close(&zs);
	if (rc < 0) warn("closedir");
	close(fd);
	return 0;
}

static void unescape(char *buf, size_t len, const char *str) {
	struct buf *ob = bufnew(1024);
	houdini_unescape_url(ob, (unsigned char *)str, strlen(str));
	if (ob->size < len) len = ob->size;
	strncpy(buf, (char *)ob->data, len);
	buf[len] = '\0';
	bufrelease(ob);
}

static int dpi_serve_zet_search(int fd, char *qs) {
	int rc;
	struct zet_search zs;

	char *query = NULL, query_unescaped[1024];
	char *name = qs, *next_name;
	while (name != NULL) {
		char *value = strchr(name, '=');
		if (value != NULL) *value++ = '\0';
		next_name = strchr(value != NULL ? value : name, '&');
		if (next_name != NULL) *next_name++ = '\0';

		if (!strcmp(name, "q")) query = value;

		name = next_name;
	}
	if (query != NULL) {
		unescape(query_unescaped, sizeof(query_unescaped), query);
		query = query_unescaped;
	}

	rc = zet_search_start(&zs, NULL, query);
	if (rc < 0) return dpi_respond_err(fd, "Unable to list");

	rc = dpi_send_header(fd, "text/html");
	if (rc < 0) { warn("dpi_send_header"); close(fd); return 0; }
	rc = dprintf(fd,
		"<!doctype html><html><head>"
		"<title>Notes</title>"
		"<meta charset=utf-8>"
		"</head>"
		"<body style=\"margin:0\">"
	);
	rc |= write_topbar(fd, PAGE_SEARCH, query, NULL);
	rc |= write_buf(fd, "<ul>");
	if (rc < 0) { warn("write"); close(fd); return 0; }
	const char *id;
	while (1) {
		rc = zet_search_next(&zs, &id);
		if (rc < 0) {
			rc = dprintf(fd,
				"\n<strong>Error</strong>: %s\n",
				strerror(errno));
			if (rc < 0) warnx("dprintf");
			close(fd);
			return 0;
		}
		if (id == NULL) break;
		char title_buf[128];
		char *title = zet_get_title(id, title_buf, sizeof(title_buf));
		if (title == NULL) {
			warn("zet_get_title");
			title = title_buf;
			strncpy(title, id, sizeof(title)-1);
			title[sizeof(title)-1] = '\0';
			return 0;
		}
		rc = write_buf(fd, "<li>");
		rc |= write_zet_link(fd, id, title);
		rc |= write_buf(fd, "</li>");
		if (rc < 0) { warnx("dprintf/write_html/write_buf"); close(fd); return 0; }
	}
	rc = dprintf(fd, "</ul></body></html>");
	if (rc < 0) { warn("dprintf"); close(fd); return 0; }
	rc = zet_search_close(&zs);
	if (rc < 0) warn("closedir");
	close(fd);
	return 0;
}

static int dpi_serve_not_found(int fd) {
	int rc = dpi_send_header(fd, "text/html");
	if (rc < 0) { warn("dpi_send_header"); close(fd); return 0; }
	write_buf(fd, "Not Found");
	close(fd);
	return 0;
}

static int dpi_serve_zet_new(int fd) {
	int rc = dpi_send_header(fd, "text/html");
	if (rc < 0) { warn("dpi_send_header"); close(fd); return 0; }
	dprintf(fd,
		"<!doctype html><html><head>"
		"<title>New Note</title>"
		"<meta charset=utf-8>"
		"</head>"
		"<body style=\"margin:0\">");
	write_topbar(fd, PAGE_NEW, NULL, NULL);
	dprintf(fd,
		"<table style=\"width:100%%; height:100%%; border-collapse:collapse\"><tr>"
		"<td><form method=post action=\"%snew\" enctype=\"multipart/form-data\">"
		"<textarea name=text cols=64 rows=8 style=\"width:50%%\"></textarea><br>"
		"<input type=submit value=\"Save\">"
		"</form></td></tr></form></html>"
		, server_url);
	close(fd);
	return 0;
}

static void parse_req_uri(char *path, char **hashp, char **queryp) {
	char *hash = strchr(path, '#');
	if (hash != NULL) *hash++ = '\0';
	*hashp = hash;

	char *query = strchr(path, '?');
	if (query != NULL) *query++ = '\0';
	*queryp = query;
}

static int
md_rndr_link(struct buf *ob, const struct buf *link, const struct buf *title, const struct buf *content, void *opaque)
{
	struct zet_renderopt *options = opaque;

	if (link != NULL && (options->html.flags & HTML_SAFELINK) != 0 && !sd_autolink_issafe(link->data, link->size))
		return 0;

	BUFPUTSL(ob, "<a href=\"");

	if (link && link->size > sigil_size) {
		if (link->data[0] == '#') {
			BUFPUTSL(ob, ssb_channel_base);
			houdini_escape_href(ob, link->data + 1, link->size - 1);
		} else if (link->data[0] == '#' || link->data[0] == '@'
		  || link->data[0] == '&' || link->data[0] == '%') {
			BUFPUTSL(ob, ssb_ref_base);
			houdini_escape_href(ob, link->data, link->size);
		} else if (!strncmp((char *)link->data, "§", sigil_size)) {
			houdini_escape_href(ob, link->data + sigil_size,
					link->size - sigil_size);
			const char *query = options->query;
			if (query != NULL) {
				bufputc(ob, '?');
				bufputs(ob, query);
			}
		} else
			houdini_escape_href(ob, link->data, link->size);
	}

	if (title && title->size) {
		BUFPUTSL(ob, "\" title=\"");
		houdini_escape_html0(ob, title->data, title->size, 0);
	}

	if (options->html.link_attributes) {
		bufputc(ob, '\"');
		options->html.link_attributes(ob, link, opaque);
		bufputc(ob, '>');
	} else {
		BUFPUTSL(ob, "\">");
	}

	if (content && content->size) bufput(ob, content->data, content->size);
	BUFPUTSL(ob, "</a>");
	return 1;
}

static int
md_rndr_image(struct buf *ob, const struct buf *link, const struct buf *title, const struct buf *alt, void *opaque)
{
	struct zet_renderopt *options = opaque;
	if (!link || !link->size) return 0;

	BUFPUTSL(ob, "<img src=\"");
	BUFPUTSL(ob, ssb_ref_base);
	houdini_escape_href(ob, link->data, link->size);
	BUFPUTSL(ob, "\" alt=\"");

	if (alt && alt->size)
		houdini_escape_html0(ob, alt->data, alt->size, 0);

	if (title && title->size) {
		BUFPUTSL(ob, "\" title=\"");
		houdini_escape_html0(ob, title->data, title->size, 0);
	}

	(void)options;
	bufputs(ob, "\"/>");
	return 1;
}

static void put_link_truncated(struct buf *ob, const struct buf *link, int max_length) {
	char *buf = (char *)link->data;
	size_t len = link->size;

	if (!strncmp(buf, "http", 4)) {
		if (!strncmp(buf + 4, "://", 3)) {
			buf += 7;
			len -= 7;
		}
		if (!strncmp(buf + 4, "s://", 4)) {
			buf += 8;
			len -= 8;
		}
	}
	if (len < (size_t)max_length) {
		houdini_escape_html0(ob, (unsigned char *)buf, len, 0);
		return;
	}

	houdini_escape_html0(ob, (unsigned char *)buf, max_length, 0);
	BUFPUTSL(ob, "…");
}

static int
md_rndr_autolink(struct buf *ob, const struct buf *link, enum mkd_autolink type, void *opaque)
{
	struct zet_renderopt *options = opaque;

	if (!link || !link->size)
		return 0;

	if ((options->html.flags & HTML_SAFELINK) != 0 &&
		!sd_autolink_issafe(link->data, link->size) &&
		type != MKDA_EMAIL)
		return 0;

	BUFPUTSL(ob, "<a href=\"");
	if (type == MKDA_EMAIL)
		BUFPUTSL(ob, "mailto:");
	if (type == MKDA_ZET)
		houdini_escape_href(ob, link->data + sigil_size, link->size - sigil_size);
	else if (type == MKDA_SSB) {
		if (link->data[0] == '#') {
			BUFPUTSL(ob, ssb_channel_base);
			houdini_escape_href(ob, link->data + 1, link->size - 1);
		} else {
			BUFPUTSL(ob, ssb_ref_base);
			houdini_escape_href(ob, link->data, link->size);
		}
	} else
		houdini_escape_href(ob, link->data, link->size);

	if (type == MKDA_ZET) {
		char title_buf[128];
		char *title = zet_get_buf_title(link, title_buf, sizeof(title_buf));
		if (title != NULL) {
			BUFPUTSL(ob, "\" title=\"");
			houdini_escape_html0(ob, (unsigned char *)title, strlen(title), 0);
		}
	}

	if (options->html.link_attributes) {
		bufputc(ob, '\"');
		options->html.link_attributes(ob, link, opaque);
		bufputc(ob, '>');
	} else {
		BUFPUTSL(ob, "\">");
	}

	/*
	 * Pretty printing: if we get an email address as
	 * an actual URI, e.g. `mailto:foo@bar.com`, we don't
	 * want to print the `mailto:` prefix
	 */
	if (bufprefix(link, "mailto:") == 0) {
		houdini_escape_html0(ob, link->data + 7, link->size - 7, 0);
	} else if (link->data[0] == '&' || link->data[0] == '@' || link->data[0] == '%') {
		put_link_truncated(ob, link, 8);
	} else if (!strncmp((char *)link->data, "§", sigil_size)) {
		put_link_truncated(ob, link, 9);
	} else {
		put_link_truncated(ob, link, max_cols);
	}

	BUFPUTSL(ob, "</a>");

	return 1;
}

static int dpi_serve_zet(int fd, char *path) {
	int rc = 0;
	char *hash, *query;
	parse_req_uri(path, &hash, &query);

	if (!strcmp(path, "/")) return dpi_serve_zet_all(fd);
	if (!strcmp(path, "/all")) return dpi_serve_zet_all(fd);
	if (!strcmp(path, "/recent")) return dpi_serve_zet_recent(fd);
	if (!strcmp(path, "/search")) return dpi_serve_zet_search(fd, query);
	if (!strcmp(path, "/new")) return dpi_serve_zet_new(fd);

	char path_buf[_POSIX_PATH_MAX];
	char *id = path+1;
	ssize_t sz = snprintf(path_buf, sizeof(path_buf), "%s/%s", zet_dir, id);
	if (sz < 0 || (size_t)sz >= sizeof(path_buf)) return dpi_respond_err(fd, "read_file");

	int note_fd = open(path_buf, O_RDONLY);
	if (note_fd < 0 && errno != ENOENT) return dpi_respond_err(fd, "open");

	int rows = count_lines(note_fd);
	if (rows < 0) return dpi_respond_err(fd, "count_lines"); 
	static const int max_rows = 57, min_rows = 8;
	if (rows > max_rows) rows = max_rows;
	else if (rows < min_rows) rows = min_rows;
	if (note_fd >= 0) rc = lseek(note_fd, 0, SEEK_SET);
	if (rc < 0) return dpi_respond_err(fd, "lseek");

	char buf[128];
	char *title = zet_get_title_fd(note_fd, buf, sizeof(buf));
	if (title == NULL) title = id;
	if (note_fd >= 0) rc = lseek(note_fd, 0, SEEK_SET);
	if (rc < 0) return dpi_respond_err(fd, "lseek");

	rc = dpi_send_header(fd, "text/html");
	rc |= dprintf(fd,
		"<!doctype html><head>"
		"<title>");
	if (title != NULL) rc |= write_html(fd, title, strlen(title));
	rc |= dprintf(fd,
		"</title>"
		"<meta charset=utf-8>"
		"<style>"
		"pre { white-space: pre-wrap; }"
		"td { padding: 0; }"
		"</style>"
		"</head>");

	rc |= write_buf(fd, "<body style=\"margin:0\">");
	rc |= write_topbar(fd, PAGE_ZET, id, title);
	rc |= dprintf(fd,
		"<table style=\"width:100%%; height:100%%; border-collapse:collapse\"><tr>"
		"<td style=\"width:50%%\"><form method=post action=\"%s%s\" enctype=\"multipart/form-data\" style=\"height:100%%\">"
		"<textarea name=text cols=64 rows=%d style=\"width:100%%\">\n"
		, server_url, id, rows);
	rc = passthrough_note_html(fd, note_fd);
	if (rc < 0) { warnx("passthrough_note_html"); close(fd); return 0; }
	rc = dprintf(fd, "</textarea><br>"
		"<input type=submit value=\"Save\">"
		" <input type=submit name=add_new_id value=\"Add New ID\">"
		"</form></td>"
		"<td>"
		);
	if (rc < 0) { warn("dpi_send_header"); close(fd); return 0; }
	if (note_fd >= 0) rc = lseek(note_fd, 0, SEEK_SET);
	if (rc < 0) {
		rc = dprintf(fd, "\n<strong>Error</strong>: %s", strerror(errno));
		if (rc < 0) warnx("dprintf");
		close(fd);
	}

	char *text = note_fd >= 0 ? read_full(note_fd) : NULL;
	if (text == NULL) {
		rc = dprintf(fd, "\n<strong>Error</strong>: %s", strerror(errno));
		if (rc < 0) warnx("dprintf");
		close(fd);
	}

	struct sd_callbacks callbacks;
	struct zet_renderopt options;
	struct sd_markdown *markdown;
	struct buf *ob = bufnew(128);
	sdhtml_renderer(&callbacks, &options.html, HTML_ESCAPE);
	options.query = query;
	callbacks.link = md_rndr_link;
	callbacks.image = md_rndr_image;
	callbacks.autolink = md_rndr_autolink;
	static const unsigned int extensions =
		MKDEXT_NO_INTRA_EMPHASIS |
		MKDEXT_TABLES |
		MKDEXT_FENCED_CODE |
		MKDEXT_AUTOLINK |
		MKDEXT_STRIKETHROUGH |
		MKDEXT_SPACE_HEADERS |
		MKDEXT_LAX_SPACING;
	markdown = sd_markdown_new(extensions, 16, &callbacks, &options);
	sd_markdown_render(ob, (unsigned char *)text, strlen(text), markdown);
	free(text);
	sd_markdown_free(markdown);
	rc = write_all(fd, ob->data, ob->size);
	if (rc < 0) warn("write_all");
	bufrelease(ob);
	rc = dprintf(fd, "</td></tr>");
	if (rc < 0) warn("dprintf");

	rc = dprintf(fd, "<tr><td></td><td>");
	if (rc < 0) warn("dprintf");
	struct zet_search zs;
	bool first = true;
	rc = zet_search_start(&zs, id, NULL);
	if (rc < 0) warn("zet_search_start");
	do {
		const char *result_id;
		rc = zet_search_next(&zs, &result_id);
		if (rc < 0) warn("zet_search_next");
		if (result_id == NULL) break;
		if (first) {
			first = false;
			rc = dprintf(fd, "Backlinks:<ul>");
			if (rc < 0) warn("dprintf");
		}
		char title_buf[128];
		char *result_title = zet_get_title(result_id, title_buf, sizeof(title_buf));
		if (result_title == NULL) {
			warn("zet_get_title");
			result_title = title_buf;
			strncpy(result_title, result_id, sizeof(result_title)-1);
			result_title[sizeof(result_title)-1] = '\0';
			return 0;
		}
		rc = dprintf(fd, "<li><a href=\"%s%s%s\">", result_id,
				query ? "?" : "", query ? query : "");
		rc |= write_html(fd, result_title, strlen(result_title));
		rc |= write_buf(fd, "</a></li>");
	} while (1);
	if (!first) (void)dprintf(fd, "</ul>");
	rc = dprintf(fd, "</td></tr>");
	if (rc < 0) warn("dprintf");
	(void)zet_search_close(&zs);

	rc = write_buf(fd, "</table>");
	if (rc < 0) warn("write_buf");
	rc = write_buf(fd, "</body></html>");
	if (rc < 0) warn("write_buf");

	close(fd);
	return 0;
}

static int handle_dpi_client(int fd) {
	int rc;
	char url[2048];
	rc = dpi_check_auth(fd);
	if (rc < 0) {
		warn("dpi auth");
		close(fd);
		return 0;
	}
	rc = dpi_read_request(fd, url, sizeof(url));
	if (rc < 0) {
		if (errno == ESHUTDOWN) return -1;
		warn("dpi request");
		dpi_respond_err(fd, "Unable to read request");
		return 0;
	}
	if (!strncmp(url, "dpi:/zet/", 9)) {
		return dpi_serve_zet(fd, url + 8);
	}
	return dpi_serve_not_found(fd);
}

static char *next_line(char *str) {
	char *nextline = strchr(str, '\n');
	if (nextline != NULL) {
		if (nextline[-1] == '\r') nextline[-1] = '\0';
		else *nextline = '\0';
		nextline++;
	}
	return nextline;
}

static char *parse_header(char *line) {
	char *value = strchr(line, ':');
	if (value != NULL) {
		*value++ = '\0';
		while (*value == ' ') value++;
	}
	return value;
}

static int http_serve_index(struct http_request *req) {
	write_buf(req->fd, "HTTP/1.0 200 OK\r\nConnection: close\r\n\r\n");
	close(req->fd);
	return 0;
}

static void generate_id(char id[64]) {
	if (!seeded) {
		srandom(time(NULL) ^ getpid());
		seeded = true;
	}
	(void)snprintf(id, 64, "%08lx%08lx", random(), random());
}

static int save_part(struct http_request *req, int note_fd) {
	int rc = write_all(note_fd, (unsigned char *)req->data, req->len);
	if (req->add_new_id) {
		char id[72] = "\n§";
		generate_id(id + 1 + sigil_size);
		rc |= write_all(note_fd, (unsigned char *)id, strlen(id));
	}
	rc |= close(note_fd);
	free(req->full_data);
	return rc;
}

static int parse_multipart(struct http_request *req) {
	size_t boundary_len = req->multipart_boundary != NULL
		? strlen(req->multipart_boundary) : 0;
	if (boundary_len == 0) return -1;
	ssize_t len = req->content_length;
	if (len < 0) return -1;
	if (req->len < (size_t)len) {
		req->full_data = malloc(len+1);
		memcpy(req->full_data, req->data, req->len);
		char *rest = req->full_data + req->len;
		int rc = read_all(req->fd, (unsigned char *)rest, len - req->len);
		if (rc < 0) return -1;
		req->data = req->full_data;
		req->len = len;
	}
	req->data[req->len] = '\0';

	// iterate through parts
	char *part, *next;
	const char *boundary = req->multipart_boundary;
	for (part = strstr(req->data, boundary); part != NULL; part = next) {
		part += boundary_len;
		if (part[0] == '-' && part[1] == '-') break; // end of parts
		if (*part == '\r') part++;
		if (*part == '\n') part++;
		next = strstr(part, req->multipart_boundary);
		char *end = next;
		if (end != NULL) {
			if (end[-1] == '\n') end--;
			if (end[-1] == '\r') end--;
			*end = '\0';
		}

		// iterate through headers in part
		char *line, *nextline;
		char *cdisp = NULL;
		for (line = part; line != NULL; line = nextline) {
			nextline = next_line(line);
			if (!*line) break; // end of headers
			char *name = line;
			char *value = parse_header(line);
			if (!strncmp(name, "Content-Disposition", 3)) cdisp = value;
		}
		char *name = NULL;
		if (cdisp != NULL && !strncmp(cdisp, "form-data; name=\"", 17)) {
			name = cdisp + 17;
			char *end = strchr(name, '"');
			if (end != NULL) *end = '\0';
		}

		// handle part body
		char *body = nextline;
		if (body == NULL) continue;

		if (!strcmp(name, "text")) {
			req->data = body;
			req->len = end == NULL ? strlen(body) : (size_t)end - (size_t)body;
		} else if (!strcmp(name, "add_new_id")) {
			req->add_new_id = true;
		}
	}
	return 0;
}

static int http_serve_new(struct http_request *req) {
	int rc;
	char note_path[_POSIX_PATH_MAX];
	char id[64];

	rc = parse_multipart(req);
	if (rc < 0) {
		write_buf(req->fd, "HTTP/1.0 400 Bad Request\r\n"
			"Content-Type: text/plain\r\n"
			"Connection: close\r\n\r\n"
			"Unable to parse form submission");
		close(req->fd);
		return 0;
	}

	(void)mkdir(zet_dir, 0700);

	generate_id(id);
	(void)snprintf(note_path, sizeof(note_path), "%s/%s", zet_dir, id);
	int note_fd = open(note_path, O_CREAT|O_WRONLY|O_TRUNC, 0640);
	if (note_fd < 0) {
		dprintf(req->fd, "HTTP/1.0 500 Internal Server Error\r\n"
			"Content-Type: text/plain\r\n"
			"Connection: close\r\n\r\n"
			"Unable to open file: %s\n", strerror(errno));
		close(req->fd);
		return 0;
	}

	rc = save_part(req, note_fd);
	if (rc < 0) {
		dprintf(req->fd, "HTTP/1.0 200 OK\r\n"
			"Content-Type: text/plain\r\n"
			"Connection: close\r\n\r\n"
			"Error saving: %s", strerror(errno));
		close(req->fd);
		return 0;
	}

	dprintf(req->fd, "HTTP/1.0 302 Found\r\n"
		"Content-Type: text/html\r\n"
		"Location: dpi:/zet/%s\r\n"
		"Connection: close\r\n\r\n"
		"<!doctype html><head>"
		"<title>Created: §%s</title>"
		"<meta charset=utf-8>"
		"</head><body>"
		"Created: <a href=\"dpi:/zet/%s\">§%s</a>"
		"</body></html>"
		, id, id, id, id);
	close(req->fd);
	return 0;
}

static int http_serve_not_found(struct http_request *req) {
	dprintf(req->fd, "HTTP/1.0 200 OK\r\n"
		"Connection: close\r\n\r\n"
		"Not found\n");
	close(req->fd);
	return 0;
}

static int http_serve_zet(struct http_request *req) {
	int rc;
	char note_path[_POSIX_PATH_MAX];
	char note_path_backup[_POSIX_PATH_MAX];
	char *id = req->path + 1;

	rc = parse_multipart(req);
	if (rc < 0) {
		write_buf(req->fd, "HTTP/1.0 400 Bad Request\r\n"
			"Content-Type: text/plain\r\n"
			"Connection: close\r\n\r\n"
			"Unable to parse form submission");
		close(req->fd);
		return 0;
	}

	(void)snprintf(note_path, sizeof(note_path), "%s/%s", zet_dir, id);
	(void)snprintf(note_path_backup, sizeof(note_path_backup), "%s/%s~", zet_dir, id);

	rc = rename(note_path, note_path_backup);
	if (rc < 0 && errno != ENOENT) warn("rename");

	int note_fd = open(note_path, O_CREAT|O_WRONLY|O_TRUNC, 0640);
	if (note_fd < 0) {
		if (errno == ENOENT) return http_serve_not_found(req);
		dprintf(req->fd, "HTTP/1.0 500 Internal Server Error\r\n"
			"Content-Type: text/plain\r\n"
			"Connection: close\r\n\r\n"
			"Unable to open file: %s\n", strerror(errno));
		close(req->fd);
		return 0;
	}

	rc = save_part(req, note_fd);
	if (rc < 0) {
		dprintf(req->fd, "HTTP/1.0 200 OK\r\n"
			"Content-Type: text/plain\r\n"
			"Connection: close\r\n\r\n"
			"Error saving: %s", strerror(errno));
		close(req->fd);
		return 0;
	}

	dprintf(req->fd, "HTTP/1.0 302 Found\r\n"
		"Content-Type: text/html\r\n"
		"Location: dpi:/zet/%s\r\n"
		"Connection: close\r\n\r\n"
		"<!doctype html><head>"
		"<title>Saved: §%s</title>"
		"<meta charset=utf-8>"
		"</head><body>"
		"Saved: <a href=\"dpi:/zet/%s\">§%s</a>"
		"</body></html>"
		, id, id, id, id);
	close(req->fd);
	return 0;
}

enum http_method parse_method(const char *method) {
	if (!strcasecmp(method, "GET")) return HTTP_METHOD_GET;
	if (!strcasecmp(method, "HEAD")) return HTTP_METHOD_HEAD;
	if (!strcasecmp(method, "POST")) return HTTP_METHOD_POST;
	return HTTP_METHOD_OTHER;
}

static int handle_http_client(int fd, int firstchar) {
	int rc;
	struct http_request req;
	char buf[2048];
	buf[0] = firstchar;
	size_t len = sizeof(buf)-1;
	rc = read_some(fd, (unsigned char *)buf+1, &len);
	buf[len+1] = '\0';
	len++;
	if (rc < 0) { close(fd); return 0; }

	char *nextline = next_line(buf);
	req.path = strchr(buf, ' ');
	if (req.path == NULL) { close(fd); return 0; }
	*req.path++ = '\0';
	req.method = parse_method(buf);
	req.http_version = strchr(req.path, ' ');
	if (req.http_version != NULL) *req.http_version++ = '\0';

	req.referer = NULL;
	req.host = NULL;
	req.content_length = -1;
	req.content_type = NULL;
	req.multipart_boundary = NULL;
	req.add_new_id = false;

	char *line = nextline;
	while (line != NULL) {
		nextline = next_line(line);
		if (!line[0]) break;
		char *name = line;
		char *value = parse_header(line);
		if (!strncmp(name, "Host", 3)) req.host = value;
		else if (!strncmp(name, "Referer", 7)) req.referer = value;
		else if (!strncmp(name, "Content-Length", 14)) req.content_length = atoi(value);
		else if (!strncmp(name, "Content-Type", 14)) req.content_type = value;
		// else fprintf(stderr, "%s = %s\n", name, value);
		line = nextline;
	}

	if (req.content_type != NULL
	  && !strncmp(req.content_type, "multipart/", 10)) {
		char *subtype = req.content_type + 10;
		char *boundary = strstr(subtype, "; boundary=");
		if (boundary != NULL) {
			*boundary = '\0';
			boundary += 11;
			if (boundary[0] == '"') {
				boundary++;
				char *end = strchr(boundary, '"');
				if (end != NULL) *end = '\0';
			}
			*--boundary = '-';
			*--boundary = '-';
			req.multipart_boundary = boundary;
		}
	}

	if (req.referer == NULL || strncmp(req.referer, server_url, strlen(server_url))) {
		dprintf(fd, "HTTP/1.0 403 Forbidden\r\n"
		        "Connection: close\r\n\r\n"
		        "Invalid Referer\n");
		close(fd);
		return 0;
	}

	if (req.host != NULL && strcmp(req.host, server_hostname)) {
		dprintf(fd, "HTTP/1.0 403 Forbidden\r\n"
		        "Connection: close\r\n\r\n"
		        "Invalid Host\n");
		close(fd);
		return 0;
	}

	if (req.method != HTTP_METHOD_POST) {
		write_buf(fd, "HTTP/1.0 405 Method Not Allowed\r\n"
			"Content-Type: text/plain\r\n"
			"Connection: close\r\n\r\n"
			"Expected POST request");
		close(fd);
		return 0;
	}

	ptrdiff_t offset = nextline - buf;
	req.data = nextline;
	req.full_data = NULL;
	req.len = len - offset;
	req.fd = fd;

	parse_req_uri(req.path, &req.hash, &req.query);

	if (!strcmp(req.path, "/")) return http_serve_index(&req);
	if (!strcmp(req.path, "/new")) return http_serve_new(&req);
	return http_serve_zet(&req);
}

static int handle_client(int server_fd) {
	int fd;
	do {
		fd = accept(server_fd, NULL, NULL);
		if (fd < 0 && errno != ENETDOWN    && errno != EPROTO
		           && errno != ENOPROTOOPT && errno != EHOSTDOWN
		           && errno != ENONET      && errno != EHOSTUNREACH
		           && errno != EOPNOTSUPP  && errno != ENETUNREACH
		) return -1;
	} while (fd < 0);
	int firstchar = read_char(fd);
	if (firstchar < 0)  {
		// ignore errno
		close(fd);
		return 0;
	}
	if (firstchar == '<') return handle_dpi_client(fd);
	return handle_http_client(fd, firstchar);
}

void get_server_address() {
	struct sockaddr_storage addr;
	struct sockaddr *addrp = (struct sockaddr *)&addr;
	socklen_t addr_len = sizeof(addr);
	char host_buf[128];
	const char *host;
	unsigned short port;
	int rc = getsockname(STDIN_FILENO, addrp, &addr_len);
	if (rc < 0) err(1, "getsockname");
	if (addr.ss_family == AF_INET) {
		struct sockaddr_in *addr_in = (struct sockaddr_in *)&addr;
		port = ntohs(addr_in->sin_port);
		host = inet_ntop(AF_INET, &addr_in->sin_addr, host_buf, sizeof(host_buf));
	} else if (addr.ss_family == AF_INET6) {
		struct sockaddr_in6 *addr_in6 = (struct sockaddr_in6 *)&addr;
		port = ntohs(addr_in6->sin6_port);
		host = inet_ntop(AF_INET6, &addr_in6->sin6_addr, host_buf, sizeof(host_buf));
	} else {
		errx(1, "Unknown server address family: %d", addr.ss_family);
	}
	int wrote = snprintf(server_hostname, sizeof(server_hostname), "%s:%hu", host, port);
	if (wrote <= 0 || wrote >= (int)sizeof(server_hostname)) {
		errx(1, "Unable to write hostname");
	}
	wrote = snprintf(server_url, sizeof(server_url), "http://%s/", server_hostname);
	if (wrote <= 0 || wrote >= (int)sizeof(server_url)) {
		errx(1, "Unable to write local URL");
	}
}

int main(int argc, char *argv[]) {
	(void)argc;
	(void)argv;

	warnx("started");

	const char *home = getenv("HOME");
	int len = snprintf(zet_dir, sizeof(zet_dir), "%s/.zet", home);
	if (len < 0 || len >= (int)sizeof(zet_dir)) {
		err(1, "unable to build directory name");
	}

	// Since dpi requests don't support a request body, we POST via HTTP
	// to our dpi server socket which is already listing on a local TCP port.
	get_server_address();

	// handle connections one at a time
	while (handle_client(STDIN_FILENO) == 0);

	warnx("exiting");
}